NUREG-1864 A Pilot Probabilistic Risk Assessment Of a Dry Cask Storage System At a Nuclear Power Plant

Nuclear Regulatory Commission (2007-03)

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This is a horrible example of how far off our Nuclear Regulatory Commission is in estimating problem. This PRA has fatal flaws, such as:

FATAL FLAW 1: No appreciation of Chloride Induced Stress Corrosion Cracking (CISCC) or any other sort of corrosion.

8.3 Corrosion

The MPC, which acts as the confinement boundary for the HI-STORM dry cask storage system, is constructed entirely from austenitic stainless steel Types 304, 316, 304L, or316L. All of these stainless steel grades are corrosion resistant in high-humidity and industrial environments. Therefore, coastal and industrial atmospheres should have no effect on the confinement ability of the MPC (Reference 51 -- 51. American Society for Metals, "Corrosion Resistant Materials," Metals Handbook Desk Edition, Materials Park, Ohio, 1985.)

FATAL FLAW 2: ISFSI is in unreasonably secure area.

The assumptions in the PRA are BEST CASE rather than WORST CASE.

Other than a spur track from a railway line, there are no railway lines near the route of the storage cask from the reactor building to the storage pad or at the storage pad.

Within a radius of 8 km (5 miles) of the subject plant, there are no manufacturing or chemical plants, refineries, storage facilities, mining operations, military bases, military bombing ranges, aircraft low-level flight patterns, missile sites, transportation facilities, oil or gas wells, or underground storage facilities. The area within this radius of the subject plant is mostly rural; the land is either residential or agricultural. The area is not expected to change significantly in the foreseeable future.

FATAL FLAW 3: No aging effects

Used a thick cask in a test that only could evaluate the aging of the contents, not the thin canisters used in the rest of the evaluation.

1.2.2.9 Aging Effects

To evaluate possible aging effects, a CASTOR-V/21 dry storage cask was examined for degradation (Reference 6). This cask was produced for use in testing aging effects on long-term dry cask storage. (This cask design was not put into production.) The examination consisted of remote indirect visual examination [cask internal, lid seals, and pressurized-water reactor (PWR) spent fuel assemblies] and temperature measurements of selected spent fuel assemblies. Interior crud samples were taken, and surface gamma and neutron dose rates were measured. Selected fuel rod assemblies were removed from One assembly, visually examined, and subjected to nondestructive, destructive, and mechanical examination. The helium inerting gas was sampled for analysis.

After 14 years of storage, no evidence of degradation that would affect the performance of the cask or integrity of the fuel was evident. The fuel was intact; there was no evidence of creep or rod bow. Crud found on the fuel rods was attributed to oxidized steel while the fuel was in the reactor; none of the oxidation is attributed to dry storage. Of 16 stitch welds that attached borated plates to the basket, 15 were cracked. The stitch weld cracking was attributed to the tight fit of the assemblies in the basket, not to storage. Small amounts of air mixed in with the helium were attributed to the process of inerting the cask.

While the results for the CASTOR-V/21 dry cask suggest that there will be no significant aging effects for the subject cask, it is unclear whether the two casks experience similar conditions. Accordingly, except for possible cask and fuel corrosion (see Section 8.3), aging effects are beyond the scope of this study.

• ML071340012.pdf: NUREG-1864 A Pilot Probabilistic Risk Assessment Of a Dry Cask Storage System At a Nuclear Power Plant

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