Decontamination Work Research Articles

Towards long-term responses in Fukushima

Towards long-term responses in Fukushima

Risk and preventive factors for heat illness in radiation decontamination workers after the Fukushima Daiichi Nuclear Power Plant accident.

The aim of this study was to reveal factors related to heat illness in radiation decontamination workers and determine effective preventive measures. A self-administered questionnaire was sent to 1,505 radiation decontamination workers. The questionnaire included age, sex, duration of decontamination work, previous occupation, education provided by employers regarding heat illness, preventive action against heat illness, and subjective symptoms of heat illness during work. We included 528 men, who replied and answered all questions, in the statistical analysis. Subjective symptoms of heat illness were categorized as "no symptoms", "Grade I" and "Grade II" according to severity. A multiple linear regression model was used to determine the factors associated with the severity of heat illness. The mean age of the subjects was 47.6 years old (standard deviation: 13.4). Of the 528 workers, 316 (59.8%) experienced heat illness symptoms (213 at Grade I and 103 at Grade II). The results of the stepwise selection revealed that age, outdoor manual labor, adequate sleep, use of a cool vest, and salt intake were selected as preventive factors, whereas living in a company dormitory or temporary housing, wearing light clothing, and consuming breakfast were selected as risk factors for heat illness. Both working conditions and living environment are associated with heat illness in radiation decontamination workers. Type of housing and sleep are also strongly related to heat illness during work. Employers should consider not only the working conditions of the employee but also the employee's daily living conditions, in order to prevent heat illness.

Study of the radiological impact caused by the extraction of the residue of a dicalcium phosphate industrial plant

In recent years, a decontamination project has been under way to remove the polluted sludge on the riverbed of the Ebro river, particularly in the area of Flix (Tarragona, Spain). This project started in 2011 and consists of the removal of the sludge and its treatment in a process that will eventually restore the river to its natural conditions. The sludge is a product of the historical dumping of contaminants by a chemical complex situated next to the river, and it contains a range of contaminants, such as heavy metals, semi- and volatile organic compounds, and radionuclides. Downstream of the complex, in the town of L’Ampolla, a drinking water treatment plant (DWTP) is located. This plant collects the water from the Ebro river and, after potabilisation, the plant supplies drinking water to the population of southern Catalonia. Due to the possible presence of radionuclides in the river water, it was considered important to monitor and control the radioactivity parameters regulated under current legislation for water consumption. For this reason, in this study, our aim is to evaluate if the decontamination work carried out in Flix has any effects on the radioactivity levels of both Ebro river and treated water, by means of the determination of gross alpha activity, gross beta activity and a group of gamma emitter radionuclides at three different sampling points in the period between 2008 and 2012. One sampling point was located a few kilometres from the Flix area and the other two were located before and after the DWTP, respectively. From the results obtained, it could be observed that no significant differences were obtained between the samples taken before and after the beginning of the decontamination process began, so it is important to highlight that this project has not affected the quality of the water supplied by the DWTP.

Research on Decontamination of Chemical Accident Disposal to Reduce the Harm to the Environment

Toxic and harmful substances can pollute the air and object surface after chemical accidents. Toxic gas is omnipresent in the contaminated zone and poisonous liquid can penetrate into the depth of surface caused by pollution. This will last for a few hours, more than a few days, months or even longer, the ecological environment will be seriously polluted. So the efficient and fast decontamination is needed after chemical accident, decontamination work is an important part of chemical accident disposal work, which can prevent chemical accidents secondary disasters effectively.

