付属資料 1-3

Advisory Opinions for Improving
Radiation Protection Measures in Japan

March 2022

Japan Health Physics Society
Japanese Association for Radiation Accident/Disaster Medicine
Japanese Society of Radiation Safety Management
The Japanese Radiation Research Society
The Representatives’ Council of the Japanese Umbrella-structured
Platform for Radiation Protection

These advisory opinions are based on surveys and studies conducted by the JapaneseSociety of Radiation Safety Management, Japanese Radiation Research Society, and aworking group on the effective doses and operational quantities of radiation establishedby the Representatives’ Council of the Japanese Umbrella-structured Platform for
Radiation Protection. Some measures required for the promotion of radiation safetymeasures in Japan were compiled by the Representatives’ Council of the Japanese
Umbrella-structured Platform and are published jointly by the academic societies
participating in the Radiation Protection Academia.

Contents
1 Introduction.….….….….….….….….….….….….….….….….….….….….….…… 1
2 Urgent advisory opinions for improving radiation protection measures in Japan……. 4(1) Measures for preventing accidents and adverse events from occurring at radiation
facilities and for handling the aftermath….….…..….….….….….….….……. 4
1) Background of the advisory opinions
2) Current situation and problems
3) Advisory opinions(2) Measures for improving the radiation dose estimation in cases of large-scale
radiation disasters….…….….….….….….….….….….….….….….…...…. 16
1) Background of the advisory opinions
2) Current situation and problems
3) Advisory opinions
3 Mid- and long-term advisory opinions for the globalization of radiation protection
measures in Japan….….….….….….….….….….….….….….….….….….…… 23(1) Measures for the adoption of new concepts regarding effective dose andoperational quantities in Japan
1) Background of the advisory opinions
2) Current situation and problems
3) Advisory opinions
4 Conclusion….…..….….….….….….….….….….….….….….….….….….….….….30
5 References….….….….….….….….….….….….….….….….….….….….….….…. 32
6 Acknowledgments….….…..….….….….….….….….….….….….….….….….…. 34

1 Introduction
In recent years, two events that had a social impact have occurred; these provided
opportunities to review Japan’s preparedness for accidents at radiation facilities andradiation disasters.
The first event, an accident resulting in radiation exposure, occurred on May 29, 2021
during the inspection of a measuring device that uses X-rays (Ministry of Health, Labourand Welfare, MHLW, 2021). According to media reports, the workers inspecting thedevice may have been exposed to anywhere from several times to several tens of times
the annual radiation dose limit for workers; however, many aspects of this accident remain
unknown. For example, normally, the power switch on such devices is turned off during
inspection, but in this case, for some reasons, the device continued to emit X-rays.
Although the Labor Standards Inspection Office investigated this accident, the details
have not been disclosed, partially because the authority might consider the privacy of theindividuals who were exposed to radiation.
The second event was the 32nd Summer Olympic and Paralympic Games held in Tokyo
from July 23, 2021 to August 8, 2021 and August 24, 2021 to September 5, 2021. These
games were held when the Japanese medical system was under intense pressure owing to
the novel coronavirus disease 2019 pandemic. If a major terrorist attack were to occur
under such circumstances, the difficulty in securing medical facilities that can admit large
numbers of injured and exposed patients would have been expected to greatly surpass
current hypothetical scenarios. In such a case, it is necessary to triage the victims
according to their injuries and health conditions and allocate them to appropriate medical
facilities while simultaneously starting the collection of information and samples for
dosimetry. However, there are numerous problems associated with these activities thatneed to be solved. These problems include the small number of experts/specialists who
are able to perform radiation dose assessments, the need to develop technologies forradiation dose assessments, and the need for cooperation between various relevantorganizations.
In Radiation Protection Academia 1 , academic societies with various interests andspecialties have cooperated to propose the priority topics for radiation safety andregulation studies and discussed the problems related to securing and training human1

One member body of the Radiation Protection Research Network formed by the Radiation Safety Regulation
Research Strategic Advancement Project of the Nuclear Regulatory Authority, Japan. Four academic societies related
to radiation protection participate in Radiation Protection Academia. A representatives’ council composed ofrepresentatives from the participating organizations of the Japanese Umbrella-structured Platform for Radiation
Protection makes decisions on the activities of this network.

1resources in the field of radiation protection. In fiscal year 2020, academic societies
selected themes related to radiation accidents and disasters in response to each concern,
collated new knowledge from countries other than Japan, and conducted surveys on
domestic circumstances regarding each selected theme. These surveys and studies
conducted by the academic societies resulted in two important conclusions detailed below.
Thus, we decided to propose urgent advisory opinions requiring specific roles to beplayed by the national government, local government, private industries, and specializedorganizations (described in this paper).
1) It is of vital importance that organizations establish detailed regulations and manuals
for preventing accidents and incidents from occurring and for handling the aftermath
in case they occur.
2) Dose assessment is an essential part of dealing with accidents, and therefore there isa need for Advanced Radiation Emergency Medical Support Centers (AREMSCs)
and related institutions to rapidly develop technologies that improve and link theirsystems, particularly for performing dose estimates during large-scale radiation
disasters.
In addition, the Radiological Protection Academia has proposed urgent measures forthe national government, local government, private industries, and specialized institutions
to solve various related problems.
With an eye toward global trends, the International Commission on RadiologicalProtection (ICRP) began conducting reviews for revising its 2007 recommendations, andin July 2021, it released “Keeping the ICRP Recommendations Fit for Purpose” (Clement
et al., 2021). Beginning with this and continuing over the next several years, experts fromaround the world will conduct discussions to improve the radiation protection system andbring it in line with scientific advancements and societal changes. The abovementioned
document specifies the adoption of changes in operational and protection quantities,
which were proposed by the International Commission on Radiation Units andMeasurements (ICRU) in its 2007 recommendations (ICRU, 2020). The changes inoperational and protection quantities are expected to have a major influence on radiation
regulations worldwide. Thus, in 2020 a working group (WG) consisting of members
recommended by five academic societies2 related to radiation protection was formed.
2

The five are the Japan Health Physics Society, Japanese Association for Radiation Accident/Disaster Medicine,Japanese Radiation Research Society, Japanese Society of Radiation Safety Management, and the subcommittee ofHealth Physics and Environmental Science of the Atomic Energy Society of Japan.

2This WG examined the preparations necessary to adopt new concepts of operational andprotection quantities into Japanese regulations. Based on these surveys and studies, midand long-term advisory opinions were to be made to radiation-related ministries,
radiation-related academic societies/associations, and those engaged in radiation-related
research and development (R&D), management, and medicine.
For the Radiation Protection Academia, summarizing these advisory opinions is thefirst step toward activities that will contribute to future radiation regulations. For experts
in this field, contributing to the improvement and appropriate application of radiation
regulations and protection is part of their raison d'être. Nevertheless, the involvement of
academic societies/associations in the field of radiation protection is less than in the fields
of nuclear power and medical use of radiation. This may be attributable to the fact thatradiation protection covers a wide range of areas such that academic
societies/associations are generally segmented by the field of expertise and specificissues3. This shows that, as a practical matter, it is difficult to consolidate the various
views of experts and specialists. Therefore, the Japan Health Physics Society, Japanese
Association for Radiation Accident/Disaster Medicine, Japanese Radiation ResearchSociety, and Japanese Society of Radiation Safety Management have been working
toward solving problems related to radiation protection and have shared their information
and awareness of the issues with the Atomic Energy Society of Japan, Society for Risk
Analysis Japan, and Japan Network for Research and Information on Medical Exposure(J-RIME).
Some major challenges remain for the continuation of these activities. The activities of
the academic societies/associations are primarily based on the voluntary activities of its
members, and their contributions to regulation and protection are no exception. Unlesseach individual member of the academic societies/associations is aware of theircontribution to radiation regulation and protection, it will be difficult to continue these
activities as part of their contributions. For raising awareness among experts that one of
the goals of his/her researches is contribution to the improvement of regulations, it isimportant to satisfy the need to strengthen the collaboration among regulators, private
industries, and experts while simultaneously experiencing repeated successes.
As the first step in this direction, the academic societies/associations involved inradiation protection will collaborate in the future to exchange opinions with regulators,
3

The Atomic Energy Society of Japan has approximately 6,500 individual members and approximately 200 groups
that are supporting members. The Japan Radiological Society has approximately 10,000 individual members. The
member body of the Radiation Protection Academia with the highest number of members is the Japan Health Physics
Society, with approximately 800 members.

