ML20236F779

Safety Evaluation Authorizing Request for Temporary Relief from Requirement of Subsection IWA-5250 of ASME Code,Section XI for Plant,Unit 1

ML20236F779
Person / Time
Site:	Calvert Cliffs
Issue date:	06/30/1998
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20236F777	List: ML20236F774 ML20236F779
References
NUDOCS 9807020336
Download: ML20236F779 (5)

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.= NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 30006 00M i

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I SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATIO*i ON TEMPORARY RELIEF FROM ASME CODE. SECTION XI. SUBSECTION IWA-5250 REQUIREMENT FOR CALVERT CLIFFS NUCLEAR POWER PLANT. UNIT NO.1 BALTIMORE GAS AND ELECTRIC COMPANY QQCKET NO. 50-317

1.0 INTRODUCTION

The Technical Specifications for Calvert Cliffs Nuclear Power Plant, Unit No.1 state that the inservice inspection and testing of the American Society of Mechanical Engineers (ASME) Code Class 1,2, and 3 components shall be performed in accordance with Section XI of the ASME  ;

Boiler and Pressure Vessel Code (ASME Code) and applicable Addenda as required by 1 10 CFR 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). 10 CFR 50.55a(a)(3) states that attematives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed attematives would provide an acceptable level of quality and safety or (ii) compliance with the -

specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1,2, and 3 components (including supports) shall meet the requirements that become effective subsequent to editions specified in 10 CFR 50.55a(g)(2) and (g)(3), except the design and access provisions and the preservice examination requiren'.ents, set forth in the ASME Code,Section XI, " Rules for Inservice inspection of Nuclear Power Plant Components,' to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require thkt inservice examination of components and system pressure tests conducted during the first i ten-year interval and subsequent intervals comply with the requirements in the latest edition and I

'_ addenda of Section XI of the ASME Code incorporated by refaience in 10 CFR 50.55a(b) on the date twelve months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable edition of St.ction XI of the ASME Code for the second ten-year inservice inspection interval for Calvert Clif"s, Unit Nos.1 and 2 is the 1983 Edition, including the Summer 1983 Addenda. The components (including supports) may meet tho' requirements set forth in subsequent editions and addenda of the ASME Code incorporated by reference in 10 CFR 50.55s(b) subject to the limitations and modification,s listed therein and subject to Commlulon approval.

Pursuant to 10 CFR 50.55a(g)(5)(iii), if the licensee determines that conformance with an  !

examination requirement of Section XI of the ASME Code is impractical for its facility information, ;

it should be submitted to the Commission in suppon cithat determination. After evaluation of  ;

the determination, pursuant to 10 CFR S0.55a(g)(6)(i), the Commission may grant re ief and may 9907020336 980630 l PDR ADOCK 05000317 '

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impose altemative requirements that are determined to be autherized by law; will not endanger life, property, or the common defense and security; and are otherwise in the public interest, giving due consideration to the burden upon the licensee that could result if the requirements were imposed.

By letter dated May 12,1998, Baltimore Gas and Electric Company (licensee) requested a temporary relief from the requirement of subsection IWA-5250 of the applicable ASME Code, i Section XI to defer locating and renairing a minor leak in the refueling pool liner identified during i the April 1998 refueling outage until the period of time when the pool is in a long-term drained  ;

condition, i.e., prior to fuel movement from the reactor vessel during the spring 2000 outage of  !

Unit No.1. '

. The NRR staff, has reviewed and evaluated tiie licensee's proposed altemative to the Code requirements, pursuant to 10 CFR 50.55a(s)(3)(i) for Calved Cliffs Unit No.1.

2.0 DISCUSSION Component Apolicable forTemoorary Code Reliaf:

Portion of refuel pool liner below 45 ft elevation which becomes an extension of spent fuel pool pressure boundary when the fuel transfer tube connecting both pools, is open. This is designated as ASME Code Class 3.

Code Reaulrements Affected by the Proposed Relief Reauest: -

The 1983 Edition through Summer 1983 Addenda, ASME Code,Section XI, subsection IWA-5250, states: "(a) The source of leakages detected during the conduct of a system pressure test shall be located and evaluated by the Owner for corrective measures as follows:"  !

"(2) repairs or replacements of components shall be performed in accordance with IWA-  !

4000 or IWA-7000, respectively."

Licensee's Proposed Attemative:

The licensee found evidence of leakage from the refueling pool during the current refueling outage and proposes to monitor the leakage for the remainder of the time that j

the refueling pool is flooded and the transfer tube is open to ensure that the leakage does not increase significantly. This will provide adequate assurance of safety until the defect can be i located. Reasonable efforts will be made to locate the defect prior to fuel movement from the reactor vessel during the next scheduled Unit No.1 refueling outage (spring 2000). The licensee further states that should the leakage from the liner increase substantially, the licensee will reevaluate its analysis.

