ML20236K902

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Informs of Region II 930217 Request for NRR Assistance in Reviewing Licensee Technical Evaluation on LER Re Containment Ice Condenser Ice Basket row-groups.Proposed Response to TIA 93-002 Encl
ML20236K902
Person / Time
Site: Sequoyah  Tennessee Valley Authority icon.png
Issue date: 08/24/1993
From: Barrett R
Office of Nuclear Reactor Regulation
To: Hebdon F
Office of Nuclear Reactor Regulation
Shared Package
ML20236J990 List: ... further results
References
FOIA-98-155 TAC-M85952, TAC-M85953, NUDOCS 9807100133
Download: ML20236K902 (7)
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MEMORANDUM FOR: Frederick J. Hebdon, Director Project Directorate II-4 Division of Reactor Projects - East Office of Nuclear Reactor Regulation FROM: Richard J. Barrett, Chief Containment Systems and Severe Accident Branch Division of Systems Safety and Analysis Office of Nuclear Reactor Regulation .

I

SUBJECT:

TIA 93-002, SEQUOYAH ICE BASKET WEIGHTS (TACs MB5952 and i M85953)

By memorandum dated February 17, 1993, Region II (E. Merschoff) requested NRR assistance in reviewing licensee technicci evaluations. The evaluations relate to a licensee event report indicating that Sequoyah Units 1 and 2 operated with less than the minimum required amount of ice in certain containment ice condenser ice basket row-groups. In addition to requesting assistance in l reviewing the evaluations, the TIA requested an NRR position regarding whether the ice weighing program requi.ed by TS 4.6.5.1.d requires a deterstnation and evaluation of as-found ice basket weights. A proposed reply to the TIA is 7 enclosed.

Regarding the licensee's evaluations, we have had separate telecon discussions with the licensee and the MSSS vendor. We have also reviewed available background infomation regarding ice condenser perfomance. Based on our findings, we conclude that the licensee has perfomed an acceptable analysis of the event. ,

Regarding Sequoyah Technical Specification 4.6.5.d, and whether it requires an as-found surveillance test and evaluation, it is our conclusion that the TS does not specifically include such a requirement but that 10 CFR 50.73(a)(2)(v) does.

With the exception of certain Appendix J tests, licensee's may, during an outage, perform planned maintenance prior to surveillance testing. Also, once surveillance testing is begun, if the need for additional maintenance is indicated, the tests may be discontinued and started over again later. Such actions are not prohibited by the TS and are routine. However, 10 CFR 50.73(a)(2)(v) requires a 30-day report (LER) upon discovery of any l condition that could have prevented the fulfillment of a safety function. It is our position that once it becomes obvious to personnel perfoming a surveillance test that the test has failed or will fail, the reporting requirement invokes the need for an operability evaluation.

We will consider TACs M85952/3 to be open for additional SCSB effort until such time as you confirm that Unresolved item 92-31-01 is satisfactorily resolved.

9807100133 980624 N

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4 . //EMN Frederick J. Hebdon 2 Questions or comments regarding this subject should be directed to W. Long (301) 504-3026.

Original signed by Richard J. Barrett, Chief Containment Systems and Severe Accident Branch Division of Systems safety and Analysis Office of Nuclear Reactor Regulation

Enclosure:

As stated DISTRIBUTION Central File Docket File (2)

SCSB R/F Plant R/F WLong RBarrett RLobel JKudrick CGrimes BGrimes GKlingler A TSB Background Book CMoon FManning

. RLo SCSB:DS DSSA OTSB: DORS SC WLong:1bk CGrimes 8/g/93 hRLobel 8/22;/93 RB tt 8/Q/93 8/20/93 0FFICIAL RECORD COPY 89 DOCUMENT NAME: A:SQN I

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o ENCLOSURE RESPONSE TO TIA 93-002 CONTAINMENT SYSTEMS AND SEVERR ACCLDENT BRANCH SEOUOYAH NUCLEAR POWER PLAN" UNI"$ 1 AND 2 Backaround: Region II TIA 93-002 (memorandum from E. Merschoff to G. Lainas dated February 17,1993), requested NRR technical assistance in reviewing licensee evaluations relating to Sequoyah LER 92-023. A list of background documents received with the TIA is appended.

LER 92-023 reported instances of low ice basket row-group weights found during surveillance testing. The TIA requested NRR's position on whether the TS requires an "as-found" determination and evaluation of ice basket weights.

This item is being tracked as Unresolved Items 327/92-31-01 and 328/92-31-01 for Inspection Reports dated November 5, 1992.

