ML17310A490

LER 93-007-02:on 930512,concluded That TS SR 4.7.9.e Incorrectly Interpreted.Pvngs Snubber Testing Program Will Be Revised to Correctly Implement TS Requirements Prior to Commencing Next Testing Cycle

ML17310A490
Person / Time
Site:	Palo Verde
Issue date:	07/28/1993
From:	Bradish T ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:
Shared Package
ML17310A489	List: ML17310A488 ML17310A490
References
LER-93-007, LER-93-7, NUDOCS 9308060303
Download: ML17310A490 (18)

Text

LICENSEE EVENT REPORT (LER)

FACILITYNAME (I) DOCKET NUMBER (2) PACE 3 TITLE (8)

Palo Verde Unit 1 osooo528>or09 Snubber Testing not in Accordance with Technical S ecifications EVENT DATE (5), LER NUMBER (8) REPORT DATE P> OTHER FACIUTIES INVOLVED(8)

MONTH DAY YEAR FACIUTY NAMES DOCKET NUMBER(S)

NUMBER NUMBER MONTH DAY Palo Verde Unit 2 0 5 0 0 0 5,2 Palo Verde Unit 0 5 0' 0 5 3 f: (Cheek one or more ol Ihe Iollowlno) (11) 9'PERATINO

.THIS REPORT IS SUBMIITEDPURSUANT TO THE REOUIREMENTS OF 10 CFR MODE (8)

] 20A02(b), 20AOS(e) 50.73(a)(2) (Iv) 73.71(b)

POWER 20AOS(a)(1)(I) 5046(e)(1) SO.73(a)(2)(v) 73.71(e)

LEVEL (10) 20AOS(a)(1)(II) 50.36(e)(2) 50.73(a)(2)~ OTHER (SpeettytnAbetreet below anrtin Terrb HRC %%dmr 20AOS(a)(1+i) 50.73(a)(2)(I) 50.73(a)(2) yS)(A). 366A) 20AOS(a)(1)(tv) 50.73(a) (2)(II) 50.73(a)(2)(m)(B) 20AOS(a)(1)(v) 50.73(a)(2)(tii) 50.73(a)(2)(a)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER Thomas R. Bradish, Manager, Nuclear Regulatory Affairs COMPLETE ONK LIIIEFOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13) 602393 5'421 MANUFAC- EPORTABIE MANUFAC CAUSE SYSTEM COMPONENT TURER TO NPRDS. CAUSE SYSTEM COMPONENT TURER SUPPLEMENTAL REPORT EXPECTED (I 8) MONTH DAY YEAR EXPECTED SUB 880SION DATE (15)

YES (llyen oonplete EXPEC7ED SUSMISSIOH DATE) NO ABSTRACT (Urn(I to 1400 epaeea 7 eappredmatety stteen ebr0teepaee typevrrt Iten Farce J (16)

On May 12, 1993, at approximately 1330 MST, APS Management and the NRC discussed APS'nterpretation of Technical Specification 4.7.9.e, for snubber testing. APS concluded that it had incorrectly interpreted the Technical Specification. Additionally, APS had not informed the NRC Regional Administrator that the surveillance requirement, would be implemented differently than previously identified.

Palo Verde Units 1, 2, and 3 entered the ACTION for Limiting Condition for Operation 3.7.9,,at approximately 1330 MST on May 12, 1993, and a Notice of Enforcement Discretion was requested. At approximately 1400 MST on May 14, 1993, APS was notified of the Commission's intent to exercise discretion in enforcing compliance with the ACTION statement of TS 3.7.9, until the NRC takes action on a request for a license amendment.

There have been no previous similar events reported pursuant to 10CFR50.73.

9308060303 930728 PDR ADOCK 05000528 8 ,PDR,,

0 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITYNAME DOCKET NUMBER LER NUMBER PACE YEAR SEQUENTIAL @'I REVISION NUMBER NUMBER Palo Verde Unit 1 osooo528 0 0 7 0 2 0 2 OF 0 9 DESCRIPTION OF WHAT OCCURRED:

A. Initial Conditions:

At approximately 1330 MST on May 12, 1993, Palo Verde Units 1 and 3 were in Mode 1 (POWER OPERATION) operating at 100 percent power.

Unit 2 was in Mode 6 (REFUELING) with cold loop temperature at approximately 87 degrees Fahrenheit.

B. Reportable Event Description (Including Dates and Approximate Times of Major Occurrences):

Event Classification: Operation prohibited by the plant's Technical Specifications.

