nuClear News No.94 April 2017 The UK’s Office for Nuclear Regulation (ONR) has published its assessment of the Periodic Safety Review (PSR) for Hunterston B (HNB) and Hinkley Point B (HPB). ONR has also accepted EDF’s revised graphite core safety case for both sites, but has included a number of recommendations as part of this acceptance. Acceptance of the safety case is reliant on a revised inspection and monitoring strategy. (1)
To comply with a nuclear site licence, a periodic review – a comprehensive study of plant safety – is carried out every ten years to justify continued safe operations. This requirement means that the site licence company regularly reviews and reassesses safety at nuclear sites, making improvements where necessary. The four Hunterston B and Hinkley Point B advanced gascooled reactors (AGRs) started up in 1976 are scheduled to close in 2023.
Graphite The graphite core of each of the reactors is made up of around 6000 graphite bricks – 3000 of these are the graphite bricks containing fuel channels – which are all connected together. Graphite ageing is one area used to determine the lifespan of an AGR nuclear power station. EDF says greater understanding of the ageing process by sampling and modelling can lead to them operating safely for longer.
In November 2015, EDF Energy said it had found cracks in three of the graphite bricks in one of the Hunterston B reactors. Similar cracks were found in October 2014 in two of the graphite bricks of the other reactor. A recent BBC Radio Programme revealed that the
ONR was considering doubling the limit it had set on the percentage of cracked bricks it is willing to accept from 10% to 20%. This has been a particularly controversial part of this process with people living near theses reactors finding it difficult to understand why the definition of “safe” seems to be changing. ONR has now agreed to this increased limit. It says:
“Continued operation of HPB/HNB reactors is now supported by NGL’s [EDF’s] safety case NP/SC 7716 which sets an operational limit of 20% cracking in the core. The justified period of operation of each reactor at HPB/HNB is therefore dependent upon the findings from the inspections at each outage.”
The ONR is also concerned about a very specific form of cracking. The keyway is a slot that holds each brick to the adjacent brick, the bricks underneath and the bricks on top. These keyways, which are acknowledged to be the limiting factor in the life of these reactors, are beginning to fracture. John Large points out that this will make the graphite blocks a very loose set of bricks. Seven of the keyways have been discovered to have cracks at Hunterston B. John Large believes the presence of keyway cracks casts doubt on the safety of the reactor in the event of an emergency like an earthquake. If the core becomes misaligned, and the fuel modules get stuck in the core, the fuel temperature will get raised and could undergo a melt. If the radioactivity gets into the gas stream and the reactor is venting because it’s over pressurised then you have a release to the atmosphere and you have dispersion and a contamination problem.
John Large says that if the cracks get any worse it could jeopardise the reactor’s stability in the event of a significant disaster – such as a small earthquake – and make it impossible to lower control rods to shut the reactor down. He said: “These keyways are beginning to fracture… that means the locking together – the way that force can be transferred from one brick to another – is lost, so it becomes a very loose stack of bricks.” Allan Jeffrey of Stop Hinkley added: “This weakness in the graphite core could end up distorting the channels the fuel and the boron control rods use. In cases of emergency there are sudden changes in temperature and pressure which could all end up starting to deform these channels. If you can’t get the control rod down then you can’t control the temperature inside the reactor and you’re heading for accidents – possibly even meltdowns.” (2)
ONR said that EDF had attempted to predict the rate of KWRC. Originally the first cracks were not expected to occur until 2019, but the first KWRC was observed at Hunterston B in 2015.
Inspection will “play a crucial role in supporting the period of safe operation of the reactor in later life,” the regulator said, adding that certain improvements are necessary, such as the development of a capability to measure the condition of control rod channels. EDF Energy should develop improved inspection and monitoring technology; in particular equipment capable of performing visual inspection and dimensional measurements of control rod channels, it said. http://www.no2nuclearpower.org.uk/nuclearnews/NuClearNewsNo94.pdf
This summer, a giant Russian typhoon-class nuclear submarine, 172 metres in length, is expected to pass Denmark.
