ML20199F335

Part 21 & Deficiency Rept Re Failure of Disc Guide Assembly Springs in HCV-247 & HCV-248.Initially Reported on 860314. Springs Replaced & Valves Tested Quarterly.Other Utils Contacted Via Nuclear Network Sys

ML20199F335
Person / Time
Site:	Fort Calhoun
Issue date:	03/17/1986
From:	Andrews R OMAHA PUBLIC POWER DISTRICT
To:	Martin R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
REF-PT21-86, REF-PT21-86-098-000 LIC-86-094, LIC-86-94, PT21-86-098-000, PT21-86-98, TS-FC-86-165, NUDOCS 8603280163
Download: ML20199F335 (4)

Text

i A-Omaha Public Power District 1623 Harney Omaha. Nebraska 68102 2247 402/536 4000 March 17, 1986 r TS-FC-86-165 h,?i @ Lgp 1:'a c p' . t LIC-86-094 1

! MAR I 91986 l i

Mr. R. D. Martin b ' ' ~~~ ~- ~

Regional Administrator U.S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011

Reference:

Docket No. 50-285

Dear Mr. Martin:

10 CFR 21 Report on Failure of Disc Guide Assembly Springs in HCV-247 and HCV-248 Omaha Public Power District, holder of Operating License DPR-40, has investi-gated and found the recent failure of the disc guide assembly springs in HCV-247 and HCV-248 to be 10 CFR 21 reportable. OPPD notified Mr. Doyle Hunnicutt of the Region IV office on March 14, 1986, of the attached information. The attached report provides the necessary details of this event as required by 10 CFR 21.

Sincerely, 24 R. L. Andrews b

Division Manager Nuclear Production RLA/rh 8603280163 860317 Attachment P79 ADOCK 05000205 G PDR cc: Mr. James M. Taylor, Director Office of Inspection and Enforcement (3)

LeBoeuf, Lamb, Leiby & MacRae 1333 New Hampshire Avenue, N.W.

Washington, DC 20036 Mr. E. G. Tourigny, NRC Project Manager Mr. P. H. Harrell, NRC Senior Resident Inspection C) p~ '

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i 10CFR21 REPORT ON FAILURE OF DISC GUIDE ASSEMBLY SPRINGS IN HCV-247 and HCV-248 INTRODUCTION During the 1985 refueling outage valve failures were discovered in HCV-247 and HCV-248. These valves are 2 inch Series V526 Valcor solenoid operated globe valves (Model V526-6190-4, P/N 454660001). HCV-247 and HCV-248 were. installed in December of 1982 as redundant valves, per the requirements of 10CFR50, Appen-dix A, Sect IV, Criterion 35, for the long term core cooling system. HCV-248, in series with HCV-239, provides a flow path from the charging pumps to loop 2A. HCV-247,. in series with HCV-238, provides a flow path from the _ charging pumps to loop 2B (Ref. P&ID E-23866-210-120 Sh. 1 of 2). These valves were purchased from Valcor Engineering Corporation, 2 Lawrence Road, Springfield, New Jersey 07081 ((201) 487-8400).

Problems with HCV-247 and HCV-248 were first experienced in August 1985 during equipment rotation. The valves closed during this equipment rotation and could not be reopened without securing all charging pumps. Increased valve stroke times were also noted. Discussions with Valcor Engineering Corporation deter-mined that the problem was most likely to be the main disc bleed hole in the valve. Plant Staff concluded that continued operation with the existing valve p'roblems would not be adverse to plant safety (FC-1243-85) and, therefore, operation was continued until the end of the fuel cycle.

During the subsequent refueling outage the valves were disassembled and exam-ined to determine the cause of the valve malfunction. It was found that failure of both disc guide assembly springs (P/N V52604-6190-4 and V52615-6190-4) in both valves had resulted in the valve malfunctions. The failure of the spring was complete and catastrophic, in that nearly all of the spring coils had failed. Most remaining pieces were only 1-2 coils in length compared to an 1

initial length of 25 coils. Construction of the valves is such that the spring remnants were retained in the valve internals.

