Photo collection shot inside Fukushima nuke plant to be released in March
The building housing reactor No. 3 of the Fukushima No. 1 Nuclear Power Plant still shows stark signs of the disaster in September 2016
Photographer Joe Nishizawa will offer a rare look inside the Fukushima nuclear plant damaged in the March 2011 earthquake and tsunami disaster with the release this March of a photo book recording of decommissioning work over a 3 1/2-year period.
Published by Misuzu Shobo, “Decommissioning Fukushima: A Photographer’s Journey into the Depths of the Fukushima Daiichi Nuclear Power Plant” will present roughly 150 photos of workers in protective gear and restorative efforts, arranged to show the passage of time. “I want to convey the scene exactly as it is,” the Takasaki, Gunma Prefecture-based photographer explains.
For the last 15 years, Nishizawa has taken photos of steel work factories, expressways and other construction scenes to cover Japan at various work sites. After the nuclear disaster occurred on March 11, 2011, plant operator Tokyo Electric Power Co. (TEPCO) released photos but they were blurred and difficult to make out. Nishizawa said he felt the need to document the state of the reactor for future generations. After negotiating with TEPCO, the photographer was granted access to the plant roughly once a month.
Wearing a mask and a protective suit covering his entire body, he first stepped foot on the grounds of the nuclear plant in July 2014. At the time, there was still debris on the premises scattered along the coastline and the destruction from the accident was still starkly evident. Once, a worker at whom he pointed his camera glared back and asked, “Just what are you photographing?”
Still, he continued to document the equipment used to purify water contaminated by radioactive materials, as well as the construction site filled with tanks of processed water. Along with the flow of time, Nishizawa also sensed the gradual progress of decommissioning efforts. Still, radiation levels around the reactor buildings are high, and the difficult labor conditions continue to this day.
“The decommissioning won’t end with this generation,” says Nishizawa. “We can’t afford to let the accident fade into the past, so I will continue taking photographs.”
How did the Fukushima disaster affect air pollution?
February 14, 2018
In March 2011, a post-earthquake tsunami triggered nuclear meltdowns, hydrogen-air explosions and the release of radioactive materials from the Fukushima Daiichi Nuclear Power Plant in Fukushima Prefecture, Japan. The Fukushima disaster has been called the most significant nuclear incident since the 1986 Chernobyl disaster. Professor Rodney C. Ewing, Frank Stanton Professor in Nuclear Security and co-director at the Center for International Security and Cooperation (CISAC) in the Freeman Spogli Institute for International Studies (FSI), as a member of a team of Japanese researchers, today published a report on the details of what exactly — at the particle level — was released into the air after the disaster.
In the discussion that follows, Ewing explains the team’s findings and why they are important for health and environmental safety.
Why did you decide to study the Fukushima disaster?
The Fukishima Daiichi event surprised me. I now teach a freshman seminar on this event. I am particularly interested to understand why the accident occurred and what the long-term impact will be on the environment. This research paper reflects my interest in answering these questions.
We’ve heard lots about possible health effects from contaminated water after the Fukushima disaster, but less about particulates in the air. What did you find?
During the core melt-down events at Fukushima Daiichi, radioactivity was released as fine particulates that traveled in the air, sometime for distances of tens of kilometers, and settled onto the surrounding countryside.
In order to understand the health risk, it is very important to understand the form and chemistry of these particulates.
Recently, in a previous paper we have described a new type of particulate that is Cs-rich (some Cs isotopes are highly radioactive). The highly radioactive Cs-rich particles formed in the reactor by condensation from a silica-rich vapor, formed from the melting of core and concrete structures. In this paper, we describe the first identification of fragments of the melted core that were entrapped by the Cs-particles and transported away from the reactor site, some 4 kilometers. This is an important discovery because this provides us with samples of the fuel and melted core.
This is a special contribution because it uses very advanced electron microscopy techniques that allow for imaging of individual atoms or clusters of atoms. This advanced technique is required because the particles are so small — nanometers in size.
How did you come to work with your collaborators in Japan?
I have had long standing collaborations with Japanese scientists for decades. The lead researcher for the group, Professor Satoshi Utusunomiya, was once a member of my research group when I was at the University of Michigan. We have always collaborated on topics that involve radioactive materials and the use of electron microscopy. This collaboration is an entirely natural outgrowth of previous collaborations.
What, if any, policy recommendations would you suggest based on your findings?
The most direct result would be to design monitoring systems so that we have a good record of released particulates. Also, we need to push the development of advanced analytical techniques so that these particulates can be quickly identified and characterized.
Fukushima 7th Anniversary Events List
Fukushima 7th Anniversary Events List As of today this is the list of the major events organized in various countries and towns worldwide for the commemoration of the March 11 2011 beginning of the Fukushima nuclear disaster, ongoing for 7 years now:
JAPAN
In Koriyama – March 11 3・11 Fukushima Anti Nuclear Action ‘ 18 Location : KORIYAMA City Cultural Center , Big Hall Starts at 13:00 After the rally we have demonstration to Koriyama Station http://fukushimaaction.blog.fc2.com/blog-entry-361.html
In Tokyo — March 9 http://www.foejapan.org/energy/evt/180309.html
In Osaka – March 17 https://www.facebook.com/events/1955332334716083/
In Kyoto – March 11 https://www.facebook.com/events/1599975136756649/
SOUTH KOREA
In Seoul March 10 from 13:00~17:00.
Place: Gwanghwamun Square, King Sejong the Great, + Gwanghwamun march
https://www.facebook.com/311fukushimaparade/
USA
In New York – March 10 https://www.facebook.com/events/802843189916923/
In San Francisco – March 11 The 68th Every 11th of Month No Nukes Rally in San Francisco, in front of the S.F. Japanese Consulate
In Richmond, Virginia – March 11 at 11 AM – 12 PM Remembering Fukushima
https://www.facebook.com/events/786967918175803/
UNITED KINGDOM
In London – March 9 – March 11 – March 14 https://www.facebook.com/events/336322393516248/
FRANCE
In Paris – March 11 http://www.sortirdunucleaire.org/11-mars-2018-grand-rassemblement-pour-la-sortie
In Flamanville – March 15 https://leblogdejeudi.fr/tag/cano/
In Grenoble – March 17 at 6pm Conferences Meeting with three families evacuated from Fukushima Mothers’ tour to protect children from radiation after the Fukushima accident. Bibliothèque Centre-Ville 10 Rue de la République 38000 GRENOBLE
Mail : voisins311@gmail.com
https://www.facebook.com/events/1986157938311149/
In Valence – March 19 at 8:30pm Conferences Meeting with three families evacuated from Fukushima Mothers’ tour to protect children from radiation after the Fukushima accident. Maison pour Tous Petit Charran 30 Rue Henri Dunant 26000 VALENCE
Mail : voisins311@gmail.com
https://www.facebook.com/events/1986157938311149/
In Lyon – March 20 at 7pm Conferences Meeting with three families evacuated from Fukushima Mothers’ tour to protect children from radiation after the Fukushima accident. Hôtel Novotel Lyon Confluence 3 Rue Paul Montrochet 69002 LYON
Mail : voisins311@gmail.com
https://www.facebook.com/events/1986157938311149/
SWITZERLAND
In Geneva – March 16 Conferences Meeting with three families evacuated from Fukushima Mothers’ tour to protect children from radiation after the Fukushima accident.
Mail : voisins311@gmail.com
BELGIUM
In Namur – March 8 https://www.quefaire.be/tu-n-as-rien-vu-a-fukushima-843749.shtml
RUSSIA
In Saint Petersburg – March 11 https://www.facebook.com/events/1882949795348632/
GERMANY
In Berlin – March 10 https://www.facebook.com/events/204920653395925/
In Regensburg – April 26 https://www.facebook.com/events/169657723642015/
AUSTRALIA
In New South Wales – March 11 https://www.facebook.com/events/343840736130676/permalink/343966142784802/
Drone to probe Fukushima N-plant interior
February 10, 2018
Tokyo Electric Power Company Holdings Inc. plans to use a small unmanned aerial vehicle to closely inspect conditions inside the No. 3 reactor building of the Fukushima No. 1 nuclear power plant as early as this month.
TEPCO will use the drone to examine the location of scattered debris and the level of radiation inside the reactor building, among other things.
It will be the first drone-based research conducted inside the plant’s Nos. 1, 2 and 3 reactor buildings, in which nuclear meltdowns occurred.
The drone, called Riser, was developed by a British company. It measures 83 centimeters by 93 centimeters and weighs about four kilograms.
Riser is equipped with cameras and a dosimeter that can measure up to 2.5 sieverts of radiation per hour.