Effect of Ionizing Radiation on the Living Body

Since the Fukushima nuclear plant accident following the great East Japan earthquake on March 11, 2011, we have been warned to be careful about possible radiation exposure almost every day in newspapers and on TV. Radioactive iodine ((131)I) and cesium ((134)Cs, (137)Cs) produced by nuclear reactions were released into the air during and after the accident, and have been scattered by the winds in Tohoku and in the Kanto district. Even today, 2 years after the accident, there is great public concern about possible pollution of foodstuffs and fishery products with radioactive cesium, not only in Japan, but also in other countries. On the other hand, decontamination work has been proceeding, including removal of contaminated soil near the accident site. Since the accident, many media reports have continued to tell us only that current dose levels of radiation are not dangerous to human health. But, many people are not satisfied with such vague statements, and want to understand the situation in more detail. So, it is important to provide basic education about the effects of radiation to the general public. I am a professor of the Department of Radiation Biosciences at Tokyo University of Science, and so I am very familiar with radiation and its dangers. So, in my lecture today, we would like to explain the effects of radiation and put the present situation into perspective, so that people will better understand the risks, and not be unnecessarily afraid.

1P2-E08 線量計による放射線源分布推定における計測経路の評価(サーチ&レスキューロボット・メカトロニクス(2))

Building a map of the distribution of radiation activities is needed to assist in decontamination work. The authors have proposed a method to estimate the intensities of point-like radiation sources from the radiation dose measured by moving a dosimeter in three-dimensions and 3-D map of the environment, and it was found that the accuracy of estimated distribution of radiation sources depended on the trajectory of dosimeter. To improve the problem we propose a method to plan a best trajectory of measurement of dosimeter in estimation of radiation sources. In this paper, the difference of likelihood distribution caused by trajectory of dosimeter is shown to evaluate the trajectory.

ブラストによる除染作業の効率化(<メカライフ特集>転のものづくり)

ブラストによる除染作業の効率化(<メカライフ特集>転のものづくり)

Development of a gamma camera to image radiation fields

Measurement of radioactive contamination and confirmation of the decontamination effects are important for the recovery from the nuclear accident at the Fukushima Dai-ichi Nuclear Power Plant. We have developed a gamma camera which can visualize the gamma-ray intensity distribution in real time. Experiments were conducted to investigate its performance. An energy resolution of 2.3 % and spatial resolution of 0.68 m at a distance of 5 m were confirmed. In addition, field tests were conducted in the Fukushima Dai-ichi Nuclear Power Plant. The gamma-ray intensity distribution was successfully visualized within as short a time as 10 seconds in an environment with an air dose rate of 1 - 10 mSv/h. Prominent gamma-ray radiation was found from the penetration holes, which connect the inside and outside of the primary containment vessel. From this result, it was found that shielding the penetration holes will improve the work environment during decontamination and cleanup activities. These results indicate the gamma camera will contribute to decontamination work and radiation exposure reduction for workers.

Measurement of Internal Radiation Exposure among Decontamination Workers in Villages near the Crippled Fukushima Daiichi Nuclear Power Plant

Decontamination workers may face a high risk of exposure to internal irradiation through inhalation during decontamination activities; there is, however, little previous research on the levels of internal contamination during decontamination procedures. The authors reviewed the medical records, including whole body counter measurements, of decontamination workers in villages near the crippled Fukushima Daiichi Nuclear Power Plant to assess their levels of internal radiation exposure. In total, 83 decontamination workers were enrolled in this study. They were regularly engaged in decontamination activities in highly contaminated areas where surface 137Cs deposition density was over 100 kBq m-2. The present study showed low levels of internal exposure among the decontamination workers near the Fukushima Daiichi nuclear plant. The cesium burdens of all the decontamination workers were below detection limits. They had reported no acute health problems. The resuspension of radioactive materials may cause minimal internal contamination during decontamination activities.