The submarine will depart from Russia, pass Norway and then sail into the North Sea and the Skagerrak, onwards into the Baltic, where it will finally dock in St Petersberg, the Barents Observer writes. The sub will pass underneath the Øresund Bridge as the water is not deep enough by the Great Belt Bridge or at Flintreden.
All the preparations are underway, and now all that is needed is the signature of Russian President Vladimir Putin.
No nukes, please!
The submarine was built in 1981 and has the capacity to carry up to 20 missiles and 200 nuclear warheads at a time. However, nowadays it is used as a test platform for ballistic missiles and is based in the town of Severodvinsk in western Russia.
The age of the vessel might be cause for concern, though, according to Norwegian atomic physicist Nils Bøhmer.
“I’m worried when a 40-year-old atomic submarine with a relatively large reactor aboard sails along the Norwegian coast and into the Baltic,” he told Barents Observer.
“The authorities have to know the exact time of its voyage in order to be prepared. It is also vital to ensure there are not atomic weapons on board.”
Workers incorrectly opened and shut certain valves, causing water to flood from a massive storage tank to an area of the reactor known as the torus. The torus plays a role in depressurizing and cooling down the reactor in case of a serious accident.
“This was a breakdown in the process that shows lack of adherence to procedure,” according to a spokesman for the Nuclear Regulatory Commission. He said there were no immediate safety concerns.
At noon on Friday, Pilgrim operators were flushing pipes in the reactor’s cooling system in preparation for an upcoming refueling. They opened a valve on the torus without first closing the valve on the water storage tank. Water being drained into the torus, setting off an alarm in the control room.
“This volume of water placed the torus level above the administrative limit for readiness should an unplanned event occur,” a spokesman for plant owner Entergy Corp. told the Cape Cod newspaper. “Station personnel appropriately responded to close the valves and processed and filtered the water from the torus back to the condensate storage tanks.”
Friday’s flood was the second recent serious incident involving operator error. On March 27, workers triggered the wrong switch, causing the temporary shutdown of a coolant injection system that is essential to cool the plant in a severe emergency.
Federal regulators in 2015 labeled Pilgrim as one of the three worst performers in the country and placed under increased oversight for safety violations and unplanned shutdowns.
Soon thereafter, Entergy announced it would close Pilgrim permanently in mid-2019 due to poor market conditions and increased operational costs. The closure will remove 680 megawatts of capacity from the New England power grid.
There have been a number of problems and violations at the aging nuclear power plant in recent years. Pilgrim has reportedly logged $40 million in annual losses.
Intelligence agencies fear ISIS and other terrorist groups could have developed ways to plant explosives in laptops and mobile phones which can bypass airport security screening methods, the Telegraph reports. Last month, Britain and the US banned travellers from a number of countries carrying laptops and large electronic devices on board.
They also fear terrorists, foreign spies and hackers could try to break into nuclear power station security systems.
Jesse Norman, the energy minister, said nuclear plants must ensure they ‘remain resilient to evolving cyber threats’.
Mr Norman told the paper: ‘The Government is fully committed to defending the UK against cyber threats, with a £1.9 billion investment designed to transform this country’s cyber security.’
Terrorists are feared to have developed the technology after getting hold of airport screening equipment allowing them to experiment.
FBI experts have tested how explosives can be hidden inside laptop battery compartments so that it can still be turned on.They are said to have concluded that the technique would be achievable using everyday equipment.
In a statement, the US Department of Homeland Security said: ‘Evaluated intelligence indicates that terrorist groups continue to target commercial aviation, to include smuggling explosive devices in electronics.
‘The US government continually reassesses existing intelligence and collects new intelligence. ‘This allows us to constantly evaluate our aviation security processes and policies and make enhancements when they are deemed necessary to keep passengers safe.’
Last year al-Shabaab, an al-Qaeda affiliate group in Somalia, detonated a bomb on a flight from Mogadishu to Djibouti by hiding it in a part of a laptop where bomb-makers had removed a DVD drive.
