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 Hirokazu Tachikawa, Nuclear Safety Research Association (NSRA)
Commenting on behalf of the organisation

H.Tachikawa, R.Dobashi, O.Tochiyama

Radioactive Waste Disposal Safety Research Center, Nuclear Safety Research Association (NSRA)

 First of all, we appreciate the effort that the ICRP Task Group has put into this document. This publication will be a benchmark for geological disposal. However, we have some suggestions for improving this document and have identified some critical issues that we feel should be scrutinized:


General 1

Although the new term “oversight” is introduced in the document, ICRP Publication 81, as well as IAEA Safety Standards, uses “institutional control.” It should be clearly explained why the latter term has been superseded.

 General 2

This report refers to “distance,” but it is deemed that it does not adequately address the concept of “isolation”. This issue is specifically addressed in IAEA Safety Standards Series SSR-5 “Disposal of Radioactive Waste.” For example SSR-5 paragraph 3.32 says “The disposal facility is also designed to retard the dispersion of radionuclides in the geosphere and biosphere and to provide isolation of the waste from aggressive phenomena that could degrade the integrity of the facility” and paragraph 3.44 (which describes supplementary requirement for the isolation of radioactive waste) says, “It also means design to minimize the influence of factors that could reduce the integrity of the disposal facility” and “Sites and location with higher hydraulic conductivities have to be avoided.” Therefore “isolation” could be assured by distance, the integrity of the disposal facility and oversight.

 Executive Summary, p. 5 (c), (d)
Conform the wordings of “development” and “evolution” to “evolution”.
According to “Cobuild”
the gradual growth or formation of something.
a process of gradual change that takes place over many generations, during which species of animals, plants, or insects slowly change some of their physical characteristics.


Table 1, Column of No oversight

This column is deemed controversial. Non-design basis evolution involving significant exposure to people and the environment conditions are explained in paragraphs No. 52 and 58, and the emergency exposure situation and existing exposure situation are deemed to be allocated automatically. Actually the future authority may take some measure against disturbance. Under these conditions, the explanation of “no oversight” is not clear and is difficult to convey clearly. In addition, paragraphs No. 52 and 53 mention reference levels for each condition, and these criteria could be applicable to periods of direct oversight and indirect oversight. However during the period of no oversight, the linkage with reference levels and the radiological exposure situation cannot be mentioned explicitly. Perhaps during periods other than non oversight the viewpoint of determination for the situation is fixed for now, but on the other hand, the people would recognize the situation that exists during the period of no oversight would be generations in far future. Therefore, the column of no oversight should be graded as shaded and some supplemental explanation should be added in a footnote.


Line 285, 1010: There will be no worker involving the facility during the period of no oversight.

Original text is deemed that workers involving the facility will exist during the period of no oversight.


Line313: ... is required (IAEA,2011, IAEA, 2009).

IAEA (2011) Disposal of Radioactive Waste. IAEA Safety Standards Series SSR-5

IAEA (2009) Classification of Radioactive Waste, IAEA Safety Standards Series GSG-1


Line325: ...stable physical and chemical condition...

Physical condition is also important.


Line 330: ...concentrate and contain...



Paragraph (13) : Near surface disposal facility is out of this report and previous ICRP recommendations are still valid. If so, the term “institutional control” used in ICRP Publ.81 is valid and the question “what is difference between “oversight” and “institutional control” would emerge. Therefore, some supplemental explanation on this issue should be added. See general comment 1.


Line 466: ... harmful effect of ionizing radiation, ...

Editorial error.


Line 536 ...possible future evolution...

See comment on (c) and (d).


Line 587: …A baseline survey of environmental condition…



Line 713:… tens to around a hundred years…

The operational period of the facility would not extend to hundreds of years. It would extend to around 100 years at most.


Line 815: ...rehabilitation of contaminated land.

The term “previously occupied land” is vague.


Line 869: Paragraph (46) line 3 “ this suggests that these are uncertain and hence treated as potential exposure.”
Exposures due to eventual release of some radioactive substance in far future should not be treated as potential exposures. In (42), a potential exposure is defined as “an exposure that is not expected to be delivered with certainty but that may result from an accident at a source or an event or sequence of events of a probabilistic nature, including equipment failures and operating errors.” and in (43), it is stated that “planned exposure situations may give rise both to exposures that are reasonably anticipated to occur (normal exposures) and to higher exposures that are anticipated to occur with a lower likelihood (potential exposures).” Therefore, “potential exposure” implies that the exposure is “not normal.” As for this point, (45) states that “Given the potentially vast time periods involved in the period of no oversight, the possibility of an eventual release of some radioactive substances is inherent in the concept of geological disposal even if the system operates as intended (i.e., without deviations from procedures in operations, construction or accidents).” Thus, eventual release in the far future is expected even if its probability and endpoint cannot be certain. Large uncertainty does not mean low probability of occurrence. If the exposure due to eventual release is treated as potential exposure, it may lead to misunderstanding that no exposure occurs under future normal evolution. In conclusion, it may be claimed that large uncertainty makes it difficult to clearly distinguish normal exposure and potential exposure and may be treated as a whole.


Line 952:…(IAEA,2011, IAEA, 2009).

IAEA (2011) Disposal of Radioactive Waste. IAEA Safety Standards Series SSR-5


Line 964: …to concentrate, contain and isolate …

See paragraph 22, the strategy for the disposal is “to concentrate, contain and isolate the waste”.


Line 971: ...monitoring of release and surveillance of the facility)

IAEA Safety Standards address not only monitoring but also surveillance.


In paragraph 83 the last sentence is vague. Regarding a representative person, IAEA draft safety guide DS355, “The Safety Case and Safety Assessment for Disposal of Radioactive Waste,” which is under publication, says the following:


“5.31. For long term dose assessments, it can be assumed that radioactive contamination of the biosphere due to releases from the disposal facility is likely to remain relatively constant over periods that are considerably longer than the human life span. It is then reasonable to calculate the annual dose or risk by averaging over the lifetime of the individuals, which means that it is not necessary to calculate doses to different age groups; the average annual dose can be adequately represented by the annual dose or risk to an adult [ICRP Publ.101 and 103].”


We support the above-mentioned guidance and recommend adding to paragraph 83 of this report some comments that will give perspective on this issue.