IAEA Final Report on Recycling of Removed Soil etc. Arising from Decontamination Activities (Vol. 4)

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 review for volume reduction and recycling of removed soil arising from decontamination activities, which the Japanese national government has been promoted, this article covered the background for the review conducted by the IAEA, and this article covered the overall evaluation made by the IAEA.

In addtion, in this article, key points for the ‘Chapter III: Regulatory aspect’ were elaborated.

As a continuous work from the previous, this article covers the ‘Chapter IV: Volume reduction and the managed recycling of removed soil’ of the final report.

In other words, this article covers, for example, the following questions:

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

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. 4)

Now, let’s take a look at the contents of the ‘Chapter IV: Volume reduction and the managed recycling of removed soil’ of the final report.

What is the ‘Volume reduction and the managed recycling of removed soil’ mentioned in the IAEA final report?

The ‘Volume reduction and the managed recycling of removed soil’, which is here covered, is the volume reduction and recycling of removed soil arising from off-site environmental remediation activities after the accident of the Fukushima NPS, which has been so far explained.

It could be a bit difficult to have an image for the ‘volume reduction’ of removed soil, but it is an approach to reduce volume of soil to be finally disposed of, by concentrating radioactive caesium, through technologies like classification and burning, as explained in this article.

Evaluation written in the ‘Chapter IV: Volume reduction and the managed recycling of removed soil’

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 IV.1 Overall approach to volume reduction and the managed recycling of removed soil

First of all, it is evaluated, that the projects have been progressed in line with the Technology Development Strategy and Roadmap, which underlies the projects.

In addition, as mentioned this article, it is a bit touched upon in the point f. in the overall evaluation in the final report, but importantly, it is evaluated not only that measures for the volume reduction and recycling of removed soil contribute to the reconstruction of the affected areas, but also that it is valuable as a sustainable process.

The IAEA Safety Standards (GSG-18), which is here mentioned, is the General Safety Guide 18: ‘Application of the Concept of Clearance’ (please refer to this website).

As the appendix of this Safety Guide, there is a part named ‘SCREENING LEVELS FOR RECYCLING OR DISPOSAL IN LANDFILLS OF MATERIAL AND WASTE IN A POST-EMERGENCY SITUATION’, and in this part a concept of ‘the screening level’ comes up.

In the planned exposure situations, there are concepts like clearance and specific clearance, in which waste with low level radioactivity is excluded from the regulatory system of radioactive materials.

In the GSG-18, however, another concept is introduced under the existing exposure situations, like after the accident of the Fukushima Daiichi Nuclear Power Station.

This concept is ‘the screening level’, and with regard to the recycling of removed soil, radioactivity concentration of 8,000Bq/kg (or less) corresponds to the screening level.

Here it is evaluated that measures taken by the MOEJ are consistent with the concept of the screening level mentioned in the GSG-18.

Here the necessity is underlined, to confirm that radioactivity level of recycled material (removed soil treated according to its purpose for use) is lower than relevant screening level (8,000Bq/kg or less and depending on its purpose for use), mentioned in the above point b.

Radioactivity concentration of removed soil arising in Fukushima Prefecture is measured in the Temporary Storage Sites (please refer to this article), before they are transported into the Interim Storage Facility (ISF) (please refer to this article), and stored in the ISF, by separating removed soil with radioactivity concentration of 8,000Bq/kg or less, and more than 8,000Bq/kg.

I think that here it is pointed out, for example, that radioactivity concentration should be measured again before removed soil is transported again out of the ISF for recycling in the future, and results and conditions for the measurements should be recorded.

It is explained in this article, but it is considered important from now on for radioactive caesium (especially radioactive caesium 137) to be focused on, of radioactive materials released into the environment, taking account of their released amount and physical half-lives.

The MOEJ has measured radioactivity concentration of radioactive materials in the removed soil, and it has confirmed that radioactive concentrations of strontium and plutonium are almost same as the level of pre-accident (this website (in Japanese)(Please refer to the material of the 4th WG on consideration of recycling of removed soil in the ISF), and it will focuses on radioactive caesium during the recycling projects.

Here the point emphasizes the importance of its effort to keep explaining such scientific evidences to people.

Section IV.2 Interim storage of removed soil and waste

With regard to the ISF, please refer to the aforementioned this article, this article, this article and this article.

The ISF was constructed with various backgrounds, especially based on the difficult decisions of people in Okuma and Futaba Towns, home to the ISF, but here the temporal transportation of removed soil to the ISF is evaluated to be reasonable.

I understand that there are pros and cons for the approach for the ISF to be constructed and for the final disposal to be implemented in another place, but here the approach has obtained to some extent positive evaluation.

In addition, the team of expert visited the ISF actually on-site during the first Experts Meeting, and it evaluates here that removed soil is properly stored there.

Section IV.3 Technologies for volume reduction

As covered in this article, currently the development and evaluation of volume reduction technologies (almost equal to technologies for concentrating radioactive materials) are in progress, and it is mentioned here, that among these technologies, effectiveness of classification, heat treatment and fly ash cleaning technologies has been confirmed.

It is not touched upon in the aforementioned article, but the fly ash cleaning technology is a technology to clean fly ash to separate, re-adsorb and stabilize radioactive caesium, taking account of its characteristic to be likely to be dissolved into water when it is attached to fly ash, although it is firmly attached to soil particle.

On the other hand, in an expert meeting established by the MOEJ, for example, chemical treatment has issues when enlarging scale of the project (For details please visit the materials of the WG on consideration of recycling of removed soil in the ISF, in this website (in Japanese).

When choosing options for volume reduction, various kinds of factors are supposed to be taken into account.

