ML19281B683
| ML19281B683 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 04/24/1979 |
| From: | Jennifer Davis CALIFORNIA, STATE OF |
| To: | Harold Denton, Herring K Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7905300651 | |
| Download: ML19281B683 (2) | |
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DIVISION OF MINES AND GEOLOGY fy)
O(VisK)N HEA000ARTERs (fuiC PUBLjC DOCUMEN* Poov) i4:e nium srmr. soom is4:
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April 24,1979 Dr. Harold Denton Director of the Office of Nuclear Reactor Regulations Nuclear Regulatory Comission W4sbington,D.C.
20555 Attention: Mr. Kenneth Herring During our recent conversations with your staff and our further review of the ground rnotion input used for the Rancho Seco Nuclear Plant Unit I, we have developed several additional questions. The questions are as follows:
1)
It is understood that the design spectra shown in Figura SK-6292-5-61 of Vol. VI of the FSAR represent freefield ground motion at the site.
Would you provide infonnation concerning the development of the shapes of design spectra shown in that figure? For e erplo:
if these shapes result from the analysis of a set of strong motinn records, what was the inethod of analysis and what records were in the data set?
- 2) It is our understanding that the time history record from Taf t 1952 adjusted to a peak horizontal acceleration of 0.259 was used to develop
. response spectra for equipment design at various levels within the reactor structure. These spectra,were derived from a rmdel of tha entire structure including soil damping values of 101 for translation and 9% for rocking. Please advise us if this statement which si"varizes our account of your comunication in the phone conversation of Aortl 20 is correct.
3)
It is also understood that the spectral response information shown in Figure SK-6292-S-61 was used as basic ground motion input for a inodal response spectrum analysis of the reactor structure as a whole.
We concluded from the April 20 conversation that the soil damping value of 30% for translation and 9% for rocking was employed.
If none of the curves of Figure SK-6292-S-61 represents tha input, ploose provide us with the appropriate curve or with the spectral accelaration, i
period and damping used for each rnode of the reactor structure analysis in this evaluation.
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Dr. Harold Denton April 24, 19/9
- 4) As a result of conversations between COMG and NRC staf f on April 70 we understood that there was to be a written discussinn of tha irole-mentation of Regulatory Guide 1.60 as it was appliad to plants licensed prior to 1973.
It was understood that the implemntation sortion nut-lined the policy for the application of Regulatnry Guitle 1.60_to exist-ing as well as planned facilities; are we mistaken? The facsimile transmission of 19 April 1978 did not contain this infnmation: pleasp transmit a copy of the implementation section or NRC policy relating to this matter.
We very much appreciate your attention to this matter.
ir you hava questions please contact John Ragsdale at (916) 322-9317. _We hope for a timely reply.
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/ State Geologist cc Or. Harold Denton g
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