Even in indoor spaces inaccessible to GPS signals, the drone is capable of determining its position and avoiding obstacles using lasers.
The same model was used for decommissioning work at the Sellafield nuclear facility in Britain.
TEPCO’s plan is for the drone to enter the No. 3 reactor building through a bay for large cargo on the first floor, then fly upward through a series of openings from the first to the fifth floor.
The drone will check areas including the building’s third floor, which has not been sufficiently monitored because radiation levels are too high.
According to TEPCO, key equipment such as that used to cool spent nuclear fuel pools are located on the third floor.
Confirming the location of possible obstacles and the level of radiation is necessary before decommissioning work can progress.
Riser also has a mapping function that enables it to produce three-dimensional graphic images of its surroundings using lasers.
Combining these images with measurements of radiation levels allows for the production of maps outlining contamination levels inside the reactor buildings. TEPCO will consider making this kind of distribution map in the future.
A hydrogen explosion inside the No. 3 reactor building on March 14, 2011, destroyed the building’s upper structures.
Work is currently under way to construct a dome-shaped roof over the building to facilitate the removal of fuel that remains in the spent fuel storage pools.
Rubble storage at Fukushima plant shown to media
The operator of the Fukushima Daiichi nuclear plant has completed a facility to store radioactive rubble from the March 2011 accident.
Tokyo Electric Power Company showed the new storage facility in the compound to the media on Thursday.
The Number 1 to Number 3 reactors suffered meltdowns and the reactor buildings were badly damaged after a quake-triggered tsunami hit the plant on March 11th, 2011.
As part of decommissioning work, rubble scattered after the accident needs to be cleared before spent nuclear fuel can be removed from storage pools in the upper parts of the reactor buildings.
At the Number 1 reactor building, work to clear more than 1,500 tons of rubble began in January. Its pool stores 392 fuel units.
The newly-completed facility is capable of storing more than 60,000 cubic meters of rubble.
Officials say a special vehicle that blocks radiation will take rubble from the Number 1 reactor building to the storage facility, and remote-controlled forklifts will be used to carry the rubble inside it.
The storage facility is 2 stories above ground and 2 below. The more radioactive the debris, the deeper underground it will be stored.
Officials say the facility can block radiation of levels up to 10 sieverts per hour, as it is covered by concrete walls up to 65 centimeters thick.
Kazuteru Ofuchi, a TEPCO official in charge of waste disposal, says the firm will make sure to minimize workers’ exposure to radiation, by working remotely.
Radioactive Micro-particles at Fukushima Daiichi
Caesium-rich micro-particles: A window into the meltdown events at the Fukushima Daiichi Nuclear Power Plant
Abstract
The nuclear disaster at the Fukushima Daiichi Nuclear Power Plant (FDNPP) in March 2011 caused partial meltdowns of three reactors. During the meltdowns, a type of condensed particle, a caesium-rich micro-particle (CsMP), formed inside the reactors via unknown processes. Here we report the chemical and physical processes of CsMP formation inside the reactors during the meltdowns based on atomic-resolution electron microscopy of CsMPs discovered near the FDNPP. All of the CsMPs (with sizes of 2.0–3.4 μm) comprise SiO2 glass matrices and ~10-nm-sized Zn–Fe-oxide nanoparticles associated with a wide range of Cs concentrations (1.1–19 wt% Cs as Cs2O). Trace amounts of U are also associated with the Zn–Fe oxides. The nano-texture in the CsMPs records multiple reaction-process steps during meltdown in the severe FDNPP accident: Melted fuel (molten core)-concrete interactions (MCCIs), incorporating various airborne fission product nanoparticles, including CsOH and CsCl, proceeded via SiO2 condensation over aggregates of Zn-Fe oxide nanoparticles originating from the failure of the reactor pressure vessels. Still, CsMPs provide a mechanism by which volatile and low-volatility radionuclides such as U can reach the environment and should be considered in the migration model of Cs and radionuclides in the current environment surrounding the FDNPP.
The nuclear disaster at the Fukushima Daiichi Nuclear Power Plant (FDNPP) in March 2011 caused partial meltdowns of three reactors1,2,3, which caused the second-most serious nuclear accident in history4, resulting in serious environmental threats with the release of ~5.2 × 1017 becquerels (Bq) of radionuclides5 in Fukushima prefecture. Many of the resulting problems, including radioactive caesium contamination of the surface environment, have yet to be resolved6. The most challenging issue remaining is the treatment of the four damaged reactors. Decommissioning of Units #1–4 is currently ongoing7, although the properties of the melted fuels mixed with reactor components, referred to as debris, and the conditions inside the reactors remain unknown because the high-radiation field prevents access7.
Until now, the reactions that occurred in the FDNPP reactors have been only inferred based on indirect evidence3. It is believed that radioactive Cs was liberated from the irradiated fuel when the temperature of the fuel rose above 2,200 K8 after the cooling systems shut down in Units #1–3. Other radionuclides were released in amounts depending on their respective volatilities9 rather than in amounts based on their estimated presence in the nuclear fuel, which was primarily composed of UO28,10. Thus, a large portion of the fission products (FPs), including radioactive Cs still remain in the damaged reactors and in contact with the cooling water11. To carry out an adequate decommissioning process, it is of critical importance to understand the physical and chemical state of the radionuclides inside the reactors12. In particular, most of the irradiated fuels melted in Units #1 and #3, while a lesser amount or none of the fuels underwent melting in Unit #23,13. Melted fuel accumulated at the bottom of the reactor pressure vessels (RPVs), which eventually caused the RPVs to rupture, leading to reactions with the concrete pedestals of the primary-containment vessels (PCVs)14, a process known as molten core concrete interaction (MCCI)15. There remains considerable uncertainty about the extent of the MCCI in the reactors and the state of the melted fuel.
Caesium-rich micro-particles (CsMPs) originating from the FDNPP were first found in atmospheric particles some 170 km southwest of the FDNPP16,17. These particles represent condensed matter that formed within the reactors during meltdown, and they provide important information on the physical and chemical characteristics of the radioactive material inside the reactors. This study unravels the formation process of the CsMPs based on their chemical and structural properties at the atomic scale utilizing a high-resolution transmission electron microscopy (HRTEM) in conjunction with conventional radio-analytical techniques.
Methods
Sample description
The sampling campaign was conducted on 16 March 2012. The Ottozawa soil sample (OTZ) was collected from the top ~1 cm of soil in a paddy located ~4 km west of the FDNPP in Okuma Town, Futaba County, Fukushima. The soil was primarily composed of clay minerals, quartz and feldspars. Because entering the area was still restricted due to the high radiation dose, the locality had not been artificially disturbed. The radiation dose ~1 m above the ground was 84 μSv/h. The gravel sample from Koirino (KOI) was collected under the drainpipe of the assembly house. The house is located 2.9 km southwest of the FDNPP. The radiation dose beneath the drainpipe was extremely high compared with the surroundings, with a sampling area dose as high as 630 μSv/h. The gravel samples were carefully collected from the surface of the ground using a hand shovel, and placed in plastic bags. The aquaculture centre (AQC) soil samples were collected from the side ditch of an aquaculture centre located ~2 km south of the FDNPP.
Separation of CsMPs
The procedure for separating CsMPs from the soil samples is schematically illustrated in Fig. S1. Prior to the procedure, both samples were sieved through a 114 μm mesh. The powder samples were dispersed on grid paper and covered with a plastic sheet, and an imaging plate (Fuji film, BAS-SR 2025) was placed on the samples for 5–25 min. Autoradiograph images with pixel sizes of 50–100 μm were recorded using an imaging-plate reader. After the positions of intensely radioactive spots were identified, droplets of pure water were added to these positions and then drawn using a pipette to produce suspensions with small amounts of soil particles by dilution with pure water (Procedures 3–9 in Fig. S1). This procedure was repeated until the suspension did not contain a significant amount of soil particles. Subsequently, positions containing hot spots were selected using pieces of double-stick carbon tape that were cut as small as possible with a blade. The pieces of tape were checked by autoradiograph imaging so that scanning electron microscopy (SEM) observation could be performed to obtain the CsMPs with maximum efficiency. Prior to SEM analysis, the pieces of tape were placed on an aluminium plate and coated with carbon using a carbon coater (SANYU SC-701C). The CsMPs were found using an SEM (Shimadzu, SS550 and Hitachi, SU6600) equipped with an energy dispersive X-ray spectrometer (EDX, EDAX Genesis) using acceleration voltages of 5–25 kV for imaging details of the surface morphology and 15–25 kV for elemental analysis, including area analysis and elemental mapping.
