RADIATION RE-EDUCATION MATERIALS THE UNIV. OF TOKYO DOC No. 38 (2020)1. Registration and maintenance of radiation workers 12. Radiation effects on people and the environment and radiological protection 33. Management of Small Amount of Nuclear Materials and Their Wastes (Case of Kyoto Univ.) 64. Safety usage of X-ray irradiator “Category C” in UTokyo 8

Edited by Division for Environment, Health and Safety

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1. Overview The Division for Environment, Health and Safety has constructed a Radiation Workers

Management System (namely, UTRadMS) to mainly manage radiation workers. This radiation system is not only for a department and/or graduate school radiation control offi ce but also for radiation workers themselves. In this chapter, we show some features of this UTRadMS, especially focusing on functions that the radiation workers use frequently.

2. New features of the Radiation Workers Management System After the new management system starts working, almost all the procedures for

registering radiation workers as well as recording the information needed to control them will be completed on the Web. The list below shows some of the functions added to the new system. Note that announcement and content of the department workshop (i.e., re-education training) remain same as before.

1) A personal ID is ABSOLUTELY needed for your procedure2) Information service by E-mail3) Cumulative and/or total exposd dose and results of medical examination for radiation

workers can be confi rmed on the Web 4) Medical questionnaire on the Web5) Almost all the procedures can be done on the Web

3. Important features of the new Radiation Workers Management System A personal ID and E-mail address will be required, for details, please see below.

1 Registration and maintenance of radiation workers (started within 2020)

Radiation Workers Management System

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・Check and/or obtain your personal ID before starting your lab experiments using radioisotopes. Your personal ID is needed for almost all the procedures (i.e. new registration, regular medical checkup and so on). In our system, you certainly input 10 digits of your personal ID on this new system completely.

・Your E-mail address is needed for receiving E-mail announcement from this system in case you will have to take regular medical checkup and so on.

4. Details of major changes Except for the confirmation of the results of medical examinations, UTRadMS enables

all the radiation workers to maintain and confirm their personal data.・ Exposure dose results

Everytime when your departmental radiation office will register your exposure dose results to the Radiation Workers Management System, you will receive an E-mail from this system and be able to confirm your exposure dose results on the Web.

・ Results of the medical examinations The results of the medical examination will also be notified on the Web. The staff

members confirm the results on the ” 人 事 情 報 MyWeb”, and the students check the results on the Health Checkup result online, so it is important to note that the checking method differs depending on your position.

・ Regular RI medical examinations questionnaire When the regular RI medical checkup starts, you will be notified of its guidance

in your E-mail address. So you should login to the UTRadMS and answer the questionnaire. If there is any deficiency in your answer, you should correct and resubmit your answer.

・ Making alteration of your personal information(s) In case you have altered or updated your registration concerning your affiliation,

handling materials and so on, you might receive an E-mail stating your appropriate guidance for medical checkup and/or training.

5. NOTE

・Personal ID When your position/status changes, your personal ID may also be changed. In

particular, when the status of the radiation worker changes from student to staff, your personal ID always changes. You cannot change it by yourself, so please contact to your departmental radiation safety office.

If your personal ID are not provided to you, or you are not an employee of The University of Tokyo, please contact your departmental office to register yourself into UTRadMS.

・ Your E-mail addressPlease check the E-mail address that you submitted to UTRadMS. Otherwise you

may not receive important informations and may not carry out your experiments using radiation and radioactive materials.

6. Conclusion UTRadMS will be convenient for all the radiation workers in The University of Tokyo

who handle/operate radioisotopes. Please keep in mind that it is important for all radiation workers in The Universty of Tokyo to maintain and update their information by themselves.

Division for Environment, Health and SafetyKeiji KIMURA, Satori KUKITA and Rie MIZUNO

Re-Education Theme: Laws and Handlings

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Radiation protection of people and the environment Radiation protection systems have been established to limit the adverse health effects

of exposure to the use of radiation and radioactive materials. The effects of radiation on humans have been divided into two categories.

