ML20028A041

Forwards 821105 Interim Deficiency Rept Re Diffuser Cap Screws on Reactor Coolant Pumps

ML20028A041
Person / Time
Site:	Satsop
Issue date:	11/09/1982
From:	Leddick R WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC
References
GO3-82-1162, NUDOCS 8211160300
Download: ML20028A041 (1)

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Washington Public Power Supply System Box 1223 Elma, Washington 98541 (206)482-4428 Docket Number 50-508 November 9, 1982 G03-82-ll62 Document Control Desk U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Subject:

POTENTIAL 10CFR50.55(e) DEFICIENCY DIFFUSER RETAINING CAP SCREWS -

REACTOR COOLANT PUMPS (D/N #46)

Attached is a copy of an interim report provided to Region V concern-ing a potential 10CFR50.55(e) deficiency associated with the subject condition.

Should you have any questions or desire further information, please contact me directly.

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Program Director, WNP-3 DRC:nj Attachment cc: J. Adams - NESCO, wo/a D. Smithpeter - BPA, wo/a Ebasco - New York, wo/a WNP-3 Files - Richland, wo/a 8211160300 821109 PDR ADOCK 05000508 S PDR

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Attention: Mr. D. M. Sternberg E d

Chief, Reactor Projects Branch No. 1 g '

Subject:

POTENTIAL 10CFR50.55(e) DEFICIEN Y Q hh !

DIFFUSER RETAINING CAP SCREWS - , V g i;

REACTOR COOLANT PUMPS (D/. f4 \ g !y c g%

a On October 7, 1982 the Supply S stem n ti ict ur o fite of a potential k -4

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b( Q 10CFR50.55(e) deficiency conc 'nin< the ~ai uf f diffuser retaining  ; g cap screws in the Reactor Co a ing. On October 8, 1982 the u ly X stem P 1p: s op e by Combustion Engineer- o notified CE that they b

were responsible for reporting th< s b ?ct deficiency to the Nuclear . .

Regulatory Commission in accordoqct ,i i the provisions of 10CFR21. d,g To date, the engineering evaluatibn the subject deficiency has not been complete . dU  %

Attached is C current assessment of the deficiency. Based on'CE's '

prelimina if left un kc tion, Ebasco has determined that the deficiency, al te would not adversely affect th'e safety of operations rr( [$NO of the plant.\ we r :a final determination of the safety significance Jq -

t ni t'bemadeN; 1 CE. completes their evaluation. Therefore, a final or in erim repo'rt will be submitted to your office by February 4,1983. (/ A Shoul v have any ontac me directly.

questions or desire further information, please @

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R. S. eddick (760) g "'~ ~ ~

Program Director, WNP-3 ' 6 l

DRC:nj g l Attachments' [ 'y cc: J. Adams - NESCO S8E D. Smithpeter - BPA .E SE Ebasco - New York o '

WNP-3 Files - Richland l< -

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o SYSTEM 80 REACTOR COOLANT PUMP DESIGN DEFICIENCY C-DESCRIPTION OF DEFICIENCY. -

Diffuser retaining cap screws of the Reactor Coolant Pumps have recently failed in the CE-KSB test loop. These cap screws support the diffuser suction ring assembly of an idle pump. With the pump running, hydraulic forces unloaded the sixteen cap screws in question. Two cap screws secure each retaining ring segment and locking devices retain the cap screws. The screws that have failed to date have failed either under the head or at the first thread. The heat treatment condition of the material of these screws caused the material, to be susceptible to hydrogen embrittlement / stress corrosion cracking.

SAFETY IMPLICATIONS If both cap screws per segment ring failed a loose ring segment / cap screw element would exist. While this element is trapped above the impeller it

• would be free to move around above the im,peller and some damage might occur. Should all or some of the diffuser retaining cap screws fail CE would not anticipate any increase in risk to the health and safety of the public. Rather CE considers this problem as a risk to the continued operational capability of the RCP. CE is continuing its evaluatica of the problem and some potential solutions. The results of this effort

. will be presented in a final report.

CORRECTIVE ACTIONS The cap screw material heat treatment will be changed to a condition so that the material is not susceptible to hydrogen embrittlement / stress corrosion cracking. Some other minor changes will be included in the change out to alleviate the load these screws receive.

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