Preparation of the TEM specimen
A focused ion beam (FIB) instrument (FEI, Quanta 3D FEG 200i Dual Beam) was utilised to prepare a thin foil of individual CsMPs with diameters of a few μm. Gallium was used as an ion source, and W deposition was used to minimise damage from the ion bombardment. Prior to application of the FIB, each SEM specimen was coated with ~40 nm-thick gold. The current and accelerating voltage of the ion beam were adjusted from 100 pA to 30 nA and 5–30 kV, respectively, depending on the progress of the thinning and on sample properties such as hardness and size. Each thinned piece was attached to the semilunar-shaped Cu grid for FIB and further thinned by an ion beam operating at 5 kV.
TEM analysis
HRTEM with EDX and a high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) were performed using a JEOL JEM-ARM200F and JEM-ARM200CF with an acceleration voltage of 200 kV. The JEOL Analysis Station software was used to control the STEM-EDX mapping. To minimise the effects of sample drift, a drift-correction mode was used during acquisition of the elemental map. The STEM probe size was ~0.13 nm, generating ~140 pA of current when 40 μm of the condenser lens aperture was inserted. The collection angle of the HAADF detector was ~97–256 mrad.
Gamma spectrometry
The 134Cs and 137Cs radioactivities of the CsMPs were determined using gamma spectrometry. The radioactivity of an additional micro-particle with a size of ~400 μm obtained from the surface soil in Fukushima was precisely determined at the radioisotope centre in Tsukuba University, Japan, and utilised as a standard point specimen for 134Cs and 137Cs. The radioactivity of the point source standard was 23.9 Bq for 134Cs and 94.6 Bq for 137Cs as of 29 September 2015. The measurement of radioactivity was performed on the CsMPs and the point source standard using germanium semi-conductor detectors GMX23, GMX30 and GMX40 (all from SEIKO E&G) at the centre for radioisotopes in Kyushu University, Japan. The acquisition times were: 12,305 s for the KOI sample, using GMX30; 86,414 s for the OTZ sample, using GMX40; and 263,001 s for the AQC sample, using GMX23.
Results
The CsMPs were discovered in three samples within ~4 km of the FDNPP: in gravel soil at the assembly house in Koirino, in soil from a side ditch at an aquaculture centre and in paddy soil in Ottozawa (Fig. 1). The samples are hereafter labelled KOI, AQC and OTZ, respectively. The radioactivity of the CsMPs and the relevant parameters are summarised in Table 1. The 134Cs/137Cs radioactivity ratio of the samples is 0.97–1.1, with an average of 1.04, which approximately corresponds to ~26 GWd/tU according to OrigenArp calculations18. Because of the heterogeneity within even the irradiated fuels in a single reactor, the source reactor unit could not be determined based only on the isotopic or radioactivity ratios. The radioactivity per unit mass of the CsMPs calculated assuming that the radioactivity for SiO2 glass19 with a density of 2.6 g/cm3 varies from 9.5 × 1010 to 4.4 × 1011 (Bq/g), which is comparable with values reported for CsMPs from Tokyo20.
Figure 1
Locations of the samples used in this study.
Table 1
Summary of the radioactivity and the associated parameters of three CsMPs in the present study.
The KOI CsMP was mainly composed of Si, Fe, Zn and Cs (Fig. 2 and Table S1). A HAADF-STEM image of the cross section shows two large pores of approximately 500 nm and numerous small pores in sizes ranging from 10–200 nm, indicating that some gases (such as H2, H2O, CO and CO2) were trapped through sparging during the MCCI (Fig. 3a). Selected area electron diffraction (SAED) patterns revealed diffuse diffraction maxima that correspond to an amorphous structure (Fig. 3b). Trace elements, including K, Cl, Sn, Rb, Pb and Mn, were detected by STEM energy dispersive X-ray (EDX) area analysis (Table S1).
Figure 2
Secondary electron images of three CsMPs; KOI, OTZ, and AQC, associated with the energy dispersive X-ray spectrum (EDX) maps of the major constituents.
Figure 3
(a) HAADF-STEM image of the focussed ion beam (FIB)-prepared specimen of the KOI Cs-rich micro-particle, with its original shape traced by a white dotted line. The yellow and orange open triangles indicate rod-like nanoparticles consisting primarily of Cs. (b) SAED pattern of the area indicated in (a). (c) A HAADF-STEM image associated with elemental maps of the major constituents. (d) HAADF-STEM image with the elemental maps of the CsMP at high resolution, showing the heterogeneous occurrence of Fe–Zn-oxide nanoparticles associated with Sn and Cs. (e) HRTEM image of the Fe–Zn oxide and the fast Fourier transformed (FFT) image. (f) A HRTEM image of a rod-shaped Cs nanoparticle present in a pore indicated by the yellow arrow in (a).
An elemental map of the CsMP constituents shows the synchronised distribution of Si, O, Fe and Zn, although only Cs is concentrated in the particle cores (Fig. 3c). Although the SAED exhibits diffuse diffraction maxima (Fig. 3b), a magnified image reveals that Zn, Fe, Sn and Cs are associated with nanoparticles as small as <10 nm distributed within the SiO2 matrix (Fig. 3d) that were identified to be franklinite structures (ZnFe2O4, Fd3m, Z = 8)21 (Fig. 3e). Several rod-like nanoparticles, indicated by yellow arrows, are present (Fig. 3a). An HRTEM image of the rod-shaped nanoparticle reveals a mostly amorphous contrast, with a small portion that is still crystalline (Fig. 3f). Based on the d-spacing in the HRTEM image (Fig. 3g) and the composition of primarily Cs and O (Fig. 4a–c), these rod-shaped particles were identified as Cs hydroxides, CsOH•H2O22. Nano-sized inclusions of ZnCl2 and CsCl were also identified (Fig. 4d,e).
Figure 4
(a) The STEM-EDX spectrum of a rod-like nanoparticle shown in Fig. 3a. (b) HAADF-STEM image of the core region in the KOI obtained in the second session, showing that the rod-like Cs nanoparticle in the large pore degraded. (c) EDX spectrum of the area indicated by the red square in the left image. The composition of the degraded particle also revealed the Cs as the major constituent. (d) HAADF-STEM image of nano-sized inclusion of ZnCl2. (e) HAADF-STEM image of nano-sized inclusion of CsCl.
In the OTZ CsMP, there are no pores, and the particle appears to have a homogeneous composition except for an Fe-oxide inclusion (Fig. 5a,b). However, like the KOI CsMP, the OTZ CsMP is composed of an amorphous SiO2 glass matrix along with Fe–Zn-oxide nanoparticles of <10 nm in size (Fig. 5c); these nanoparticles were identified as franklinite, based on the FFT image and SAED pattern (Fig. 5d,e). Franklinite was the only nanomaterial for which the structure was convincingly characterized. Caesium, Cl and Sn were associated with the franklinite for the most part; however, an inclusion of CsCl associated with ZnCl is also present (Fig. 5f). Remarkably, the area indicated by the yellow square in Fig. 5a contains nanoparticles with peaks of U Mα, Lα and Lβ in the EDX spectrum (Fig. 5g). Point analyses of the particles (edx1 and 2) exhibited further distinctive U peaks without interference from Rb (red line in the spectrum). The HAADF-STEM image resolved no UO2 crystal, only franklinite associated with a small amount of U.
Figure 5
(a) HAADF-STEM image of the FIB-prepared OTZ CsMP. The inset is the SAED pattern obtained from the top thin area. White dotted curves represent the original shape of the particle before FIB thinning. (b) Elemental maps of the CsMP showing the distribution of major constituents. (c) Enlarged HAADF-STEM image with the elemental maps of major constituents, showing numerous Fe–Zn nanoparticles associated with Sn, Cs and Cl in the Si matrix. (d) Fe–Zn-oxide nanoparticle identified as franklinite. (e) SAED pattern exhibiting faint diffraction rings in diffuse halo, which are confirmed to be caused by franklinite. (f) HAADF-STEM image with elemental maps revealing the presence of CsCl domains. (g) HAADF-STEM image of the area indicated by the yellow square in (a) showing aggregation of franklinite nanoparticles. Comparison of edx spectra (edx1 and 2 in red line) of the point analysis with the spectrum obtained by the area analysis (black line) reveals the presence of U peaks.
The AQC CsMP exhibits a spherical shape (Fig. 6a) containing a spherical W oxide core as large as ~1 μm in diameter (Fig. 6b), which indicates that W oxide initially melted to form a droplet that served as a nucleation centre for CsMP formation. Otherwise, the AQC CsMP has a composition similar to that of the KOI and OTZ CsMPs, that is, Zn–Fe-oxide nanoparticles embedded in an SiO2 glass matrix (Fig. 6c–e). Some fission-product nanoparticles consisting of Ag and Sb were characterized in the CsMP as well (Fig. 6f).