Deterministic effects, including various tissue damage caused by the loss of cells by radiation, and stochastic effects caused by single cell mutations. Stochastic effects are known to occur at higher doses. It is assumed that stochastic effects occur at low doses. Stochastic effects include hereditary diseases and cancer risk, but since hereditary diseases have not been identified in humans so far, the risk of cancer (mortality and morbidity) is the sole concern. The purpose of radiation protection is to prevent deterministic effects and to reduce stochastic effects to “acceptable” levels.

It is relatively recent that we have started to look at the environmental impact. At the time of the ICRP 1990 Recommendations, it was written as follows: “The Commission (ICRP) believes that the standard of environmental control needed to protect man to the degree currently thought desirable will ensure that other species are not put at risk. ... At the present time, the Commission concerns itself with mankind’s environment only with regard to the transfer of radionuclides through the environment, since this directly affects radiological protection of man. “(Paragraph 16). It can be seen that non-human species are not considered for radiation protection.

However, with the growing interest in environmental issues worldwide, it is not enough to “believe” that if humans are protected, then the environment is also protected. It has become necessary to build a mechanism that can show this properly. Among the ICRPs, the framework for environmental radiation protection has been developed, and in the 2007 Recommendations, “Environmental Radiation Protection” was taken up as an independent chapter and has continued to evolve to the present.

[Purpose of environmental protection and reference animals and plants]The objectives of environmental protection are to (1) maintain biodiversity, (2) preserve

species, and (3) protect the health of ecosystems.To clearly demonstrate that the environment is protected, a framework for assessing the

relationship between exposure to radioactive materials in the environment and exposure levels, the relationship between exposure levels and radiation effects, and the relationship between effects and effects will become necessary.

In the case of humans, the concept of “reference person” was effective in calculating the dose received from surrounding radioactive materials and considering the effects. Following this, the concepts of “reference animals” and “reference plants” (RAPs) were introduced. Twelve species of animals and plants have been selected as representatives of environmental creatures. The selection was made to cover a wide range of habitats across a wide range of species (see table).

2 Radiation effects on people and the environment and radiological protection

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[Radiation levels and effects, and dose limitation]In the case of human beings, there are guidelines (dose limits, dose constraint values

or reference levels) for limiting doses according to the situation, based on the relationship between cancer risk and dose.

In the case of environmental organisms, it has been determined for each species what effects (e.g., premature death, reduced reproductive rate, or illness leading to these diseases) at what dose rate levels. Known information has been compiled. The results indicated dose rates above which some effects need to be considered. This is the “Derived Consideration Reference Level (DCRL)”, which is indicated as a broad “band” of dose rates (see table).

[Integration of protection of people and of the Environment]For humans and the environment, their goals are consistent in that their purpose is to

protect humans and environmental organisms from radiation.Just as “reference animals and plants” were introduced following “reference person”,

environmental protection systems have been built with reference to human protection systems. However, there are some differences. For example, human protection is targeted at individuals, whereas in the case of the environment, the protection is a “group” of species. In human protection, the effect is considered as “dose”, whereas in environmental protection, it is “dose rate”. This may be because environmental protection starts with the awareness of the rise in radioactivity levels due to the release of radionuclides into the environment by human activities.

With these issues in mind, the ICRP has set up a group to consider “integrating human and environmental protection”.

Table Characteristics of the reference animals and plants and corresponding derived consideration reference levels (DCRLs).

Wildlife group Ecosystem RAPDCRL (mGy / day)

0.1-1 1-10 10-100Large terrestrial mammals T Deer

Small terrestrial mammals T Rat

Aquatic birds F, M DuckLarge terrestrial plants T Pine TreeAmphibians F, T FrogPelagic fish F, M TroutBenthic fish F, M FlatfishSmall terrrestrial plant T Grass

Sea weeds M Brown Seaweed

Terrestrial insects T BeeCrustacean F, M CrabTerrestrial annelids T Earth worm

T, terrestrial environment; F, freshwater environment; M, marine environment.