April 2, 2017 Britain: Britain raised its terrorism alert in the past 24 hours saying that the Islamic State (IS, formerly ISIS) group operating in Syria and Iraq may have developed ways of bypassing nuclear power station security measures.
According to Intelligence agencies, the terrorist groups have developed ways to plant explosives in laptops and mobile phones that can evade airport security screening methods.
Energy minister Jesse Norman said that the government was “fully committed to defending the UK against cyber threats, with a £1.9 billion investment designed to transform this country’s cyber security.”
The growing threat of attack on Britain’s 15 operational reactors, which account for nearly a fifth of the country’s electricity from terrorists, foreign spies and “hacktivists” remains high.
Norman said the civil nuclear strategy published in February sets out ways to ensure that the civil nuclear sector “can defend against, recover from, and remain resilient in evolving cyber threats.”
Deputy director-general Professor Malcolm Chalmers of the Royal United Services Institute, an independent think tank for defence and security, said that it was crucial for the Government to “respond rapidly”.
ISIS ‘can plant bombs in laptops and mobile phones that will get through airport screening undetected’ http://www.mirror.co.uk/news/world-news/isis-can-plant-bombs-laptops-10146339Experts fears terrorists made a breakthrough after obtaining airport screening equipment to experiment and there are fears they will use the techniques at US and European airports, BY TOM PARR, 2 APR 2017
Intelligence agencies believe ISIS has developed ways to plant explosives in laptops and mobile phones that can evade airport security screening methods.
The warning by security services has led to Britain’s airports and nuclear power stations being instructed to tighten their defences against terrorist attacks.
It is this new information which is thought to have led the US and Britain to ban travellers from a number of countries carrying laptops and large electronic devices on board.
Now there are concerns that terrorists will use the techniques to bypass screening devices at European and US airports.
Some experts fears terrorists made a breakthrough after obtaining airport screening equipment to allow them to experiment. FBI experts have tested how the explosives can be hidden inside laptop battery compartments in a way that allows a computer still to be turned on.
Manny Gomez, a former FBI special agent, said: “We had the shoe bomber, cartridge attempt, now this is the next level. We need to be several steps ahead of them.”
The explosives were hidden in a part of a laptop where bomb-makers had removed a DVD drive. The bomber was blown out of the window but the plane survived.
Now, the Nuclear Power Corporation of India (NPCIL) plans to deploy drones for the purpose at the Madras Atomic Power Station (MAPS) near Kalpakkam in Tamil Nadu.
While MAPS would be the first such facility in the country to use drones for general surveillance and intrusion detection, they were famously deployed by Japanese engineers at the Fukushima Daiichi nuclear power plant after the nuclear accident of 2011.
The Kalpakkam plant, located 70 km from Chennai, is also in the vicinity of other sensitive installations of the Department of Atomic Energy (DAE) such as the Indira Gandhi Centre for Atomic Research, the Fast Breeder Reactor Project, the BARC-run nuclear desalination demonstration plant and Kalpakkam fuel reprocessing plant.
Sources close to the development said tenders are likely to be floated by the NPCIL for procuring the drones and their control systems this fiscal. The use of drones will also require clearances from the Atomic Energy Regulatory Board (AERB), the regulator for all atomic energy institutions in the country.
Both aerial and ground level drones are capable of large-scale territorial surveillance. They are fitted with video cameras and other sensors that allow continuous surveillance of facilities.
Sources said the cameras mounted on the drones could be programmed to scan for certain topographical features on the ground and if there is a mismatch between the programmed image and the live feed from drones, alarms would go off.
Lt Gen DS Hooda (Retd), who served as Chief of Northern Army Command, told BusinessLine that the Army had been using drones on the India-Pakistan border and in Kashmir region. Drones allow the forces to get a bird’s eye view of the terrain and identify intruders hiding in tall structures. Drones would prove to useful in securing large installations, he said.
In 2016, the No. 1 tourist destination of Ukraine was the lifeless town of Pripyat, evacuated after the deadly reactor meltdown at Chernobyl in 1986. Today, Ukraine relies on nuclear power for 53 percent of its power generation, but is risking another nuclear accident on a scale greater than Europe — and the world — could imagine.