3

business operators, and even concerned international organizations in order to realize
these advisory opinions. Through these regulatory activities, research activities, andglobal cooperative activities, experts will solidify the roles to be played in improving
radiation protection measures in Japan.
The abovementioned bodies will continue to cooperate and study various issues suchas (i) the creation and collection of scientific knowledge on low-dose exposure (public
and occupational exposure) and emergency exposure, (ii) proposals for the formulationof protection systems and safety standards, and (iii) human resource development forradiation protection.
March 4, 2022
Japan Health Physics Society
President： Hiroko YOSHIDA
Japanese Association for Radiation Accident/Disaster Medicine
President: Makoto AKASHIJapanese Society of Radiation Safety Management
President: Satoru NAKASHIMAThe Japanese Radiation Research Society
President: Yoshiya SHIMADAThe Representative Council of the Japanese Umbrella-structured
Platform for Radiation Protection
Chair: Seiji KODAMA

42 Urgent advisory opinions for improving radiation protection measures in Japan(1) Measures for preventing accidents and adverse events from occurring at radiation
facilities and for handling the aftermath1) Background of the advisory opinions
Numerous incidents of mishandling of radiation and radioactive materials or accidents
at facilities that handle them have been reported in Japan and abroad. Among these, casesof unplanned exposure to radiation have also been reported. In May 2021, an accident
involving radiation exposure occurred during the inspection of a measuring device thatuses X-rays in Japan. To prevent such accidents and incidents from occurring and to deal
with them swiftly when they do occur, it is important to elucidate the causes of such
accidents and incidents both in Japan and abroad, identify problems with the way they
were handled, and share the results of such analyses widely.
Therefore, the Japanese Society of Radiation Safety Management (2021) conducted asurvey on radiation exposure accidents4 that occurred in countries other than Japan since2000 (International Nuclear and Radiological Event Scale [INES] level 2 and above). To
use the results of the survey as reference material for responses to accidents involving
radiation exposure in Japan, these accidents and incidents were classified into thefollowing three categories: I) radiation exposure due to the dispersal of unsealed
radioisotopes (RI) during work-related tasks, II) exposure of those engaged ininterventional radiology (IVR) to radiation doses exceeding dose limits for workers, andIII) underestimation of the dose and/or risk. The cases of errors resulting in the accidents
and exposure were analyzed and the lessons learned were extracted.
The Japanese Society of Radiation Safety Management (2021) also categorized
incidents that occurred in Japan since 2013 that were required to be reported by law.
Typical cases of the following four categories were analyzed to identify the causes of theincidents and problems: 1) missing unsealed RI, 2) missing “Approved Device with
Certification Label,” i.e., design-certified RI instrument, 3) leakage of RI due to damage,and 4) fire. A questionnaire survey was also conducted on the state of preparation ofmanuals on how to handle eight problems that were identified based on these incidents.
The results showed that approximately 20%–50% of the facilities in Japan had inadequate
manuals for dealing with similar problems (Japanese Society of Radiation Safety
Management, 2021).
4

The term “accident” refers to an event of level 4 and above according to the International Nuclear and Radiological
Event Scale (INES) that has a local impact such as the nuclear accident that occurred at Tokai-mura, Japan, in 1999.
However, in this document, the term “radiation exposure accident” refers to serious incident of INES 3 or higher thatis associated with unusual radiation exposure.

5

The Radiation Protection Academia verified the aforementioned report provided by theJapanese Society of Radiation Safety Management and determined that in order to preventthe occurrence of accidents involving radiation exposure and handle the aftermath in theevent that they do occur, the following are important and thus required: a) an independentand continuous review of radiation management methods and systems in place at
workplaces throughout Japan, and b) guaranteeing the effectiveness of these methods andsystems. Thus, it was decided that specific advisory opinions would be issued for
improving the radiation hazard prevention regulations and measures provided inemergency response manuals followed at workplaces. In addition, advisory opinions
would be made to the regulatory authority to enforce the Plan-Do-Check-Act (PDCA)
cycle throughout Japan to prevent recurrences of accidents that occurred in the past.
2) Current situation and problems
The current situation and problems related to accidents involving radiation exposure that
occurred in countries other than JapanThe Japanese Society of Radiation Safety Management extracted comprehensive data
pertaining to accidents that occurred since 2000 across countries other than Japan frompublic databases of the Landelijk Kernenergie Archief Foundation (LAKA) in the
Netherlands 5 . There were 473 cases of accidents/incidents related to radiation safety
management, graded as INES level 2 and above, reported between January 1, 2000 and
December 4, 2020. Many of them occurred in Europe and North America and were gradedas INES level 2.
In addition, there have been numerous reports of “unusual exposure” worldwide.
Among all accidents/incidents graded as INES level 2 or above that occurred in RI
facilities, the history, cause, and handling of the aftermath of 203 accidents/incidents weresurveyed. Based on the survey results, the Japanese Society of Radiation Safety
Management judged that the countermeasures for the following three cases might beinsufficient in many facilities in Japan and consequently further examined each domestic
countermeasure.
I．Measures to prevent the dispersion of unsealed RI during work
Accidents have occasionally occurred around the world in which workers have been
exposed to splashed RI solution due to unsafe operation, resulting in the contaminationof eyes and hands. In 2019, the following happened in a hospital in Switzerland. When aworker handling a radiopharmaceutical inserted a syringe into the mouth of a vial
containing Ga-68 solution to draw out a sample, droplets of the solution scattered and5 https://www.laka.org/docu/ines/

6contaminated the worker’s right eye (INES 2). The worker was not wearing protective
eyeglasses at the time, and although the worker followed measures such as eye washing,
the lens of the eye was judged to have been exposed to an equivalent dose of 27 mSv.
In 2017, a worker at an organization affiliated with the Australian Nuclear Scienceand Technology Organisation (ANSTO) accidentally dropped a vial of a solution
containing Mo-99. The solution dispersed and contaminated the worker’s hands.
Although the worker was wearing double gloves at the time, erythema and blisters
appeared on the worker’s hands. This indicates that the skin of the hands had been
exposed to a radiation dose equivalent to 10–20 Sv, meaning that the accident wasgraded as INES level 3, i.e., a serious incident. The Australian Radiation Protection and
Nuclear Safety Agency (ARPANSA) analyzed the causes behind the incident andpointed out i) the lack of organizational systems that would have allowed the learning ofeffective lessons from minor and near-miss incidents, ii) the insufficient recognition of
the risk of accidents among the workers, iii) the insufficient notations alerting theworkers about hazards during work-related tasks in workplace manuals and so on, andiv) the shortcomings in the training related to the safe performance of work-related tasks(ARPANSA, 2018). ARPANSA provided guidance to ANSTO regarding its
preparations to reduce radiation exposure and the training of its workers.
Similar accidents might occur in Japan as well; therefore, there is a need for workers
and workplaces to ensure that the measures shown below in Table 1 are fully implemented.
Table 1. Measures to prevent and reduce radiation exposuredue to the dispersion of unsealed RI during work-related tasks
TargetIndividual
workers
Business
operators

MeasureEnsure to wear protective eyeglasses and other protective gear
Prepare an organizational system that facilitates effective learningfrom near-miss accidents
Provide appropriate training to workers
Review workplaces and work procedures for reducing radiation riske.g., ・Adjust lead shields in drafts based on ergonomics
・Automate tasks that are currently performed manually by workers
・Reduce the concentration of RI in quality control samples

Establish systems that facilitate the early implementation of
decontamination and other emergency medical measures forradiation exposuree.g., ・Educate occupational health physicians and health nurses
・Conduct prior consultation with the organization implementing the
medical treatment for radiation exposure

7

II．Countermeasures for IVR physicians and others who are at high risk of being exposed
to doses exceeding the dose limits for workers
During IVR procedures, physicians are exposed to radiation from X-rays that scatterfrom patients. Thus, physicians who perform higher numbers of IVR procedures are likely
to be exposed to doses that exceed the dose limits for workers even if no particular
accidents have occurred.
There have been reports from outside Japan of medical practitioners being exposed tounusual doses of radiation during IVR procedures when classified using INES. An
incident that occurred in the UK in 2019 reported that the estimated equivalent doses tothe lens of the eye were 25.8 mSv.6 This dose was considered a realistic assumption basedon the worker’s recollection of their use of personal protective equipment (PPE).
In 2017 in a hospital in Saint-Denis, France, an incident occurred in which theequivalent dose of radiation that the hand of a radiologist was exposed to in one quarter
exceeded the annual limit (500 mSv). This occurred due to the fact that the physician’s
hand entered the irradiation field when performing IVR under computed tomography
fluoroscopy. The Autorité de sûreté nucléaire (ASN) in France surveyed this incident on
January 24, 2018 and reported the results of its assessment of the cause, measures to make
improvements, and assessment of INES on its website. 7 Prior to this incident, ASN
announced that they cooperated with related professional associations, industries, andregulatory authorities for improving training provided to operators when installing new
equipment.8
One frequent problem in medical settings in Japan is the failure to use personal
dosimeters or wear PPE (Kunugita, 2019; Hosono et al., 2021). In addition, it is estimatedthat many of the cases in which occupational radiation exposure exceeds the dose limits
are in the medical field.9 Most of them, however, are discovered only when the Labor
Standards Inspection Office conducts on-site inspections to investigate reports ofoccupational accidents and problems in work schedule management. Therefore, there arelimited number of cases in which exposure exceeding the dose limits is found as a
violation of the established laws and regulations.
6
In the European Union, member nations are required to legislate directives for Basic Safety Standards (BSS). In the
United Kingdom, an analysis of the effects of regulations for the development of laws was conducted in 2017. In
accordance with the demands in the EU directive, national regulations that reflect the equivalent dose limitation (100mSv/5 years) for the lenses of the eyes that are stipulated in Part 3 of the General Safety Requirements (GSR) of the
IAEA were to come into effect by February 6, 2018.
7
http://www.french-nuclear-safety.fr/Information/News-releases/A-radiologist-suffers-radiation-overexposure-ofthe-hands
8
https://www.asn.fr/espace-professionnels/activites-medicales/radiologie-et-scanographie/guides-de-lasn/recommandations-relatives-a-la-formation-a-l-utilisation-des-dispositifs-medicaux-emetteurs-de-rayonnementsionisants9
http://www.kosenkyo.jp/siryou/gyousyu31.PDF

