ML18057A558

LER 90-018-00:on 900930,inadequate Flows Through Hot Leg Injection Check Valves occurred.W/901030 Ltr

ML18057A558
Person / Time
Site:	Palisades
Issue date:	10/30/1990
From:	Roberts W, Slade G CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-018, LER-90-18, NUDOCS 9011130105
Download: ML18057A558 (5)

Text

consumers Power l'OWERINli MICHlliAN'S l'ROliRESS Palisades Nuclear Plant: 27780 Blue Star Memorial Highway, Covert, Ml 49043 October 30, 1990 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-255 -LICENSE DPR-20 -PALISADES PLANT -GB Slade General Manager LICENSEE EVENT REPORT 90018 -INADEQUATE FLOWS THROUGH PCS HOT LEG INJECTION CHECK VALVES Licensee Event Report (LER) 90018 (Inadequate Flows Through PCS Hot Leg Injection Check Valves) is attached.

This.event is reportable to the NRC per 10CFR50.73(a)(2)(ii)(B). .

• Ger a 1 d B Slade General Manager CC Administrator, Region III, USNRC NRC Resident Inspector

-Palisades Attachment

--r _: '-..j A CMS' ENERGY COMPANY

.... NRC For111318

• (IMIJJ U.I. NUCLEAR REGULATORY Al'l'ROVED OM!! NO. 31110-0104 LICENSEE EVENT REPORT (LER) EXPIRES: 1!/311115 FACILITY NAME 111 !DOCKET NUMIER 121 I 1;s1 Palisa.des Nuclear Plant 0 I 5 I 0 I 0 I 0 I 2 15 15 1 I OF DI 4 TITLE 141 INADEQUATE FLOWS THROUGH HOT LEG INJECTION CHECK VALVES EVl!NT DATE Clll LER NUMBER 191 REPORT DATE 171 OTHER FACILITIEI INVOLVED Ill MONT QAY YEAR YEAR FACILITY DOCKET NUMllERISI N/A 0151010101 I I o I 9 3 lo 9 o 9 lo -o 11 1 s -o Io 110 31 o 9 p N/A 01s1010101 1 1 Ol'ERATINO MOOE Ill N THll REPORT IS IUIMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Ch<<:k OM or mtNI of rlN fo//owin11J C111 20.402(bl 20.40ll(cJ ll0.73Coll2111¥1 ll0.73Coll21Cwl ll0.73Coll2ll*HI ll0.731oll211*111llAJ ll0.7llCoJC21 lwlllllll ll0.73C1112111J 73.711111 73..711*1

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--l50.73Coll21Cllll LICENSEE CONTACT FOR THIS LER (121 NAME TELEPHONE NUMBER AREA CODE William L. Roberts, Staff Licensing Engineer 6 1 1 1 6 7 1 6 1 t+1-1 s 1 9 1 1 1 3 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRllED IN THll REl'ORT 1131 CAUSE SYSTEM COMPONENT TURER MANUFAC* TUR ER I I I I I I I N .:i:.=:::::1:::*:,:::::=:::::::l:ll:::::,:11::.:,::::

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I I I I I I I IUl'PLEMENTAL REPORT EXPECTED (141 MONTH DAY YS:AR Xl YES (If Yft. comp/er. EXPECTED SU/JM/SS/ON DATE) EXPECTED SUBMISSION DATE (151 AllTRACT (Limit ID 1400 -* I.* .* epproximeroly flftwn lln11l**11>>**

/inn! C1GI NRCFonn:lll (9-831 ABSTRACT On September 30, 1990, at 1632 hours0.0189 days <br />0.453 hours <br />0.0027 weeks <br />6.20976e-4 months <br /> the plant was shutdown and on shutdown cooling. The Surveillance Test R0-65, "HPSI/RHPSI Check Valve Test", which provides for full stroke testing of certain High Pressure Safety Injection (HPSI) pump suction and discharge check valves and the Hot Leg Injection (HLI) check valves was being conducted.

Technical Specification 4.0.5a requires testing of valves in accordance with the ASME Boiler and Pressure Vessel Code,Section XI, edition and addenda as specified by 10CFR50.55a(g).

The Code requires that check valves be exercised "to the position required to fulfill their function." The NRC has interpreted this to mean full stroke testing is required or,if full stroking of the disc cannot be verified, full flow testing. The resultant flow rates for each of the two PCS hot legs were less than the acceptance criteria of 250 gallons per minute (gpm). The failure of the test to satisfy the acceptance criteria was reported to the system engineer and the shift manager and a corrective action document was issued. Subsequent analysis on October 12, 1990 determined that the flow delivered to the hot legs was less than that required by the plant safety analysis.

This event is reportable as a condition outside the design basis of the plant.

NllCF.,.mJleA 111-831 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION U.S. NUCLEAll llEOULATOllY COMMlalON APl'ROVED OMI NO. 31 !I0-010.

NAME 111 DOCKET NUMSEll 121 Liii Ill F..a.lisades Nuclear Plant TEXT (If --i8 ....,._, -.-W NltC Fomt .-..*al 1171 NIOC *OllM!IMA 111-131 EVENT DESCRIPTION On September 30, 1990, at 1632 hours0.0189 days <br />0.453 hours <br />0.0027 weeks <br />6.20976e-4 months <br /> the plant was shutdown and on shutdown cooling. The Surveillance Test R0-65, "HPSI/RHPSI Check Valve Test", which provides for full stroke testing of High Pressure Safety Injection (HPSI) pump suction and discharge check valves and the Hot Leg Injection (HLI) check valves was being conducted.