Establishment of New Regulations for Radiological Protection for Decontamination Work Involving Radioactive Fallout Emitted by the Fukushima Daiichi APP Accident

In response to the accident at the Fukushima Daiichi Atomic Power Plant (APP) on March 11, 2011, the Japanese government decided to carry out decontamination projects around the plant. For the radiological protection of the decontamination workers, the Japanese government needed to establish new regulations because the existing regulation did not fit into “existing exposure situations” in which radioactive sources were scattered and spread in a wide area around the plant. The new regulations aim to set the appropriate protection standards in accordance with the risk of the ambient dose rate, radioactivity concentration, and type of radio nucleolus resulting from the APP accident, which is equivalent to or more than the typical protection required in planned situations. To maintain practicability, the Japanese government employed a validated and simplified measurement methodology for the internal exposure, ambient dose rate, and radioactivity concentration, considering restrictions in human resources and shortages of supplies in the affected areas. The article also identifies key challenges which require further research.

Molecular Mechanism of Heavily Adhesive Cs: Why Radioactive Cs is not Decontaminated from Soil

Two years having passed since the nuclear crisis at Fukushima, radioactive 137Cs with a half-life of ∼30 years has come to the forefront of our largest concern. To gain an insight into current unsuccessful 137Cs decontamination from soil, heavily adhesive Cs adsorption, referred to as specific Cs adsorption here, is highlighted for layered clay minerals. Besides the interlayer Cs+ cations, a population of Cs is able to adsorb on the surfaces of open nanospaces with their sizes of ∼0.3 and ∼0.9 nm, which are formed by one- and two-clay nanosheet insertion into interlayer spaces. They are adsorbed on the surfaces of the open nanospaces so strongly that they cannot be removed even by a hydrochloric acid solution of pH 1.0; these open nanospaces thus act as the specific Cs adsorption sites. The characteristic local molecular structures as a clay-nanosheet edge and a wedge-shaped frayed part available in the open nanospaces are responsible for the specific Cs adsorption. Radioactive 137Cs that is not cleaned up after the decontamination work would originate from the specific Cs adsorption clarified in the present work.

Technical know-how on the decontamination work taking into consideration of the transport behavior of radiocaesium accompanied with transport and deposition of soil particles, and stream flow

Technical know-how on the decontamination work taking into consideration of the transport behavior of radiocaesium accompanied with transport and deposition of soil particles, and stream flow

Decontamination Work in the Area Surrounding Fukushima Dai-ichi Nuclear Power Plant: Another Occupational Health Challenge of the Nuclear Disaster

ABSTRACT This article describes occupational health measures for workers involved in decontamination of radioactive material discharged around Fukushima Dai-ichi Nuclear Power Plant after the explosions in 2011. Decontamination is performed by removing radioactive particles (mainly cesium) from surfaces of soil, grass and trees, and buildings. Measurement of radiation doses is necessary to reduce exposure, and to determine whether workers can work below dose limits. Protective equipment for decontamination is determined based on the concentration of radiation in contaminated soil and the exposure to dust. Health examinations by physicians are mandated for decontamination workers upon hiring and every 6 months. While there is no possibility of acute radiation injury from decontamination, workers may be anxious about the unclear effects of chronic low level radiation exposure on health. Measures to protect the decontamination workers are the top priority.

Fukushima: the consequences

The accident at Japan's Fukushima Daiichi nuclear plant a year ago, caused by an earthquake and tsunami that left 19,126 people dead or missing, has had many consequences. Though no one is known to have suffered serious illness after being exposed to radiation from the plant, health hazards remain. Decontamination work will last for decades and around 100,000 people who were evacuated have yet to return home. The accident has caused many governments to take stock of nuclear energy plans and has slowed the global growth of nuclear power.