8

Medical facilities that use radiation must comply with Article 44 of the Regulation on
Prevention of Ionizing Radiation Hazards. The MHLW has implemented the Subsidy
Project for the Renovation of Facilities to Reduce Radiation Exposure (MHLW, 2020)
and the Project to Support the Adoption of Occupational Safety and Health Management
Systems Related to the Management of Radiation Exposure (Nuclear Safety Technology
Center, 2020).
Thus, a wide range of support programs for workplaces have been implemented for
reducing the exposure of medical practitioners to radiation. Along with the continuationof these programs, it is hoped that workplaces will actively work toward this goal. In the
future, increased cooperation between regulators and experts to ensure strict adherence toradiation dose limits is necessary (Table 2).
Table 2．Measures for handling exposure to medical radiationthat is of particularly high likelihood to exceed dose limits
TargetImprovements, etc.

Individual
workers(medicalpractitioners)

Ensure that personal dosimeters and PPE are used

Business
operators

Conduct trainings on radiation protection for medical practitioners
handling radiation and RI
Ensure that protective measures and training information is updated
particularly when new devices are introduced

Regulators

Provide continuous assistance to workplaces for reducing medical
practitioners’ radiation exposure
Classify the INES level, report to the International Atomic Energy
Agency (IAEA), and release reports on the website regarding
incidents in accordance with Article 44 of the Regulation on
Prevention of Ionizing Radiation Hazards
Provide educational information to help prevent the recurrence ofaccidents/incidents throughout the nation

Experts

Establish a system in which academic societies/associations thathave expert opinions on the reported cases can cooperate toprovide assistance for problem solving based on the backgroundconditions of the workplace in question

9III．Dealing with underestimated doses and risk assessments
In many cases of radiation exposure accidents that occurred overseas, the exposure
dose and risks were initially underestimated. In addition, there have been cases in which
the doctors who conducted the medical examinations initially diagnosed the symptoms asallergies or insect bites, resulting in serious illnesses due to the lack of appropriate
treatments.
The event in which the hand of a worker was contaminated (mentioned in Section I
above; Australia, 2017) was also a case in which the exposed dose was underestimated.
At first, ANSTO estimated an equivalent dose to the hand of 0.85 Sv; however, as
erythema and blisters appeared on the worker’s hand > 2 weeks after the accident, theestimate was revised to between 10 and 20 Sv, which was considered more valid under
the circumstances (ARPANSA, 2018). ARPANSA identified the following problems andprovided guidance to ensure that they would not occur again: the scene of the radiation
exposure was not appropriately preserved, which made it impossible to collect data thatwere important to estimate the dose, and preparations for the dose assessment system,
among other things, were not appropriately handled.

Table 3. Roles of those who estimate the dose and risks
in the occurrence of radiation exposure accidents/incidents
TargetExperts (radiationdose assessment)Role
In cases of local exposure, the experts ascertain the dose anddistribution of the exposed part on the body as accurately as
possible and estimate the severity of damage (the degree oftissue reaction, such as inflammation or necrosis, that may
occur within several weeks to several months of exposure).

Experts (radiation
In some cases of local exposure, symptoms such as pain,
emergency medicine)erythema, and blisters do not appear immediately after
exposure. Thus, experts collect a wide range of information
regarding the patient’s positions, behaviors, and surrounding
circumstances, confirm the possibility of radiation exposure,and determine medical treatment based on this information.
Business operators(management)

Provides education to occupational health physicians regarding
the aspects of radiation exposure.

Business operators
When an event occurs, experts collect and preserve data usefulfor dose estimation (photos of the site of exposure, monitoring(e.g., radiation
protection supervisors
data, descriptions/records of behaviors, and available samples
and occupationalthat could be useful in retrospective dosimetry, such as
health physicians)
clothing, nail clippings, etc.) in as much detail as possible sothat the regulatory authorities and specialized organizations
are able to easily perform retrospective verification.

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In May 2021, a radiation exposure accident occurred in Japan during an inspection ofa measuring device that used X-rays. The workers were believed to have been exposed toa dose that vastly exceeded the established limits, but the final result of the estimated dose
was not disclosed. Instead, based on the lessons learned from the ANSTO incident, theroles of those involved in estimating doses and risks have been summarized as shown in
Table 3.
Current status of and problems related to accidents/incidents that occur at radiation
facilities in JapanThe Nuclear Regulation Authority publishes information on accidents and notificationsof measures to be taken in case of danger on its website, which correspond to legal
reporting events reported by business operators. Among 29 cases that occurred between
April 2013 and November 2020, the Japanese Society of Radiation Safety Management
categorized and surveyed four cases in detail and summarized the following four incidents
that could potentially occur at many radiation facilities. They identified eight problems(for details, see Japanese Society of Radiation Safety Management, 2021).
 Missing unsealed RI (occurred on December 21, 2017, corporation)
Summary: In the time between sterilization and proper disposal, animal carcasses instorage that had been administered C-14 were lost.
Problem i. Records on the use of the RI-administered animals were inadequate.
 Missing “Approved Device with Certification Label” (occurred on December 16, 2019,
corporation)
Summary: The location of a Cesium-137 gamma ray source for standardizing exposure
rate was unknown.
Problem ii: Records on the use of “Approved Device with Certification Label” were
inadequate.
 Leakage of RI due to damage (degradation over time) (occurred on October 29, 2013,
university)
Summary: The contamination spread from a sealed source of tritium in storage.
Problem iii: Insufficient awareness regarding the management of sealed radioactive
sources, including tritium and electroplated radiation sources; i.e., insufficientawareness regarding degradation over time, sealed radiation source equipment, and thecriteria for urgent reporting as well as insufficient details on the code of conduct interms of responding to unusual events.
 Fire (occurred on July 1, 2016, university hospital)

11

Problem iv: Inaccurate radiation rate estimates. In this case, measurements taken using
an ion chamber survey meter 10 indicated a radiation rate of 0.5 µSv/h, whichappeared to be 10 times the usual radiation rate; however, this measured value wasinsignificant and inaccurate.
Problem v: Incomplete records on the quantity and species of the radionuclides.
Problem vi: Delays in urgent reporting to the Nuclear Regulation Authority andreleasing information to neighboring residents. In this case, the quantity and speciesof the radionuclides could not be ascertained (cf. Problem v), which delayed the
public release of information.
Problem vii: Insufficient cooperation between multiple management departments. In
this case, the departments involved in building management, RI room management,
and radiation handling were different, which delayed information sharing andsystemic response to emergencies.
Problem viii: Insufficient response to the absence of personnel in charge of radiation
handling.
Sixteen individuals affiliated with private companies, medical, and educational
facilities that use radiation conducted a survey on emergency response manuals andregulations for the prevention of radiation damage at the facilities of their affiliation in
response to problems i through viii extracted from the abovementioned four incidents.
They assessed whether measures designed to prevent “preventable incidents,” i.e.,
incidents whose occurrence can be controlled in the course of normal management tasks,
were sufficient, and whether “nonpreventable incidents,” i.e., incidents whose occurrence
cannot be controlled in the course of normal management tasks, could be responded towithout any problems (Table 4).
As a result, it was found that the percentages of facilities that had established regulations
for the prevention of radiation and emergency response manuals describing responses todeal with some of the eight abovementioned problems were low. They lacked in thefollowing aspects (in the given order from the lowest): Problem i: completeness of therecords on animals administered radioactive substances, problem iii: appropriate
awareness and management of sealed radioactive sources, problem ii: completeness of
the records on the use of “Approved Device with Certification Label,” and problem vi:
appropriate release of information. It is hoped that facilities that do not have establishedregulations covering problems i through viii will check their regulations and make thenecessary improvements.
10

If an ion chamber survey meter is used assuming a high dose rate but the actual dose rate is low (<1μSv/h), an accurate value may not be obtained.