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Priority in emergency situations is also an important issue. The ICRP states, “Protection of people is a priority in emergency exposure situations. However, it is recommended that emergency response be considered with regard to the environmental impact after the end of the emergency (Publication 124).

Concluding remarksThe table shows that DCRL for environmental organisms is at a higher level compared

to human dose standards. This is a reflection of the high sensitivity of humans to radiation. And, when humans and environmental species coexist, it might be said that “if humans are protected, environmental species are also protected.”

The concept of radiation protection of the environment has not been incorporated in the Japanese laws and regulations, however, for those who are involved in radiation use including nuclear power production, to have a broad perspective and consider the protection of the environment even where there are no humans.

Tokyo Healthcare UniversityKazuo SAKAI, Prof./Ph.D.

Re-Education Theme: Radiation Effects

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1. Small Amount of Nuclear MaterialsThe permission for the use of nuclear materials in universities is determined by the

material type and inventory amount. A facility approved for an inventory amount above 300 g of natural/depleted uranium or also not exeeding 900 g of thorium, or an inventory of specific fissionable material of enriched uranium, uranium-233 and plutonium-239 is called “J-Facility” derived by the material balance area code. On the other hand, a facility approved for an inventory of small amount of nuclear materials not exceeding 300 g of natural/depleted uranium and 900 g of thorium is called “K-Facility”.

K-Facility is requested to weigh and control the nuclear material; the setting of controlled area is not needed. Nuclear materials in K-Facility are maily used for cytological staining, α-ray emitter, tracer experiments, and measurement of physical properties of nuclear compounds. Particularly, cytological staining for microscopy applies uranyl acetate or nitrate in biological researches. J-Facility and K-Facility have a common problem for storing the nuclear wastes in their laboratories because the way to treat of nuclear wastes has not been determined by the government.

2. Checking the Safety in K-FacilityKyoto University checks K-Facilities every half a year. A check list was prepared by

Agency for Health, Safety and Environment of Kyoto Univ. When a management deficiency is found, the faculty is obligated to submit an improvement report and photos, and PDCA improvement must be approved by Agency for Health, Safety and Environment. Representative targets for checking the wastes are locks and measures to prevent the storage cabinet from tipping over, crack and corrosion of waste bottle and bag, the use of a divided tray, ziplock and tray for countermeasures against expansion of contamination.

3. Management of Reagents and Wastes in K-FacilityKyoto University uses two types

of stickers, color stikers and sealing stickers, for effective management. Color stickers are for visualization of use condition. Sealomg stickers are for idetifying unused materials. The red, green, yellow, and blue stickers indicate reagent bottles in use or planned to use, samples in use, reagent bottles wi thout usage p lan, and wastes, respectively. The inventory amount of nuclear materials for red, green, and yellow is weighed in the nuclear material accounting report to The Secretariat of the Nuclear Regulation Authority. The wastes with blue stickers possess the management number “-W” at the end, and their weights are measured despite the unnecessity for the submission of the report. The sealing stickers are

3 Management of Small Amount of Nuclear Materials and Their Wastes (Case of Kyoto Univ.)

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patched at the bottle and cap for the reagent bottles without usage plan (yellow) and closed wastes after reaching their capacity (blue). The unopened sticker with the sealing date on it guarantees no change of the sample weight after the sealing. Weight measurement and contamination checking of the bottle surface are omitted by the observation of the unopened sticker.

4. Management of Wastes of Small Amount of Nuclear Materials

The wastes exhausted in K-Facility are separately stored in the laboratories as solid wastes and liquid wastes. The key for effective management is to reduce their volume. For solid wastes, Agency for Health,

Safety and Environment gives a guidance to put only the wiping area into the waste container by tearing the wiping cloth. As for liquid wastes, only the neat solution is directly transferred to the container. The primary and secondary wash liquids are transferred into a beaker, and then treated by evaporation to dryness using an infrared lamp or a hot stirrer. Nuclear materials hardly remain in the beaker. Volume reduction is achieved by repetitively using a dedicated beaker for evaporation to dryness.

