ML18102A264

LER 96-010-00:on 960619,identified Pressurizer Relief Tank Hydrodynamic Loads Had Not Previously Been Considered in Support Design.Caused by Failure to Consider Hydrodynamic Loads Caused by Water Discharge.Supports Revised

ML18102A264
Person / Time
Site:	Salem
Issue date:	07/16/1996
From:	Hassler D Public Service Enterprise Group
To:
Shared Package
ML18102A263	List: ML18102A262 ML18102A264
References
LER-96-010-01, LER-96-10-1, NUDOCS 9607230297
Download: ML18102A264 (3)

Text

I.* . NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB ND. 3150-0104 (4-95) EXPIRES 04130/98 ESTIMATED BURDEN PER RESPONSE TD COMPLY WITH THIS MANDATORY INFORMATION COUECTIOll REDDEST

50.0 HRS. REPORTED LESSONS LEARNm ARE INCORPORATED INTO LICENSEE EVENT REPORT (LER) THE UCENSINS PROCESS AND Fm llACI TO INDUSTRY.

FORWARD COMMENTS REGARimoG BURDEN ESTIMATE TD THE INFORMATION AND RECORDS MANAGEMENT BRANCH ll-8 F331. U.S. NUCLEAR REGULATORY COMMISSllJN, WASHINGTON.

DC 20555-0001, AllD TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT ANO BUDGET, (See reverse for required numiler of WASHINGTON.

Dt 20503. digits/characters for each block) FACILITY IAME 111 DOCKET IUMllH 121 PAGE 131 SALEM GENERATING STATION UNIT 1 05000272 1 OF 3 TITLE 141 Inadequate Pressurizer Relief Tank Supports EVENT DATE 151 LER NUMBER (61 REPORT DATE 171 OTHER FACILITIES INVOLVED 181 I I FACllTY IAME DOCKET IUlllllER MOITH DAY YEAR YEH SEDUEITIAL ftEVISIOI l!OITH DAY YEAR IUlllEI I UMBER Salem, Unit 2 05000311 06 19 96 96 -010 00 07 16 96 FACll.ITYIAME DOCKET IUlllEn -OPERATING

• N THIS REPORT IS SUBMITTED PURSUANT TO THE REDUIREMENTS OF 10 CFR I: !Checkon11ormora)

(11) MODEl91 20.22011bl 20.22031all2Jlv) 50.73(11112161 50.73(a)l2)(viii)

POWER 000 20.2203(11)(1) 20.2203(1Jl3llil x 50.73111J(2)6i) 50.73!all2Hxl LEVEL!1DI 20.220311112Jlil 20.2203la)(3Jfiil 50.73(1)(2Jfiiil 73.71 20.2203!all211iil 20.2203lull4J 50.73(1J(216vl x OTHER ::::::.o:.::

20.2203!all211iiil 50.3&1cll1J 50.731all2llvl Spm:lfy In Abstr1ct below or In ::::::::::

.*.*.*.w 20.2203(11)(2J6vl 50.361cll21 50.73111J(2Jlviil LICENSEE CONTACT FOR THIS LER 1121 IAME TELEPHOIE IUMIEft (llldlll1 Ano c.411 Dennis v. Hassler, LER Coordinator 609-339-1989 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (131 CAUSE SYSTEM COMPOIEIT MAIUFACTUREft REPORTABLE TO.IOI CAUSE IYmM COll'OIEIT MAIUFACTUIER REPORTABLE TO IPRDS ' : ;j :*.

SUPPLEMENTAL REPORT EXPECTED 1141 EXPECTED MONTH DAY YEAR IYES x IND SUBMISSION Pf yes, complete EXPECTED SUBMISSION DATE). DATE(151 ABSTRACT (Limitto 1400 spaces, i.11., approximately 15 single-spaced typBWl'itten lines) 1161 On June 19, 1996, an engineering review concluded that the pressurizer relief tank (PRT) supports are inadequate to preclude damage to the combined pressurizer safety valves discharge header. A reactor coolant system (RCS) over pressure event resulting inthe simultaneous lift of the three pressurizer safety valves.would cause the relief tank to move upward resulting in crimping the discharge header. The discharge header is the sole relief pathway for the safety valves, thus RCS overpressure protection could have reduced effectiveness.