12

Table 4. State of preparing emergency response manuals and regulations for theprevention of radiation hazards at the respective facilities (responses from 16 facilities)
Assessment%*
perspective
i: Completeness of the records Do theMissing unsealed RI
on animals administered
50%
radioactivity
radioactive substances
hazard prevention
ii: Completeness of theregulations at
Missing “Approved
Preventable records on the use ofyour facility
Device with58%
“Approved Device withincidents
include sufficientCertification Label”
Certification Label”
response
instructions forLeakage of RI due toiii: Appropriate awarenessdamage (degradationand management of sealed the cases listed on 50%
the left?
over time)
radioactive sources
iv: Accurate measurements of73%
dose rate
Does thev: Records on the use of73%
emergency
nuclides and their quantities
response manual
Nonprevent vi: Appropriate release ofat your facility
60%
Fire
able
information
includeincidents
vii: Cooperation between
instructions for a 79%
management systems
smooth responseviii: Selecting a representative to fire?
for the responsible
73%
individuals*Percentage of facilities that have implemented the regulations
Incident

Category

Problems assessed3ሻ Advisory opinions
Analysis of the accidents/incidents involving radiation exposure that occurred outside
Japan since 2000 and events in Japan that were legally required to be reported since 2013
revealed the following: continuous and independent reviews of a facility's own systems
and management methods are more important in workplaces than tightening regulations
to prevent the occurrence of such accidents/incidents and respond to them in the eventthat they do occur. In particular, the following actions are recommended for establishingregulations and manuals that cover specific measures that should be implemented and for
confirming and improving the continued efficacy of these measures:
1．When devices that emit radiation are newly adopted or when “near-miss” incidents
occur, the effectiveness and validity of reviewing protective measures and the detailsof training should be examined on an organizational level and appropriate changes

13

should be made as soon as possible. These changes should then be included inregulations and manuals. When a worker makes a proposal to a workplace to make
improvements to their working sites and work processes for reducing the risk ofradiation exposure, the workplace should consider the effectiveness and validity ofsuch proposals as an organization and establish a system to facilitate theirimplementation.
2．To ensure a swift response to any incidents involving radiation exposure,
information/education should be provided to ensure that everyone at the workplace isaware of how important dose and risk assessments are. Further, manuals should be
prepared/updated and training must be held for collecting and storing samples as wellas various necessary data.
3．When creating a ledger for radioactive waste, checks should be continuously made to
determine any potential blind spots, such as whether appropriate records are being kept
for tracking all uses or whether records are being stored with regard to animals(carcasses) administered radioactive substances. When necessary, revisions should bemade to the regulations and manual. The regulations and manual should also include
entries ensuring that all users who create records are aware of all updates and revisions,and mechanisms to ensure the same must be established.
4．To prevent contamination due to the loss of integrity of sealed radiation sources, it isnecessary to periodically check for leakages or comply with the working life as
stipulated by the International Organization for Standardization (ISO).
5．The legal regulations for “Approved Device with Certification Label” are notparticularly strict. Hence, management practices tend to be insufficient. Therefore,
regular checks should be performed to ensure “Approved Device with Certification
Label” are stored in appropriate and dedicated containers and that those containers are
kept stored in locked safes.
6．In cases in which fire or other accidents occur, a system should be established thatallows the necessary data to be compiled, enables prompt reporting to the Nuclear
Regulation Authority, local governments, and related organizations, and facilitates
announcements to the residents of local communities.
To ensure that the aforementioned advisory opinions are followed, the rules andregulations will be reviewed and the implementation system will be improved asnecessary. Rules and systems will be periodically reviewed for improvement.
In cases in which radiation exposure following an accident/incident occurs at aradiation-related facility, it is essential for analysis and verification to be conducted by
the regulatory authority and a third-party organization. The regulatory authority will

14

particularly encourage the workplace to release information regarding theaccident/incident and ensure that analysis and verification is performed by a specializedorganization as well as that the PDCA cycle is carefully followed to provide feedback
about the results of the analysis and verification process to all employees. In cases inwhich an examination on reinforcing regulations is performed following theimplementation of the PDCA cycle after an accident/incident involving radiation, it isdesirable to ensure cooperation among various stakeholders, such as policy makers,
researchers, and those in the industry in order to ensure risk-based management for
optimizing resource distribution by introducing the graded approach of radiation
management into regulations recommended in IAEA GSR part 3 (IAEA, 2014) and GSG7 (IAEA, 2018). Alternatively, more reasonable regulations should be established basedon an analysis of the effects of the regulations.

15

(2) Measures for improving the estimation of radiation doses in cases of large-scale
radiation disasters
1) Background of the advisory opinions
In response to the Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power
Plant accident (Fukushima Nuclear Accident), the air radiation dose rates were measured
based on the release of radionuclides into the environment and the external exposure dose
was estimated using those measured values. These estimates were far beyond what wasin place at the time of the Chernobyl Nuclear Power Plant accident (the JapaneseRadiation Research Society, 2021). There was also greater awareness on the importanceof measuring and assessing individual doses. Prior to the Fukushima Nuclear Accident,
actual measurements using personal dosimeters for estimating external exposure anddirect measurements for estimating internal exposure had been thought to be necessary
mainly for validating the results of dose assessment using models. Hence, they had been
assumed to be conducted in a limited number of cases. However, from the perspective of
health management and risk communication, these measurements were performed on alarge number of residents during the Fukushima Nuclear Accident, although there were
no individuals who required medical treatment for acute injury or internal radiation
exposure.
Assessments of individual doses are more important in the early treatment of acuteradiation syndrome and internal radiation exposure or for the screening of subjects whoshould undergo detailed dosimetry. In such cases, biodosimetry is likely to be an effective
method of assessment. After the 9/11 terrorist attack in the United States in 2001, thedevelopment of a biodosimetry system for use in large-scale radiation disasters became a
global issue, and as a result, the United States began the development of a highthroughput system that would allow biodosimetry assessments to be performed on tensof thousands of people (Grace et al.、2011, Wang et al., 2020).
Using the lessons learned from past accidents and disasters (including terrorist attacks)that have occurred both in Japan and overseas, efforts to develop a variety of technologies
and improve systems related to dosimetry in Japan are currently in progress. However,efficient improvement and guarantees of effectiveness require cooperation between awide range of organizations and individuals, including national and local governments,
specialized organizations, experts/specialists, private industries, and medical facilities.
The AREMSCs, which were designated by the Nuclear Regulation Authority in 2015,
play important roles in establishing cooperation among various organizations andindividuals by acting as a liaison with academic organizations. Thus, the JapaneseRadiation Research Society conducted surveys both in Japan and overseas pertaining to16

dosimetry methods during large-scale radiation-related disasters, surveyed all AREMSCs,
and performed analyses of their current status (Japanese Radiation Research Society,2021).
The Radiation Protection Academia reviewed the results of the surveys conducted by
the Japanese Radiation Research Society. As a result, it was concluded that thebiodosimetry systems in place in Japan (e.g., dicentric chromosome frequency, prematurechromosome condensation [PCC], and cytokinesis-block micronucleus [CBMN] assay)
are insufficient to assess the doses of 100–1,000 individuals for the purpose of triaging
highly exposed patients or screening residents who may have been exposed to high doses;
thus, it was determined that measures should be implemented as soon as possible. Thus,
the Radiation Protection Academia decided that specific advisory opinions would be
provided to the national government, local governments, and AREMSCs.
2) Current situation and problems
According to a survey conducted by the Japanese Radiation Research Society (2021),
the state of preparedness of the AREMSCs for large-scale disasters is as follows:
Dose assessment methods for use during large-scale radiation-related disasters
AREMSCs are able to conduct physical dose assessments in Japan using methods
whose implementation is based on technical standards that conform to global standards.
These methods include dosimetry for measuring external exposure among exposed
persons using individual dosimeters and remotely gathering information (such as data ofenvironmental radiation monitoring/measurement, data of surface contamination surveys
using GM survey meters, and data of internal exposure examination performed by thyroid
dose monitoring using NaI survey meters and whole-body counters). Regarding thyroid
dose monitoring, which was a problem during the Fukushima Nuclear Accident, theNuclear Regulation Authority has taken the lead in designing a system that will link withthe development of dedicated measuring devices and is cooperating with relevantorganizations (Nuclear Regulation Authority, 2021). It plans to intensify these efforts inthe near future.
Regarding biodosimetry, there has been a history of discussion focused on handling up
to 10 patients considering high-dose exposure dosimetry. For this, the AREMSCs canconduct biodosimetry using the dicentric chromosome method (triage method). The
disadvantage of dosimetry using chromosome analysis is that it is time-consuming toculture blood cells (up to 48 hours) and analyze chromosome aberrations. Thus, both inJapan and overseas, efforts are being made to automate the process and develop highthroughput analysis methods using artificial intelligence and other technologies. In Japan,