Description of recorted event: In LER 92-023, dated December 31, 1992, the licensee reported that Sequoyah Units 1 & 2 operated for some length of time (Unit I during Cycles 4 and 5 and Unit 2 during Cycle 4), with the 955 confidence level minimum average basket weights for certain ice basket row-groups being below the 993-pound design analysis assumption. The discovery was a result of a licensee QA audit of maintenance activities. During initial ice basket weighing conducted at the end of Unit 1 Cycle 5, 11 of the 24 ice bays failed a preliminary sampling test. Within the 11 failed bays, additional baskets were weighed. The number of additional baskets weighed was less than the number specified by TS (i.e., 20) as necessary to assure a 95% level of confidence that the minimum average basket weight is est. Subsequent licensee analyses revealed low as-found row-group weights for row-group 1 in Unit I for Cycles 4 and 5, and row-group 3 for Cycle 4.

Quoting from LER 92-023:

The evaluation concluded that if a row-group .in the ice condenser has a weight less than 993 pounds per basket, the ice condenser would have operated outside its design analysis assumption. A review of as-found data from Unit 1 Cycles 4 and 5 identified that the average ice weight for Row 1 Group 1, at a 95-percent confidence, was 944 and 827 pounds per basket, 3 l respectively. A review of the as found data for Unit 2 Cycle 4 '

identified that the Row 1 Group 3 ice weight at a 95-percent confidence, was 982 pounds per basket."

The data also shows (sic) that an acceptable total amount of ice present and that on a per-bay basis, the ice was adequately distributed.

The licensee concluded that there would have been no significant adverse effect on peak accident pressure had a DBA-LOCA occurred. LER 84-019,82-130 and 81-015 also reported similar events for Unit 1. LER 83-107 reported an earlier

1 1

2 Unit 2 similar event.

An AE00 Technical Review Report (Memorandum from M. Manning to P. Las dated November 9,1988) intended to provide perspectives on safety dgnificance of ice condenser LERs did not indicate serious concern regarding 13 reports of low ice weights.at ice condenser facilities.

TS Requirements: The SQN ice condenser (and those of other plants) contains 1944 ice baskets in three groups. Each of the three adjacent groups consists of eight adjacent bays. Each bay has a nine-by-nine array of ice baskets installed in a supporting lattice framework. The outside row of baskets, adjacent to the containment wall, is identified as row 1. The inner row of baskets, adjacent to the crane wall is row 9. Each ice basket is actually four weighable ice baskets coupled into a 48-foot high column. The ice baskets have a 12-inch diameter.

Technical Specification Surveillance Requirement 4.6.5.d requires that the ice bed be determined operable at least once per 18 months by:

(a) Weighing a representative sample of at least 144 ice l baskets and verifying that each basket contains at least i 1155 lbs of ice. The representative sample shall  !

include 6 baskets from each of the 24 ice condenser bays I and shall be constituted of one basket each from Radial Rows 1, 2, 4, 6, 8 and 9 (or from the same row of an adjacent bay if a basket from a designated row cannot be -

obtained for weighing) within each bay. If any basket is found to contain less than 1155 pounds of ice, a representative sample of 20 additional baskets from the ,

same bay shall be weighed. The minimum average weight  !

of ice from the 20 additional baskets and the discrepant j basket shall not be less than 1155 pounds / basket at the '

95% level of confidence.

(b) The ice condenser shall also be subdivided into 3 groups of baskets, as follows: Groups 1 - bays I through 8, Group 2 - bays 9 through 16, and Group 3 - bays 17  !

through 24. The minimum average ice weight of the sample baskets from Radial rows 1, 2, 4, 6, 8 and 9 in each group shall not be less than 1155 pounds / basket at the 95% level of confidence.

l (c) The minimum total ice condenser ice weight at a 95%

l 1evel of confidence shall be calculated using all ice l

basket weights determined during this weighing program and shall not be less than 2,245,320 pounds.

The original ice condenser surveillance requirements, issued for DC Cook I on October 1974, only required.60 baskets to be weighed, with a minimum of two from each bay. The DC Cook 1 TS were amended in Amendment 18, issued February 16, 1977, to upand the surveillance requirements based on results of the DC Cook I initial surveillance described in a series of five reports describing the results of the initial ice weighings at DC Cook Unit 1. The Cook surveillance

3 requirements were expanded to includ criteria.