EVALUATION Discussions with the Valcor representative revealed that this was not the first time that Valcor had experienced such a valve failure. A similar malfunction had occurred at' Prairie Island Nuclear Generating Plant on the Containment Hot leg Sample Line. Examination of the failed spring at Prairie Island was conduct-ed by Fairfield Testing /Labtech, Inc.. This testing found that this failure was due to hydrogen embrittlement (Lab Reports S1588 and-S1531). OPPD submitted the failed valve springs from HCV-247 and HCV-248 to Orr Metallurgical Services for examination. It was their opinion that the failure of these springs was also the result of hydrogen embrittlement (02/26/86 letter from Orr Metallurgical).

Such a common mode of failure at more than one nuclear generating station would.

seem to imply that this problem may well be experienced by any Valcor valve us-ing precipitation hardened stainless steels for internal components which may be exposed to primary coolant conditions.

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The failure of these two. valves has th'e potential to render both of.the normal charging paths to the reactor coolant system inoperative. Such 3

failure would result in loss of charging 'or makeup until alternate charg-3 ing paths were established. Alternate charging paths are available through

the pressurizer spray line and the safety injection system. Charging paths i as required by Technical Specifications Sect. 2.2 part 2d. would still be j available, however, it -is likely that in case of a total' failure, reactor 3

shutdown would be required to resolve the problem.

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At the time HCV-247 and HCV-248 were purchased, two other valves, HCV-2988 and HCV-249 were also purchased and installed as part of the modification i

to provide redundancy for long term core cooling. These valves are also'

, Valcor V526 Solenoid operated globe valves. HCV-249 is .in parallel with l HCV-240 and provides a flow path from the charging system to the auxiliary -

1 pressurizer spray line. HCV-2988 is in parallel with HCV-308 and provides

a cross-tie between the safety injection system and the charging system.

Inspection of the internals of these valves was conducted after the fail-ure of HCV-247 and HCV-248 disc guide assembly springs was' discovered..The .

springs in these valves were found to be in good condition. It is believed

, that this is due to the fact that these valves are normally closed and are l on dead legs of piping in the chemical and volume control system (Ref.

P&ID E-23866-210_-120 Sht.1 of 2 and E-23866-210-130 Sht.1 of 2). It is

! also believed that the lower temperature conditions at these valve loca-

tions are less conducive to accelerated hydrogen embrittlement.

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Other Valcor valves are also used at Fort Calhoun Station. None of these, however, are installed in primary systems where the potential for hydrogen  :

embrittlement exists. HCV-921 and HCV-922 are isolation valves for the main steam radiation monitor. HCV-820A, HCV-821A, HCV-883A, HCV-8848, HCV-8208, and HCV-8218 are all valves which allow sampling of. the contain-ment air system for hydrogen. There is no reason to believe that these j valves are subject to a similar malfunction.

i HCV-247 and HCV-248 were repaired by replacing the disc guide assembly

! springs and re-assembling the valves. The replacement' springs were also

constructed of 17-4PH stainless steel because springs made of inconel

could not be obtained in time to meet the reactor startup date. This i inspection and repair of HCV-247 and HCV-248 was completed on November 18,

1985. It is expected that, based on previous experience,-the replacement  ;

} springs will function properly for approximately 18 months, which is well i

beyond the next refueling outage. Additionally, valves are tested quar-j terly to ensure that they cycle properly. EEAR FC-85-179 has been reis- '

l sued to replace HCV-247, HCV-248, HCV-249, and HCV-2988 during the next '

j refueling outage scheduled for March of 1987.

I l CONCLUSIONS 1

i It is recommended by this utility that all plants having Valcor valves.in primary systems examine their records for this ' defect. It would appear 1 that this problem would be primarily limited to PWR's as they utilize

! excess dissolved hydrogen for chemistry control.

l' Valcor Engineering has indicated to OPPD that it has now replaced the stainless steel springs with springs constructed of inconel for all valves used in such applications. Valcor has also stated that they have informed all utilities owning such valves of the potential for failure of these

_ stainless steel springs.

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It is anticipated that this report will aid other utilities in identifica'-

1 tion and correction of this potential problem. OPPD has sent a notice to other utilities via the Nuclear Network System to inform them of this pro-blem and encourages other utilities to contact us for more information -if necessary.

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