Figure 6
(a) A HAADF-STEM image of the cross-section of AQC CsMP prepared by FIB. (b) The STEM-EDX elemental maps of the major constituents. (c) SAED pattern of top thin area of FIB specimen shown in (a). (d) Magnified HAADF-STEM image of the thin area of FIB specimen associated with STEM-EDX elemental maps. (e) HRTEM image of a Zn–Fe oxide and the FFT image of the area outlined by the white square. (f) HAADF-STEM image of a fission product nanoparticle consisting of Ag and Sb.
The STEM-EDX area analysis (~100 × 100 μm) and point analyses of individual Zn–Fe oxides revealed that the Si concentrations are linearly correlated with the Zn + Fe content (Fig. 7a,b), indicating that the CsMPs are essentially composed of SiO2 glass and Fe–Zn-oxide nanoparticles, with the number of nanoparticles directly reflecting the concentrations of Fe and Zn. The Cs concentration derived from the area analysis also has a linear correlation with the Si content (Fig. 7c), whereas the Cs concentrations in the individual Fe–Zn oxide particles are scattered without correlation to the Si content (Fig. 7d). Such differences can be attributed to either variations in the concentration of Cs associated with Fe–Zn-oxide nanoparticles and/or intrinsic Cs species such as Cs(OH) and CsCl. Indeed, some area analyses of the KOI CsMP tended toward high Cs content (yellow circles) because of the presence of intrinsic Cs particles trapped inside the CsMP. The Zn concentration is positively correlated with Fe concentration towards the ideal Zn/Fe ratio of franklinite, as indicated by the solid line (Fig. 7e). The deviation toward a higher amount of Zn is a result of the presence of ZnCl2 inclusions.
Figure 7
(a–d) Diagrams showing compositional relationship between Si and Fe + Zn (a,b), and between Si and Cs (c,d). (a,c): results of area analysis. (b,d): results of point analysis. (e) Correlation between Zn and Fe contents with a line of ideal composition of franklinite (ZnFe2O4). Correlations between all other elements measured in the CsMPs are given in Figs S2 and S3. *The TKY data are from Imoto et al. (2017)20.
Discussion
As was shown in previous experiments15,23,24, the occurrence of Cs and other FP nanoparticles strongly suggests that volatile FPs (Cs, I, Xe, Te, Ag and Rb)9, which accumulated in the gap between the fuel and the cladding during reactor operation, were released either immediately after cladding failure or during the melting of the fuel rods in the FDNPP prior to MCCI. Thus, the atmosphere inside the RPVs must have been filled with aerosol particles associated with Cs, gaseous Cs species, water vapour and hydrogen gas. Interactions between the melted core and Fe in the structural materials of the reactor during vessel failure then produced large amounts of Fe–Zn-oxide nanoparticles.
As recent results20,25 showed, the major and trace elements of the CsMPs were derived from elements inside the reactor during the meltdowns; however, the compositions are markedly different from those in the debris12, which consists of a mixture of melted core, reactor materials and concrete. Possible sources of the constituent elements are as the follows: Sn was part of a Zr–Sn alloy; Fe and Mn were constituents of the reactor pressure vessel; Si was derived from siliceous concrete released during the molten-core–concrete interaction3,23; Cs, Rb, Pb and Sn were fission products contained in the irradiated fuels; Cl was from seawater and Zn was routinely added to the reactor water to prevent radioactive corrosion of steel by formation of a protective oxide layer. Tungsten is present as an impurity in zircaloy and most stainless steels26. Although W is a promising element with extremely high heat resistance (a melting temperature of 3687 K), the oxidized form can be easily melted at relatively low temperature of ~1746 K19. It is plausible that the presence of water vapour dramatically enhanced the oxidation of the stainless steel26.
As reported in the MCCI experimental study22,23, when the melted cores hit the siliceous concrete pedestal, SiO(g) was generated as a consequence of Zr oxidation at a temperature >2,143 K. In this study, it was found that SiO(g) eventually condensed to SiO2 glass rather than forming Si metal or SiC, indicating that there was some oxygen within the reactor PCVs at the FDNPP. The presence of oxygen affects the volatilization temperature of radionuclides in the fuel such as U27. The oxidised form of U oxide fuel can volatilise at ~1,900 K by 10% of the total UO2, whereas for non-oxidized form of UO2 the figure is nearly 0% at 2,700 K28. Thus, it is plausible that the trace amounts of U associated with franklinite are evidence of the volatilisation of slightly oxidised UO2. The absence of UO2 fragments in the CsMPs suggest that fuel fragments were not directly incorporated into the CsMPs during the MCCI.
The airborne CsOH nanoparticles that formed in the PCVs prior to MCCI were trapped during the MCCI events. Considering that CsOH is stable as a solid at temperatures <615 K19, which is much lower than the temperature of SiO2 solidification, ~1995 K19, it is likely that the CsMP rapidly cooled and solidified without degrading the CsOH particles, which is consistent with the glassy structure of the SiO2 matrix. The CsOH particles might have decomposed if they were trapped in pores that contained water vapour and then recrystallized while the CsMP cooled down.
In addition, at the time of MCCI, the other gases (H2, H2O, CO and CO2) are typically sparged from the molten corium pool and must have been trapped in the micro-particles during the condensation of SiO(g). The trapped gases created the porous texture, and the SiO2(l) rapidly solidified into glassy SiO2, thus retaining numerous pores. Thus, the pore found within the KOI CsMPs was probably filled with CO2 and water vapour, in addition to possible gaseous decay daughters, due to the oxidizing conditions. The difference in the micro-texture with (KOI) or without (OTZ and AQC) pores possibly represents a local variation in the amount of vapours trapped during condensation of the SiO(g).
The formation process of CsMPs in the FDNPP was clearly different from that of the micro-particles reported in the previous MCCI experiments23,29,30. The nanoscale textures of the CsMPs revealed several processes during meltdown: (i) FPs, such as Cs, were released to form nanoparticles or were present in mist droplets during the meltdown; (ii) many Zn–Fe-oxide nanoparticles formed during the failure of the RPVs, and Cs dissolved in mist droplets attached to the surfaces of airborne Zn–Fe-oxide nanoparticles; (iii) the molten fuels that melted through the RPVs hit the concrete pedestal and generated SiO gas at >2,000 K, which immediately condensed as SiO2 over the Zn–Fe-oxide nanoparticles and incorporated the FP nanoparticles.
A recent study reported interesting phenomena during a laboratory experiment involving CsOH adsorption onto a stainless-steel surface at an elevated temperature31. The authors found that CsOH can easily adsorb onto an Fe-oxide surface. Their results are consistent with our results revealing a close association of CsOH with Fe–Zn-oxide nanoparticles. However, the resulting product of chemisorption, CsFeSiO4, which was characterized in their study, was not observed in the present study; Si occurs as pure SiO2. The difference strongly suggests that the CsMP did not form in the process where the melted fuel encountered the material of the RPV, but instead formed via another reaction process, most likely interaction with the concrete pedestal, as suggested in the present study.
As a recent study reported that ~90% of the Cs radioactivity derived from CsMPs during the initial fallout of radioactive Cs in Tokyo20, CsMPs with FP nanoparticles are significant sources of radioactive Cs and FPs for the surface environment in Fukushima. Although the contribution of the CsMPs to the total inventory of radioactivity in the contaminated area in Fukushima remains to be determined, the nanoscale physical and chemical properties of the CsMPs provide clues for understanding the mechanisms of Cs release and the stability of Cs after dispersal to the environment. Although their total activity is low, CsMPs are yet another vector for the dispersion of low-volatility radionuclides, such as U, in addition to volatile radionuclides, to the surrounding environment. Thus, the migration of CsMPs in the environment should be taken into account in the Cs transport model of the Fukushima environment in order to gain a better understanding of the impact and dynamics of radionuclide contamination.
Conclusions
The sequence of chemical and physical processes inside the reactors during the meltdowns in the FDNPP have been unravelled based on state-of-the-art atomic-resolution electron microscopy of CsMPs. The CsMPs are as small as a few microns and comprise SiO2 glass matrices and ~10 nm-sized Zn–Fe-oxide nanoparticles associated with up to ~20 wt% of Cs, occasionally accompanied by trace amounts of U. The micro-texture of the CsMPs reveals that various airborne fission-product nanoparticles were first released from the fuels before and during meltdowns. Subsequently, RPV failure occurred and a large number of Zn–Fe-oxide nanoparticles were produced. Finally, the melted core interacted with concrete and the MCCI proceeded via SiO2 condensation encompassing the Zn–Fe-oxide nanoparticles, incorporating the fission-product nanoparticles. The present study demonstrates that the CsMPs provide an important clue for understanding the reactions and conditions inside the reactors. On the other hand, because of the extremely high radioactivity per unit mass, ~1011 Bq/g, CsMPs can be a significant source of the radiation dose in the ambient environment in Fukushima. In addition, CsMPs are an important carrier by which volatile and low-volatility radionuclides such as U reach the environment.