The problems facing Ukraine’s nuclear power industry are multi-faceted, but the main issue is the same one plaguing the whole of the former Soviet republic — corruption, which is breeding a lack of accountability and mismanagement of the sector’s critical infrastructure.
Ukraine’s nuclear power plants are supposed to be regulated by the State Nuclear Regulatory Inspectorate of Ukraine (SNRIU), which by law is an independent regulatory body. In recent years, however, it has become standard practice for the leaders of SNRIU to be appointed by the state nuclear power plant operator, Energoatom, instead of through a rigorous, independent selection process.
This, perversely, subjugates the regulator to the whims of the operator. If Energoatom cannot meet certain safety standards or deadlines, its bosses simply inform the regulator of such, and the deadlines are extended or eliminated, public safety be damned.
In addition, many positions at the regulatory body remain empty. For example, the position of the chief state inspector of nuclear and radiation safety has been vacant for three years. Other key posts of the Ukrainian nuclear regulator remain vacant.
GIL SCOTT HERON – WE ALMOST LOST DETROIT (LIVE AT 98.3 SUPERFLY)
This Day in History: America’s Worst Nuclear Fears Realized at Three Mile Island Plant, VOA, 28 Mar 17, Thirty-eight years ago today — March 28, 1979 — disaster struck at 4 a.m. at the Three Mile Island (TMI) nuclear power plant in central Pennsylvania after its cooling system failed.
It remains the worst nuclear accident in American history. A simple plumbing failure prevented the main feedwater pumps from sending water to generators that remove heat from the plant’s core reactor.
During those pre-dawn hours, the temperature of the reactor rose steadily even as staffers were unaware that a valve in the emergency cooling system had become stuck in place, allowing cool water to flow through the valve — not reaching the reactor.
Instruments in the control room misled operators, who thought the cooling system was working normally.
As coolant flowed from the primary system through the valve, other instruments available to reactor operators provided inadequate information. There was no instrument that showed how much water covered the core. As a result, plant staff assumed that as long as the pressurizer water level was high, the core was properly covered with water.
As alarms rang and warning lights flashed, the operators did not realize that the plant was experiencing a loss-of-coolant accident — or, rather, the beginnings of a nuclear meltdown. And just after 6:00 am, data indicated the core reactor had overheated so much that radiation was detected inside the control room.
In the months following the accident, questions were raised about possible adverse effects from radiation on human, animal and plant life around the nuclear power plant, although none could be directly correlated to the accident.
Thousands of environmental samples of air, water, milk, vegetation, soil and foodstuffs were collected by various government agencies monitoring the area.
Among the materials with no disposition plan include weapons-grade plutonium, depleted uranium oxide, highly enriched uranium and heavy water.
Specifics about the quantity and timetables were redacted from the report. Lastly, the DOE report states that there is no disposition path for surplus plutonium stored at K-Area.
The DOE’s short-term strategy of continuing nuclear shipments to SRS runs counter to South Carolina’s long-held aversion to the state becoming a dumping ground for nuclear waste.
The latest data dump from SRS Watch includes the 2016 SRS Nuclear Materials Management Plan the group said it obtained through the Federal Freedom of Information Act.
Documents confirm that plutonium from Japan, Germany and Switzerland was shipped to the site last year, as previously reported by the Aiken Standard. The 2016 report further states the U.S. Department of Energy plans further shipments of plutonium, uranium and tritium, with some shipments expected to continue for 18 years.
“The most significant issue with respect to the current inventory of SNM (spent nuclear material) at SRS is the lack of an assigned disposition path for certain SNF (spent nuclear fuel) and plutonium materials,” the report says.
Among the materials with no disposition plan include weapons-grade plutonium, depleted uranium oxide, highly enriched uranium and heavy water.
Further, only a portion of spent nuclear fuel stored at L-Area is approved for processing at H Canyon, the report continues.