植物が混入した放射性セシウム汚染土壌の多段階土壌洗浄処理試験

Decontamination work following radiocesium exposure requires a vast reduction in the amount of contaminated soil generated. The current study subjected 4 types of contaminated soil with different properties to multistep soil washing under the same conditions. This study also determined the effectiveness of radiocesium decontamination and the extent to which the amount of contaminated soil was reduced. In addition, the effectiveness of plant matter separation, adsorbent addition, and grinding as part of multistep soil washing was determined using the same contaminated soil. Results of testing indicated that the rate of radiocesium decontamination ranged from 73.6 to 89.2% and the recovery rate ranged from 51.5 to 84.2% for twice-treated soil, regardless of the soil properties or cesium level. Plant matter in soil had a high radiocesium level. However, there was little plant matter in our soil sample. Therefore, plant matter separation had little effect on the improvement in the percentage of radiocesium decontamination of twice-treated soil. Soil surface grinding improved the rate of radiocesium decontamination of twice-treated soil. However, radiocesium in soil tightly bound with minerals in the soil; thus, the addition of an adsorbent also failed to improve the rate of radiocesium decontamination.

Decontamination and decommissioning of radioactively contaminated rooms and equipment at the Bochvar All-Russia Research Institute of Standardization in Machine Engineering

Work on decontaminating and decommissioning radioactively contaminated rooms and equipment has been conducted at the All-Russia Research Institute of Standardization in Machine Engineering since 1999. Organizational and technical measures to consolidate the material and human resources and centralized planning of all work on decontamination, rehabilitation, and waste handling have been developed at the Institute. A scientific and industrial division whose main purpose is to provide comprehensive solutions to all ecological problems of the Institute has been created. Because of the large scale of the problems, special attention is being devoted to the economics of the technical solutions adopted and to minimizing the handling of wastes with definite priority given to the safety. Experience shows that several effective, low-waste technologies must be used in each specific case for decontaminating and localizing radioactive contamination taking account of the specific nature of the object. Performing decontamination work to meet Institute's needs has fostered the development of new, effective technical means for decontamination, specifically, the development of bench facilities for laser, electrochemical, and foam decontamination and facilities for soil decontaminations, and other means.

Simultaneous measurement of specific serum IgG responses to five select agents

Select Agents are defined by CDC and the USDA Animal and Plant Health Inspection Service (APHIS) as biological agents or toxins deemed a threat to public, animal, or plant health, or to animal or plant products. They are classified on the basis of their ease of dissemination, mortality/morbidity rate, and potential for social disruption. A subset of these agents includes Bacillus anthracis, Yersinia pestis, Francisella tularensis, ricin toxin (RT), and staphylococcal enterotoxin B (SEB). Infection or intoxication with these agents has been shown to elicit an antigen-specific serum IgG response. We describe a fluorescent covalent microsphere immunoassay (FCMIA) for measurement of specific IgG antibodies to seven different antigens from five different select agents; B. anthracis [protective antigen (PA) and lethal factor (LF)], Y. pestis (F1 and V antigens), F. tularensis, RT and SEB simultaneously in human B. anthracis vaccinee sera (containing anti-PA and anti-LF IgG) which had been spiked with animal specific IgG antibodies to the other select agents. Inter-assay and intra-assay coefficients of variation were 6.5 and 13.4%, respectively (N = 4). There were no significant differences (P > 0.70) between assay responses when the assays were performed individually or multiplexed. When the observed versus expected interpolated concentrations were compared, highly linear relationships were observed (r2 values from 0.981 to 0.999, P < 0.001). Minimum detectable concentrations (MDC) ranged from 0.3 ng mL(-1) (Y. pestis F1) to 300 ng mL(-1) (RT). Finally, the curves showed responses were linear for most analytes from their MDC to 125 (SEB) to 1,300 (Y. pestis F1) x their MDC. These data indicate that multiplexed FCMIA is a sensitive and accurate method for simultaneous measurement of specific IgG in serum to CDC select agents and may be of value in screening either decontamination workers or the general population for exposure to/infection with these agents.

137Cs distribution in guava trees

This paper presents results of 137 Cs concentration measured from a guava tree cultivated after the first decontamination work of one of the sites where the worst Brazilian radiological accident occurred. The present work aims to verify how the 137 Cs is transported and distributed along the tropical trees. Bi-dimensional analyses of the radial distribution of 137 Cs in the main trunk are also presented. Neither symmetrical nor homogeneous behaviors of the specific activity distribution in the tree rings were observed.

