IAEA Final Report on Recycling of Removed Soil etc. Arising from Decontamination Activities (Vol. 5)

Hello, everyone. My name is Daichi, an expert providing the information about the radiation issues in an easy-to-understand manner.

With regard to the IAEA’s review on volume reduction and recycling of removed soil arising from decontamination activities, which have been promoted by the Japanese national government, the background of the IAEA’s review was explained in this article and the overall evaluation made by the IAEA was explained in this article.

Further to that, detailed evaluation in the ‘Chapter III: Regulatory aspect’ was elaborated in this article, and detailed evaluation in the ‘Chapter IV: Volume reduction and the managed recycling of removed soil’ was elaborated in this article.

As a continuous work from the previous, this article will cover the ‘Chapter V: Final disposal of removed soil and waste’ in the final report.

In other words, for example, this article will respond to the following questions.

– What is the ‘Final disposal of removed soil and waste’ in the final report on recycling of removed soil etc. arising from decontamination activities?
-　What kind of evaluation did the IAEA final report make for the ‘Final disposal of removed soil and waste’?

Table of contents of this article

I have been involved with the radiation-relevant issues, like the policy on the decontamination activities and the management of the Interim Storage Facility, after the accident of the Fukushima Daiichi Nuclear Power Plant in 2011.

I received a doctorate in the field of radiation, while working in Fukushima.

IAEA Final Report on Recycling of Removed Soil etc. Arising from Decontamination Activities (Vol. 5)

Now, let’s take a look at the contents of the ‘Chapter V: Final disposal of removed soil and waste’ of the final report.

What is the ‘Final disposal of removed soil and waste’ mentioned in the IAEA final report?

As covered in this article, the ‘Final disposal of removed soil and waste’ mentioned here, is the final disposal of removed soil and waste arising from off-site environmental remediation activities, which need to be completed outside Fukushima Prefecture by March 2045.

Evaluation written in the ‘Chapter V: Final disposal of removed soil and waste’

In the following parts each evaluation item is elaborated, but for the sake of convenience, alphabets (i.e., a,b,c…) are added at the beginning of each item (there are no alphabets in the actual report).

Section V.1 Overall approach to the final disposal of removed soil and waste

First of all, what is the ‘safety case’, which comes up at the beginning of this point?

In the IAEA Nuclear Safety and Security Glossary, 2022 (Interim) Edition, it is explained as follows:

A collection of arguments and evidence in support of the safety of a facility or activity.

Note 1: This will normally include the findings of a safety assessment and a statement of confidence in these findings.

Note 2: For a disposal facility, the safety case may relate to a given stage of development. In such cases, the safety case should acknowledge the existence of any unresolved issues and should provide guidance for work to resolve these issues in future development stages.

If you would like to know in detail about the safety case, please refer to the IAEA Safety Standard like IAEA SSG-23.

To put it simply, it is a set of documents, developed during assessments for the safety of facilities or activities, including results of safety assessments in terms of radiation protection.

For this project, there are still no specific candidate sites, and it is mentioned here that a generic safety assessment has already been initiated for a final disposal site based on some assumptions.

In addition, toward the final disposal to be completed by March 2045, there are still a lot of issues to be addressed, including the refinement of the safety case.

As mentioned in the above point a., the safety assessment, which MOEJ has initiated, is just a general one, and it could be possible that a lot of points could be different from those of the final disposal facilities, which will be actually constructed in the future.

Therefore, in order to reduce uncertainty, it is mentioned that site-specific sensitivity analyses should be conducted, when overall designs of the actual final disposal facilities are more specifically determined in the future.

In the IAEA Nuclear Safety and Security Glossary, 2022 (Interim) Edition, the sensitivity analysis is explained as follows:

A quantitative examination of how the behaviour of a system varies with change, usually in the values of the governing parameters.

Note 1: A common approach is parameter variation, in which the variation of results is investigated for changes in the value of one or more input parameters within a reasonable range around selected reference or mean values, and perturbation analysis, in which the variations of results with respect to changes in the values of all the input parameters are obtained by applying differential or integral analysis.

As repeatedly explained, this final disposal project needs to be completed outside Fukushima Prefecture by March 2045.

With regard to the procedures toward the completion, as covered in the Technology Development Strategy for Volume Reduction and Recycling of Removed Soil and Waste under Interim Storage (in Japanese), especially in FY2025 onward, no specific schedule has not been determined (when the final report was published).

Here the necessity to develop a specific and overall strategy and a schedule is pointed out, toward the completion of the final disposal.

It is explained in point f. of this article, but optimization of radiation protection and safety is a concept to lower the dose As Low As Reasonably Achievable (ALARA), taking account of not only the aspect of radiation protection, but also other aspects (e.g. social, environmental and economic aspects) .

This concept is of course applied to the design of the final disposal facilities, and I think that it is pointed out here, that a couple of comparable options should be presented, in order to confirm that the concept of optimization is appropriately applied.

The categories of radioactive waste are defined in IAEA GSG-1, and there are six categories namely, ‘Exempt waste (EW)’, ‘Very short lived waste (VSLW)’, ‘Very low level waste (VLLW)’, ‘Low level waste (LLW)’, ‘Intermediate level waste (ILW)’ and ‘High level waste (HLW)’.

Here it is said that removed soil and waste, which will be finally disposed of, can be treated as VLLW, lowest level of radioactive waste subject to regulation, or as LLW, one higher level above of VLLW, taking account of radioactivity concentration even after their concentration (e.g. by segregation, heating)

Therefore, it is evaluated here, that these soil and waste can be treated, according to the radioactive waste treatment system of Japan, neither in geological disposal site located in 300m-depth or deeper underground, nor in intermediate-depth disposal located in 70m-depth or deeper underground, but instead near-surface disposal facilities located close to the ground surface.