L-Area is where high and low enriched uranium used fuel is stored. H Canyon downblends this waste into low enriched uranium, which is then used to fuel Tennessee Valley Authority reactors, according to the SRS website.
Additionally, more foreign and domestic materials are expected to be shipped to L-Area through 2019 and 2035, respectively, the DOE report states.
Specifics about the quantity and timetables were redacted from the report. Lastly, the DOE report states that there is no disposition path for surplus plutonium stored at K-Area.
Options for disposing of surplus plutonium are limited. Construction of the Yucca Mountain facility in Nevada halted a few years ago, while the Waste Isolation Pilot Plant in New Mexico also isn’t equipped to handle SRS materials.
The long-term strategy for disposing of defense plutonium remains completion of the Mixed Oxide Fuel Fabrication Facility, or MOX, which would convert waste into fuel for commercial reactors.
MOX, though, is only reportedly 70 percent complete, billions of dollars over budget and years behind schedule……
The DOE’s short-term strategy of continuing nuclear shipments to SRS runs counter to South Carolina’s long-held aversion to the state becoming a dumping ground for nuclear waste.
SRS Watch Director Tom Clements said in prepared comments the DOE report illustrates why importing nuclear materials to the site must cease.
“While it is clear that DOE hopes to maintain SRS as a site that receives and processes an array of nuclear materials, that role is clearly diminishing and continues to distract from the all-important clean-up mission at SRS,” Clements said in a statement. n recent years, MOX has only received minimal funding from Congress. The DOE assessment says this trend must change.
“Decisions/funding need to be made on the appropriate disposition path; which will include processing for use as mixed oxide fuel, another use, or a waste disposition,” the DOE report states.
The DOE’s short-term strategy of continuing nuclear shipments to SRS runs counter to South Carolina’s long-held aversion to the state becoming a dumping ground for nuclear waste.
SRS Watch Director Tom Clements said in prepared comments the DOE report illustrates why importing nuclear materials to the site must cease.
“While it is clear that DOE hopes to maintain SRS as a site that receives and processes an array of nuclear materials, that role is clearly diminishing and continues to distract from the all-important clean-up mission at SRS,” Clements said in a statement.
“More effort must be put into a permanent and near-term halt to the inflow of nuclear materials into SRS and the development of acceptable disposition paths for hard-to-manage materials already at the site,” the statement continued.
A federal judge recently ruled that the DOE failed to abide by legal obligations to remove or dispose of 1 metric ton of defense plutonium per year from SRS.
But the March 20 order doesn’t impose any sanctions for missing that milestone, nor does it prevent the continued flow of nuclear materials into Aiken County.
South Korea’s Kori No. 4 nuclear reactor shut due to water level rise, http://www.reuters.com/article/us-southkorea-nuclear-idUSKBN16Y2N6South Korea’s Kori No. 4 nuclear reactor was manually shut down after the water level in a collection tank rose due to a coolant leak, a spokesman at the reactor’s operator said on Tuesday.
“We estimate the water level of the reactor’s collection tank increased after coolant was leaked,” said Lim Dae-hyun, the spokesman at Korea Hydro & Nuclear Power Co Ltd (KHNP).
Lim added that there was no release of radioactivity and that the cause of the water level increase was being investigated.
The 950-megawatt Kori No. 4 reactor is near Busan, a city more than 300 km (190 miles) southeast of the capital, Seoul.
KHNP, fully owned by state-run utility Korea Electric Power Corp (KEPCO), runs the country’s 25 nuclear reactors, which supply about a third of South Korea’s electricity. (Reporting by Jane Chung; Editing by Jonathan Oatis)
Top nuclear boss advising May on protecting atomic industry from Brexit blow Energy VoiceAlan Shields, 26 Mar 17 The German head of one of the UK’s top nuclear companies is counseling Prime Minister Theresa May’s government on what needs to be done to protect a global hub for the industry from Brexit.