On May 12, 1993, APS Management (utility, non-licensed) and the NRC discussed APS'nterpretation of Technical Specification (TS)

Surveillance Requirement (SR) 4.7 '.e. APS concluded that it had incorrectly interpreted TS SR 4.7.9.e. Additionally, APS had not informed the NRC Regional Administrator that snubber testing would be implemented differently than previously identified. At approximately 1330 MST on May 12, 1993, Palo Verde Units 1, 2, and 3 entered the ACTION for Limiting Condition for Operation (LCO) 3.7.9.

TS LCO 3.7.9, states in part "...all hydraulic and mechanical snubbers shall be operable...." [Snubbers on non-safety systems may be excluded related systems.]

if The their failure does not adversely affect safety-requirement is applicable in all MODEs for snubbers located on systems required to be OPERABLE in that MODE.

The LCO ACTION states in part "...with one or more snubbers inoperable on any system, within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> replace or restore the inoperable snubber(s) to OPERABLE status...or declare the attached system inoperable...follow the ACTION statement for that system."

SR 4.7.9, states in part "...each snubber shall .be demonstrated OPERABLE by performance of the following augmented inservice inspection program and the requirements of SR 4.0.5."

4.7.9.a. defines Snubber Type as "...of the same design and manufacturer, irrespective of capacity...." [The PVNGS Snubber Testing program identifies 5 snubber groups.

The program was implemented with three snubber types:

PSA mechanical, Steam Generator hydraulic, and Reactor Coolant Pump hydraulic.]

4,7.9.e. States in part " ..snubbers shall be tested using one

~

of the following sample plans. The sample plan shall

L'ICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACIUly NAME DOCKET NUMBER LER NUMBER PACE yEAR "~ SEOUENTIAI. P:. REVISION NUMBER lN NUMBER Palo Verde Unit 1 0 5 0 0 0 5 23 9 3 0 0 7 0 2 0 3oF 0 9 be selected prior to the test period and can not be changed during the test period. The NRC Regional Administrator shall be notified in writing of the sample .plan selected prior to the test period...,"

[The NRC Regional Administrator had been informed of APS'ntentions to use .sample plan 4.7.9.e.2, (References 1,2,3). APS did not identify a different sample plan for hydraulic snubber testing.]

4.7.9.e.l). States in part "...at least 10 percent of the total of each type of snubber shall be functionally tested...for each snubber of a type that does not meet .the functional test acceptance criteria...an additional 10 percent of that type of snubber shall be functionally tested until no more failures are found or. until all snubbers of that type have been functionally tested; or,..." [PVNGS hydraulic snubber testing meets this,SR except for random selection.]

4.7.9.e.2). States in part "...a representative sample of each type of snubber shall be functionally tested in accordance .with figure 4.7-1. If at any time the point plotted falls in the "Reject" region all snubbers of that type shall be functionally tested. If at any time the point plotted falls in the "Accept" region, testing of snubbers of that type may be terminated. When the point plotted lies in the "Continue Testing" region, additional snubbers of that type shall be tested until the point falls in the "Accept" region or the "Reject" region, or until all snubbers of that type have been tested; or...."

[Testing of hydraulic snubbers did not meet this sample plan although the NRC Regional Administrator had been informed that it would.]

e.3). Not used at PVNGS.

4.7.9. States in part "...The representative sample...shall be randomly'elected from the snubbers of each type...representative of the various configurations, operating environments, range of size, and capacity of snubbers of each type...." [PVNGS selected its sample for mechanical snubbers from the population that had not been tested. Previously failed snubbers were retested as required. Snubbers that tested acceptable were removed from the test population. Because of the

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION'ACILITY NAME DOCKET NUMBER LER NUMBER PAGE YEAR g: SEQUENTIAL Cg REVISION NUMBER I'I': NUMBER Palo Verde Unit 1 o s o o o 5 2 89 3 0 0  ?, 0 2 04oF09 fev number of hydraulic snubbers, specific steam generator .(AB)(SG) snubbers and'eactor Coolant Pump (AB)(RCP) snubbers vere scheduled to be tested each outage,],

The PVNGS. Snubber Testing Program is described in Administrative Control Procedure 73AC-9ZZ01 "Testing and Control of PVNGS Snubbers." This procedure describes the five (5) snubber groups as follows:

PSA 1/4 and 1/2 size Mechanical Snubbers (small)

PSA 1, 3, and 10 size Mechanical Snubbers (medium)

PSA 35 and 100 size Mechanical Snubbers (large)

SG Hydraulic Snubbers RCP Hydraulic Snubbers Mechanical Snubbers PVNGS implemented the mechanical snubber .testing program by treating all mechanical snubbers as one type with three groups: small, medium, and large., 'PVNGS believed this was a correct interpretation since all mechanical snubbers at PVNGS are Pacific Scientific Arrestors (PSA). The PVNGS program considered all sizes to have the same design features. This is contrary to the requirements of TS SR 4.7'.9.e.