Standard Technical Specifications RThe amended DC Coo with these Standard TechnicalThe ev 2. Specifi cations. SQN requirements are c both the peak containment pressurSAfety sienificane (i.e., upper and lower compartment containment loads and the loads on various subcompartment one must consider The containment pressure peak e load, s (e.g., occuS the containment ent loads majo,r i This period is analyzed rs using in thethe LOTI "long/G, term"pressurizer i t m

enclosures)ents) on the major compartmentsC-1 and subcompa code. The pres (su.e., after blowdown).

blowdown phase which is analyzed usi b 3

ng the TMD code.r ment structures occurs duri The licensee considered the contai cquivalent divider deck to the upper compartmen nment bypass response effects areaweights of the low using asket ice b the eringwhich a low-weight basket as a considered b s to -

bypass area.ypass area.t An empty basket would permit r mentflow to byp thatmay thuslargbe conside .

can be tolerated. The FSAR indicates a very red as equivalent may be F weight or empty This supports baskets a conclusion ise.acceptabl e bypass thatarea a c (at least 50 ft') y thatanalyses the LOTIC-1 code has the cap bi Such m Section 6.2 a

lity to analyze.1.3.4 considerable of the FSAR number indicates of low-effects ofDCice Cookmaldistribution in Santoithe resolve SQN effects. issu Safety Evaluationice Report ered maldistribution necessary S.

maldistribution has a dueice tobedtheweight resultant conservative ce condenser.upplement additional eff No. 5 discussed the ti It indicated that ice i

, Westin total is present.

and C.L.ghouse Smith) me in an informal to held on August complete telecon(This ice bed was e se meltout a reconfirmed 16, 1993 with W .-

. Long, NRC, "tubcompartmental effects to be iThe licensee determine

,hn b' significant.short-ters intercompartmental and nm that bypass may affect the validitsscond series of Westin for upper and lower compartmen $

not be significantlunderstanding y of the ice of condenser blowdown the phenemena,t phase TMD blowdown predi W tes codepressures peak cate 4

a' ho ctions the in the limiting August load. (This also y affected and thea longer term oads would pe kthe maximum ,

16, 1993 telecon)was reconfirmed by a W estinghousecontainment pressure is IS *as-fornd" reouirementsi . We therefore accept the licensee' representative s position.

determination considered unnecessaryceinbasket and evaluation viewweights.

of of the f iTS 4.6.5.1 - ound does not require an - ,

included in the minimum basket weight Such a requirement is linits whichinitial TS, issued with the operati

! publication r,ates. andacttotal that ice an weight allowance requirementsfor sublimatio after several cycles ng licenseeof operation specifymay b conservative .

The ice wet i 'efilling of ice baskets, The licensee priormayt perform maintenanc e adjusted to reflect t t.st, it becomes obvious ath t additional maintenance conducting the surveilla

, cfilling) is needed, it should be obvious ice basketIf,to the during theli (i.e.,nce.

censee that the maintenance

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' 4 to take corrective action shprogram is inadequate or programmatic deficiency ould in li 1.ntssment reporting reqt.'t and Quality r

Ve ifbe considered Failure censee em. evidence ofther

\ ment. ication. performance in theaarea

" si of *gnificant

\ [gfj;1g11 gal Safety following discovery of thNRR concludes that th es a e event.

i should have beena identified audit.

recognize andproposedpersonnel credible evaluationThe correctiv \\

White not a TS orreported reporting insiediately, . However, the evente analyses and attention, and a priorinvestigate and report a co rather than di an during operationa,l deficiency. history violation, n

of similar the failure toy promptl b' 5,

Contact:

tion which obviously urther ac dema '

(301) 504-3026W. Long NRR/DSSA/SCSB .

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e, APPENDIX A BACKGROUND DOCUMENTS FOR TIA 93-002 LER 84-019, Letter from C.A. Mason to USNRC dated April 4, 1984.

Letter from S. Black to 0. Kingsley dated March 2,1990, forwarding Amendments 131/118.

TVA Finding Identification Report #SQFIR920068208 Rev 0 dated August 20, 1992.

NRC Inspection Reports 50-327/92-31 and 50-328/92-31 dated November 5, 1992.

Bryan, R., " Evaluation of Low Ice Basket Weights for SQFIR920068208,' TVA, November 27, 1992.

Bryan, R., 8.M. Snider, and J.A. Rathjen, " Operational Evaluation of Potential Low Ice Weight in Row 1 Group 1 Baskets in SQNP Unit 1," TVA, November 30, 1992.

Bryan, R., B.M. Snider, and J.A. Rathjen, " Operational Evaluation of Potential Low Ice Weight in Row 1 Group 3 Baskets in SQNP Unit 2," TVA, December 3, 1992.

TVA " Incident Investigation Fom No. 5-92-088" dated December 2, 1992.

TVA

  • Event Notification Worksheet" dated December 1,1992.

TVA draft " Incident Investigation Event Report II No. 5-92-088' dated December l 11, 1992 with attached Maintenance History Review and Utility Survey Reports.

December 16, 1992 handout for TVA/NRC Meeting regarding Sequoyah Nuclear Plant Ice Condenser.

l LER 92023, Letter from R. French to USNRC dated December 31, 1992.

Benedict, R., " Event Followup Report 93-009," NRC, February 11, 1993.

Memorandum from E. Merschoff to G. Lainas dated February 17, 1993.

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