With European Union leaders congregating to celebrate the Treaty of Rome’s 60th anniversary, Urenco Ltd.’s Chief Executive Officer Thomas Haeberle said he’s cautiously optimistic that new rules can be negotiated to guarantee the flow of nuclear materials in and out of the U.K. after the nation leaves the bloc.
“We are making the U.K. government, which is also our shareholder, aware of the requirements our business needs to fulfill in the context of Brexit and of leaving Euratom,” said Haeberle, referring to the European Atomic Community, a part of the EU’s bedrock agreement signed on March 25, 1957 – 26/03/20
Just as bankers have made London a global financial hub, nuclear workers have turned Britain into a central cog servicing the world’s flow of atomic materials. Urenco, the world’s second-biggest maker of reactor fuel, runs a factory in Capenhurst and oversees its global distribution network from Stoke Poges outside of London.
Owned by the U.K. and Dutch governments as well as German utilities EON SE and RWE AG, Urenco has set up a working group that “deals with all the risks and the possible mitigations,” Haeberle said. He spoke with Bloomberg a week before the EU celebrates Euratom’s 60th anniversary, his first interview since becoming CEO in January 2016.
Euratom’s main function is to safeguard nuclear fuel, making sure it isn’t diverted to make weapons. The U.K. will lose that service once it departs the EU. Nuclear fuel suppliers and power plants need certification from Euratom or whatever system succeeds it to buy material on the open market.
For Urenco’s business to continue uninterrupted after the U.K. leaves the EU, negotiators will have to seal new agreements with governments around the world setting out the new regulatory system Britain will follow after it leaves Euratom……..
UK watchdog sounds alarm over doctored papers & security breaches at French nuclear parts supplier, Rt.com 25 Mar, 2017
Britain’s Office for Nuclear Regulation (ONR) has questioned the adequacy of a French nuclear forge which had already supplied parts for UK nuclear sites. It follows revelations of doctored paperwork and security breaches by the French producer.
The ONR report, obtained under a Freedom of Information request and seen by Reuters, gives details on the December 16 visit by an international monitoring team to a French Creusot forge, operated by the country’s state-owned nuclear supplier Areva.
In the report, the UK watchdog warned that safety procedures at Creusot were far below the required standards for a key nuclear equipment supplier. That, they said, could lead to severe consequences for EDF’s [the largest energy company in France] Hinkley Point nuclear project currently under construction in southwest Britain, which is set to receive forgings from Creusot.
“ONR should consider the adequacy of EDF’s… oversight and assurance arrangements for Areva as a key supplier to Hinkley Point, given the performance shortfalls at Creusot Forge and the associated risks to [nuclear] components manufacture,” the regulator said, as cited by Reuters.
Among the breaches was the continued use of correction fluid on documents at the foundry, despite an earlier ban.
The ONR report also inquired into why internal inspections and audits carried out in past decades at Creusor Forge had not discovered and dealt with any of the falsification activities.
Following the December findings, two EDF nuclear reactors were stopped for months, utilities worldwide started reviewing Areva-made parts, and Paris launched a probe into the suspected falsification of documents.
Areva unions warn about safety at France’s La Hague nuclear recycling plant Unions says cost cuts, redundancies jeopardise safety * Regulator ASN inspects plant following union warning * ASN: plant is safe but will be vigilant, adapt procedures * ASN confirms some radioactive waste containers flawed (Adds ASN comments) Nasdaq, By Geert De ClercqPARIS, March 23 (Reuters) –
Redundancies and cost savings are compromising safety at French nuclear group Areva’s <AREVA.PA> nuclear waste recycling facility at La Hague in Normandy, the firm’s unions say in an internal document. In an undated and unsigned note from the Areva La Hague Health and Safety Committee (CHSCT), seen by Reuters, the plant’s unions say that the Areva management’s “frantic cost-cutting is jeopardising long-established procedures” to prevent the risk of technical failures and human error. French nuclear safety authority ASN told Reuters it had received a copy of the note in November and had consequently inspected the plant, concluding that safety levels were acceptable.
However, it confirmed an incident in late 2016 – highlighted in the union note – in which several batches of highly radioactive waste were not properly processed during vitrification. It also said it would remain vigilant about issues signalled by the unions and may adapt its monitoring procedures.