Acknowledgments
This study is partially supported by JST Initiatives for Atomic Energy Basic and Generic Strategic Research and by a Grant-in-Aid for Scientific Research (KAKENHI) from the Japan Society for the Promotion of Science (16K12585, 16H04634, No. JP26257402). SU is also supported by ESPEC Foundation for Global Environment Research and Technology (Charitable Trust) (ESPEC Prize for the Encouragement of Environmental Studies). The authors are grateful to Dr. Watanabe for her assistance on SEM analyses at the Centre of Advanced Instrumental Analysis, Kyushu University. The findings and conclusions of the authors of this paper do not necessarily state or reflect those of the JST.
Footnotes
The authors declare no competing financial interests.
Author Contributions S.U. conceived the idea, designed all experiments, and wrote the manuscript. G.F. and J.I. performed measurements and data analysis. A.O. conducted TEM analysis. T.O. and K.N. provided navigation during field research in Fukushima. S.Y. performed gamma spectroscopy at Tsukuba University. B.G. and R.C.E. provided constructive comments and thorough editing on the manuscript.
References
Song J. H. & Kim T. W. Nucl. Eng. Tech. 46, 207–216 (2013).
Peplow M. Nature 506, 292–293 (2014).
TEPCO third progress report on the estimation of the status of nuclear fuels and primary containment vessels, and unresolved issues in units 1–αn Fukushima Daiichi Nuclear Power Plant (in Japanese) (2015).
Thielen H. Health Phys. 103, 169–174 (2012). [PubMed]
Steinhauser G. Brandl A. & Johnson T. E. Sci. Total Environ. 470, 800–817 (2014) [PubMed]
Okumura H. Ikeda S. Morita T. & Eguchi S. Proc. Natl. Acad. Sci. USA 113, 3838–3843 (2016). [PMC free article] [PubMed]
http://www.tepco.co.jp/en/decommision/index-e.html, accessed on September 28, 2016).
Grambow B. & Poinssot C. Elements, 8, 213–219 (2012).
Pontillon Y. & Ducros G. Nucl. Eng. Design 240, 1853–1866 (2010).
Ewing R. C. Nature Materials 14, 252–257 (2015). [PubMed]
Grambow B. & Mostafavi M. Environ. Sci. Processes Impacts 16, 2472–2476 (2014). [PubMed]
Burns P. C., Ewing R. C. & Navrotsky A. Science, 335, 1184–1188 (2012). [PubMed]
Bakardjieva S. et al. . Annals Nucl. Energy 74, 110–124 (2014).
Report on the Investigation and Study of Unconfirmed/Unclear Matters in the Fukushima Nuclear Accident. Progress Report No.2. 6 August 2014, Tokyo Electric Power Company, Inc.
Sevόn. T. Molten core–concrete interaction in nuclear accidents. I Theory and design of an experimental facility. VTT research notes 2311 (2005).
Adachi K., Kajino M. Zaizen Y. & Igarashi Y. Sci. Rep. 3, 2554/1–5 (2013). [PMC free article] [PubMed]
Abe Y., Iizawa Y., Terada Y., Adachi K., Igarashi Y. & Nakai I. Anal. Chem. 86, 8521–8525 (2014). [PubMed]
Bowman S. M. & Gauld I. C. OrigenArp Primer: How to perform isotopic depletion and decay calculations with SCALE/ORIGEN, ORNL/TM-2010/43 (2010).
Haynes W. M. ed. CRC Handbook of Chemistry and Physics 95th edition 2014–2015, CRC press, Taylor & Francis, Boca Raton, FL.
Imoto J. et al. . Sci. Rep. 7, 42118/1–8 (2017).
Pavese A., Levy D. & Hoser A. Amer. Mineral. 85, 1497–1502 (2000).
Černý R., Favre-Nicolin V. & Bertheville B. Acta Crystal. C 58, i31–i32 (2002). [PubMed]
Nuclear safety in light water reactors. Severe accident phenomenology. Sehgal B. R. Ed. Academic Press, Amsterdam, The Netherlands. 714pp, 2012. And references therein.
Clément B. et al. . Nucl. Eng. Design 226, 5–82 (2003).
Yamaguchi N., Mitome M., Akiyama-Hasegawa K., Asano M., Adachi K. & Kogure T. Sci.Rep. 6, 20548, 1–6 (2016). [PMC free article] [PubMed]
Handbook of Stainless Steel. Outokumpu Oyj. Sandvikens Tryckeri AB, Sweden (2013).
Pontillon Y., Ducros G. & Malgouyres P. P. Nucl. Eng. Design 240, 1843–1852 (2010).
Hiernaut J.-P. et al. . J. Nucl. Mater. 377, 313–324 (2008).
Beattie I. R. & Nichols A. L. J. Aerosol Sci. 23, 847–852 (1992).
Kissane M. P. Nucl. Eng. Design 238, 2792–2800 (2008).
Di Lemma F. G., Nakajima K., Yamashita S. & Osaka M. Nucl. Eng. Design 305, 411–420 (2016).
Articles from Scientific Reports are provided here courtesy of Nature Publishing Group
‘Global Consequences’ of Lethal Radiation Leak at Destroyed Japan Nuclear Plant
Lethal levels of radiation have been observed inside Japan’s damaged Fukushima nuclear power plant. And they are arguably way higher than you suspect.
According to Tokyo Electric Power Company (Tepco), radiation levels of eight Sieverts per hour (Sv/h) have been discovered within the Fukushima nuclear power plant, which was destroyed after a massive earthquake and a tsunami in March 2011.
Tepco, the company that operated the plant and is now tasked with decommissioning it, reported the discovery after making observations in a reactor containment vessel last month.
Eight Sv/h of radiation, if absorbed at once, mean certain death, even with quick treatment. One Sv/h is likely to cause sickness and 5.5 Sv/h will result in a high chance of developing cancer.
While 8 Sv/h is deadly, outside of Fukushima’s Reactor Number 2 foundations of a much higher level of 42 Sv/h was detected.
A strange occurrence, and experts are still arguing what caused the discrepancy. One possible explanation is that cooling water washed radioactive material off debris, taking it somewhere else.
But here’s a truly terrifying catch: according to the report, Tepco highly doubts the new readings, because, as was discovered later, a cover was not removed from the robot-mounted measurement device at the time of the inspection, NHK World reports.
Exactly one year ago, Sputnik reported that Tepco engineers discovered absolutely insane levels of radiation of about 530 Sv/h within the reactor. Such levels of radiation would kill a human within seconds. By comparison, the Chernobyl reactor reads 34 Sv/h radiation level, enough to kill a human after 20 minutes of exposure.
The levels of radiation within Fukushima reactor number 2 were so high that Tepco’s toughest robot, designed to withstand 1000 Sv/h of radiation, had to be pulled out, as it started glitching due to high radiation levels. Nuclear experts called the radiation levels “unimaginable” at the time.
On November 2017, the New York Times and other news outlets reported a much smaller figure of 70 Sv/h of radiation, more or less on par with a 74 Sv/h reading gathered before an anomalous 530 Sv/h spike.
While that radiation dosimeter cover negligence prevents precise calculations, the actual picture inside Unit 2 is thought to be much worse.
Japanese state broadcaster NHK World quoted experts saying that if the cleaning of the stricken power plant is not properly addressed, it will result in major leak of radioactivity with “global” consequences.
Richard Black, director of the Energy and Climate Intelligence Unit, says that while the readings are not reliable, they still “demonstrate that, seven years after the disaster, cleaning up the Fukushima site remains a massive challenge — and one that we’re going to be reading about for decades, never mind years.”
Mycle Schneider, independent energy consultant and lead author of the World Nuclear Industry Status Report, criticized Tepco, saying the power company has “no clue” what it is doing.
“I find it symptomatic of the past seven years, in that they don’t know what they’re doing, Tepco, these energy companies, haven’t a clue what they’re doing, so to me it’s been going wrong from the beginning. It’s a disaster of unseen proportions.”
In observing the poor maintenance of plant radiation leaks, Schneider also pointed out that the company stores nuclear waste at the site in an inappropriate way.