The cause of this occurrence is that the original tank support design calculations failed to consider hydrodynamic loads on the PRT. These loads are caused by the discharge of water, bubble oscillation, and steam condensation.

This event is reportable in accordance with 10 CFR 50.73(a) (2) (ii); any event or condition that resulted in the nuclear power plant being in a condition that was outside the basis of the plant and in accordance with 10 CFR 21. 2 ( c) . 9607230297 960716 -* --PDR ADOCK 05000272 .. s PDR NRC FORM 366 (4-951

. . l

• NRC FORM 366A (4-95) U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITY NAME ('I) SALEM GENERATING STATION UNIT 1 DOCKET NUMBER (2) LER NUMBER (6) 0 5 0 0 0 2 7 2 YEAR l SEQUENTIAL l REVISION NUMBER NUMBER 96 -010 -00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17) PLANT AND SYSTEM IDENTIFICATION Westinghouse

-Pressurized Water Reactor Reactor Coolant System Pressurizer Relief Tank Supports {RC/SPT}*

PAGE (3) 2 OF 3

• Energy Industry Identification System (EIIS) codes and component function identifier codes appear as (SS/CCC) CONDITIONS PRIOR TO OCCURRENCE At the time of identification, Salem Units 1 and 2 were shutdown and defueled.

DESCRIPTION OF OCCURRENCE As a result of an unrelated review of the adequacy of support fasteners, a review of the supports for the Pressurizer Relief Tank (PRT) for both Salem units was undertaken.

The review noted that the fastener arrangement was adequate for seismic response, however, the review identified that PRT hydrodynamic loads had not previously been considered in the PRT support design. A further review concluded that substantial upward loads could be expected during a simultaneous lift of all three safety relief valves, which could result in discharge line deformation.

The locked reactor coolant pump rotor and loss of turbine load accident analyses take credit for the safety relief valves operating at the same time. CAUSE OF OCCURRENCE The cause for the inadequate design of the PRT supports is a failure to consider hydrodynamic loads caused by water discharge, bubble oscillation and steam condensation.

Consideration of hydrodynamic loads was not incorporated in the design of Salem systems at the time of construction.

PRIOR SIMILAR OCCURRENCES A review of LERs for the past two years identified one similar occurrence.

LER 96-002 addressed an occurrence in which original plant design requirements for motor operated valves were found to be inadequate based on consideration of pressure locking and thermal binding. The corrective actions were specific to motor operated valves. NRC FORM 366A (4-95) *,:,.. ' '

.. . , ; r.=N=R=c=F=o=R=M=36=6=A=========================u=.s=.=N=u=c=L=E=A=R=R=E=G=u=L=A=T=o=R=v=c=o=M=M=1s=s=1=o=N=;i (4-95) LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITY NAME (1) SALEM GENERATING STATION UNIT 1 DOCKET NUMBER-(2)

LER NUMBER (6) 0 5 0 0 0 2 7 2 YEAR I SEQUENTIAL I REVISION NUMBER NUMBER 96 -010 -00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17) SAFETY CONSEQUENCES AND IMPLICATIONS PAGE (3) 3 OF 3 There are no safety consequences for this occurrence since neither Salem unit had experienced a simultaneous lift of the three pressurizer safety valves and the units are in a defueled status. The pressurizer sprays and the power operated relief valves (PORVs) are available to mitigate an overpressure transient.

However, these pressurizer pressure control mechanisms have been conservatively excluded from the accident analyses.

Thus, while the accident analyses do not credit pressure reduction through the pressurizer spray use and PORV opening, these mechanisms will reduce the challenge to the pressurizer safety valves. Therefore, the probability of simultaneous opening of the three pressurizer safety valves is reduced, minimizing the potential for deformation of the discharge header. The public health and safety were not affected.

CORRECTIVE ACTIONS Revise each unit's PRT support design to withstand hydrodynamic loads and complete any required modifications for each unit prior to that unit's entry into mode 3. 10CFR21 REPORTING 10CFR21 requirements are met by this LER. NRC FORM 366A (4-95)