To weigh nuclear wastes is not required for K-Facilities under the present law. However, Kyoto University prepared a documentary form for material accounting to make provision for a possible requirement in the future. The form is common to reagents and wastes, which enables to secure the constant weight in the total of reagents and wastes by filling the origin and destination of the transfer.

Kyoto UniversityAgency for Health, Safety and Environment

Kouji YASUDA, Assistant Prof./Ph.D. Re-Education Theme: Nuclear Material, Handling

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X-ray irradiators can be classified into two categories based on the position of its radiation control area being either “inside” or “outside” the device. UTokyo decides Categories A and B for the former, C, D and E for the latter, and manages all X-ray irradiators using these five categories of A to E. Even a same irradiator could be categorized into B or C based on the situation of its usage. (Fig.1)

When an irradiator was classified into Category B, the interlock of the device is always in effect. When its X-ray protection cover is opened, the power supply of the device is stopped, no X-ray is generated, and there is no possibility that users of it is exposed. On the other hand, when this was classified into Category C, the interlock of the device is sometimes invalid. X-rays could be generated under the condition that the X-ray protection cover is opened. In this case, we cannot deny the possibility for users to be exposed to X-ray. For example, one of the situations is that a sample is irradiated with X-rays when taking a Laue photograph. In addition, some older X-ray irradiators require us to release their interlocks at the time of sample change.

We have experienced unwanted exposures of X-ray users due to improper use of devices classified as Category C. Frequency of using the devices increased, and several unplanned exposures occurred during periods when users became accustomed to their operation. The main cause is that the interlock was released when the beam shutter opened, and a body part of the user was unknowingly inserted into the device. In UTokyo, all X-ray irradiators are required to receive safety check on a regular basis. Closed beam shutter means that there is no possibility of exposure. It is important to release the interlock as needed when the beam shutter is closed to prevent unplanned exposure. That is, paying attention to the open / closed state of the beam shutter does not cause unplanned exposure. Some X-ray irradiators have several alarms that indicate the opening status of the beam shutter. One of them is an irradiation lamp near the X-ray irradiation window (Fig. 2). The lighting of this lamp indicates to us that the shutter is open. In addition, some devices have an illumination lamp outside the device shown in Fig.3. In the case of

【B】 【C】

【E】

【D】【A】Controlled area Controlled area

Inside of devices

Outside of devices

Fig.1 Categorizing X-ray apparatus in UTokyo

4 Safety usage of X-ray irradiator “Category C” in UTokyo

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computer control, some devices display as shown in Fig.4. Fig. 5 shows an example of display for the shutter open on the control unit of the device.

Here, the points to be noted when using X-irradiators are listed. When releasing the interlock, check that an illumination lamp near the x-ray window is off. In addition, note that the lamp off does not always mean closure of the beam shutter, because of the possibility of a failure of the illumination lamp. Check the display for the beam shutter. You can release the interlock only when you are sure that the beam shutter is closed. After that, you can open the X-ray protection door and insert your hands etc. into the device. When irradiating a sample with X-rays in preparation for taking Laue photos, check the closure of the beam shutter, open the beam shutter after installing a fluorescent screen inside the device. If possible, observe the fluorescent plate through over lead- glass etc. Make sure the beam shutter is closed when adjusting a camera or a gonio head. Always switch off the device if any part of the body other than your hands can enter the device.

X-ray irradiator is one of the tools that provide useful experimental data for us. However, unplanned exposures without safe use can lead to our health concerns as well as wasting time after troubles. Follow the safety guidance. In the unlikely event of a problem or accident, immediately notify the administrator (radiation control office, etc.) and follow the instructions of the safety administrator.

Fig.2 The lamp near the shutter

Fig.3 The lamp out of apparatus

Fig.4 Shutter status on PC monitor Fig.5 Shutter status on control unit

The Institute for Solid State PhysicsKiyokazu NOZAWA

Re-Education Theme: X-ray