17there is a tendency to focus on the development of methods that can be easily automatedand made high-throughput and can consequently be applied to dosimetry. The
cytokinesis-block micronucleus (CBMN) assay is a triage method that has been verified
globally and for which efforts toward automating its analysis are being made extremely
rapidly. Although the accuracy of the dose assessments made by CBMN is lower than thatof those made using the dicentric chromosome method, its merit is the fact that it ispossible to use it as a dosimetry method within several months. Considering that thechanges in blood cell count vary greatly among individuals, methods using blood cellcount are considered to be inferior in terms of their accuracy in dose estimation. However,
it is now possible to conduct analysis on smaller amounts of blood than previously, andeven if there is a shortage of physicians who are knowledgeable in the field of radiation
emergency medicine, it is now possible to perform screening of those who require dose
assessments in a short duration. As a result, more consideration can be paid to theusefulness of this technology as a triage method for between 100 and 1,000 individuals.
Looking back on the JCO accident11 and Fukushima Nuclear Accident, we see that
there is a need to standardize the chromosome imaging system and establish an image
sharing system to ensure that dose assessments during large-scale radiation-related
disasters can be performed through cooperation by all AREMSCs. However, at present,
the necessary equipment will be provided by each AREMSC. No specific plans beyond
this have been formulated.
Prior to the Fukushima Nuclear Accident in 2011, the National Institute of Radiological
Sciences (currently known as the National Institutes for Quantum Science andTechnology), a regional tertiary radiation emergency hospital, took the lead inestablishing the Chromosome Network, which is composed of domestic experts in thefield of chromosome analysis for biodosimetry. Currently, the AREMSCs arecollaborating in activities such as personnel training via workshops and the establishmentof dose effect standard curves. However, they do not fully function as a network that canperform dosimetry accurately and promptly during emergencies through cooperation withexperts from around the country. Thus, the cooperative system needs to be improved.
Requesting dose assessments during large-scale radiation-related disasters
The AREMSCs assume that they will be asked to perform dose assessments under thefollowing three circumstances: i) requests in parallel with medical procedures for saving
life, ii) requests after lifesaving procedures have been completed, and iii) cases in which11

Chromosome analysis was performed on 43 individuals, including JCO employees and firefighters who were
exposed to low doses of radiation during the JCO criticality accident in 1999 and residents who were found to have
low lymphocyte counts in their blood after this accident.

18

lifesaving procedures are unnecessary but dose assessments are necessary.
In physical dosimetry, it is possible to provide dose assessment data for any of theabovementioned circumstances: i) through iii). However, the time taken until the data isprovided and the accuracy of the data is largely dependent upon the information available
at the time when dosimetry is requested.
On the other hand, requests for and acceptance of biodosimetry are dependent upon thedetermination of the exposure status of patients performed by physicians in charge ofmaking data-related decisions on site and the ability to process the analyses performed by
the laboratories of the AREMSCs. Nevertheless, at the moment, there is no system inplace for specific requests and acceptance, such as who makes the request (the examining
physician, a medical facility, or a workplace) and who receives it (laboratories, the
AREMSCs, or other specialized organizations). Hence, all laboratories are independently
accepting requests.
All AREMSCs individually examine requests for dose assessments, methods for thedelivery of samples, and the format for dose assessment information. If multiple
laboratories are to cooperate in analyzing and reporting the results obtained from samples
sent from multiple patients, there is a need to establish common guidelines for all tofollow regarding methods and formats. In addition, assessments of internal doses via
analysis of human excrement or other samples, i.e., bioassays, involve the same problem;
however, currently, as several days are required to quantify radioactivity using bioassays
after the samples are obtained and chemical separation is performed, such assessments
are not believed to be useful in triage and screening.
Involvement of dosimetry in nuclear disaster prevention drills
Each year, nuclear power-related facilities and nearly all the 24 prefectures in Japan
within a 30 km radius (UPZ) of these facilities conduct nuclear accident prevention drills,
assuming an accident with the same amount of RI release as the Fukushima Nuclear
Accident. This drill includes i) training on emergency reporting for pertinent individuals,ii) training on evacuating residents within the UPZ, iii) on-site medical training for thetreatment of multiple people suffering from contamination illness, and iv) other training
such as environment monitoring and assembly training. However, this drill does notinclude little related to performing individual dose assessments.
To prepare systems that are designed to effectively assess radiation doses when largescale nuclear disasters occur at Nuclear Emergency Core Hospitals and AREMSCs that
accept patients exposed to radiation, there is a need to conduct training including
dosimetry such as thyroid monitoring and dose assessments for local residents during
future nuclear accident prevention drills. These initiatives would allow the establishment19

of common guidelines for issues such as procedures for requesting dose assessments,
methods of delivering samples, and dose assessment report formats, as mentioned above.
3) Advisory opinions
As indicated above, the Fukushima Nuclear Accident was an opportunity to review theimportance of assessing the individual dose. There appeared to be no major technicalproblems involved in monitoring and triaging between 100 and 1,000 patients using
physical dosimetry for external exposure. Regarding chromosome analysis forbiodosimetry, it would be desirable for government agencies involved in the preventionof nuclear disasters to initially take the lead in the field of nuclear accident prevention todetermine the categories of victims and workers who would be subjected to chromosome
analysis during large-scale nuclear disasters, identify the speed and scale at which theseshould be performed, and improve the functions of the AREMSCs. In particular, in
addition to the technical aspects of dosimetry methods, there is a need to strategically
prepare soft and hard infrastructures for the purpose of collaboration among AREMSCs
and information sharing and collaboration between the disaster site, medical facilities,
and the analysis laboratories of AREMSCs.
Thus, the Nuclear Protection Academia provides the advisory opinions listed below forbiodosimetry functions at AREMSCs and requests the cooperation of experts in all related
fields in following these opinions.
1．The AREMSCs should strengthen existing systems to allow cooperation between
different centers in the event that biodosimetry is to be performed on multiple injured
individuals during large-scale disasters.
・Standardize the dicentric chromosome analysis techniques through efforts such as theintroduction of new equipment, personnel exchange, and technical training.
・Prepare a system for sharing images that allow remote analysis
・Determine the number of specimens that can be received by each laboratory andexamine the division of roles (division of labor)・ Establish common guidelines for tasks, such as requesting dose assessments,
delivering samples, and formats used to report the results of dose assessment
2. If there is a shortage of equipment or personnel when implementing theabovementioned cooperation system in AREMSCs, human resource development andexchange should be enhanced. Other measures, such as entering into contracts withorganizations other than ARMSCs and establishing processes for acceptingorganizational support in emergency situations (including cooperation with private
industries), should also be implemented.

20

3．As dicentric chromosome analysis, a method that is able to provide an accurate dose
assessment, requires both time and labor, AREMSCs should continually engage indiscussions with each other regarding methods that are appropriate for triaging large
numbers of victims. When gathering information regarding standardized methods,
expert/specialist networks both in Japan and overseas12 should be consulted.
4．It is necessary to be prepared to perform biodosimetry for various types of exposures,such as using the PCC method for exposures exceeding 5 Gy and using techniques todetect chromosomal translocations and CBMN for chronic exposures.
5. Networks that allow experts/specialists in chromosome analysis throughout Japan tocooperate in performing timely and accurate dose assessments during emergencies
should be re-established.
Many experts/specialists in dosimetry are assigned under the assumption that they will
work in laboratories. Thus, they are not considered personnel who can handle a triage (i.e.,
screening of patients who require dose assessments) of victims on site during disasters.
Therefore, there is a need to examine the cooperation among on-site responders andexperts/specialists in dosimetry who work in laboratories. The Radiation Protection
Academia recommends that training in performing dose assessments is introduced innuclear disaster prevention training programs that are implemented by national and local
governments.
Additionally, as human-derived specimens are used in biodosimetry, there is a need toestablish agreements to exchange personal information, obtain consent, and provide andshare blood, specimens, and microscopic images when exchanging information between
institutions and requesting testing. It is desirable that these agreements are conductedbased on discussions held between each AREMSC and the local governments regarding
support with biodosimetry provided by the AREMSCs. As AREMSCs are designatedbased on the Nuclear Emergency Response Guidelines, they will not be burdened withtasks requiring them to respond to incidents other than nuclear disasters, such as terrorist
attacks, other types of accidents, or natural disasters. With regard to a framework for
performing dose assessments during emergencies other than nuclear disasters, a decision
on response guidelines for the national and local governments is still pending. However,as the number of facilities that are able to systematically perform dose assessments is
12

The International Biodosimetry Network (BioDoseNet) operated by WHO is currently conducting the 3rd
BioDoseNet Survey of the systems and state of preparation of biodosimetry laboratories worldwide. The results of thissurvey are scheduled to be announced at EPR-BioDose 2022 (Okayama University of Science). The current status oflaboratories and experts in Japan is expected to be among the data announced.