Not only effectiveness of treatment and capacity of treatment (e.g., possibility for enlargement), but also the amount of secondary waste generated, cost, the amount of emission of CO₂ might need to be considered as well.

In addition, technologies applied could be different depending on recycling cases.

It is here pointed out, that selection of technologies needs to be considered, taking account of these points comprehensively.

Section IV.4 Safety assessment for the managed recycling

Additional effective dose of 1 mSv per year is considered as a dose criterion (like upper limit of dose), for workers and people around the sites for recycling projects.

It is elaborated in the point g. in this article, but here it is evaluated that this value of additional effective dose of 1 mSv per year is set appropriately.

It is evaluated that general safety assessment for the recycling is appropreately conducted in a very conservative way (by standing on a safe side), therefore, dose criterion (additional annual effective dose of 1 mSv) can be sufficiently achieved by using recycled soil of 8,000 Bq/kg or less, as introduced in the point j. in this article.

What the MOEJ has so far implemented is general safety assessment, and it is an approach applicable to every recycling site.

It means, that it has been conducted in a conservative way (standing on a safer side) and dose is supposed to be overestimated.

Here the possibility is shown that the site-specific safety assessment for recycling projects could support optimized measures without any excessive radiation protection, and also safety assessment taking account of specific conditions (e.g. topography, land use) could address people’s concerns.

It is touched upon in the point d. above, with regard to radioactive materials released into the environment due to the accident of the Fukushima Daiichi Nuclear Power Station, as elaborated in this article, among the released radionuclides, radioactive caesium (especially radioactive caesium 137) needs to be considered, taking account of physical half-life, the released amount etc.

However, the MOEJ has analysed the strontium 90 and plutonium 238 etc., whose amount released are deemed to be quite small and confirmed that their concentrations are almost same with the levels of pre-accidents.

Here it is evaluated that this confirmation is useful from the viewpoint of people’s reassurance.

It is elaborated in the point l. in this article, but sometime in the future, the time will come when the radiological management will not be necessary, due to reduction of radioactivity.

I think that here the importance is emphasized again, for the long-term safety assessments including determination and confirmation methods for the time.

With regard to the items, necessary to end the term for special attention in terms of radiation protection, which mentioned in the above point l., here it is said, that they can be developed not urgently but in the future, in consultation with relevant stakeholders.

For the recycling project of removed soil, cooperation with public authorities is indispensable, which manage the recycling sites in terms of confirmation of safety of the construction.

I think that it is pointed out here, that necessary items should to be clarified, to end the periods of time for special attention in terms of radiation protection, in consultation with ministries and agencies relevant to the public authorities.

Section IV.5 Demonstration projects of agricultural embankments

It is elaborated in this article, but in the demonstration project conducted in Iitate Village, improved removed soil is used as embankment of farmlands, and changes of surrounding air dose rate as well as radioactivity concentration of cultivated crops have been monitored.

Here it is mentioned that the project has been safely implemented, and it touches upon its effectiveness as well as expectations for continuous implementation of the project.

As elaborated in this article, the achievements of the Technology Development Strategy for Volume Reduction and Recycling of Removed Soil and Waste under Interim Storage (Technology Development Strategy) are supposed to be complied by March 2025, and in FY2025 onward (in April 2025 onward), full-scale recycling projects are scheduled to be implemented.

In order to obtain data and experience necessary for the full-scale implementation, this demonstration projects of agricultural embankments and the demonstration project of road embankment, introduced in the following section have been implemented.

Here it is evaluated, that based on these achievements, elements necessary for establishment of the system for full-scale projects have been already obtained.

This point seems to provide some details of the abovementioned point o., and major parts of recycling system is the ministerial ordinance and the technical guidelines, elaborated in the Section III.4, covered in this article.

Here it is evaluated, that scientific knowledge necessary for the development of the ministerial ordinance and technical guidelines have been sufficiently obtained.

It is well-known that radioactive caesium is likely to be firmly attached to fine soil particles, and it remains at the surface layer of soil for a long time.

Concentration of radioactive caesium in the leachate of the sites of recycling demonstration projects has continued to be less than a detection limit, therefore it could be mentioned here, that radioactive caesium in removed soil is hardly eluted into water.

Section IV.6 Demonstration project of road embankment

The demonstration project of road embankment was also briefly touched upon inthis article.

You may understand well, if you actually go and see it on-site, for example, by participating in a site visit tour, but the scale of the road is of course smaller than that of an actual road, because it is still in a demonstrative step.

Here it is said that continuation of this demonstration project is desired, for further accumulation of data necessary for implementation of larger-scale projects.

The description here is exact the same with the point p. above.

The monitoring of radioactive caesium in the leachate from road embankment had been implemented also in this demonstration project.

It is confirmed that the results have been detection level or less, therefore the description here is same with the above point q.

Summary

With regard to the IAEA Final Report on Recycling of Removed Soil etc. Arising from Decontamination Activities, this article covered the contents of conclusions described in the ‘Chapter IV: Volume reduction and the managed recycling of removed soil’.

It is impressive for me, that not only the appropriateness of goal setting for the annual additional effective dose of 1mSv and consistency with the screening level mentioned in the GSG-18, but also individual project is in detail covered.

As a whole, it is evaluated in a positive manner, but as is the case with the ‘Chapter III: Regulatory aspect’, here the long-term safety assessment is raised as one of the issues to be addressed.

Here it is mentioned that the MOEJ has initiated its consideration to address the issue, but it is necessary to continuously deepen its consideration.

You can read the same article in Japanese here.

Thank you very much for reading this article.

See you next time!