Technical Specification 4.0.5a requires testing of valves in accordance with the ASME Boiler and Pressure Vessel Code,Section XI, edition and addenda as specified by 10CFR50.55a(g).

The Code requires that check valves be exercised "to the position required to fulfill their function." The NRC has interpreted this to mean full stroke testing is required or,if full stroking of the disc cannot be verified, full flow testing. The resultant flow rates for each of the two PCS hot legs were less than the acceptance criteria of 250 gallons per minute (gpm). The failure of the test to satisfy the acceptance criteria was reported to the system engineer and the shift manager and a corrective action document was issued. Subsequent analysis on October 12, 1990 determined that the flow delivered to the hot legs was less than that required by the plant safety analysis.

This event is reportable as a condition outside the design basis of the plant. The HLI is required in a large cold-leg break to provide flow required to make up for core boil off and a small net core flushing flow (total of 225 gpm). The core flushing flow is needed to prevent excessive boric acid concentration in the core, which could result in boric acid precipitation and possible core flow blockage.

The HLI flow path is also needed to support heavy load movements in containment during reactor shutdown periods. The HLI flow path provides an alternate flow path to loop IA hot leg in the event that cold leg injection is no longer available due to a heavy load drop event. In the event that shutdown cooling is lost, the HLI flow path is required to deliver 100 gpm of flow to mitigate a heavy load drop. A preliminary evaluation of the event was completed which included a review of the basis for the flow rates specified in the acceptance criteria for the test and the plant conditions for which the system must perform its function.

The results of this preliminary evaluation showed that the check valves are required to pass approximately 225 gpm under accident condition (i.e. LOCA) and 100 gpm to support heavy load movements.

The evaluation also theorizes that the check valves failed to achieve adequate stroke as a result of as pressurized fluid being trapped on the back side of the disc's guide assembly.

As the valve disc is pushed open by HLI flow the entire water volume behind the disc is not allowed to evacuate this area, resulting in fluid compression as differential pressure across the valve disc reaches equilibrium.

At this equilibrium pressure the disc is not allowed to fully stroke since system pressure can not overcome equilibrium pressure plus the valve's spring pressure.

This failure mode is attributed to improper application for this valve design.

CMJI . LICENSEE EVENT REPORT (LEA) TEXT CONTINUATION U.a. NUCLEAll lllGULATOllY OMS N0. ,ACILITY -C1I

• DOCKIT N\Jli9111 121 Liil Cll Nuclear Plant o 1s Io Io Io I z, s I 5 91 o. -o 11 ,a -o I o D 13 oF o 11 TIXT 1/f--ii......._

---.. IWfC ........ .-..*a11171 A similar problem with the valves was discovered in 1988 when the same flow testing produced lower than expected results. However, the test results achieved were above the required flow acceptance criteria.

The results per the Section XI testing guidelines showed some flow degradation from the test baseline.

The check valves were disassembled and inspected.

The results showed no apparent problems with the mechanical clearances and freedom of operation.

One theorized interference point on the valve internals was modified under the Specification Change number 88-252. This modification removed a sharp edge interface between the valves' disc guides and the valves' closure caps. Although not identified, during the valve disassembly and inspection, *as an interference point, it was decided to provide this relief on each of the affected valves, to provide some added assurance for future operation.

Following the 1988 modification of the valves,* the R0-65 flow test was successfully completed three times with repeatable satisfactory results. Flows achieved during this testing were over 300 gpm. *

• CAUSE OF THE EVENT We are still reviewing the events to determine the actual root cause of the problem. CORRECTIVE ACTION Evaluation of the root cause of this event is ongoing. Corrective actions to prevent occurrence will be described in an update to this LER. An additional analysis is being performed to verify that the flow rate of 225 gpm, as an acceptance criteria for R0-65 test conditions, provides the correct flow rate for the hot leg injection check valves. The surveillance procedure R0-65 which the HPSI trains and the HLI check valves and the procedure basis document will be revised to resolve the hot leg injection check valve acceptance criteria and clarify requirements of the HLI system during accident conditions and heavy load movements.

Pending the results of our final analysis, all of these corrective actions will be completed prior to start-up from the present refueling outage. ANALYSIS OF THE EVENT The measured flows to the two PCS Hot Legs as a result of the R0-65 testing are (190 gpm and 210 gpm) were sufficient to support heavy load movements which require a boric acid flow path capable of supplying 100 gpm to the PCS, but less than the 225 gpm required for accident response.

.....

............. (M.31 PACILITY NAMI Ill ' LICENSEE EVENT REPORT (LER) TEXT CONTINUATION DOCKIT 121 U.I. IWCLEAll IUQULATOflY COMMlmlON -oveo °"""NO.

EX,.lllES:

1/31 In Llill 111 .... 111 l*I Nuclear Plant 0 I 5 I 0 I 0 I 0 I 2 1 5 I 5 9 I 0 -0 1 1 1 8 -0 I 0 b 14 OF D I Our analysis of this event and its consequences is continuing.

We will provide an updated report when this analysis is completed.