21

limited, in any case of radiation-related accident, there is a high probability thatorganizations designated as AREMSCs will have to perform this task. Therefore, in
addition to clarifying the roles of AREMSCs during emergencies other than nuclear
disasters, there is also a need for regional or local governments to establish agreementswith AREMSCs, as necessary, if responses are to be undertaken with different chains ofcommand and radiation medicine systems than those at the location of the nuclear disaster.

22

3 Mid- and long-term advisory opinions for globalizing the Japanese radiation protection
measures in Japan（1）Measures for the adoption of new concepts regarding effective dose and operational
quantity in Japan
1) Background of the advisory opinions
It is needless to say that dose estimation is important for radiation protection andestablishment of radiation regulations. Nevertheless, the unit system of radiation doseused in radiation protection is not always easy to understand. In particular, when the
media reports on accidents/incidents involving radiation exposure, academic
communities must be aware of and provide information regarding the concept behindabsorbed and effective doses used in emergencies and the relationship between the“Sievert” (Sv) and cancer risk so as to avoid misunderstandings among the public. As
indicated above in the introduction section, in the new recommendations to be publishedby ICRP, the adoption of changes in effective dose and protection quantities proposed by
ICRU in 2020 will be mentioned (Clement et al., 2021). These changes are expected tohave a major impact on the radiation regulations worldwide.
Thus, as part of the fiscal year 2020 Umbrella Project commissioned by the Nuclear
Regulatory Authority, a WG on the effective doses and operational quantities of radiation(Dose WG) was established under the direct control of the Representatives’ Council of
the Japanese Umbrella-structured Platform for Radiation Protection. The Dose WG was
entrusted with activities to promote the accurate understanding of radiation doses andexamine proposals for linking specific future actions. Through planning and holding
webinars related to the effective dose and operational quantities (total of five in a series),
the Dose WG gathered a variety of information on several topics, including the history of
the concept of doses, risk assessment, overseas trends, biological effects, andcommunications, and shared this information within the Radiation Protection Academia.
The information was summarized into the three below-mentioned points to conduct ananalysis of the current status:(1) Necessary investigations and preparations when a new concept of operational
quantities is introduced in Japan(2) Responses to problems faced by sites that use the effective dose(3) Limitations of risk assessments using the effective dose
The proposals regarding (1) are consolidated for regulatory authorities, facilities
involved in R&D, experts, and academic associations as well as those who perform
radiation management; those regarding (2) are consolidated for academic
societies/associations related to radiation protection and radiation-related ministries; and23

those regarding (3) are consolidated for academic societies/associations related toradiation medicine and those performing medical procedures in medical care settings(Dose WG, 2022). The Representatives Council checks the validity of the contents of
their proposals and the status of the analyses performed by the Dose WG and summarizes
and lists the key points.
2) Current situation and problems
In Japan, the ICRP recommendations released in 2007 and the recommendation tolower the lens dose limits have already been introduced into domestic laws. However,workplaces have been preoccupied with following measures; thus, they are notcompletely accustomed to the new rules. However, worldwide, the next-phase ICRP
recommendations are believed to include the adoption of changes to the effective doseand protection quantities (ICRU, 2020; ICRP, 2020).
After ICRP released its recommendations in 2007, it established Task Group 79 in 2010,
which started working on solutions to the problems surrounding the issue of doses. Oneof the problems is that the operational quantities currently in use show significant
overestimates of the protection quantities in cases of high-energy photons. Recently, inthe fields of medicine, research, and commercial aviation, the types of radiation andenergy range requiring protection have increased and these problems have become
apparent. A summary of the new concepts jointly determined by ICRU and ICRP ispresented below:i) Change the definition of the effective dose of external exposure
The operational quantities for the estimation of the effective dose will be the measured
quantities defined by reference human phantoms replaced with conventional ICRU
spheres using the conversion coefficient for fluence that does not underestimate theprotection quantities. These changes require the use of a human body phantom for both
effective dose and operational quantity as well as some changes to be made to theequipment and methods used.
ii) Change the dose used to assess tissue reaction
The absorbed dose, rather than the equivalent dose, will be used to prevent tissue
reactions, such as cataracts and acute skin damage. This means that the equivalent doseis an intermediate quantity in the effective dose calculation and will no longer bemeaningful as a protection quantity. In addition, information about the absorbed doseand relative biological effectiveness (RBE) for tissue reactions, which depend on thetype of radiation, are required.

24

International guidelines regarding these new concepts of doses and uses are being
drawn up and will be standardized in the future by the IAEA and ISO.
As opposed to when the protection quantity unit and tissue weighting factor werepreviously changed, it is not appropriate that the introduction of new operational
quantities is informed to only those involved in radiation protection and management orthat only technical problems associated with this introduction are dealt. Therefore, there
is a need to investigate the effect of changes in operational and protection quantities onsociety as a whole and respond to such changes in ways that minimize confusion.
The response to and problems associated with changes to the protection and operational
quantities
The effects of changing the definition of the operational quantities and unit of the dose
limit for the prevention of tissue reactions from the equivalent dose to the absorbed dose
have already engendered much discussion. For instance, regarding measuring devices andcalibration procedures, there seems to be a need to increase the detector response tophotons of ≥3 MeV or neutrons of ≥50 MeV and develop detectors that can measure thelens dose more accurately.
The Nuclear Safety Research Association (2020) conducted a survey on the effect of
introducing changes in the concept of operational quantities into domestic laws andregulations on the measurements and assessments of operational quantities using aradiation measurement device. The survey it made clear that such changes will result inalterations in the conversion factor for the radiation measurement device as well as the
response to standardization by the ISO, the International Electrotechnical Commission(IEC), and the Japanese Industrial Standards (JIS). They will also lead to changes in theterms and symbols used in manuals. Their report summarized that it will be difficult forcalibration laboratories, manufacturers of radiation measuring instruments, and radiation
management operators to deal with the expected changes in the concept of operational
quantities in the future by themselves and that it will be necessary to work in cooperation
with each other.
Regarding individual doses, the design of personal dosimeters, the calculation of doses
by personal dosimeter service organizations, and the management of radiation exposureby users will all have an impact. Among these changes, the change from equivalent dose(Sv) to absorbed dose (Gy) for the dose limit for the eye lens and skin will require
additional calculations that take into account the RBE of neutrons in the neutron–photon
mixed field.
There are multiple tissues and organs that are subject to tissue reactions, and the
responses vary widely, e.g., in the case of the skin, early transient erythema, main25

erythema reaction, temporary epilation, and permanent epilation may occur, anddepending on the type of radiation and amount of energy, the biological effects may differ(ICRP, 2012). Thus, examination of RBE, quality factor, and radiation weighting factor
are global issues, and Japan’s contribution, which is at the global forefront of particle
beam therapy, is greatly anticipated.
Effective doses, their use, and problems associated with them by age group
Effective dose for radiation protection is based on the average dose to human organs
and tissues (ICRP, 2007). Calculations of the equivalent dose to organs and tissues use
adult male and female reference computational phantoms. Regarding external radiation
exposure, in recent years, the ICRP has set irradiation conditions for whole-body radiation
exposure and assessed the dose conversion coefficient. In ICRP publication 144,
phantoms and the effective dose (rate) coefficients were provided based on age group(newborn, 1 year of age, 5 years of age, 10 years of age, 15 years of age, and adult; ICRP,
2020). It also provided dose coefficients based on age group for types of internal radiation
exposure, such as due to the administration of radiopharmaceuticals. Thus, improvements
are in the process of being made to the age-specific effective doses, but these will likely
be ready for inclusion in the next recommendations.
In addition, the ways to use effective dose are also being reconsidered. For example,
as nearly all medical radiation exposure is local exposure, the use of effective dose tends
to be seen as inappropriate, but its use for comparing modalities or imaging technologies
and for risk communication is approved (ICRP, 2021). Effective dose will generally be
used at doses below 100 mSv, but its use at acute doses in the range up to approximately
1 Sv is reasonable.
Effective dose is the unit that is most widespread in society as it is an approximate
indicator of the potential health risks. However, there are a large number of rules
regarding its calculation and use. Documents related to radiation created by radiationrelated government agencies for lay people include explanations of effective dose and theunit of Sv.13 However, as they are misused from time to time, it is important for the
stakeholders to have a common view of the meaning of effective dose and its intended
uses. In particular, it is necessary to prepare for the dissemination of information on
13

Examples of documents that are currently being created and revised by government authorities and agencies are as
follows: Cabinet Office, Consumer Affairs Agency, Reconstruction Agency, Ministry of Foreign Affairs, Ministry of
Education, Science, Sports, Culture and Technology, Ministry of Health, Labour and Welfare, Ministry of Agriculture,
Forestry and Fisheries, Ministry of Economy, Trade and Industry, Ministry of the Environment, Nuclear Regulation
Authority: “Basic Information on the Risks of Radiation.” Ministry of Education, Science, Sports, Culture andTechnology: “Supplementary Reader on Radiation.” Ministry of the Environment: “BOOKLET to Provide Basic
Information Regarding Health Effects of Radiation.” Consumer Affairs Agency: “Food & Radiation: Q&A.”