H draulic Snubbers Each unit has 12 hydraulic snubbers, four (4) SG and eight (8) RCP. To implement TS SR 4.7.9.e.2, as docketed to the Regional Administrator, all 12 hydraulic snubbers would require testing each outage. PVNGS tested only one of each type (2 total) during each outage. PVNGS did not notify the Regional Administrator that PVNGS'rocedures implemented a test plan meeting SR 4.7.9.e.l, except for random sample requirements.

Sam le Selection Although the selection of mechanical snubbers for testing at PVNGS was representative, it was not completely random.

Snubbers that failed the acceptance criteria vere repaired or replaced and retested during the next testing, period as required. Snubbers that tested acceptable were not, placed back int:o t:he population for possible selection during a subsequent test period. Although t'e method used by PVNGS would ensure all snubbers would eventually be tested, it did

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LICENSEE EVENT REPORT,(LER) TEXT CONTINUATION FACILITYNAME DOCKET NUMBER LER NUMBER PACE c~I SEQUENTIAL g@~ REVISION cV> NUMBER NUMBER Palo Verde Unit 1 5 2 89 3 0 0 7 0 2 0'5oFO 9 not meet the random selection criteria.

Hydraulic snubbers are scheduled for testing so that in 8 outages, the entire population of SG snubbers is tested twice and the entire population of RCP snubbers is tested once. This was done to ensure all snubbers are tested while maintaining radiation exposures As Low As Reasonably Achievable (ALARA),

C. Status of structures,,systems, or components that were inoperable at the start of the event that contributed to the event:

Other than the snubbers identifi'ed in Section I.B., that were administratively inoperable due to improperly interpreting the TS SR, no other structures, systems, or components were inoperable at the start of the event, which contributed to this event.

D. Cause of each component or system failure, if known:

This LER identifies a program failure and not. an equipment failure. All snubbers which failed surveillance testing were repaired or replaced and retested as required. No component or system failures were involved.

E. Failure known:

mode, mechani'sm, and effect of each failed component, if Failures of snubbers fall into five general modes as discussed below:

Design or Manufacturing-Failures resulting from a potential defect in manufacturing or design that gives cause to suspect other snubbers. This includes failures of any snubber that fails to withstand the environment or application for which it was designed.

Application induced-Failures resulting from environmental conditions or application of the snubber for which designed or qualified.

it has not been Maintenance, Repair, or Installation-Failures that result from damage during maintenance, repair, or installation activities, the nature of

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACIlITYN AME DOCKET NUMBER LER NUMBER PAGE YEAR @I SEOUEN TIAI.;,I", REVISION NUMBER, >4 NUMBER Palo Verde Unit 1 osooo528 9 3 00,7 0'206 OF. 0 9 which causes other snubbers to be suspect.

~ Isolated-The nature of the failure does, not lend other snubbers to be suspect, for example, failures resulting from damage during installation (i.e., missing pins, dropping equipment or tools on the snubber).

~ Unexplained-Failures that can not be categorized as design or manufacturing,,maintenance, repair, installation, application induced, or isolated. This category includes all failures for which the cause of the failure can not be determined.

There are three mechanisms of failure:

~ Breakaway or Drag-The force that will initiate motion or the force that will maintain low velocity displacement respectively..

Lockup is a breakaway or drag failure which exceeds 20 percent of rated load.

~ Activation-The function of a snubber that restrains movement when undergoing telescoping acceleration.

~ Release Rate The rate of axial snubber movement under load after activation (applicable to hydraulic snubbers only).

An evaluation is performed for snubbers which fail the functional test acceptance criteria. This evaluation determines or components to which the snubbers were attached could be damaged if systems due to the inoperable snubber. There has only been one area identified where the calculated stresses exceeded those allowed by the American Society of Mechanical Engineers (ASME) Code. This occurred on Reactor Coolant System Drain Lines RC070 and RC071.

Failures of snubbers on these lines occurred in Units 2 and 3.

Lines RC070 and RC071 were visually and nondestructively tested.

No abnormal conditions or indications of overstressing were found.

Inspection of piping and supports revealed that no damage had occurred.

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LICENSEE'EVENT REPORT (LER) TEXT CONTINUATION FACILITYNAME DOCKET NUMBER LER NUMBER PAGE SEQUENTIAL REVISION NUMBER NUMBER Palo Verde Unit 1 os o o o 5 28 9 3 0 0 7 0 2 0 7OFO 9 F. For failures of components with multiple functions, list of systems or secondary functions that were also affected:

Not applicable - no failures of components with multiple functions were involved.

G. For a failure that rendered a train of a .safety system inoperable, estimated time elapsed from the discovery of the failure until the train was returned .to service:

Not applicable - no failures that rendered a train of a safety system inoperable were involved.

