ML20127N185

Safety Evaluation Accepting Inservice Testing Program for Valves,Relief Request VR-4

ML20127N185
Person / Time
Site:	Byron
Issue date:	01/25/1993
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20127N182	List: ML20127N180 ML20127N185
References
NUDOCS 9301290121
Download: ML20127N185 (6)

Text

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UNITED STATES

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Lg ;j p NUCLEAR REGULATORY COMMISSION -

WASHINGT oN. O, C. 20555 j a...*

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i SAFETY EVALVATION BY THE OFFICE'0F NvCLEAR REACTOR REGULATION 2

'RELATED TO VALVES INSERVICE TESTING PROGRAM. RELIEF RE0 VEST VR-4 i BYRON NUCLEAR POWER STATION. UNITS 1 AND 2 1

{ DOCKET N05.-STN 50-454 AND STN 50-455

1.0 INTRODUCTION

e

! The Code of Federal Regulations,10 CFR:50.55a, requires that inservice i testing (ISI) of certain American Society of_ Mechanical Engineers (ASME).

Boiler and Pressure Vessel Code (Code)-Class.'l,-2, and 3: pumps and valves b e.

performed in accordance with'Section.XI of the ASME Code and applicable >

- addenda, except where specific written relief.has' been

requested by_ the i licensee and granted by the. Commission pursuant to Sections:(a)(3)(i),-

! (a)(3)(ii), or (f)(6)(1) = of 10 CFR 50.55a. -In _ requesting- relief,' the licensee 1 must demonstrate that: (1) the proposed' alternatives provide an: acceptable.

level of quality and safety; or (2) compliance would result'in hardship or l

unusual difficulty without a compensating increase:in the 11evel _of= qua_lity and safety; or (3) conformance is impractical .forcits facility. . Generic Letter =

! (GL) 89-04, " Guidance on~ Developing; Acceptable Inservice Testing Programs,"

i provided alternatives to.the.Section-XI requirements determined to be_ 1 i acceptable to the staff.

l By letter dated July 1,1991, Commonwealth Edison Company. (Ceco) submitted.

revision 10b for valve Relief Request VR-4, from the Byron Station ASME

, Section XI IST program. VR-4 requested relief from'the requirements'of the 7 lASME Code,Section XI, IWV-3521,-IWV-3522, IWV-3412, and IWV-3200,' full--

i flo'w/ full stroke exercise for containment'~ spray pump ? discharge: valves, t

2 1/2CS003A/B, and for containment spray to containment' ring header check

' valves, 1/2CS008A/B. Ceco proposed to disassemble and inspect the valves on a sampling basis during refueling outages.. After reassembly, Ceco proposed to-_

l perform partial flow tests on 1/2CS003A/B and leak . tests on 1/2CS008A/B.-

7 By letter dated August 16, 1991,- the staff granted relief as requested for the 4

1/2CS003A/B valves but'provided only-' interim relief for the 1/2CS008A/B r ' valves. :The. interim relief-was provided to give Ceco an opportunity to pursue-a-means of performing a non-intrusive diagnostic . test and air partial flow

test for!the 1/2CS008A/B-valves ~. By letter dated _' July 31, 1992,- Ceco provided

' the results'of the testing ' performed and requested that the ~ portion 'of: Relief '

1 Request VR-4 Revision 10b dealing with valves 1/2CS008A/B be approved for the' remainder of the first inspection interval.:

20 QESCRIPTION AND EVALUATION OF RELIEF RE0 VESTS i The licensee requ"ested relief from the exercising requirements of.Section XI,.

IWV-3200 and'-3522, for check-valves 1(2)CS008A/B on.the containment. spray _

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9301290121-930125 4

PDR. ADOCK 05000454 P. -PDR 1

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i 2-(CS) system. The licensee proposed to: (1) disassemble and inspect the valves on a sampling basis during refueling outages, and (2) leak test the 1/2C5008A/B valves following reassembly.

