Re-establishment of post-accident procedures for setting emergency dose limits based on the lessons learned in the 2011 Fukushima nuclear accident.

In response to the accident at the Fukushima Daiichi atomic power plant in 2011, the Ministry of Health, Labor and Welfare issued an exemption ordinance to increase the dose limits for emergency workers temporarily from 100 mSv to 250 mSv from 14 March to 16 December 2011. However, there were many problems with setting and applying the dose limits as well as radiation protection. Based on the lessons learned, in 2015, the Government of Japan deliberated setting emergency radiation protection standards to ensure preparedness for future nuclear emergencies. This paper aims to describe and share the experience gained in that decision-making and social consensus-building process of setting emergency dose limits. It outlines issues relating to the setting and application of emergency dose limits, restricting these to emergency workers and training them accordingly, and mid-to-long-term dose control. When deliberating on emergency dose criteria, the Government of Japan had to harmonize its efforts with international guidance documents and find a way to balance the protection of emergency workers with the prompt implementation of a crisis management plan to maintain control over the nuclear accident. The fact that leading countries have a wide range of emergency dose criteria means that the establishment of emergency dose limits requires not just a scientific basis as prescribed in international documents but also social consensus-building. Further case studies on the decision-making process for setting radiation protection standards in other countries are thus warranted.

Tertiary evaluation of the committed effective dose of emergency workers that responded to the Fukushima Daiichi NPP accident.

In January 2014, Tokyo Electric Power Company (TEPCO) learned that the committed effective dose (CED) for nine emergency workers at the Fukushima Daiichi Nuclear Power Plant accident had been assessed by a method other than the standard assessment methods, established by the Ministry of Health, Labour and Welfare (MHLW) in a secondary evaluation conducted in July 2013. The MHLW requested that the TEPCO and primary contractors review all CED data for 6,245 workers who engaged in emergency work in March and April 2011 except those previously reviewed in the 2013 secondary evaluation. This tertiary evaluation revealed that the recorded CED for 1,536 workers had more than 0.1 mSv discrepancy with the CED evaluated by the standard method. The MHLW requested that TEPCO and primary contractors revise CED data for 142 workers whose CED was 2 mSv or greater that required a CED revision of 1 mSv or greater. The average CED revision was 5.86 mSv. The revised effective dose ranged from 2.17-180.10 mSv. In addition, the number of workers whose CED exceeded 100 mSv increased by one. New issues addressed during the tertiary evaluation included the following: (a) setting of calibration coefficients to convert the CED value from whole body counters equipped with NaI scintillator (WBC(NaI)) to a CED value from WBCs with Ge semiconductor detector; (b) estimation methods for the cases where 131I was not detectable by WBC (NaI) and where 137Cs was not detectable but 134Cs was detected; (c) effects of stable iodine (KI) tablets to block the uptake of 131I by thyroid gland; and (d) complications in determining additional doses during stand-by in the seismically isolated building. To prevent the future use of non-uniform CED assessment methods in the dose assessment for workers, the MHLW issued administrative guidance documents to TEPCO and primary contractors on March 25, 2014.

Establishment of the central radiation dose registration system for decontamination work involving radioactive fallout emitted by the Fukushima Daiichi APP accident.

With respect to radiation protection for decontamination efforts involving radioactive fallout emitted by the accident at the Fukushima Daiichi Atomic Power Plant, new regulations were established and obligated employers to monitor, record, and store of workers' dose records, and to check their past dose records at the time of employment. However, cumulative doses may not be properly maintained if a worker declares incorrect values for past doses. In response, with facilitation from the Ministry of Health, Labour and Welfare, primary contractors of decontamination works decided to establish a central dose registration system. There are four major issues in the design of the system to be resolved, included the following: primary contractors (a) do not have a legal responsibility to perform dose control for subcontractors, (b) do not have the right to control decontamination sites, (c) often organize joint ventures, and (d) correspond to a wide range of ambient dose rates. To resolve the issues, requirements of the system included the following: (a) centralize the operation of radiation passbooks, which records past doses and the results of medical examinations to each worker; (b) develop a database system that could register all dose data and accept inquiry from primary contractors; (c) establish a permanent data storage system for transferred records; and (d) provide graded type of services that are appropriate to the risk of radiation exposure. The system started its operation in December 2013 and provided dose distributions in April and July 2015. The average yearly dose in 2014 was 0.7 mSv, which increased by 0.2 mSv from 0.5 mSv in 2012 and 2013. However, no cumulative dose from 2012-2014 exceeded 20 mSv, which was far below than the dose limits (100 mSv/5 years and 50 mSv/year). Although current dose distributions of decontamination workers were within appropriate levels, careful monitoring of dose distribution is necessary for preserving the proper implementation of radiation protection prescribed in the regulations.