H. Method of discovery of each component or system failure or procedural error:

Unit 2 was in a refueling outage performing required snubber testing. Because of the Unit 2 snubber failures, an increase in sampling was required. During the selection of the additional snubbers by APS Engineering personnel (utility, non-licensed), the NRC Resident Inspector (non-utility, non-licensed) questioned the selection methodology and TS testing requirements. Subsequently, as discussed in Section I.B, APS concluded that it had incorrectly.

interpreted the Technical Specification.

Cause of Event:

This condition was caused by incorrectly interpreting TS SR 4.7.9.e, and failing to recognize and inform. the NRC Regional Administrator that the SR would be implemented differently from previously identified (SALP Cause Codes A: Personnel Error).

This incident is being investigated in accordance with the APS Incident 'Investigation Program. If information is developed which would affect the reader's understanding or perception of this event, a supplement will be submitted.

,Safety System Response:

Not applicable - there were no safety system responses and none were necessary.

K. Failed Component Information:

Pacific Scientific Arrestor Models PSA-1/4, PSA-1/2, PSA-l, PSA-3, PSA-10, PSA-35, and PSA-100

k LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITYNAME DOCKET NUMBER LER NUMBER PACK YEAR SEQUENTIAL ~~g REVISION NUMBER NUMBER Palo Verde Unit 1 0 5 0 0 O'S 2 Sq 3 On 7 .0 2 0 8 OF n 9 II. ASSESSMENT OF THE SAFETY CONSEQUENCES AND IMPLICATIONS OF THIS EVENT:

No release of radiological effluent or exposure to member(s) of the public resulted from this event. APS Engineering .personnel have completed a review of the previous snubber testing conducted at PVNGS and concluded that sufficient testing was performed to assure that the snubbers can perform their intended function.

APS has concluded there is no significant safety implicati'ons to operating PVNGS'nits 1, 2, and 3 as a result of the noncompliance with TS SR 4.7.9.e. The purpose of snubbers is to protect the piping systems during seismic events while allowing thermal growth without overstressing the piping.. For snubbers not meeting the acceptance criteria during testing, stress calculations have been performed to determine if imposed stresses exceeded Code allowable stresses.

was performed with the snubbers in the as-found condition. With the This exception of the Reactor Coolant System Drain Lines RC070 and RC071, APS Engineering personnel determined that the piping was not overstressed and that the snubbers, while degraded, did not challenge the operability of piping or components. Lines RC070 and RC071 were visually and nondestructively examined. No abnormal conditions or indications of overstressing were found. Therefore, the consequences are no different than previously analyzed in the PVNGS Updated Final Safety Analysis Report for snubber failures. The probability and types of failures remain the same.

III. CORRECTIVE ACTION:

A. Immediate:

In accordance with TS 4.0.3., failure to perform a surveillance requirement constitutes noncompliance with the OPERABILITY requirements for a LCO and requires the entry into the associated ACTION statement. As discussed above, PVNGS entered the ACTION statement for TS 3.7.9., at approximately 1330 MST on May 12, 1993. This 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> action period would have ended at approximately 1330 MST on May 15, 1993, when PVNGS'nit 1 and Unit 3 would have been required to shutdown in accordance with TS 3.0.3. A Notice of Enforcement Discretion from PVNGS'nit 1, 2, and 3 TS Limiting Condition for Operation ACTION statement was requested from and subsequently granted by the Commission at approximately 1400 MST on 'May 14, 1993.

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LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITYNAME DOCKET NUMBER. LER NUMBER PAGE YEAR SEQUENTIAL <:~ REVISION NUMBER NUMBER Palo Verde Unit 1 5 2 8 OF B. Action to Prevent Recurrence:

The PVNGS Snubber Testing program will be revised -to correctly implement the TS requirements prior to commencing the next testing cycle.

An investigation of this event is being conducted according to the APS Incident Investigation Program. Additional actions. to prevent recurrence may be identified based upon the results, of the investigation. If additional actions are identified which the reader's understanding or perception of this event, a would'ffect supplement will be submitted.

IV. PREVIOUS SIMILAR EVENTS:

There have been no previous similar events reported pursuant to 10CFR50.73.

V. ADDITIONAL INFORMATION References (1) Letter 161-00296, dated June 22, 1987-, from J.G..Haynes, APS to Mr. John B. Martin, USNRC.

Subject:

Functional Testing of Snubbers. [Unit 1]

(2) Letter 161-00469, dated August 31, 1987, from J.G. Haynes, APS to Mr. John B. Martin, .USNRC.

Subject:

Functional Testing of Snubbers. [Unit 2]

(3) Letter 161-01612, dated January 12, 1989, from D. B. Karner, APS to the Document Control Desk.

Subject:

Functional Testing of Snubbers. [Unit 3]

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