Radiological Protection in Geological Disposal of Long-lived Solid Radioactive Waste

Draft document: Radiological Protection in Geological Disposal of Long-lived Solid Radioactive Waste

Submitted by S.Y. Chen, Argonne National Laboratory
Commenting as an individual

REVIEW: Draft Report for Consultation – Radiological Protection in Geological Disposal of Long-lived Solid Radioactive Waste

Comment by S.Y. Chen, Argonne National Laboratory, Argonne, IL, USA

In general, this proposed document provides updates and consolidates previous ICRP recommendations on solid waste disposal and it applies specifically to the geological disposal of long-lived radioactive waste in light of the 2007 ICRP System of Radiological Protection described in Publication 103. In a large measure, the document has achieved its objective with by a systematic approach toward various stages of protection for the waste facility under direct oversight (short term), indirect oversight (medium term), and no oversight (long term).

In reviewing the document, however, I also have a number of concerns that are described as follows. These concerns are primarily surrounding the very large uncertainties for the long-term assessment and the associated clarifications regarding the proposed system particularly if it is to be incorporated into the regulatory approach.

In Section 3.1.2 (Basic ICRP principles dealing with future generation), it emphasizes that optimization principle is of primary importance and also reinforced in the new ICRP Recommendations (Paragraph 19). For this, the concept on dose and risk is largely based on today’s knowledge on radiological health risks, and that the efforts on radiological protection are to be guided entirely by the current understanding of health and environmental effects (Paragraph 20). It follows to say (Paragraph 21) that “…the assessment of the robustness of the protection system provided by the solid waste disposal in the long-term does not need precise knowledge …in the far future.” This is because, “The challenge is rather to estimate, in an optimization process, through a comparison (using dose and risk indicators) of alternative options…is acceptable in light of the level of protection accepted today.”

There are a number of issues related to the above statements:

· It appears to be a misnomer to consider the exposure situation under the design-basis evolution to be “planned exposure situation” under the “no oversight” conditions. Considering that such exposure would be well into hundreds of thousands years from emplacement, the exposure situations will become highly probabilistic subject to many uncertainties. Thus to consider such an exposure situation as “planned” is truly unfathomable; as it implies that the exposure can be anticipated today whereas it is not. Since after such a long time when people who may be exposure would likely not have any record of such radiation sources, thus it may resemble “existing exposure situations” rather than “planned exposure situations.” The Committee ought to provide more justification and clarification on this subject.

· Radiological assessment for the long-term time frame is certainly not limited to the optimization process as stated in Paragraph 21. It also has to demonstrate that the doses or risk assessed are to meet the limits as well reference levels for various conditions (as indicated in Table 1 of the draft report). Thus the assessment is used not only for comparison of options under the optimization process; they are also intended to meet the limits and constraints in various stages of operation. Thus, the philosophy on the assessment has to be further clarified as whether it is intended to opt for conservatism or realism.

· The report needs to clarify how natural events (such as seismic events, in Section 4.3.3) would affect the protection issues, and how to “plan” for such events. In view of what’s happening in Fukushima, Japan and elsewhere today (i.e., estimate of probabilities and the related cascading affects are difficult to ascertain), further guidance is needed to deal with the assessment of the event probabilities and potential consequences.

Whereas it makes sense to preserve the consistency on protection by considering such elements as Representative Person (Section 5.1) and the related consideration of individual gender and age groups in the dose and risk assessment in the short term, the consideration appears to be largely academic in view of the very large uncertainties for the long term (particularly during the nom oversight situations). This is equivalent to artificially addressing the precision issue without adding any accuracy to the assessment. Likewise, the concern applies to the Protection of the Environment (Section 5.2). It is unclear how in the long term such assessment would make any sense using the Reference Animal and Plants when there are many unknowns (for example, there were discoveries of the baby mammoth in Russia Arctic from the last ice age, which was extinct about tens of thousands of years before). ICRP needs to focus on the appropriate treatment of the very large uncertainties. Too many artifacts have been introduced in the name of preserving the consistency of the framework. Instead, we need to develop appropriate surrogates for the assessment when such large uncertainties are expected.

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