ML20062D227

Deficiency Rept Re Water Hammer Loads Affecting Control Rod Drive Sys.Initially Reported on 811130.In-plant Test of Parameters Performed.Support Mods Will Be Complete Prior to Fuel Load.Investigation Continuing

ML20062D227
Person / Time
Site:	Shoreham File:Long Island Lighting Company icon.png
Issue date:	07/23/1982
From:	Milligan M, 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-736, NUDOCS 8208050511
Download: ML20062D227 (3)

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1. 8,M LONG ISLAND LIGHTING COMPANY wamaww SHOREHAM NUCLEAR POWER STATION P.O. BOX 618, NORTH COUNTRY ROAD e WADING RIVER, N.Y.11792 July 23, 1982 SNRC-736 Mr. Ronald C. Haynes Office of Inspection & Enforcement Region 1 U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406 Long Island Lighting Company Shoreham Nuclear Power Station - Unit 1 Docket No. 50-322

Dear Mr. Haynes:

Our letter, SNRC-639 of November 30, 1981, addressed a potenti-ally reportable condition under 10CFR50.55(e), involving water hammer loads which could affect the Control Rod Drive (CRD)

System at Shoreham. This letter summarizes the investigations and corrective actions taken to date by LILCO to resolve this issue.

Summary On October 14, 1981 Reactor Controls, Inc. informed the NRC that the rapid opening of the Control Rod Drive (CRD) System Insert Scram Valves could potentially result in a significant hydraulic transient affecting the CRD Insert lines and supports in several BWR plants, including Shoreham. A preliminary evaluation concluded that the best method of quantifying the effects in the Shoreham plant would be by means of an in-plant test. A test plan was developed to obtain the most meaningful system response parameters as determined by general knowledge of the system characteristics, supplemented by an analytical evaluation. The test at Shoreham was successfully completed by LILCO, Stone &

Webster Engineering Corp. and Wyle Laboratories during the first week of May, 1982.

Test Description The test was run under system conditions associated with a start-up scram event. This was considered to be the worst condition since the combination of zero pressure in the Reactor Vessel and a pressure of approximately 1500 psi in the CRD HCU Accumulators results in a large differential pressure across the Insert Scram Valves.

8208050511 820723 DRADOCK05000g g7/7

SNRC-736 July 23, 1982 Page 2 The instrumentation for the startup scram test was located on three sets of Insert and Withdraw lines, between the Hydraulic Control Units and the CRD housing. These sets of Insert and Withdraw lines were selected as being representative of worst case conditions based on limiting variations in piping geometry and a preliminary analysis conducted by Stone & Webster. All lines are located in one typical quadrant of the CRD System. The following parameters were measured:

1. Valve stroke time on each of the three Insert and Withdraw Valves

2. Piping displacement at six locations

3. Pressure in each of the three Insert and Withdraw lines

4. Piping segment forces (support reactions) at twelve locations

5. Pipe bending strain at twenty-four locations

6. Pipe support strain at four locations The test matrix consisted of scrams on each of the three individ-ual sets of lines, with three initial positions of the Control Rod (i.e., fully withdrawn, mid-position, and fully inserted).

Additionally, simultaneens scrams of all lines in the test quad-rant were run at each of the three initial rod positions. Each of these twelve conditions was run at least twice to assure repeatability of results. All tests were run with the system operating at full pressure in the Accumulator and with an unpressurized Reactor Vessel, which was the predicted limiting test case.

Test Results and Actions Taken The test results indicated a high correlation with the predic-tions of preliminary analysis. However, a lower amplitude was measured than was predicted by analysis. Initial rod position was not found to be an important parameter.

The testing procedure resulted in a maximum measured bending stress in the Insert piping of 6700 psi and a maximum single line support load of 225 lbs. Typically, the measured pipe stress is in the 4000 psi range and support loads are in the 50 lb. range.

The magnitude of pipe stress and support loading has proved to be significant and will, therefore, be formally incorporated into the final piping stress analyses and support designs for the Shoreham CRD Insert piping.

v j SNRC-726 July 23, 1982 t Page 3 Further analytical review has determined that the effects of a normal operating scram is also a potential area of concern. Such an event would be substantially less severe on the Insert lines.

However, significant stress levels and support loadings could result in the Withdraw lines due to high differential pressure across the Scram Discharge Valves during the operating scram event. The effects of this event are still being investigated and will also be incorporated in the final pipe stress analyses and support design.

Date of Full Compliance Since both the startup scram and the normal operating scram cause significant hydraulic events, piping stress levels due to water hammer loads are being incorporated by Stone & Webster Engineering Corp. into the Insert and Withdraw line pipe stress calculations to verify that stress allowables are not exceeded.

All CRD pipe supports will be reviewed and modified, if required, to accommodate the loads associated with these hydraulic trans-ients. Re-evaluation of the pipe supports by Reactor Controls, Inc. is currently in progress. All support modifications resulting from these re-evaluations will be completed prior to Fuel Load.

Please do not hesitate to contact us if you have any questions on this matter. ,

Very truly yours, e o AY'N 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 All parties