2.1 Lttensee's Basis for Reliel The 1/2CS008A/B check valves are the inboard containment isolation valves (CIVs) for the spray heeder piping and function in the ooen direction to allow flow. They function in the closed direction to provide for containment isolation, which is a redundant function to the outboard CIVs. These valves can not be full flow tested during unit operation or cold shutdown as water fro'n the CS pumps would be discharged through the CS ring headers, causing undesirable effects on many critical components inside containment. ,

Additionally, the full flow testing of these check valves during periods of cold shutdown, using the CS pumps, would fill the reactv refueling cavity with borated water from the refueling wat r storage tank (RWST). This would adversely affect the reactor head components (e.g., control rod drives). The filling of the cavity, via temporarily installed large bore piping, would require the removal of the reactor vessel head so as to precitide equipment dan < age from borated water. The erection of temporary piping from the CS line to the reactor cavity would take an estimated nine to twelve shifts, compared to one to two shifts for valve inspection. This estimate does not take into account the time required to drain and remove the piping from containment.

Testing in this manner would also require overriding protective electrical interlocks in the pump start circuitry, full flow recirculation flow paths do not exist from the discharge of the CS pumps through these check valves to the RWST.--The addition of such flow paths q would require extensive modifications to existing plant design, including edditional penetrations of the containment boundary, and electrical system changes to allow for pump start without the need of jumping protective interlocks. ,

Partial stroking of the 1/2CS008A/D valves with air using existing local leak- <

rate test (LLRT) connections does not provide adequate flow to obtain any - '

meaningful acoustic monitoring data relative to valve condition or'its performance parameters. This acoustic testing was attempted at Byron Station per special process procedure, SPP 91-054. i l

The A and.B train valves in each group'are of-the same design (manufacturer,  !

size, model: number, and-materials of construction) and have the same service - ,

conditions, including orientation, therefore, they form a sample disassembly I group.

UNIT 1 GROUP 1 GROUP 2 lCS003A IC5008A 1C5003B JCS008B

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_ _ _ _ _ _ _mm i

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1 UNil 2 -

l GROUP 1 GROUP 2 i =. ,. a 2CS003A 2CS008A i 2CS003B 2C5008B l One valve from each group, on a per ur,it basis, will be examined each refueling outage. If a disassembled valve is not capable of being manually

, full-stroke exercised or if there is binding or failure of internals, the l remaining valve on the affected unit will be inspected, i

. In addition to the above, the 1/2CF008A/B are required to be leak tested i before and af ter visual inspection per Appendix J reoutrements. The leakage

test following reassembly of the valve into the system will serve as post-j maintenance verification that the valve was installed correctly,

The 1/2CS008A/B valves are removed from the system and visually examined per i the strict detailed inspection requirements of the station check valve

program. This inspection adequately verifies that the valves are mair,tained l in a state of operational readiness and that the valve's performance

parameters are adequately assessed, lhe valves are verified to be functional l by performing a thorough visual inspection nf the internals and by performing a manual full-stroke exercise of each disk. Previous inspections of these particular valves at both Byron and Braidwood Stations have repeatedly shown

them to be in good condition.

! The wafer type design of the valve body make removal of these vilves a simple process with little chance of damage to_ their_ internals._ Also, there is no

' disassembly of internal parts required; all wear surfaces are accessible to visuai examination. After inspection and stroke testing, the valve is reinstalled into the line and post-maintenance testing is performed. The

1/2C5008A/B' valves are incal leak rate tested oer the requirement of 10 CFR

. 50, Appendix J. These tests verify proper installation of the check valves.

The valve inspection procedure requires post-inspection visual examination of i the check valves to ensure that the pin is orienteo properly and the flow I direction is correct.

i The alternate test frequency is justifiable in-that the maintenance history i and previous inspection of these valves at both Byron and Braidwood stations have shown no evidence of degradation or physical impairments. In addition, industry experience, as do;.umented in nuclear plant reliability data system l (NPRDS), shows no history of problems with these valv o ,

A company wide check valve' evaluation addressing the "I'PRI Applications Guidelines for Check Valves in. Nuclear Power Plants" revealed that the location, orientation, and application are such that these valves are not conducive to the type of wear or degradation correlated with SOEA 86-03 type

-problems. However, they still require some level of monitoring to detect hidden problems.