The classification of radioactive waste described in GSG-1, mentioned in the above point e., is a merely concept and specific radioactive concentration for the classification is not defined (it can be decided at the discretion of each country.)

Here it is implied, that the screening level of 8,000Bq/kg or less, elaborated in the point b. of this article, is suitable to differentiate between LLW and VLLW or VLLW and Exempt Waste.

The structures of final disposal facilities could be different according to the radioactive concentrations, although specific examples have not been presented.

Therefore, I think that it is pointed out here, that the screening level could be used to define the classification of the types of the final disposal facitilites.

This is also covered in the point e. of this article, and it is here evaluated, that the approach for volume reduction and recycling of removed soil, which have been implemented by the MOEJ, is in line with the concept ‘The generation of radioactive waste must be kept to the minimum practicable level by means of appropriate design measures and procedures, such as the recycling and reuse of material.’, which is described in the No.7 of the IAEA Safety Fundamentals: ‘Protection of present and future generations’.

In addition, it is pointed out that an optimal approach needs to be adopted, taking account of their advantages and disadvantages, because there are a variety of approaches toward its realization.

The MOEJ is supposed to complete the selection of technologies for volume reduction and recycling by the end of FY2024, and I think that it is expected here for these technologies to be evaluated in terms of different points of view.

Section V.2 Measurement of radioactivity concentration

I think that ‘to excavate’ in this context means to excavate of soil which is stored in the Soil Storge Facilities in the Interim Storage Facility, and here it is mentioned that the MOEJ has a plan to re-measure its radioactivity concentration.

With regard to the Soil Storage Facilities in the Interim Storage Facilities, there are ones for higher radioactivity concentration (i.e. over 8,000 Bq/kg) and ones for lower radioactivity concentration (i.e. 8,000 Bq/kg or less).

The radioactivity concentration could vary, depending on the objective for use for recycling, and structure of the final disposal facilities, so I think that it is mentioned here that radioactivity concentration needs to be measured again.

The final report mentions a consecutive measuring facility of radioactivity concentration of removed soil, and this is the facility to measure radioactivity concentration of removed soil on a conveyor belt consecutively, using for example, NaI scintillator.

This is the facility initially used in the Interim Storage Facility, and it is mentioned that this technology will be applied for the measurement during transportation process.

Section V.3 Safety case including generic safety assessment

The measures for structures and maintainance of final disposal facilities, which the MOEJ currently considers and are described in the final report, include for example the followings:

– Prevention of scattering and leakage
– Prevention of groundwater pollution, as necessary
– Conservation of the living environment (e.g., odor, noise, vibration)
– Surrounding enclosures (e.g., fences) and sign
– Landfill capping
– Measurement of air dose rate
– Keeping records

These are the measures during the operational period (probably the period of landfill of removed soil and waste) and the maintenance period (probably the period of maintenance of the facility followng the landfill), and here it is evaluated that these measures cover the essential elements to ensure safety in the construction period (probably the aforementioned operational period is also included) and the maintenance period.

The ‘post-closure’ here could describe situation when the maintainance of the facility is not necessary anymore, and the facility itself is closed.

I think that the necessecity of designing is here underlined, by taking account of the securement of the safety of the facility in terms of radiation protection after its closure (until when the radiaction protection measures will be taken).

In other words, I think this is the comment, that the facility needs to be designed based on the assumption for the necessary period of time for the measures, which can be estimated based on the amount of soil and waste to be disposed of in the final disposal facility, as well as kinds of radionuclides included.

And here the fact that they have been already actually initiated, and expectation for them to be implemented more detailed according to the progress of the project, are mentioned.

Here the importance of implementation of post-closure safety case from the outset (=before the construction of final disposal facilities) is reiterated, which is mentioned in the above point k.

I think that this is a comment that the development of post-closure safety case in advance could lead to reassurance of local people who would accept the final disposal facility, because rough schedule and future prospect could be clarified, for example, how long the final disposal facility would exist there, and until when the radiation protection measures would be taken.

With regard to the recycling projects, you can see the similar description in the point m. of this article, but this is the description for the final disposal facilities.

The necessity is mentioned here, for the document to be developed, in which processes are clearly described: how the operational function of the MOEJ informs the regulatory function of the MOEJ, under what kind of situations and eventualities (both the usual and emergency situations), and how the regulatory function of the MOEJ provides advice etc. to address the issues, because the final disposal facility is supposed to be operated by the MOEJ.

With regard to the impact of relevant radionuclides in the recycling projects, it is mentioned in the point k. of this article, and here relevant radionuclides for the final disposal facilities are described.

It is not stipulated here, but I think that main radionuclides could be radioactive caesium and other radionuclides to be considered could include Sr-90 and Pu-238.

It has benn already found out that the influence is almost same with the background level, but here it is mentioned that the impact will be continuously considered in terms of reassurance.

Summary

With regard to the final report on the IAEA-MOEJ Experts Meetings on volume reduction and recycling of removed soil, this article covered the contents of conclusions in the ‘Chapter V: Final disposal of removed soil and waste’.

The positive perspectives expressed for the approach for the basic design and measures concerning the final disposal facilities, toward the completion of the final disposal, will support the projects.

On the other hand, a lot of issues to be addressed are still remaining, according to the progress of the projects, including the development of the safety case for the facilities after their closure, and for individual facility as well.

I think that they might be less urgent compared with the recycling projects, but they need to move forward steadily.

You can read the same article in Japanese here.

Thank you very much for reading this article.

See you next time!