26

effective doses by age group as it is likely to attract public attention in the process of
being improved and completed.
Explanation of the risks of and problems associated with the use of effective dose
As for the relationship between effective dose and risk, the ICRP 2007
recommendation states that the nominal risk coefficient after detriment adjustment isabout 5% per Sv. This implies that exposure to 100 mSv of radiation is assessed asincreasing the risk of death due to cancer in the cohort by 0.5%. The calculation of thisdetriment-adjusted nominal risk coefficient is based on whole-body exposure to low-dose(rate) radiation because dose and dose-rate effectiveness factor (DDREF) and tissue
weighting factor (wT) are used. Therefore, this risk factor was used for risk
communication with regard to the Fukushima Nuclear Accident, and it is widely used inJapan.
Previously, DDREF, wT, and radiation weighting factor (wR) used the same values
regardless of sex or age group. However, more detailed phantoms such as those for fetuses
and pregnant women became available, leading to the development of extremely detailed
absorbed dose assessment based on age group. Hence, improvements in effective dose by
age group are underway, as mentioned above.
On the other hand, looking at the situation in Japan, more than 10 years have passed
since the Fukushima Nuclear Accident. Eventually, when the latency period for cancer
has passed, the causal relationship between individual exposure dose and the induction ofcancer will become an issue. Therefore, there is growing need to explain the contributionof radiation exposure from the Fukushima Nuclear Accident on cancer induction. In
addition to risk communication during the response to an emergency, there is also a needto provide an explanation of the risk consistent with a variety of radiation exposures in
day-to-day radiation care settings.
The ICRP released Publication 147 to elucidate the use of dose in relation to healthrisks (ICRP, 2021). Effective dose is used in medicine for a variety of reasons, including
comparing doses from different medical procedures, informing judgments on justification,and establishing constraints for carers and volunteers in medical research. When
explaining the risk of medical radiation exposure to patients and clinicians, there is acontinued need to be careful to avoid creating misunderstandings such as that “theeffective dose can be substitute for specific risk analysis for individuals.” Thus, the ICRP
(2021) recommends the use of general terms such as “can be ignored,” “minimum,” and“extremely low” and phrases such as “the radiation risk to those aged between 0 and 9
years is approximately double that of those in their thirties.”
An effective dose of up to 1 Sv can be used exceptionally in cases of radiation

27

emergencies. However, in the case of the plutonium internal radiation exposure accident
that took place in Japan in 2017, the committed effective dose was reported to be 12 Sv.14
It was confused with “the exposure of the whole body to 12 Sv of radiation” and led tothe misunderstanding that it was similar to that in the case of the JCO criticality accident
that occurred in 1999.
As effective dose values tend to be perceived as directly linked to risk in medical
settings, those involved in medical care need to understand the meaning and limitationsof effective dose and provide appropriate explanations regarding this information.
3) Advisory opinions
As mentioned above, because the changes in the protection and operational quantities
are so significant internationally, it is important to have a system for understanding
international trends and discussing the status of domestic studies in a comprehensive andlong-term manner. The Radiation Protection Academia proposes that regulatory
authorities, R&D organizations, experts/specialists, and those involved in radiation
management consider how to deal with issues such as how to best perform the calibrationof measuring devices, confirm the validity of measurement methods, and standardize
calibration (ISO, IEC, and JIS); how to handle situations in which validity cannot be
guaranteed; and the effects of changes made to dose records. When doing this, it isdesirable to promote communication between manufacturers, those involved in service
tasks and regulations, and stakeholders so that they understand the background to any
changes made and sufficiently discuss about the changes made. In addition, relevant
academic societies/associations and those involved in radiation management are expected
to collect and sort out the data on RBE and ascertain the effects on the various tasks they
perform, whereas R&D organizations and experts are expected to provide information onscientific data regarding RBE and the predicted impact on tasks they perform tointernational organizations.
In addition, in the view of the social background, such as the increase in the use ofradiation in medicine and social concern about radiation risks, it is necessary to correctly
understand the use of effective doses and effective doses by age group, not only for those
involved in radiation protection but also the general public. Therefore, it is recommended
that academic societies/associations related to radiation protection work together toprepare a report that structurally organizes information that can act as the basis ofproviding such information to promote the understanding of such concepts. This can be
14

The Japan Atomic Energy Agency (JAEA) published “Contamination at Plutonium Fuel Research Facility of Oarai
Research and Development Center (follow-up report)” (June 9) and stated in the table of measurement results of “Nasal
smear and lung monitor measurements” that “Inhalation of 2.2 × 104 Bq of Pu-239 is equivalent to a committed
effective dose of approximately 12 Sv.”

28

prepared in the form a glossary on the aspects of internal and external exposure, radiation
management, and medical exposure, making it possible to establish a common
understanding of the meaning of effective doses as defined by the ICRP and theimplications of the use of effective doses by age group. To efficiently disseminate thiscommon understanding within the Japanese society, it is proposed that radiation-related
ministries reflect the various contents of the report prepared by the academic
societies/associations in their own publications for the general public. When academic
societies/associations prepare their reports and when government agencies update their
publications, it is desirable for them to cooperate in conducting academic conferences,
symposia, seminars, and workshops and solicit opinions online via websites so as to revise
together with the involved stakeholders and disseminate information throughout society.
Furthermore, there are cases in which effective dose is used to explain the health risks
while justifying the application of radiation diagnoses. Therefore, those involved in
medical care should have a sufficient understanding of the meaning of effective dose andits limitations in medical use. As a result, the Radiation Protection Academia proposesthat the academic societies related to radiology sort out the issues concerning the uses ofeffective dose in medical care settings and the meaning of the risks, inform those involved
in medical care, and prepare standard publications that provide patients with appropriate
explanations of these issues in cooperation with the academic societies/associations
related to radiation protection. In addition, it is expected that academic societies related
to radiology will assume the task to continuously update the methods of explanation topatients in accordance with feedback from practitioners in the medical field and advancesin diagnostic radiology technology.

29

4 Conclusion
The basis for ensuring the safe and secure use of radiation is the prevention of
unplanned radiation exposure. However, as it is impossible to completely eliminate
human errors, and incidents such as the dispersion of unsealed RI during work-related
tasks and exposure of operators to radiation during IVR tasks will continue to occur.
Workers should wear dosimeters and PPEs during work to take appropriate measures tominimize exposure when such events occur. It is also important for business operators toreview work processes, training contents, manuals, etc., when introducing new irradiationequipment or occurrences of near-miss cases, to implement the PDCA cycle, and toconstantly share information so that the causes of accidents can be investigated and theireffects can be verified. As for the incidents of contamination of sealed sources of tritiumthat occurred in Japan in 2013 and the loss of animal carcasses administered RI in 2017,
the survey found that half of the radiation facilities in Japan still do not include theresponse to such incidents in their manuals for radiation hazard prevention regulations or
emergency response. Therefore, the Radiation Protection Academia makes specificadvices to business operators regarding accident prevention and the swift handling of theaftermath of accidents. In addition, regulatory authorities are expected to implement a
PDCA that will promote the disclosure of information related to accidents and incidents
by workplaces, thereby promoting their analysis and verification by specializedorganizations, which will eventually provide feedback on the results of these efforts to all
related workplaces.
In the events of a large-scale radiation/nuclear accident and nuclear terrorism, there isa possibility that large numbers of people will be exposed to radiation. The Fukushima
Nuclear Accident provided an opportunity to reaffirm the importance of individual
radiation dose assessment. Consequently, in the field of physical dosimetry, attempts tosolve problems associated with the monitoring and triage of 100–1,000 patients are
ongoing. As for biodosimetry, several methods are available, each with its own strengths
and weaknesses. Thus, there is a need for specialized organizations to cooperate inresolving the weaknesses of the dicentric chromosome method while simultaneously
developing dosimetry methods that are suitable for the triage of large numbers of patients.
Therefore, the Radiation Protection Academia provides specific advices to AREMSCs on
the development of infrastructure for cooperation among them and requests experts andspecialist to cooperate. It has also proposed that the national and local governments,
which plan and implement nuclear power disaster prevention drills, should incorporate
training in dosimetry into their drills.

