ML20039A170
| ML20039A170 | |
| Person / Time | |
|---|---|
| Site: | Shoreham File:Long Island Lighting Company icon.png |
| Issue date: | 11/30/1981 |
| From: | Milligan M LONG ISLAND LIGHTING CO. |
| To: | Haynes R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, SNRC-639, NUDOCS 8112160303 | |
| Download: ML20039A170 (2) | |
Text
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<psau/ww SHOREHAM NUCLEAR POWER STATION P.O. BOX 618, NORTH COUNTRY ROAD e WADING RIVER, N.Y.11792 November 30, 1981 SNRC-639 Qx Mr. Ronald C.
Haynes
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LONG ISLAND LIGHTING COMPANY Shoreham Nuclear Power Station - Unit 1 Docket No. 50-322
Dear Mr. Haynes:
On October 19, 1981 we notified Region I verbally of a design condition within the Shoreham Control Rod Drive (CRD) System which could be potentially reportable in accordance with 10CFR50. 55 (e).
We became aware of this situation through a copy of a letter, dated October 14, 1981, from Reactor Controls, Inc.
(RCI) to your office entitled, "A Potential Reportable Condi-tion."
This letter serves as our 30-day written report on this potentially reportable condition.
Description of the Potential Deficiency Information from the referenced RCI letter indicates that sub-stantial loads are introduced to the CRD system under certain circumstances when a fast opening scram inlet valve actuates.
RCI explained that, while performing stress analysis of the pip-ing and supports for a BWR-6 unit with a " Fast Scram" feature, the opening time for the scram inlet valves was found to be 20 milliseconds.
This factor resulted in substantial hydrodynamic (water hammer) loads effecting the design of system pipe sup-ports.
The hydrodynamic loads become a design problem during a start up scram event (i.e.,
the RPV is at essentially "0"
pres.-
sure, resulting in the highest differential pressure between the RPV and CRD accumulator).
The RCI letter also points out that the CRD System has a history of many years of successful operation at all plants without any reported difficulties from this load.
RCI's findings are the result of analysis using computer programs that may not parallel the system closely enough to represent the actual condition.
8112160'30 Y l
r SNRC-639
- Nov;mber 30, 1981 Page -
'Our preliminary review of the Shoreham design ~indipates,,that there are_several aspects of the CRD System which will' serve to decrease the. subject hydrodynamic loads for Shorchsi.7CFirst, the; scram inlet'~ valve opening times at Shoreham are,1conside slower.than the 20 milliseconds noted by RCI at khe BWR-6 rably unit
- with the " Fast Scram" feature.
We anticipate that this' factor alone will substantially decrease the magnitude of the subject Jhydrodynamic loads.
Additionally, Shoreham's CRD accumulator operates at a lower pressure resulting in a lower differential
. pressure duringlthe start up scram event and thus is expected to produce smaller loads.
The Shoreham CRD System design more closely approximates-designs used in aperating.BWR facilities rather than the design used in the BWR-6 unit with the " Fast Scram" feature.
We, therefore, anticipate that the successful operating history of CRD systems at BWR facilities can be appro-priately applied to Shoreham.
Corrective Action At present, we are actively pursuing an evaluation of the Shore-ham CRD System with respect to the analysis performed by RCI.
As pointed out'by RCI, the ability of the computer program to
. accurately parallel the physical system represents a substantial engineering effort.
We anticipate completing this effort _in June, 1982.
If, during the course of our evaluation, we deter-mine that the operation of the CRD system would be adversely.
affected as the result of these hydrodynamic loads, we will notify your office _immediately.
Please do not hesitate to contact us if you have any questions on this matter.
Very.truly yours, M. H. Milligan Project Engineer Shoreham Nuclear Power Station CKS/ law cc:
Mr. Richard DeYoung, Director NRC Office of Inspection & Enforcement Division of Reactor' Operations Inspection Washington, D.C.
20555 Mr. J. Higgins, Site NRC