This 21st century atomic potboiler is actually unfolding through the hard work of scientists at the Bhabha Atomic Research Centre (BARC), whose laboratory actually shares a wall with the famous property where Raj Kapoor used to live. Here, they are working overtime to find out the real cause of the leaks at the twin reactors in southern Gujarat.
To avoid panic and further accidents, Indian nuclear watchdog Atomic Energy Regulatory Board (AERB) has shut down the affected plants till the cause has been found. Nuclear experts say the pipes, made from a rare alloy, have contracted what seems like small pox, and this contagion has spread all over the critical tubes in two Indian Pressurised Heavy Water Reactors (PHWR) at the Kakrapar facility. To make matters worse, more than a year into the investigation, the teams of scientists can’t figure out what has gone wrong.
It was on the morning of March 11, 2016, and as fate would have it, exactly five years after the Fukushima reactors in Japan began exploding, Unit Number 1 of the 220-MW PHWR at Kakrapar developed a heavy water leak in its primary coolant channel and a plant emergency was declared at the site.
The indigenously built nuclear plant had to be shut down, but no worker was exposed and there were no radiation leaks, the Department of Atomic Energy confirmed. Operator Nuclear Power Corporation of India Limited (NPCIL) said the reactor had shut down safely, and confirmed that safety systems had functioned normally.
The atomic thriller really begins when experts were trying to find out why a leak recognition system failed, when it should have raised an alarm. “There is a leak detection system in place in all PHWRs, but in this case it failed to detect the leak on March 11, 2016,” confirms AERB Chairman SA Bhardwaj. The watchdog body suspects the crack developed so rapidly that the electronic leak detection system just did not have the time to react.
Subsequent investigations revealed that the leak detection system was fully functioning and the operator had not shut it down to cut costs. Nothing in the core of a nuclear reactor can be done in a jiffy, and several weeks after the first leak, the initial probe using a specially designed tool revealed four big cracks in a coolant tube had led to the massive leak.
The mystery unfolds
The discovery of the crack was only the beginning of the mystery. Further efforts to find the cause established that the outside of the tube, the part not exposed to high-temperature heavy water, was corroded due to unknown causes.
This was a stunning discovery, since the outside of the failed tube was exposed only to high-temperature carbon dioxide and there had been no recorded case of a similar corrosion on the outside of any tube. It is also very hard to access this part since the space is tiny in the annulus.
The AERB then ordered that all tubes made of a special zirconium-niobium alloy be checked on the outside. To their surprise, they discovered that the contagion of the nodular corrosion, ‘small pox-like’ in layman’s parlance, was widespread in many of the 306 tubes. Similar tubes from the same batch used at other Indian reactors continued to operate without corrosion.
The needle of suspicion now pointed to carbon dioxide, a gas known to be very stable in high-radiation environments. A further post mortem revealed that Unit-2, which is twin of the affected reactor, had also been affected by a similar leak on July 1, 2015. Investigations into Unit-2’s failure were made but no conclusive result had been found. This back-to-back failure of two fully functional nuclear reactors befuddled engineers.
BARC begins probe
Undaunted, AERB ordered that the entire assembly and not just the affected tube be safely pulled out and brought to BARC, India’s foremost nuclear laboratory, for detailed failure analysis.
In addition, since India operates another 16 similar nuclear plants, a full-fledged investigation was carried out on coolant channels at all atomic power plants. The investigating team found the ‘small pox-like’ corrosion was confined only to the two units at Kakrapar.
While NPCIL heaved a sigh of relief, the finding made it all the more difficult to discern the true cause of the leaks at Kakrapar. Mr. Bhardwaj says investigators are wondering if the carbon dioxide used in Kakrapar may have been contaminated, which caused the nodular corrosion.
The source of the carbon dioxide was traced backwards, and it seems only the Kakrapar plant was sourcing its gas from a Naptha cracking unit, where it was possibly contaminated by hydrocarbons.