“This is an area of the planet that gets hit by tornadoes and all kinds of heavy weather patterns, which is a problem. When you have waste stored above ground in inappropriate ways, it can get washed out and you can get contamination all over the place.”
Fukushima operator aims to double visitors by Tokyo Olympics
A lot of minimizing PR propaganda in this article, only one line states the real situation though:
“However, levels of radiation in areas around the three melted-down reactors remain extremely high, hampering the plant’s decommissioning process, which is expected to take decades.”
The reactor number 2 building at the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power plant in Okuma, Fukushima, Japan, on Jan 31, 2018.
FUKUSHIMA DAIICHI NUCLEAR PLANT, JAPAN (AFP) – Fukushima’s nuclear power operator is hoping to double the number of visitors to its tsunami-ravaged facilities by 2020, seeking to use the Olympic spotlight to clean up the region’s image.
A massive undersea earthquake on March 11, 2011 sent a tsunami barrelling into Japan’s northeast coast, leaving more than 18,000 people dead or missing and sparking the Fukushima crisis, the worst nuclear accident since Chernobyl in 1986.
Initially, visitors to Fukushima Daiichi Nuclear Power plant were strictly limited to a handful of nuclear experts, lawmakers, government officials and selected media.
Visitor numbers have gradually increased as levels of radiation in most of the compound have dropped low enough to allow workers to operate without special protective equipment.
Tokyo Electric Power Co. (Tepco), which runs the plant, is now accepting requests for tours from groups of local residents, embassy officials and school students, although it has yet to accept individual applications.
The number of visitors for the fiscal year to March last year rose to around 10,000 – a figure the operator aims to double to 20,000 in 2020 when Tokyo hosts the Summer Games, said Takahiro Kimoto, a Tepco official.
“Our objective is not to send a message saying ‘It’s safe. It’s secure’,” Kimoto told AFP.
“It is more important for us to have people watch what’s really going on… without a prejudiced eye,” he said.
“The inspections will help revitalise the region and reduce reputational damage,” Kimoto said, adding that the company would be happy to show around International Olympic Committee officials.
Next era
Fukushima is expected to be in the spotlight during the Games as it will stage Olympic baseball and softball matches as part of Japan’s effort to regenerate the area.
Tepco also hopes that a football training centre used as a base for the plant’s workers after the disaster will host teams competing in the 2019 Rugby World Cup.
Kimoto stressed that the company is responsible for not only reviving the region but also conveying bitter lessons to future generations.
Decontamination work is under way inside the plant, with thousands of workers enjoying hot meals, taking showers and buying sweets at a convenience store.
However, levels of radiation in areas around the three melted-down reactors remain extremely high, hampering the plant’s decommissioning process, which is expected to take decades.
The scars of the catastrophe remain visible – steel frames are gnarled and walls are missing, ripped off by the tsunami and hydrogen explosions.
‘Strictly controlled’
With the seventh anniversary of the disaster looming, AFP journalists given exclusive access to the roof of the plant’s No. 3 reactor saw stagnant water stored inside a deep pool under which lay more than 560 fuel rods.
Each worker is required to wear a protective suit, three sets of gloves and a heavy-duty mask and carry a dosimeter, used to measure exposure to radiation.
Workers only stay a maximum of two hours per day on the roof where electric gauges showing current radiation levels hang on every corner.
A gigantic steel dome is now being built on the roof to prevent radiation leaking when the fuel rods are transferred from the pool to remote storage later this year.
As the initial stages of decommissioning the plant draw to a close, the biggest challenge is a protracted battle against high radiation, said Daisuke Hirose, a plant official.
“We have to lower radiation exposure to workers, but this prevents them from working for a long time up there,” Hirose said.
“We want them to work under strictly controlled exposure plans. That’s the big difference from working conditions at ordinary sites,” he said.
The total costs for decommissioning, decontamination and compensation are estimated to reach 21.5 trillion yen (US$255 billion) and Tepco aims to dismantle the plant in three to four decades.
Fukushima nuclear disaster: Lethal levels of radiation detected in leak seven years after plant meltdown in Japan
Workers of theTokyo Electric Power Co, which is tasked with the job to decommission the nuclear power plant in Okuma, Fukushima
Lethal levels of radiation have been detected at Japan’s Fukushima nuclear power plant, seven years after it was destroyed by an earthquake and tsunami.
The Tokyo Electric Power Company (Tepco), which operated the complex and is now responsible for its clean up, made the discovery in a reactor containment vessel last month.
The energy firm found eight sieverts per hour of radiation, while 42 units were also detected outside its foundations.
A sievert is defined as the probability of cancer induction and genetic damage from exposure to a dose of radiation, by the International Commission on Radiological Protection (ICRP). One sievert is thought to carry with it a 5.5 per cent chance of eventually developing cancer.
Experts told Japanese state broadcaster NHK World that exposure to that volume of radiation for just an hour could kill, while another warned the leaks could lead to a “global” catastrophe if not tackled properly.
It came as Tepco said the problem of contaminated water pooled around the plants three reactors that is seeping into the ground has caused a major headache in its efforts to decommission the plant.
Thousands of workers have been hired by the company to as it attempts to secure the plant, which was the scene of the most serious nuclear accident since Chernobyl in 1986.
Three of its reactors went into a meltdown after the earthquake and tsunami which killed at least 15,000 people.
Tepco has admitted that it could be until 2020 until the contamination issue is resolved. Only then can it move onto the second stage of removing nuclear debris at the site, including the damaged reactors.
Richard Black, director of the Energy and Climate Intelligence Unit, said the high levels of radiation found in and around the reactor last month were “expected” and unlikely to pose a danger.
He told The Independent: “Although the radiation levels identified are high, a threat to human health is very unlikely because apart from workers at the site, no-one goes there.
“The high readings from fuel debris would be expected – the higher reading from the foundations, if confirmed, would be more of a concern as the cause is at present unclear. But as officials indicate, it might not be a genuine reading anyway.
“What this does demonstrate is that, seven years after the disaster, cleaning up the Fukushima site remains a massive challenge – and one that we’re going to be reading about for decades, never mind years.”
But Mycle Schneider, an independent energy consultant and lead author of the World Nuclear Industry Status Report, said that Tepco “hasn’t a clue what it is doing” in its job to decommission the plant.
He added that the contaminated water that is leaking at the site could end up in the ocean if the ongoing treatment project fails and cause a “global” disaster, he told The Independent.
“Finding high readings in the reactor is normal, it’s where the molten fuel is, it would be bizarre if it wasn’t,” he said.
“I find it symptomatic of the past seven years, in that they don’t know what they’re doing, Tepco, these energy companies haven’t a clue what they’re doing, so to me it’s been going wrong from the beginning. It’s a disaster of unseen proportions.”
Mr Schneider added that the radiation leaks coupled with the waste from the plant stored in an “inappropriate” way in tanks could have global consequences.
“This is an area of the planet that gets hit by tornadoes and all kinds of heavy weather patterns, which is a problem. When you have waste stored above ground in inappropriate ways, it can get washed out and you can get contamination all over the place.
“This can get problematic anytime, if it contaminates the ocean there is no local contamination, the ocean is global, so anything that goes into the ocean goes to everyone.”
He added: “It needs to be clear that this problem is not gone, this is not just a local problem. It’s a very major thing.”
The Independent contacted Tepco for comment, but the energy giant had not responded at the time of publication.
Lethal radiation detected at Fukushima plant reactor 2
The operator of the crippled Fukushima Daiichi nuclear power plant has released the results of its latest probe of the site.
A remote-controlled inspection of the Unit 2 reactor containment vessel last month detected a maximum of 8 sieverts per hour of radiation.
Experts say exposure to such radiation for about an hour would be fatal.
Officials from Tokyo Electric Power Company, or TEPCO, released the results on Thursday.
They said the radiation reading was taken near what appeared to be fuel debris, the term used to describe a mixture of molten fuel and broken interior parts.
The finding shows that nearly 7 years after the meltdowns, radiation levels remain so high that they present a major challenge to decommissioning work.
During the probe, 42 sieverts per hour of radiation was also detected outside the foundations of the reactor.
But officials said they have doubts about the accuracy of the reading because a cover had not been removed from the measuring instrument at the time.
They added that they don’t know why radiation levels were lower near the suspected fuel debris than around the foundations.
They gave a number of possible reasons, such as that cooling water may have washed radioactive materials off the debris.
TEPCO’s Chief Decommissioning Officer, Naohiro Masuda, says the company will develop debris-removal technology based on the outcome of the investigation.