Evaluation of radioactivity induced in the accelerator building and its application to decontamination work

For decommissioning of the cyclotron and electron synchrotron facilities, the residual radioactivity in surface and core samples of concrete, collected from various parts of buildings, was determined by gamma-ray spectrometry. It was found that the concrete samples were activated mainly by neutrons and that the major radioisotopes were 152Eu, 60Co, 134Cs, 22Na and 54Mn. The maximum activity induced by thermal neutron capture was observed at the depth of 10 cm in the concrete wall near the deflector of the cyclotron. Tritium was also produced by the neutron reaction, because its concentration was proportional to the activities of 152Eu and 60Co. The surface dose rates inside the accelerator room were also monitored to define the decontamination area. The surface dose rate was proportional to the residual radioactivity, such as 60Co. A careful evaluation was very useful in order to minimize the radioactive waste during decontamination.

Chernobyl Record: The Definitive History of the Chernobyl Catastrophe

The Chernobyl Record is a collection of documents relevant for practically all aspects of the Chernobyl accident. Eyewitness reports, photographs and excerpts of technical and scientific publications are all compiled to give a multi-faceted picture. The introduction contains an informative description of early health effects due to acute radiation exposures. Concerning dose quantities related to low level or protracted exposures, the reader might prefer to read the original reports of the ICRP. In the Chernobyl Record basic aspects of nuclear power reactors of type RBMK-1000 are presented together with maps and several pictures of the plant at Chernobyl - before and after the accident. The detailed reconstruction of the accident is enriched by several eyewitness reports. Many photographs and drawings illustrate the construction of the sarcophagus that was build to shield the environment from the radionuclides inside the demolished reactor. The environmental release of radionuclides during the accident and resulting radiation exposures are compared to the other major population exposures that occurred in the past sixty years. The use of nuclear power in the world is summarised and accidents that have happened in nuclear power plants are listed. An overview of the early medical response to the Chernobyl accident provides reports of members of the medical staff involved. Methods of dose reconstruction are reviewed and dose estimates for the emergency worker are given. Histories of patients with acute radiation syndrome are followed-up. Psychological illnesses are frequently observed among the emergency workers. The evacuation and the resettlement of the population in the contaminated territories are again illustrated with many photographs. Extensive information is given on the contamination of the environment and of foodstuffs, doses to the population, and on decontamination work. The discussion includes an overview of the development of radiation safety standards in the former USSR and compares it with internationally adopted standards. For the population that continued to live in the contaminated territories, psychological and social problems have been reported in various surveys. An overview is given on studies of late health effects that are known to be related to exposures to ionising radiation, including brain damage in utero, mental retardation, reproductive health patterns, and haematological, thyroid and ocular diseases. General aspects of radiation-induced cancer and risk specification are summarised. Subsequently, the increased thyroid cancer incidence rate among those who were exposed due to the Chernobyl accident during childhood or adolescence is described. Finally, the book gives an informative insider view, the Legaslov testament, together with the comments of his widow. Valery Legaslov, the first deputy director of the Kurchatov Institute of Atomic Energy, Moscow, died two years after the Chernobyl accident, and his personal experiences during the accident, together with a description of the problems in the USSR which contributed to the catastrophe, were published in 1988 in Pravda, and now translated for publication in the Chernobyl Record. In summary, the Chernobyl Record is worthwhile reading for the interested layman as well as for the expert who will find information in the book that is not easily accessible otherwise. Unfortunately, the author sometimes gets lost in an overwhelming number of details, and it is difficult for the reader to derive a clear general message. Smaller parts of the book are not fully adequate, e.g. the ICRP recommended dose limit of 1 mSv for the population is given and it is not made clear that this limit does not apply to an accidental situation. However, in total, the Chernobyl Record is recommended as an historical overview with a unique collection of documents, and an extensive and useful list of relevant references.