ML20245A404
| ML20245A404 | |
| Person / Time | |
|---|---|
| Issue date: | 03/23/1987 |
| From: | Novak T Office of Nuclear Reactor Regulation |
| To: | Speis T Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20236K304 | List:
|
| References | |
| FOIA-87-380, RTR-NUREG-0612, RTR-NUREG-612, TASK-082, TASK-82, TASK-OR TAC-53347, NUDOCS 8703270106 | |
| Download: ML20245A404 (6) | |
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March 23.1987
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cn0 M DuM FOP: Themis P. Speis, Director, l
Division of Safety Review and Oversight FROM:
Thomes H. Novak, Acting Director Division of PWR Licensing - A SURJECT:
PEER REVIEV 0F DRAFT BNL PEPORT "BEYOND DESIGN-BASIS ACCIDENTS IN SPENT FlfEL POOLS (GENERIC ISSllE 8?)" (TAC NO. 53347)
The Division of Pk'R Licensing-A (DPL-A) has reviewed the draft BNL report "Beyond Design-Basis Accidents in Spent Fuel Pools (Generic Issue 8?)",
as reouested by your February 10, 1987 memorandum. This review was performed by the Reactor Systems Branch (RSB), Plant Systems Branch (PSB) and Engineering Branch (EB). The comments from each branch are provided in Enclosures 1, 2 and 3. respectively.
EB's coments deal mainly with the spent fuel pool seismic fragility analysis; PSB's coments are associated with the cask handling and load drop assumptions; RSB's coments are mainly related to the effects on the fuel.
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Generally, the review branches agree with the conclusions of the report, which suggest further study of the issue before any decisions are made regarding what actions, if any, should be taken.
If you require further information regarding the enclosed coments, please contact Norm Romney (EB) at x24709, Walt Brooks (RSB1 at x?Bd34 or Bill LeFave (PSR1 at x28945.
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Thomas M. Novak, Acting Director Division of PVR Licensing - A cc:
P. Brooks N. Romney A. Masciantonio J. Craig j
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EFCLOSURE 1 PEEP REVIEW 0F REACTOR SYSTEMS RRAf!CH (DPL-A)
DRAFT BNL REPORT REGARDING GENERIC ISSUE B2 (TAC NO. 53347) 1.
The discussion is limited to a loss of pool water with consequent fuel I
heatup. Another beyond design basis event which may warrant consideration is criticality in the pool. The same initiating event (seismic, missile, etc.) which causes pool rupture may cause sufficient damage to the racks that criticality may result (either with or without pool rupture). The criticality event would increase the stored energy in the fuel, which could significantly affect the consequences.
P.
The heatup calculations appe6r to treat the relevant parameters. We found the definition of the inlet orifice dimension to be confusing.
Perhaps a sketch of the assumed rack design would clarify this.
3.
The calculation of offsite consequences seems to be adecuate for assessing the relative importance of these events as risk contributors.
4 We concur with the conclusion that the issue warrants further study, with about the sane priority as core melt events. See Comment I for a suggested expansion of the study.
ENCLOSURE 2 PEER REVIEW OF PLANT SYSTEMS BPANCH (DPL-A)
DRAFT BNL REPORT REGARDING GENERIC ISSl'E 82 (TAC NO. 53347) 1.
We feel that the estimated spent fuel pool fire probabilities identified 1
in Table S.1 may be overly conservative for pool failures due to cask drop. The risk calculations did not take into account the resolution of Generic Task A-36, " Control of Heavy Loads Near Spent Fuel", which is presented in NUREG 0612. " Control of Heavy Loads at huelear Power Plants." The subject study relies on information from the Reactor Safety
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Study which was performed wr ~1 before the resolution of A-36.
The resolution of A-36 for Ginna and many other plants was based on the availability of a single failure proof crane for cask handling to C
significantly reduce the load drop probability. The single failure-proof crane is designed to maintain the cask even under safe shutdown earthquake leads.
The intent of A-36 was to reduce the probability of unacceptable load drop accidents to an insignificant level. The sub,iect report should be revised to take into account the resolution of A-36 including the probabilities developed in NUREG-0612. Such consideration may eliminate the cask drop accident from further study.
Throughout the subject report, it is noted that "many new plants have pool configurations and administrative procedures which would preclude this failure mode." It should also be noted that fo11 ewing the resolution of A-36, many older plants were found to have the same protection to preclude the failure mode, t
PEER PEVIEW 0F ENGINEERING BRANCH (DPLA)
DRAFT BNL REPORT REGARDING GENERIC ISSUE (TAC No.: 53347) 1.
We agree with sne last sentence of the first paragraph of Section 2.2.1.3.
In order for a structural failure of a pool with a stainless steel liner to result in leakage from the pool the fuilure must be accompanied by enough deflection of the concrete to cause a rupture of the liner. Thus, for pools with liners, the forcing function causing a structural failure of the pool must have enough energy to cause a deflection considerably beyond the plastic limits of both the reinforced concrete structure and the stainless steel liner.
2.
Section 2.2.1.3 is not clear as to an intent to develop a generic fragility curve to be used for all BWR plants, and a corresponding generic fragility curve for use on PWR plants.
3.
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The use of fragility curves developed for the Oyster Creek Reactor Building and the Zion Plant Auxiliary Shear Walls is questioned. The structural design and geometry of the Reactor Building and Shear Walls are different than the storage pools of the subject plant in this report.
4.
Are the effects of the pool liner considered in assessing the uncertainty contained in establishing confidence limits?
5.
It. is not clear how " engineering judge.nent" is considered when arriving at a weighting factor (i.e., what factors are evaluated to arrive at a weightedfactortobeappliedtohazardandfragilitycurves).
6.
When assessing cask drop accidents in the pool the concern should be expanded beyond the pool edge. A loaded shipping cask falling some distance and striking the pool floor could cause a rupture of the liner.
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Alternately the shipping cask could strike a column of.the storage rack and, depending on the design and geometry of the rack, could result in a sharply concentrated load at the rack footing.
Such a concentrated load could cause a " punching shear" failure of the pool liner and pool floor.
7.
The Engineering Branch concurs with the Reactor Systems Branch Content No. 1, as it relates to the rack structure being damaged by a missile.
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