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Japan’s planned Olympics torch relay route found to have high levels of radiation

the proposed torch route samples had the highest mean radioactivity due to their close proximity to the plant. Based on the measurement, we estimated qualitatively that the radiation exposure of people living near the Azuma Sports Park area was 20.7 times higher than that of people living in Tokyo. The main tourist and proposed torch routes had radiation exposure of 24.6 and 60.6 times higher, respectively, than in Tokyo.

our results showed that the highest radioactivity level was at the proposed torch route, which is located to the northeast of the plant.

Olympic officials should consider using the results of this project to decide whether the radioactivity level at the proposed torch route and the Olympic venues are within acceptable level.

Measuring Radioactivity in Soil and Dust Samples from Japan   Fukushima IQP Final Report. An Interactive Qualifying Project Report Submitted to the Faculty of the Worcester Polytechnic Instituteby Thang Pham Steven Franca Son Nguyen

Abstract

A radioactivity map of Cesium-137, a radioactive material emitted from the Fukushima Dai-ichi Nuclear Power Plant, was created by examining 30 soil and dust samples originating from Japan. A Sodium Iodide (NaI) detector measured gamma rays emitted from the samples. Qualitative evaluation of human exposure to radio-cesium in five sets of locations in Japan shows the radioactivity of tested samples. The Fukushima section of one of the Olympic proposed torch route has a 60 times higher activity of Cesium-137 than the activity of the samples from Tokyo.

Acknowledgements…….

Executive Summary

Overview

On March 11th, 2011, a magnitude 9.0 earthquake hit the Fukushima Prefecture of Japan (AESJ, 2015, p.19). This resulted in major structural damage to the surrounding area. Following the earthquake, a 13-meter tsunami hit the Fukushima Dai-ichi Nuclear Power Plant and disabled the backup the diesel backup power generator and the cooling water pumps needed to keep the Power Plant running in the event of a disaster. Since power restoration was unsuccessful and there was major structural damage caused to the Units by the tsunami, there were high concentrations of nuclear particles released into the air.

The amount of radioactive materials emitted from the Power Plant raised health and environmental concerns to the people living in the areas around the Fukushima Dai-ichi Nuclear Power Plant. In fact, several studies conducted after the accident determined the activity of radioactive isotopes in the environments. These studies around Fukushima provided excellent understanding of the activity of radioactive isotopes in the environment and the health effects on humans.

 With the upcoming XXXII Olympiad in 2020 hosted by Japan, it is necessary to look into the radioactivity of Olympic venues as well as tourist attractions in the host cities. Previous studies pose a major gap because they focused on regions that are closer to the Fukushima Daiichi Nuclear Power Plant, where the highest concentration of radioactive fallout is located. On the other hand, the radioactivity in other locations in Japan is relatively less studied. Since thousands of athletes and millions of visitors are travelling to Japan for the Olympics, there has been widespread concern from the international community about radiation exposure. Therefore, it is important to investigate the extent of radioactive fallout from the Fukushima Dai-ichi incident.

Project goals and Objectives

The goals of the project were to measure the radioactivity of Cesium-137 in soil and dust samples from Japan and to generate a map that illustrates the activity of Cesium-137 in five locations in Japan.Understanding the radioactivity in Japan soil would help in giving an estimation of human exposure to radioactivity in the studied areas. The primary objectives of this project were to:

  • Perform soil sample preparation for measurement, including categorizing, drying and sub-sampling
  • Measure the activity of Cesium-137 in the samples and analyze the radioactivity at different locations in Japan.
  • Generate a map to illustrate the radioactivity level in Japan soil.
  • Estimate qualitatively human exposure to radioactivity for people living in the studied areas.

Development of methodology

 The employment of various study methods and experiment designs helped complete the objectives. Through literature review and discussion with advisors and lab instructors, we were able to develop main steps and setting for our study.

Primarily, we performed preparation for 87 soil and dust samples collected in Japan and transferred to Worcester Polytechnic Institute (WPI). The samples were classified into five categories based on their original location: Tokyo samples, Azuma Sports Park samples, proposed torch route samples, tourist route samples and non-Olympic samples. All the samples were dried and sub-sampled so that their physical conditions were consistent throughout the testing phase. From the 87 samples that are dried and sub-sampled, we eventually further narrowed to 30 samples for radioactivity measurement.

