Management of Commercially Generated Radioactive Waste - U.S. ...

Comment
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3-9
Comment
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in-situ tests, it appears prudent to provide capability for retrievability Based on Project Salt Vault data (ORNL-4555, Chapter 12) the mine layout
of the wastes for the normal operating life of the repository and for as design postulated by GEIS for a repository in salt would therefore be
many years thereafter as may be needed to retrieve the emplaced wastes. inadequate. This would necessitate a different design that would consider
The GEIS should address retrievability in a fashion that the potential for the thermomechanical effects on salt mass behavior. Extraction ratios
such retrievability can be properly assessed. may have to be reduced, room and pillar dimensions changed, etc.
The following examples are cited: 3.c.6 pp. 3.1.28, 3.1.36, 3.1.41, 3.1.120, 8.4.7
The subject of occupational radiation exposure is not adequately addressed
A conclusion that readily retrievable conditions in a repository in salt in the GEIS. It should be considered in connection with short term environ-
would prevail in storage rooms for at least five years is based on linear mental impacts and the probability of various accidents occurring during
thermomechanical analyses. The time behavior of salt under thermal and the handling and emplacement of waste canisters.
mechanical loading cannot be approximated as a linear relationship. The
GEIS makes an allowance of two feet to accommodate for expected closures 3.c.7 p. 3.1.36
(expected closures are not specified). The statement is made in the fourth paragraph that the costs for additional
support necessitated by the reduction in rock strength due to radiation,
Project Salt Vault, Chapter 12 presents several figures (Figure 12.36, are not expected to be significant. The basis for this conclusion should
etc.) that describe pillar behavior as a function of mechanical and thermal be presented.
loading and time. A 50% shortening of a pillar is expected when subjected
to a load due to 8000 psi stress and 100 0 C temperature during a period of 3.c.8 p. 3.1.37
200 hours. Similar results presented are 28% shortening under 6000 psi at The statement, ".... maintaining retrievability longer than needed to
22.5 0 C for 30,000 hours and 45% shortening under 200 psi at 200 0 C for reasonably assure repository operation increases the occupational and
500 hours. The behavior exhibited is not linear and a significant under- general populace risk." is unsubstantiated.
estimation of closure will be obtained if a linear approximation is used.
3-10
3.c.9 pp. 3.1.104, 3.1.107, 3.1.110, 3.1.112, K.17, K.113, K.115
If later studies have been used to discount the results of Project Salt pp. 7.2.22, 7.4.4; DOE/ET-0028
Vault, they have not been identified in GEIS. Consideration of the creep A major deficiency in the design of the repositories in granite, shale, and
behavior of salt under thermomechanical loading is important for the basalt is that they have been designed as if the host rock were salt. The
design of a repository in salt because it will affect the short (operational) repositories in the four geologic media should not be of similar design.
and long (retrievability) term stability of storage rooms and access ways. For instance, the inherent structural characteristics of granite have not
If stability is compromised, the integrity of the impermeable barrier been taken into consideration. The design of a mine in hard rock is
between the salt bed and overlying aquifers that is assumed by GEIS, may substantially different from that in salt. Where, by the nature of the
be compromised. This would lead to problems associated with groundwater material, a repository in salt is confined to a single level, a repository
movement in salt that have not been addressed. in massive granite need not be. The long term stability of large rooms in
granite is well known. Transportation could be by track systems - either
Co