A recommended epidemiological study design for examining the adverse health effects among emergency workers who experienced the TEPCO fukushima daiichi NPP accident in 2011.

Results from medical examinations conducted in 2012 of workers who were engaged in radiation work in 2012 as a result of the 2011 Fukushima Daiichi Nuclear Power Plant (NPP) accident showed that the prevalence of abnormal findings was 4.21%, 3.23 points higher than the 0.98% that was found prior to the accident in the jurisdiction area of the labor inspection office which holds jurisdiction over the NPP. The Ministry of Health, Labour and Welfare (MHLW) concluded that the 2010 and 2012 data cannot be easily compared because 70% of the enterprises within the jurisdiction of the office that reported the 2012 results were different from those that did so in 2010. In addition, although the radiation workers' estimated average dose weighted by number of workers was 3.66 times higher than decontamination workers' dose, the prevalence among radiation workers was only 1.14 times higher than that among decontamination workers. Based on the results of the medical examinations, however, the MHLW decided to implement an epidemiological study on the health effects of radiation exposure on all emergency workers. This article explains key issues of the basic design of the study recommended by the expert meeting established in the MHLW and also identifies challenges that could not be resolved and thus required further consideration by the study researchers. The major issues included: (a) study methods and target group; (b) evaluation of cumulative doses; (c) health effects (end points); (d) control of confounding factors; and (e) study implementation framework. Identified key challenges that required further deliberation were: (a) preventing arbitrary partisan analysis; (b) ensuring a high participation rate; (c) inquiry about the medical radiation doses; and (d) the preparedness of new analytical technology. The study team formulated and implemented the pilot study in 2014 and started the full-scale study in April 2015 with funding from a research grant from the MHLW.

Fact-finding Survey in Response to the Manipulation of Personal Alarm Dosimeter Collection Efficiency: Lessons Learned About Post-Emergency Radiation Protection from the TEPCO Fukushima Daiichi APP Accident.

During emergency work at TEPCO Fukushima Daiichi Atomic Power Plant on December 1, 2011 a subcontractor demanded that its contracted workers cover their personal alarm dosimeters (PAD) with 3-cm-thick lead plates to lower dosimeter readings. As a response, the Ministry of Health, Labour and Welfare (MHLW) conducted a fact-finding survey to identify similar cases and devise measures to prevent a recurrence of this incident. To screen the suspected cases, the MHLW extracted: a) cases in which a PAD reading was at least 15% higher than the reading obtained from a radio-photolumine-scence dosimeter (RPD), where the dose was greater than 5 mSv in a month (1813 data points), and b) dose data in which PAD readings were less than 50% of the expected dose, where exposure dose may exceed 1 mSv in a day (56 workers, 17,148 data points). From these screenings, the MHLW identified 50 instances from TEPCO and nine primary contractors, including four general contractors, two plant manufacturers, and three plant maintenance companies as the subjects of the due diligence study of exposure data, including interviews. The results of the survey provide lessons that can also be applied to transition from emergency radiation protection to normal operation, as the application of emergency dose limits had ceased on December 16, 2011, in the affected plant. Based on the results of the survey, the MHLW provided administrative guidance documents to TEPCO and 37 primary contractors. The major points of these documents include: a) identification of recorded dose values by comparison of PAD readings to RPD readings, b) storage and management of RPDs and control badges, c) circulation management of PADs and access control to the affected plant, d) estimation of planned doses and setting of alarm values of PADs, e) actions to be taken by contractors if worker dose limits are reached, and f) physical measures to prevent recurrence of the incident.

Governmental re-evaluation of the committed effective dose received by emergency workers at the TEPCO Fukushima Daiichi NPP accident.

In April 2013, the Ministry of Health, Labour and Welfare (MHLW) noticed that significant discrepancies were present between the committed effective dose (CED) data for emergency workers at the TEPCO Fukushima Daiichi Nuclear Power Plant provided by TEPCO and that reported by five primary contractors. The MHLW, based on re-evaluation of the data, provided administrative guidance which required TEPCO and the five primary contractors to readjust the CED data for 479 workers (2.5% of 19,346 emergency workers). Of these, data for 450 workers from the primary contractors were readjusted based on the change in assessment methods. Doses were readjusted to higher values for 431 workers and doses were readjusted to lower values for 19 workers, CED data were corrected due to calculation errors for 29 workers from seven contractors, 12 additional workers were found to have received more than 50 mSv but no more than 100 mSv, an increase of 1.7% over the previously established count of 723 workers who had received that dose. Six additional workers were found to have received more than 100 mSv, an increase of 3.6% compared with the previous count of 167 workers. Major issues addressed during re-evaluation included: a) selection of intake scenario for the calculation of the residual activity ratio; b) assumptions about the intake date; c) assessments of exposure to radiation from (132)I and (132)Te; and d) assumptions about (131)I exposure in cases where (131)I was undetectable. Regarding the divergent CED data of 138 workers, the MHLW also confirmed that the CEDs assessed by the primary contractors were valid. To prevent the recurrence of similar incidents, the MHLW issued administrative guidance documents to TEPCO and primary contractors to employ standardized CED assessment methods on July 5. 2013.