Previous studies on radioactive nuclides accumulation in soil and dust samples from Japan identified that Cesium-137 had the highest concentration among radionuclides in Japan soil (Saito et al., 2015). Therefore, we set our goal to measure the activity of Cesium-137 in the samples from Japan. A thallium-activated sodium iodine detector, or NaI (TI) detector, measured the concentration of Cesium-137 in the soil samples. The calibrating sources used for Cesium137 measurement were Cesium-137, Sodium-22 and Manganese-54. The experiment reported the radioactivity of the background and the radioactivity of Cesium-137 in the samples above the background. Measurements were made in triplicate to provide counting variability statistics.

At the beginning of the project, samples were selected randomly for measurement. Our focus then shifted, as we looked deeper into the four main areas that will be important to the XXXII Olympiad in 2020. These Olympic areas included Azuma Sports Park, tourist attractions in Tokyo, a proposed torch route, and official designated tourist routes. Time constraint and large amount of samples, limited testing which resulted in results on only a limited part of each sample set.

After finishing measuring, the radioactivity of the soil and dust samples helped generate a map that shows the activity of Cesium-137 in Japan soil. Since there was a large variation in the measured activity between samples at different locations, we decided to analyze the results based on the samples’ original locations.

 Our results were cross-referenced with information and results gathered from literature reviews. Understanding the activity of Cesium-137 in Japan soil, we were able to give a qualitative estimation of human exposure.

Results and Analysis

 By the end of the project, we were able to measure the activity of Cesium-137 in 30 soil and dust samples. The results showed a great variation in radioactivity between samples from different locations. The activity of Cesium-137 in the 30 samples ranged from 38.6 Bq/kg to 28041.5 Bq/kg with the mean radioactivity of 4903.3 Bq/kg (standard deviation, σ= 6611.0 Bq/kg).

Among the five categories of locations, the Tokyo sample set had the lowest radioactivity mean of 117.6 Bq/kg. The following locations are ordered by increasing mean of radioactivity: Azuma Sports Park samples (2703.9 Bq/kg), main tourist routes samples (3206.0 Bq/kg) and proposed torch route samples (7896.0 Bq/kg). Only one of the non-Olympic samples, which originates from the Entrance to Fukushima Dai-ichi waste mounds, had a radioactivity of 14119.8 Bq/kg. Due to this outlier, this sample set was omitted from the other sets.

The measured results showed that the Tokyo sample set had the lowest radioactivity level, which was understandable based on its significant distance from the Fukushima Nuclear Power Plant. On the contrary, the proposed torch route samples had the highest mean radioactivity due to their close proximity to the plant. Based on the measurement, we estimated qualitatively that the radiation exposure of people living near the Azuma Sports Park area was 20.7 times higher than that of people living in Tokyo. The main tourist and proposed torch routes had radiation exposure of 24.6 and 60.6 times higher, respectively, than in Tokyo.

The results in this study were in agreement with published results qualitatively. Saito et al. reported a much higher deposition of Cesium-137 in the area to the northeast of the Fukushima Nuclear Power Plant and the further away from the plant, the lower the deposition of Cesium-137 (2015). Accordingly, our results showed that the highest radioactivity level was at the proposed torch route, which is located to the northeast of the plant. The further away from the plant for example, in Tokyo and the Azuma Sports Park, the lower the activity of Cesium137. However, because of the differences in sampling techniques and reported unit of radioactivity, there could not be an established direct comparison.

Recommendations

Given the aforementioned results, there is significant evidence through our testing, that there are still high amounts of radiation in areas close to the Fukushima Prefecture. Past and current tests found that high amounts of radiation remain at the origin of the disaster. The results showed a significantly higher amount of radioactive materials in the proposed torch route compared to those in Tokyo.

 Given the results from testing, we confidently make the following recommendations:

  1. Further study on the activity of Cesium-137 on the proposed torch route is necessary to understand how much radioactive materials remain.
  2. A more detailed study with more soil and dust samples can give a more accurate map of specific areas of interest.
  3. Olympic officials should consider using the results of this project to decide whether the radioactivity level at the proposed torch route and the Olympic venues are within acceptable level. 4. Qualified health professionals should use this data to make connections about short and long-term effects on health.

Authorship……….

Table of Contents…….   47 pages   Very well supplied with references, diagrams, maps, … https://web.wpi.edu/Pubs/E-project/Available/E-project-031418-011249/unrestricted/Fukushima_IQP_Final_Report.pdf

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May 12, 2018 - Posted by | environment, radiation

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