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The alternate test method is sufficient to ensure operability of these valves and is consistent with GL 89-04. The hardship involved with full-stroke i exercising these check valves, if the Section XI requirements were imposed, does not provide a compensating increase in safety of these CS system valves. .

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2.2 IyaluatiqD

} Using the containment spray pumps to full-stroke exercise valves 1/2CS008A/B

would result in containment spray down and equipment damage. The A$ME Code i i required testing could only be performed af ter significant system modifications which would not be practical because of the excessive burden.

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1he licensee proposed to verify the full-stroke open capability of these check valves oy sample disassembly and inspection, following reassembly, the i 1/2CS008A/D valves are leak tested. Valves 1/2CS00fA/B are downstream of the j motor-operated isolation valves in a portion of piping that is isolated until i the CS system actuates and the isolation valves open. Therefore, 1/2CS008A/B *

! are not partial-flow exercised quarterly when the CS pumps run in'a recircula-I tion mode. Byron Station partial-stroked 1/2C5008A/B with air using existing i LLRT connections, but the test did not appear to provide-meaningful acoustic

monitoring data because of inadequate flow. By adding test piping downstream ,

i of 1/2C5008A/D to allow for recirculation of the fluid, the valves can be ,

partial-stroke tested with water without resulting in a spray nozzle ,

discharge: however, such a modification would be extensive and costly and l

impose an undue burden on the licensee.

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! The NRC staff position regarding check valve disassembly and inspection is explained in GL 89-04. The minutes of the public meetings on GL 89-04 i regarding Position 2, " Alternative to full flow Testing of Check Valves,"

further stipulate that a partial-stroke exercise' test using flow is expected i_ to be performed, if possible, before the valve is returned to service after l disassembly and inspection. Full-stroke exercise using flow should be

performed if pnssible._ This post-inspection testing provides a degree of i confidence that the disassembled valve has been reassembled properly and that i the. disk in the valve moves freely. Disassembly and inspection is considered i by the NRC to be a maintenance procedure with inherent risks which make its

use as a routine substitute for Section XI testing undesirable when other -

! testing methods are possible. The licensee should actively _ pursue the use of j non-intrusive diagnostic techniques to demonstrate that the disks in the j valves fully open during partial-flow testing, if another method is developed

[ to verify the full-stroke capability of these check valves, this relief should

, be revised or withdrawn, i

i Based on the determination that compliance with the ASME Code requirements is

. impractical, and considering the burden on the licensee if the ASME Code 3 requirements were imposed, relief is granted pursuant 10110 CFR f

SC.55a(f)(6)(i), provided the valves are disassembled and inspected in accordance with Position 2 of.GL 89-04.

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3.0 Gt4CLUS10f4 Valve relief request VR-4 is granted, provided that the subject valves are disassembled and inspected in accordance with Position 2 of GL 89-04. The implementation of IST program commitme*,ts is subject to inspection by f4RC. <

The Commission concludes that granting this relief will not compromise the reasonable assurance of the operational readiness of the valves to perform their safety-related functions. The Commission has determined that granting relief pursuant to 10 CFR 50.55a(f)(6)(i) is authorizes by law and will not endanger life or property, or the common defense and security and is otherwise in the public interest. In making this determination the staff addressed the impracticality of performing the required testing considering the burden if.

the requirements were imposed. The granting of relief is based upon the fulfillment of.any commitments made by the licensee in its basis for the relief request and the proposed alternate testing.

Principal Contributor: - K. Dempsey Date: January 25, 1993

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Mr. Thomas J. Kovach -?- )

compliance would result in hardship without a compensating increase in safety 2 provided conditions described in the SE are met.

I Sincerely, l

0@nal66 9nod cy: l

{

I James E. Dyer, Director l 1 Project Directorate 111-2 l Division of Reactor Projects Ill/IV/V

Office of Nuclear Reactor Regulation 1

j

Enclosure:

Safety Evaluation i cc w/ enclosure:

See next page

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