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Changes in the effective dose and operational quantities and the adoption of thesechanges in Japan are issues that will continue to be discussed for several years. Although
not urgently relevant to the two abovementioned recommendations, the Radiation
Protection Academia provides advisory opinions that those involved in R&D andmanagement of radiation cooperate with manufacturers and service organizations instandardizing radiation dose meters and calibration methods. In addition, in Japan, where
social interest in radiation has been high since the Fukushima Nuclear Accident, the useof effective doses, especially the appropriate explanation of health risks using effective
doses, is an ongoing issue. To ensure that effective doses by age group, which are still in
the process of being improved, are not misunderstood as risk indicators for specificindividuals, academic societies/associations involved in radiation protection andradiology should cooperate in establishing a common understanding of the meaning andlimitations of effective doses. It is also hoped that this information will be sharedthroughout the society with the cooperation of radiation-related ministries.

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5 References
1．Introduction
Ministry of Health, Labour and Welfare, Chief of Occupational Health Division, Safety
and Health Department, Labor Standards Bureau: Improving efforts to prevent
exposure during the inspection of X-ray devices, June 1, 2021
https://www.mhlw.go.jp/content/000787485.pdf
Clement, C., Rühm, W., Harrison, J. et al: Keeping the ICRP Recommendations Fit for
Purpose, J. Radiol. Prot. doi: 10.1088/1361-6498/ac1611, 2021
International Commission on Radiation Units & Measurements (ICRU): Operational
quantities for external radiation exposure. J. ICRU. 20(1), 2020
2．Emergency recommendations for improving radiation protection measures in Japan
Japanese Society of Radiation Safety Management: Survey of the progress of radiation
protection measures and recommendations, created February 2021; revised September
2021 http://www.umbrella-rp.jp/R2JRSM_report.pdf
Australian Radiation Protection and Nuclear Safety Agency (ARPANSA): Report toParliament – Radiation exposure of a worker at ANSTO Health, Lucas Heights on 22
August 2017, Tabled in Parliament 26 February 2018https://www.arpansa.gov.au/about-us/corporate-publications/reportsparliament/report-parliament-radiation-exposure-worker-ansto
Kunugita, N.: Fact-finding survey of workers who are highly likely to receive radiation
exposure to the lenses of the eyes even when sufficient protective gear is used(material used in the 5th Investigatory Committee on Re-evaluating the Limits to
Radiation Exposure of the Lenses of the Eyes, No. 2), June 20, 2019https://www.mhlw.go.jp/content/11201000/000519683.pdf
Hosono, M. et al.：Survey study of the current status of radiation exposure in the
medical radiology field and efforts to reduce radiation exposure (Occupational
Accident and Disease Clinical Research Project Financial Assistance Study, Material
for use by the Radiation Protection Research Group Joint Liaison Group), May 31,
2021
http://www.radher.jp/J-RIME/report/rousaijigyou_siryou_20210531.pdf
Ministry of Health, Labour and Welfare, Labour Standards Bureau, Safety and Health
Department: Recruiting organizations (executive offices) under the auspices ofFinancial Assistance for the Renovation of Facilities to Reduced Radiation Exposure
Doses (Indirect Financial Assistance) [recruitment outline], February 2020
https://www.mhlw.go.jp/content/11300000/000599446.pdf
Nuclear Safety Technology Center: 2020 Description of assistance in adopting systems
for the management of radiation exposure, outsourced project of the MHLW,
recruitment outline, July 2020
https://ms.nustec.org/wp-content/uploads/2020/07/boshuyoukou.pdf
International Atomic Energy Agency (IAEA): Radiation Protection and Safety ofRadiation Sources: International Basic Safety Standards No. GSR Part 3, 2014
International Atomic Energy Agency (IAEA): Occupational Radiation Protection, IAEA
Safety Standards Series No. GSG-7, 2018
The Japanese Radiation Research Society: Survey and recommendations for theadvancement of radiation protection measures in the field of radiation effects andhiring and training personnel in the field of radiation protection, created February322021/revised September 2021 http://www.umbrella-rp.jp/R2JRR_report.pdf
Grace, M. B., Cliffer, K. D., Moyer, B. R. et al: The U.S. government's medical
countermeasure portfolio management for nuclear and radiological emergencies:
Synergy from interagency cooperation. Health. Phys. 101(3), 238-247, 2011
Wang, Q., Lee, Y., Shuryak, I. et al: Development of the FAST-DOSE assay system forhigh-throughput biodosimetry and radiation triage. Scientific Reports 10, 12716, 2020.
Nuclear Regulation Authority: Report from the “Team investigating thyroid radiation
exposure monitoring during emergencies” (Fiscal 2021 34th Nuclear Regulation
Committee Report No. 2), September 22, 2021
https://www.nsr.go.jp/data/000365637.pdf
3．Mid- and long-term recommendations for globalizing the Japanese radiation protection
measures
Clement, C., Rühm, W., Harrison, J. et al: Keeping the ICRP Recommendations Fit for
Purpose, J. Radiol. Prot. doi: 10.1088/1361-6498/ac1611, 2021
Effective Dose and Practical Dose WG: Summary and Recommendations for the
Accurate Understanding of Dose as it relates to Radiation, March 2022
International Commission on Radiation Units & Measurements (ICRU): Operational
Quantities for External Radiation Exposure, Journal of the ICRU, 20(1), 2020
International Commission on Radiological Protection (ICRP): Dose coefficients forexternal exposures to environmental sources. ICRP Publication 144. Ann. ICRP.
49(2), 2020
Nuclear Safety Research Association: Fiscal 2019 Radiation Measures Commissioned
Project Report, Fact-Finding Survey on Measuring Practical Doses related to
Radiation Management, March 2020 https://www.nsr.go.jp/data/000319356.pdf
International Commission on Radiological Protection (ICRP): ICRP Statement on
Tissue Reactions / Early and Late Effects of Radiation in Normal Tissues and Organs– Threshold Doses for Tissue Reactions in a Radiation Protection Context. ICRP
Publication 118. Ann. ICRP 41(1/2), 2012
International Commission on Radiological Protection: The 2007 Recommendations of
the International Commission on Radiological Protection. ICRP Publication 103.
Ann. ICRP 37 (2-4), 2007
International Commission on Radiological Protection (ICRP): Use of dose quantities inradiological protection. ICRP Publication 147. Ann. ICRP 50(1), 2021

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6 Acknowledgments
The Radiation Protection Academia express their appreciation to the following
individuals for their cooperation and advice:

Keiichi AKAHANE
Masaaki AKAHANE
Makoto AKASHI
Satoshi FURUSAWA
Shoji FUTATSUGAWA
Kanya HAMASAKI
Arifumi HASEGAWA
Makoto HASHIMOTO
Shogo HIGAKI
Shigekazu HIRAO
Nobuyuki HIROHASHI
Tomoko HIROI
Tomonori HOKAMA
Masahiro HOSODA
Yoshio HOSOI
Takeshi IIMOTO
Hiroyuki IIZUKASatoshi IWAI
Kazuki IWAOKA
Michiaki KAI
Reiko KANDA
Atsushi KASAI
Shinsuke KATO
Junya KOBAYASHI
Seiji KODAMA
Munehiko KOWATARI

Akira KUDO
Yuji KUGE
Osamu KURIHARA
Tadahiro KUROSAWA
Kazuhiko MAEKAWA
Naoki MATSUDA
Taichi MIURA
Tomisato MIURA
Takumaro MOMOSE
Kento NAGATA
Satoru NAKASHIMA
Keiji ODA
Yasuharu OKAMURA
Yasutaka OMORI
Makiko ORITA
Kimiaki SAITO
Kazuo SAKAI
Tetsuya SANADA
Michiya SASAKI
Takuya SAZE
Yoshiya SHIMADA
Yoichi SHIMIZU
Nobuyuki SUGIURA
Yumiko SUTOGen SUZUKI
Chie TAKADA

34

Akihisa TAKAHASHI
Masaomi TAKAHASHI
Akira TAKEDA
Kotaro TANI
Hideo TATSUZAKI
Hiroaki TERATO
Shinji TOKONAMI
Takako TOMINAGA
Takakiyo TSUJIGUCHI
Yuichi TSUNOYAMA
Toshiyuki UMATAWANG Bing
Takahiro YAMADA
Yutaka YAMADA
Ichiro YAMAGUCHI
Naoyuki YAMAMOTO
Hiroshi YASUDA
Sumi YOKOYAMA
Shunsuke YONAI
Hidenori YONEHARA
Hiroko YOSHIDA
Mitsuaki YOSHIDA
Yukari YOSHIDA
Hironori YOSHINO
Michio YOSHIZAWA