250 mSv: temporary increase in the emergency exposure dose limit in response to the TEPCO Fukushima Daiichi NPP accident and its decision making process.

The Great East Japan Earthquake on March 11, 2011, led to an accident at the Fukushima Daiichi Nuclear Power Plant of the Tokyo Electric Power Company (TEPCO). In response to this accident, on March 14, 2011, the Ministry of Health, Labour, and Welfare (MHLW) of Japan enforced an ordinance that temporarily increased the radiation exposure dose limit allowed to 250 mSv during the emergency. This article explains the processes of a) temporarily increasing emergency dose limits, b) controlling for the combined emergency and normal exposure doses, and c) reducing the limit back to 100 mSv. Major issues addressed when deliberating the reduction of the emergency limits includes the following: a) political initiative, b) a phased reduction of dose limits, and c) transitional measures for workers who were exposed to more than 100 mSv. This article also identifies key challenges that need further deliberation to be resolved. These include: a) establishing a pre-defined protocol for applying pre-accident emergency dose limits and/or amending post-accident limits; b) designating the conditions in which to apply or amend emergency dose limits; c) selecting methods of radiation control for individuals who are exposed to more than the normal exposure dose limit during emergency work; and d) designating the conditions under which to terminate or reduce emergency dose limits after the accident.

New regulations for radiation protection for work involving radioactive fallout emitted by the TEPCO Fukushima Daiichi APP accident--disposal of contaminated soil and wastes.

The accident at the Fukushima Daiichi Atomic Power Plant that accompanied the Great East Japan Earthquake on March 11, 2011, released a large amount of radioactive material. To rehabilitate the contaminated areas, the government of Japan decided to carry out decontamination work and manage the waste resulting from decontamination. In the summer of 2013, the Ministry of the Environment planned to begin a full-scale process for waste disposal of contaminated soil and wastes removed as part of the decontamination work. The existing regulations were not developed to address such a large amount of contaminated wastes. The Ministry of Health, Labour and Welfare (MHLW), therefore, had to amend the existing regulations for waste disposal workers. The amendment of the general regulation targeted the areas where the existing exposure situation overlaps the planned exposure situation. The MHLW established the demarcation lines between the two regulations to be applied in each situation. The amendment was also intended to establish provisions for the operation of waste disposal facilities that handle large amounts of contaminated materials. Deliberation concerning the regulation was conducted when the facilities were under design; hence, necessary adjustments should be made as needed during the operation of the facilities.

New regulations for radiation protection for work involving radioactive fallout emitted by the TEPCO Fukushima Daiichi APP accident: application expansion to recovery and reconstruction work.

The accident at the Fukushima Daiichi Atomic Power Plant that accompanied the Great East Japan Earthquake on March 11, 2011 released a large amount of radioactive material. To rehabilitate the contaminated areas, the government of Japan decided to carry out decontamination work. In April 2012, the Nuclear Emergency Response Headquarters (NERH) started dividing the restricted areas into three sub-areas based on the ambient dose rate. In accordance with the rearrangement of the restricted area, NERH decided to allow resumption of business activities, including manufacturing and farming, as well as operation of hospitals, welfare facilities, and shops and related subordinate tasks, such as maintenance, repair, and transportation. As a result, the government needed regulations for radiation protection for workers engaged in those activities. The issues that arose in the deliberation of the regulations were distilled into two points: 1) whether radiation protection systems established for a planned exposure situation should apply to construction and agricultural work activities in an existing exposure situation, and 2) how to simplify the regulation in accordance with the nature of the work activities. Further research and development concerning the following issues are warranted: a) the relationship between the radioactive concentrations of materials handled and the risk of internal exposure, and b) the relationship between the radioactive concentration of the soil and the surface contamination level.

Lessons learned: medical and health care management for emergency workers at the TEPCO Fukushima Daiichi APP accident.

