BECO-84-036, Forwards GE Supporting Proposed Change to Control Rod Drive Weekly Surveillance Tech Specs,Per P Leech 840203 Telcon Request

Forwards GE Supporting Proposed Change to Control Rod Drive Weekly Surveillance Tech Specs,Per P Leech 840203 Telcon Request

ML20087B558
Person / Time
Site:	Pilgrim
Issue date:	03/05/1984
From:	Harrington W BOSTON EDISON CO.
To:	Vassallo D Office of Nuclear Reactor Regulation
References
BECO-84-036, BECO-84-36, NUDOCS 8403090152
Download: ML20087B558 (4)

Text

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BOSTON EDISON COMPANY B00 BOVLaTON STREET IBGETON, MAESACHUSETTs 02199 U.'. ,'.'.*U.I.."[."."' " *

• March 5, 1984 w == BEco 84-036 Mr. Domenic B. Vassallo, Chief Operating Reactors Branch #2 Division of Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D. C. 20555 License No. DPR-35 Docket No. 50-293 i

Additional Information on Proposed Change to Control Rod Drive Weekly Surveillance Technical Specification

Dear Sir:

By telephone conversation on February 3,1934, your Mr. Paul Leech requested a i copy of the General Electric correspondence which supports our proposed change to control rod drive weekly surveillance technical specifications for the Pilgrim Nuclear Power Station (submitted by letter dated September 12, 1983, BECo 83-238). The attached letter f rom Mr. R. F. Thibault, General Electric, to Mr. C. J. Mathis, Boston Edison, dated March 4, 1983 is provided in response to this request.

Please contact us if we may provide any further information in support of this proposed technical specification char.ge.

Very truly yours,

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Attachment:

Letter from Mr. R. F. Thibault, General Electric, to Mr. C. J. Mathis, Boston Edison, dated March 4,1983 r

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GENERAL $ ELECTRIC DOMESTIC APPARATUS AND ENGINEERING SEfMCES OPERATION GENERAL ELECTRIC COMPANY

• ONE 'JNNERSITY OmCE PARK,29 SAWYER ROAD e WALTHAM, MASSACHUSETTS 02254 * (617) 647-7200 G-BK-3-028 March 4, 1983 Mr. C. Mathis Manager of Operstions Boston Edison Company

. Pilgrim Nuclear Power Station RFD #1 Rocky Hill Road Plymcuch, MA 02360

SUBJECT:

PILGRIM NUCLEAR POWER STATION CONTROL ROD DRIVE (10-31 AND 22-39) CONSULTATION

Reference:

Boston Edison Company " Clarification of CRD 10-31 and 22 issues" (PNPS File NO. TCH-83-54), dated February 16, 1983

Dear Mr. Mathis:

This letter responds to Boston Edison's (BECo) request for General Electric's -

(GE) concurrence with the conclusions and concerns with Control Rod Drive (CRD) (10-31) and (22-39) stated in the Reference. Justification for techni-cal specification ralief on the weekly exercise requirements for the subject rods is also provided.

The reference si;ates that CRDs (10-31) and (22-39) are currently experiencing ~

difficulty with rod withdrawal, excessive withdraw stall flows and high CRD temperatures. Data taken during rod movements indicate that the subject drives would insert and withdraw (once unlatched) with normal drive pressure.

The reference concludes that the most probable cause of the observed CRD problems is degraded stop-piston and collet-piston seals.

GE concurs with the stated conclusions of the referenced letter and the concerns resulting from these conclusions with the following exception:

Instead of using GE data on CRD tests with various seals removed as at indication that the measured scram times are " essentially as bad as can be anticipated", it is more appropriate to point out the conditions existing in the CRD's in question, i.e.,:

a) The current _ measured insert stall flow is low (approximately 2 GPM),

b) There has been no reported problem of rud insertion at normal drive water pressure and

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. c) The measured- 90% scram insertion time history has been relatively stable (approximately 3.4 to 3.9 seconds) for the subject rods "during the past year.

These are indications that there is a high probability that insertion times will not'de5rade significantly further.

Although potentially not directly applicable, tests conducted at GE's Control Rod Drive Test Facility indicate that with various failed stop-piston and

. collet-piston . seals, 90% scram insertion times varied between 3 and 10 seconds. The slower portion of this time band was achieved with all stop-piston, drive-piston and collet-piston seals physically removed. This latter condition is considered to be a worse condition than the current-reported condition of CRDs (10-31) and (22-39).

Pilgrim technical specifications require that all CRDs be exercised at least

- one notch on a weekly basis. This weekly exercise criterion is based on:

- a) A 1974/75 collet housing problem (not collet finger),

b) The need to demonstrate that CRDs will move and latch as a result of notch insert or withdrawal signals.

c) The need to flush the crevices under the seals to minimize corro-sion on the nitridad surfaces.

An alternative CRD veekly rod exercise, wherein the requirement for latching need not be demonstrated as long as rod movement under normal insert drive

- pressure has been confirmed, is considered acceptable to GE for problem rods such as CRD (10-31) and (22-39) with improved collet retainer tubes (SIL 139, LSupplement 5). The basis for this relief is as follows:

a) The improved collet retainer tube has effectively eliminated tha cracking problem, and b) A partial insert to an intermediate position indication (e.g.,

" 46" : to "45") and a settle back to the original notch position would' satisfy the requirement of confirming that water pressure is getting to the CRD, that the CRD inserts and the seals are being flushed. This motion, with the resultant settling back into _ the

original notch will also demonstrate mechanical integrity of the collet fingers. (Note

This does'not apply to notch position "48" since the rod does not latch. Consequently, GE recomnends that the subject rods be inserted to notch "46" or farther).

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- In suunary, GE concludes that for drives there is a high which probability have the of same insertion characteristics as a as drives (10-31) ~and (22-39)Furthermore, elimination of the latching require-result of a scram signal. even numbered position) during weekly rod

-ment. (i.e. , moving into the next surveillance testing can be justified for these problem CRDs.

Very truly yours.

R .

Service Manager - Nuclear .

RFT:JFH:mac cc: R.M. Butler A.V. Morisi ,

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