Installation of a dome-shaped rooftop cover near completion at Unit 3 reactor
Japan Fukushima Cleanup
In this Thursday, Jan. 25, 2018 photo, an installation of a dome-shaped rooftop cover housing key equipment is near completion at Unit 3 reactor of the Fukushima Dai-ichi nuclear power plant ahead of a fuel removal from its storage pool in Okuma, Fukushima Prefecture, northeast Japan, during an exclusive visit by The Associated Press. The hardest-hit reactor at the Fukushima plant in the March 2011 disaster is moving ahead of the other two melted reactors seven years later in what will be a decades-long cleanup. (AP Photo/Mari Yamaguchi)
Government to test safety of burying radioactive soil
Government to test safety of burying radioactive soil this spring
Bags of debris contaminated with radiation are seen stored in a field in the town of Okuma, near the Fukushima No. 1 nuclear plant, in this August 2015 photo.
The government plans to conduct a demonstration project sometime this spring to test the safety of burying waste generated by decontamination work following the 2011 Fukushima nuclear disaster, the Environment Ministry said Wednesday.
In the project, soil waste from eastern and northeastern areas of the country other than Fukushima Prefecture will be covered with uncontaminated soil at sites in the village of Tokai, Ibaraki Prefecture, and the town of Nasu, Tochigi Prefecture, with radioactivity levels around the locations being measured.
The government plans to determine its disposal policy for contaminated soil in the fall or later depending on the outcome of the experiment, according to the ministry.
A total of 56 municipalities in seven prefectures — Iwate, Miyagi, Ibaraki, Tochigi, Gunma, Saitama and Chiba — have completed cleanup work with financial support from the central government.
But some 330,000 cubic meters of soil waste has been temporarily kept at around 28,000 locations — including public spaces such as schools and parks — in 53 municipalities, prompting local residents to call for disposal of the waste at the earliest opportunity.
The project will be carried out on the premises of the Tokai Research and Development Center’s Nuclear Science Research Institute in Tokai and at a public space in Nasu.
Some 2,500 cubic meters of soil waste temporarily kept at two locations in Tokai and about 350 cubic meters of soil waste kept at the public space in Nasu will be used in the project.
After the waste is buried, workers’ exposure levels to radiation will also be measured.
“Households in storage locations continue shouldering the burden. I hope (the project) will prove the safety of burying it (soil waste) and lead to the disposal (of contaminated soil),” a Nasu town official said.
“It took time to conduct (the project) but it’s good,” said an official in Tokai, adding that more and more local residents have been asking for the removal of soil waste from a park.
After being asked by municipalities to demonstrate a way to dispose of soil waste, the ministry had been searching for proper locations to carry out the demonstration project.
Radioactive soil disposal method to be tested
Japan’s Environment Ministry will carry out tests at 2 sites where soil generated in decontamination work following the 2011 Fukushima nuclear accident is buried.
Outside Fukushima Prefecture, where the crippled Fukushima Daiichi nuclear plant is located, some 330,000 cubic meters of soil are stored in 53 cities, towns and villages in 7 prefectures in eastern Japan.
The soil is currently kept at some 28,000 locations, including schoolyards and parks.
Local residents have called on the government to safely dispose of the soil as quickly as possible. The environment ministry will start testing soil disposal methods in the spring.
The sites chosen are a nuclear research institute in Ibaraki Prefecture and a sports ground in Tochigi Prefecture.
Ministry officials say the stored soil will be buried in the ground and then covered over again with clean new earth. They will then measure radiation levels at areas surrounding the sites and the amount of radiation that workers were exposed to.
The ministry will start negotiating with local governments regarding a full-scale disposal after verifying the test method’s safety and drawing up an appropriate disposal plan.
Landfilling of Radiation-Tainted Soil to Start outside Fukushima
Tokyo, Jan. 31 (Jiji Press)–The Environment Ministry said Wednesday that landfill work for soil tainted with radioactive materials released from the disaster-stricken Fukushima No. 1 nuclear power station will start outside Fukushima Prefecture, northeastern Japan.
The work will be carried out in the village of Tokai, Ibaraki Prefecture, and the town of Nasu, Tochigi Prefecture, on a trial basis from this spring. Both prefectures are south of and adjacent to Fukushima.
In Fukushima, work has already started to store such soil at interim facilities for up to 30 years before its final disposal.
The work in Tokai and Nasu will involve about 2,500 and 350 cubic meters, respectively, of soil removed from ground during decontamination work following the accident at the Tokyo Electric Power Company Holdings Inc. <9501> plant, which was heavily damaged in the March 2011 earthquake and tsunami.
The soil will be buried underground, with the land surface to be covered with a layer of clean soil more than 30 centimeters thick.
Worst-hit reactor at Fukushima may be easiest to clean up
By MARI YAMAGUCHI
In this Thursday, Jan. 25, 2018, photo, an installation of a dome-shaped rooftop cover housing key equipment is near completion at Unit 3 reactor of the Fukushima Dai-ich nuclear power plant ahead of a fuel removal from… (AP Photo/Mari Yamaguchi)
OKUMA, Japan (AP) — High atop Fukushima’s most damaged nuclear reactor, the final pieces of a jelly-roll shaped cover are being put in place to seal in highly radioactive dust.
Blown apart by a hydrogen explosion in 2011 after an earthquake and tsunami hit Japan’s Fukushima Dai-ichi plant, reactor Unit 3 is undergoing painstaking construction ahead of a milestone that is the first step toward dismantling the plant.
The operating floor — from where new fuel rods used to be lowered into the core — has been rebuilt and if all goes as planned, huge cranes will begin removing 566 sets of still-radioactive fuel rods from a storage pool just below it later this year.
It has taken seven years just to get this far, but now the real work of cleaning up the Tokyo Electric Power Co. plant can begin.
“If you compare it with mountain climbing, we’ve only been preparing to climb. Now, we finally get to actually start climbing,” said Daisuke Hirose, an official at the plant’s decommissioning and decontamination unit.
Cleaning up the plant’s three reactors that had at least partial meltdowns after the earthquake and tsunami is a monumental task expected to take three to four decades. Taking out the stored fuel rods is only a preliminary step and just removing the ones in Unit 3 is expected to take a year.
Still ahead is the uncharted challenge of removing an estimated 800 tons of melted fuel and debris inside the cracked containment chambers — six times that of the 1979 Three Mile Island accident.
The area in and outside of Unit 3 is part construction site and part disaster zone still requiring protection from radiation. A makeshift elevator, then a wind-swept outdoor staircase, takes visitors to the operating floor, more than 30 meters (100 feet) above ground.
Daylight streams in through the unfinished section of the new cover, a tunnel-like structure sealed at both ends to contain radiation. An overhead crane that moves on rails stands at the side of the storage pool, the maker’s name, “Toshiba,” emblazoned in large red letters.
The explosion left major chunks of debris that have been removed from the storage pool, a painstaking operation done using remote-controlled machinery and with utmost care to avoid damaging the fuel rods. Smaller rubble lines the pool’s edge. The water’s surface is obscured by a blue netting to prevent more debris from accidentally tumbling in.
The severe damage to Unit 3 has, in the end, made it easier to clean up than the other two reactors.
Under the latest government roadmap approved last September, removal of the fuel rods from units 1 and 2 was delayed by three years until 2023, a second postponement from the original 2015, because further decontamination and additional safety measures are needed.
Unit 1 fell behind because of a delay in removing debris and repairing key components on the operating floor. The Unit 2 building remained intact, keeping high radiation and humidity inside, which makes it more difficult for workers to approach and decontaminate.
Radioactivity on the Unit 3 operating floor has fallen to a level that allows workers in hazmat suits and filter-masks to stay up to two hours at a time, though most work still needs to be done remotely.
The segments of the new cover were pre-assembled and are being installed one by one by remote-controlled cranes. With two pieces left, the plant operator says the cover will be completed in February.
Removing the fuel rods in Unit 3 will be done with a fuel-handling crane. It will move the rods out of their storage racks and pack them in a protective canister underwater. A second Toshiba crane, a 10-meter (33-foot) -high yellow structure across the operating floor, will lift the canister out of the pool and load it onto a vehicle for transport to another storage pool at the plant.
Crane operators and others assigned to the project, which requires caution and skill, have been rehearsing the procedures.
The 1,573 sets of fuel rods stored in spent fuel pools at the three reactors are considered among the highest risks in the event of another major earthquake. Loss of water from sloshing, structural damage or a power outage could cause meltdowns and massive radiation leaks because the pools are uncovered.
Hirose said that starting fuel removal at Unit 3 would be “a major turning point.”