During the emergency work at the Fukushima Daiichi Atomic Power Plant (APP), the Tokyo Electric Power Company (TEPCO) and the Japanese government experienced various problems in medical and health care management issues, including special medical examinations, on-site triage and initial treatment, patient transportation, lodging and food, and long-term health care for emergency workers. To resolve these problems, the Ministry of Health, Labor and Welfare (MHLW) issued a series of compulsory directives and provided administrative guidance to TEPCO. Based on the experiences and lessons learned, the MHLW recognized that the proper management and implementation of medical and health care management in response to a similar accident would require sufficient measures and systematic preparation, including the following: 1. In case of large-scale nuclear accidents, the government needs to assist in dispatching medical staff to the affected plants. 2. Nuclear facility operators, medical facilities and fire departments should make an agreement to clarify the division of the roles played prior to the accident and should conduct emergency drills periodically with the full attendance of related personnel to identify and resolve the problems. 3. Operators need to develop a support base at a safe distance from the plant and to prepare to develop makeshift lodgings in case of emergency. 4. Operators need to come to an agreement to share food stocks among closely located nuclear plants and prepare cooking equipment that can be used in case of blackout to provide warm foods and drinks to as many workers as possible. 5. It is necessary to conduct long-term follow-up for emergency workers, including health care system, medical examinations and mental health consultations.

Engineering case report.

During the emergency work at the Fukushima Daiichi Atomic Power Plant, Tokyo Electric Power Company (TEPCO) and the Japanese government experienced various problems in radiological exposure management for emergency workers. Radiological exposures resulted from the inappropriate use of respiratory protection, the improper use of protective garments, and insufficient worker training. Among the efforts to reduce external exposure, there were problems associated with the control of working hours, the effective use of a radiation shielding, and the lack of well-prepared work plans. To reduce the exposure dose, the following lessons should be shared with other atomic power plants (APPs) and various stakeholders: (a) to prevent internal exposure, it is necessary to monitor the radioactive concentration of the workplace indoor air during an emergency, to stockpile and use appropriate respiratory protection and train newcomers how to use, fit, and fit-test the respirators; (b) to prevent unnecessary beta-ray exposure, liquid-proof garments should be mandatory when workers handle contaminated water; (c) to reduce external exposure, it is indispensable to develop well-prepared work plans prior to the work and to monitor the ambient dose rate of the work area to develop proper working procedures; (d) the earlier deployment of remote-controlled vehicles and the utilization of tungsten shielding vests can contribute to exposure reduction. Further research and development of remote-controlled devices to monitor and survey affected areas are urgently required.

Lessons learned: Radiological protection for emergency workers at the TEPCO Fukushima Daiichi APP (part 1).

During the emergency work at the Fukushima Daiichi Atomic Power Plant (APP), Tokyo Electric Power Company (TEPCO) and the Japanese government experienced various problems in radiological exposure management for emergency workers. To improve the implementation of appropriate radiological protection, the Ministry of Health, Labour and Welfare (MHLW) issued a series of compulsory directives and provided administrative guidance to TEPCO. Based on the experiences and lessons learned, the MHLW recognized that to properly manage radiological exposure should a similar accident occur at another APP, sufficient measures and systematic preparation for radiological management should be ensured, including the following: a) Should an APP accident occur, assistance from the power company's corporate office or off-site support facilities outside the evacuation area is indispensable; b) Primary contractors must independently implement exposure management operations for the employees of their sub-contractors; c) APP operators should compile an operations manual, stockpile personal protective equipment, and personal alarm dosimeters (PADs) and prepare emergency systems and whole body counters (WBCs); and the labor standards authorities should compile an emergency operations manual.

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.

Monitoring human exposures to upper-room germicidal ultraviolet irradiation.

After decades of neglect, the resurgence of tuberculosis in the United States between 1985 and 1992 renewed interest in the use of upper room ultraviolet germicidal irradiation to interrupt the transmission of airborne infections. More recently the bioterrorism threat and the appearance of new pathogens with the potential for airborne spread, such as severe acute respiratory syndrome (SARS), have stimulated installations of upper-room irradiation systems. The objective is to flood the entire volume of a room above 6.5 ft with high intensity ultraviolet germicidal irradiation, while minimizing unintentional irradiance below 6.5 ft to avoid eye and skin irritation. Air exchanges between the upper and lower room result in air disinfection of the occupied space. Designers of these systems have adopted the practice of limiting the maximum lower room irradiance at every point to less than the continuous 8-hour time-weighted average threshold limit value, severely limiting the irradiation intensity in the upper room and thereby reducing one of the two major factors determining germicidal effectiveness, the other being room air mixing. The hypothesis of this study is that eye and skin exposure will be well below the recommended safe dose even when maximum eye-level irradiance levels in the room exceed the 8-hour continuous exposure threshold limit. The method employed was to have subjects wear a small photometer that recorded total ultraviolet dose over the period of exposure while subjects went about their normal routine, and comparing this value with a hypothetical dose calculated from the highest measured eye-level irradiance. The results of the study, based on a limited number of observations, confirmed the hypothesis. Observed doses were one-third to a factor of a hundred or more lower than the doses calculated from maximum eye-level irradiances measurements in the occupants' spaces.