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Supportino information and Basis for Reauestina Relief:

L l On April 22,1998, while performing general housekeeping during the outage, the licensee found evidence of leakage at the exit location of the overflow line for the refueling pool which penetrates the pool liner at the 67'-6" elevation and exits the concrete pool base at the 32' elevation. The leakage appeared to be on the order

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of one-to-two drops per second when the leak was found and substantially reduced with each subsequent visual examination. On May 4,1998, visual examination of concrete surface identified no drops of leakage except some wetness at the leak

' location. The refueling pool was drained of water as a part of scheduled outage activities. A visual examination and vacuum box testing of the most likely areas within the Code boundary ll failed to locate the leak. Therefore, it is not known if the leak originates from the Code portion of t L the refueling pool. 1 o The refuel pool is a reinforced concrete pool with a stainless steel liner. Leakage from the pool appears to be migrating between the liner and the concrete wall, and exiting the concrete at the location where the pool overflow line comes through the concrete.

An evaluation has been done to address possible robar corrosion due to contact with

!' borated water (similar to the water contained in the refueling pool). The evaluation l

shows that the corrosion rate of rebar in reinforced concrete is not accelerated under the contlitions available in the refuel pool.

o . The rate of leakage from the defect is small. This would be indicative of a small flaw l

t which is supportive of difficulty in locating it.

( o The refuel pool is not subject to the containment design basis pressure and thermal L stress fluctuation. The pool is open to the containment atmosphere and, therefore, l- cannot be pressurized. Additionally, the water in the poolis cooled by the spent fuel

( pool (SFP) cooling system and the shutdown cooling system. Even if the cooling l systems were to totally fail, the pool cannot be subject to temperC.ures greater than i 212 F.

1 o . Due to the structural support provided by the concrete portion of the refuel pool and the small size of the flaw, it was determined that catastrophic failure of the liner due to this defect is not credible.

Based on these observations, an initial determination was made that the refueling pool fs able to perform its safety and non-safety functions. Therefore, the system was determined to be ,

! operable. Howe.ver, because of the identified leakage in the refueling poolliner and the  !

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. possibility that the leek may be in the Code portion of the refue! pool, Technical Specification <

Action Statement 3.4.10.1.c, Structural Integrity of ASME Code Class 3 Components, will be entered when fuel loading begins. This Action Statement does not restrict startup or continued  ;

i power operation. The licensee intends to locate the defect and restois the structural integrity of the liner as required by IWA-5250 prior to fuel movement from the reactor vessel during the next Unit No.1 refueling outage (spring 2000), when the transfer tube is closed and the pool is drained.

3.0 EVALUATION The staff has evalucted the licensee's proposed alternative to defer locating the source of leakage from the refueling poolin regard to the requirement of paragraph iWA-5250 of the ASME Code Section XI and performing necessary Papairs until the period of time when the pool is in a long-term drained condition, i.e., prior to fuel movement from the reactor vessel during the next scheduled Unit No.1 outage (6pring 2000). The staff noted that the visual examination of the exterior concrete surface of the refueling poolinitially detectesd a leaksge of one-to-two drops per second which subsequently disappeared, leaving a wet spc' at the leak location. The staff,

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l therefore, believes that the leakage pathways from the pool is through the liner and the concrete

- wall and exiting the concrete wall at the location where the pool overflow line comes through the concrete. The rate of leakage is extremely small and, hence is indicative of a small through-

. wall flaw in the refueling pool liner. The staff further believes that such a flaw in the pool liner will have negligible impact on the structural integrity of the refueling pool or on the inventory of both the pools when the fuel transfer tube is open during refueling. Following refueling, however, the pool is drained and the fuel transfer tube is closed.

The staff noted that the licensee attempted to locate the leak in the refueling pool after draining the pool during the outage by performing a visual examination and a vacuum box testing of most <

likely areas within the Code boundary But, the leak could not be located. The staff, therefore, )

l has determined that the licensee's proposed attemative is acceptable in regard to monitoring the l L leakage for the remainder of the current outage until the time that the refueling pool is filled with  !

borated water to ensure that the leakage does not increase significantly. Since the pool will be  !

i drained following the outage prior to bringing the unit on line, the location of the leak can ba j deferred until fuel movement from the reactor vessel during the next scheduled refueling outage l of Unit No.1. '

4.0 CONCLUSION

A minor leak was detected in the Unit No.1 refueling pool during the April 1998 outage of the unit. The location of the leak could not be determined from visual and vacuum box testing of l most likely areas of the Code boundary of the pool. The staff has determined that the small-  !

, leakage from the pool during the time that the fuel transfer tube remains open to maintain water j level in the refueling pool with borated water from spent fuel pool, does not affect the structural

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integrity of the refueling pool or the required water inventory of both pools. The staff concludes that the licensee's proposed attemative of monitoring the leakage during the current outage and l to defer locating the defect and repairing the leak until prior to fuel movement from the reactor -l vessel during the next scheduled outage of the unit, provides an acceptable level of quality and -

safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the licensee's proposed attemative is y authorized until the next scheduled refueling outage of Calvert Cliffs Unit No.1.

Principal Contributor: P. Patniak Date: June ~30,1998

1 Date: June 30, 1998

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SUBJECT:

REQUEST FOR TEMPORAR RELIEF FROM ASME CODE, SECTION XI, SUBSECTION IWA-5250 REQUIREMENT - CALVERT CLIFFS NUCLEAR POWER PLANT, UNIT NO.1 (TAC NO. MA1753)

DISTRIBUTION:

EDeshet File ~

PUBLIC . - j J. Zwolinski (A)- i S. Bajwa l S. Little 1 A. Dromerick T. Harris (e-mail only. TLH3)

OGC G. Hill (2 copies) T-5C3 ACRS B. McCabe i

C. Hehl -

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