Still, after the intact fuel rods are gone comes by far the most difficult part of decommissioning the plant: removing the melted fuel and debris from inside the reactors. Obtaining exact locations and other details of the melted fuel are crucial to determining the retrieval methods and developing the right kind of technology and robots. With most melted fuel believed to have fallen to the bottom, experts are proposing that it be accessed from the side of the containment vessel, not from the top as originally had been planned, based on the cleanup after an accident at the Three Mile Island nuclear plant in the United States.
Computer simulations and limited internal probes have shown that the melted fuel presumably poured out of the core, falling to the bottom of the primary containment vessels. Robotic probes at the Unit 3 and 2 reactors have captured images of large amounts of melted fuel, but attempts so far at Unit 1 have been unsuccessful.
Despite scarce data from inside the reactors, the roadmap says the methods for melted fuel removal are to be finalized in 2019, with actual retrieval at one of the three reactors in 2021. Hirose says it is premature to say whether Unit 3 will be the first.
Lingering effects of 2011 disaster take toll in fallout-hit Fukushima, experts warn
A Buddhist priest prays on a beach in Minamisoma, Fukushima Prefecture, in March 2017. The area was hit hard by the 2011 earthquake, tsunami and nuclear disaster.
There are fewer and fewer headlines these days about the catastrophe resulting from the triple core meltdown in March 2011 at Tepco’s Fukushima No. 1 nuclear power plant. But participants at a recent symposium stressed that the disaster’s lingering effects continue to weigh heavily on people and municipalities in Fukushima Prefecture.
“In the post-disaster reconstruction, Miyagi Prefecture had to start from zero,” said former Fukushima University President Toshio Konno, who is from Onagawa, Miyagi Prefecture, and lost five relatives in the town when it was hit by tsunami caused by the Great East Japan Earthquake. “But Fukushima Prefecture had to start from a negative point because of the additional impact of the nuclear calamity. It is really hard for Fukushima to reach the zero point.”
During the symposium at Tokyo’s Waseda University on Saturday, Konno — who served on a Fukushima Prefectural Government committee tasked with judging whether deaths in the years following the March 11, 2011, earthquake and tsunami were disaster-related — said that as of Sept. 30 last year, there were 3,647 such cases in Japan, of which Fukushima Prefecture accounted for 60 percent.
What’s more, Fukushima is the only prefecture among the three disaster-hit Tohoku prefectures that still sees people die from related causes. Since March 2016, Miyagi and Iwate prefectures, which were also hit by the quake and tsunami, have suffered no disaster-related deaths, while Fukushima has seen 50, Konno said.
He also said that the number of disaster-related suicides in Fukushima has grown over time compared with Iwate and Miyagi. Fukushima saw 10 such suicides in 2011, 13 in 2012, 23 in 2013, 15 in 2014 and 19 in 2015. Corresponding figures in Iwate and Miyagi, respectively, are 17 and 22 in 2011, eight and three in 2012, four and 10 in 2013, three and four in 2014 and three and one in 2015.
Takao Suami, a Waseda professor heading the university’s efforts to provide legal support for the reconstruction, said the government’s Dispute Reconciliation Committee for Nuclear Damage Compensation was fairly helpful in addressing compensation issues until around the spring of 2014. But Suami said cases have emerged recently in which the utility, now known as Tokyo Electric Power Company Holdings Inc., refuses to accept reconciliation proposals put forward by the committee.
Yuichi Kaido, a lawyer working with some 3,000 residents of the village of Iitate on the compensation dispute resolution process, said that even though residents suffered exceedingly high levels of external radiation exposure immediately after the meltdowns — measuring 7 millisieverts on average — due to a delayed evacuation order, the committee proposed in December that only people whose exposure was 9 millisieverts or higher should be entitled to compensation, a threshold which covers just 200 people. (Nuclear power stations are legally required to limit the yearly radiation exposure for residents living nearby to 1 millisievert or less.)
Michitaro Urakawa, a professor emeritus of law at Waseda who says he supports the restart of nuclear plants, said the compensation system for victims of the nuclear disaster has a fundamental flaw. Tepco, he said, is benefitting from the injection of funds for compensation from the central government, while consumers — including low-income people in Fukushima Prefecture who did not have assets worth compensation — are helping the utility return the injected money to the government in the form of increased electricity bills.
Kaido and other lawyers called for reconstruction policies that truly meet the needs of Fukushima people, because compensation cannot cover damage that does not have a monetary value, such as the loss of communities, friendship, business ties and fears about the future, including the threat of health problems due to radiation exposure.
Another problem highlighted at the symposium was the unhealthy financial state of disaster-hit municipalities in Fukushima. Waseda professor Yoshihiro Katayama, a former Tottori governor who was internal affairs minister for the Democratic Party of Japan administration at the time of the meltdowns, said the municipalities will end up with excess personnel, creating a financial burden over the long term.
Disaster-hit municipalities in the prefecture are already facing financial strain. The town of Namie — roughly half of whose area lies within 20 km of the nuclear plant — saw its revenue grow from ¥9.48 billion in 2010 to ¥20 billion in 2016. But the portion of the funds from the central and prefectural governments increased to 87.2 percent from 68.6 percent, reducing the percentage of internal revenue to 12.8 percent from 31.4 percent.
Further, if the municipalities decide to end contracts commissioning administrative services to private firms, the local economy will suffer, Katayama said. He also expressed fear that the municipalities may have lost the know-how to assess the value of real estate, the basis of real estate taxes, an important revenue source.
Katayama also said the aging population will lead to a deep and serious problem in disaster-hit areas because many young people who evacuated will not return, causing such problems as difficulty maintaining the public health insurance system as well as city water and sewage systems. There will also be a shortage of nursing care workers and schools will be forced to close, he warned.
“Although the revenue of disaster-hit municipalities enormously expanded, the time will come when their administrative services have to shrink,” Katayama said. “Currently, the central government is taking special measures. But both the central government and the municipalities concerned must think about how to achieve a soft landing.”
TEPCO refused in 2002 to calculate possible tsunami hitting Fukushima: ex-gov’t official
The No. 3 reactor at the Fukushima No. 1 Nuclear Power Plant is seen from a Mainichi Shimbun helicopter on Nov. 21, 2017
Tokyo Electric Power Co. (TEPCO), operator of the disaster-stricken Fukushima No. 1 Nuclear Power Plant, refused in 2002 to calculate the potential effects of tsunami in case of an earthquake off Fukushima Prefecture when a now-defunct nuclear watchdog told the utility to conduct an evaluation, the Mainichi Shimbun has learned.
A former safety screening division official of the Ministry of Economy, Trade and Industry’s Nuclear and Industrial Safety Agency (NISA) told the Mainichi Shimbun on Jan. 29 that TEPCO did not accept the agency’s request even though the latter tried to convince the utility after the government released a long-term assessment report that a major earthquake could hit off the Pacific coast including areas off Fukushima Prefecture, possibly triggering massive tsunami. This is the first time that exchanges between the then nuclear agency and TEPCO following the release of the government report have come to light.
In July 2002, the government’s Headquarters for Earthquake Research Promotion released the long-term assessment report saying that an earthquake similar to the 1896 Sanriku Earthquake could hit off the Pacific from the northern Sanriku to Boso areas. The official held a hearing on TEPCO the following month as to whether the report would affect safety measures at the Fukushima No. 1 plant.
According to the official as well as the statement submitted by the government to the trial of a lawsuit filed by Fukushima nuclear evacuees against TEPCO and the state, NISA told the utility to calculate a possible earthquake-tsunami disaster off the coast from Fukushima to Ibaraki prefectures, pointing out that Tohoku Electric Power Co. had been considering conducting an assessment on areas quite far south. In response, TEPCO representatives showed reluctance, saying that the calculation would “take time and cost money” and that there was no reliable scientific basis in the assessment report. The TEPCO officials reportedly resisted for about 40 minutes on the matter. In the end, the agency accepted the utility’s decision to shelve the earthquake-tsunami estimate.
In 2006, NISA again requested TEPCO to prepare its nuclear plants for massive tsunami exceeding envisioned levels, but the company did not comply, before finally conducting a calculation in 2008. The utility concluded that waves up to a height of 15.7 meters could hit the Fukushima plant, but did not take measures according to the estimate.
The former nuclear agency official said as someone involved in the screening of earthquake resistant measures it was very unfortunate that the accident at the Fukushima plant occurred, but stopped short of commenting on the legitimacy of the agency’s handling of the matter, saying, “I can’t put it in words casually.”
The attorney representing Fukushima nuclear evacuees in the redress suit commented that the finding exposes the maliciousness of TEPCO, while also pointing to the responsibility of the central government. A TEPCO public relations official, meanwhile, said that the company would not comment on the matter because the trial was ongoing.
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