ML20043D783
| ML20043D783 | |
| Person / Time | |
|---|---|
| Issue date: | 04/30/1990 |
| From: | Stevenson J Advisory Committee on Reactor Safeguards, STEVENSON & ASSOCIATES |
| To: | Seiss C Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-CT-1969, GL-88-20, NUDOCS 9006110167 | |
| Download: ML20043D783 (3) | |
Text
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- EVENSON & ASSOCIATES $
- a structural mechanical consulting engineering firm
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< ; -- s t,.. Menue. CimlanJ. Ohio 44125. (2161587 3805 Teleu 5106(15834 Fax: (216) 587 2205 83Cl490A SEIS,
DRAFT April 30. 1990~
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Dr.-Chet Seiss 805 Hamilton Drive Champaign, IL 61820
Dear Dr. Seiss:
-Per your request I have reviewed the following documents:
1 (1)f Draft IPEEE Generic Letter No. 88-20 Supplement XX L
(2)
Draf t NUREG-XXX, Procedural and Submittal Guidance for Individual Plant L
Examination of External (IPEEE) for Severe Accident Vulnerabilit',es, j
February 1990.
-(3)
Dra f t 1 Report of the External Events Steering Group, Guidelines-for
' Conducting the Individual Plant Examination for External Events (IPEEE) and have a: number of comments.
A.
Generic Letter s
- Coment 1-Ref.: Appendix 1 - Summary of Seismic IFEEE Enhancements
-The text-of Appendix 1 appears to indicate these are different and fewer 4
- enhancements-required using PRA as compared to the SMM (e.g. Sl#1 appears to require a soil' liquefaction analysis 'and containment evaluatiori while l
PRA does not).
Actually NUREG-XXX requires the same enhancements-l independent of which method is used. Appendix 1 should be rewritten so as.
not to. appear biased toward PRA.
Coment 2 Ref. Identification of External Hazards It is noted = there has ' been no explicit identification of postulated turbine missiles and small airplane crash in the IPEEE scope.
It is my
- understanging these phenomena are usually considered enveloped in' design by the 10' 5 ornado requirement. However,-if the IPEEE. tornado is reduced I
t to the 10'-
level-(See Section 5.2.4 of NUREG-XXX)- are these other two phenomena still enveloped?
If not, they might require explicit consideration in a IPEEE program.
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Dr. Chet Seiss April 30, 1990-Page 2 B.
NUREG XXX-Procedural and Submittal' Guidance
'Coment 3 Ref. NUREG XXX Table of Contents While it may be justified by the different contributions to core malt of seismic as compared to flood and extreme wind, Section 3 for senmic acceptance methodology contains nine detailed pages of methoaology while wind and flood have only two general pages of guidance. It is recomended that a significant amount of the time in the workshop be addressed to-better development or definition of flood and extreme wind (tornado) guidance which do not appear to be nearly as well developed as do the seismic requirements.
Comment 4 - Raf. NUREG XXX Section 3.2.2 Review Level Earthquake The bining and selection of the Review Level Earthquake,RLE, appear to be based entirely on the seismic hazard at a particular site and ignore the relative conservctism of the seismic design basis of the plant which-.is contained not only in the PGA' but also in the shape of the design spectra, in my opinion bining and selection of the RLE should also depend on a-comparison of the EPRI and LLNL hazard spectra to the-plant design
- spectra, if a plant has used a relatively conservative design spectra, this should be considered in selection of both bin and RLE levels.
Coment 5 Section 3.2.2 It is not clear why-shallow soil ~ conditions sites have been singled out for special consideration.
The concern identified appears to be more a problem with use of finite element soil structure interaction analytical models with vertically propagation shear waves rather. than actual observed -
significant seismic amplification of earthquake motions at such sites. A review' of Table 3.1 suggests there are several other plants which have shallow soil conditions and/or are founded on piles which have not been identified as requiring special attention.
Such concerns if real should' be considered in a consistent manner.
C.
NRC External Event Steering Comittee Report coment 6 - Tornado Margins Methodology The report lists several seismic enhancements in pection 3.2.5 and-3.2.6.
Similar enhancements should be developed for 10' tornado effects.
As a minimum a reference shou'd be given as to where criteria associated with an increased tornado probability should be given (i.e. ANS 2.3) associated with:
(a) buildings, equipment and tanks, etc. to be evaluated for na effects I
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Dr. Chet Seiss Anril 30, 1990 Page 3 (b) wind fields (c) pressure fields (d) combinations of wind and pressure fields i
(e) missiles and missiles. combined with wind and pressure fields (f) tornado induced differential pressures within buildings at the 10*5 level in general I find a lack of balance between the seismic and other IPEEE concerns.
Please advise if you require any clarification of this letter, Sincerely,
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John D, Stevenson President JDS:ss t
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