ML20246L989

Requests Assistance in Integrating Multi-Plant Action B-94, Mark I Containment Drywell Corrosion W/Current Efforts Re Development of New Requirements for Inservice Insp of Steel Containments

ML20246L989
Person / Time
Site:	Oyster Creek
Issue date:	03/17/1989
From:	Holahan G Office of Nuclear Reactor Regulation
To:	Gillespie F Office of Nuclear Reactor Regulation
References
TAC-40566, NUDOCS 8903270001
Download: ML20246L989 (4)

Text

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.g E WASHINGTON, D. C. 20555 g March 17, 1989 MEMORANDUM FOR: Frank P. Gillespie, Director Program Management, Policy Development and Analysis Staff, NRR FROM: Gary M. Holahan, Acting Director Division of Reactor Projects III, IV, Y and Special Projects, NRR

SUBJECT:

MPA B-94, " MARK I CONTAINMENT DRYWELL CORROSION,"

RECOMMENDATION FOR RECLASSIFICATION AND PPIORITIZATION, (TAC 40566)

The purpose of this memorandum is to request your assistance in integrating MPA B-94 " Mark I Containment Drywell Corrosion," efforts with other current efforts related to development of new requirements for inservice inspection of steel .

containments.

BACKGROUND Mark I steel containment drywell vessels are supported at the bottom of the vessel by a concrete basemat. At the outer edge of the supporting concrete is a sand cushion ring which provides a gradual stress transition for the drywell, from fixed support to freestanding. The sand cushion is provided with drain piping discharging into the wetwell (torus) cha:nber of the reactor -

building. The purpose of the drains is to permit escape of any water leaking into the sand cushion. The most likely source of water leakage into the sand cushion is leakage from the refueling cavity seal at the drywell vessel head.

In 1980, while refueling, personnel at the Oyster Creek Nuclear Generating i Station observed water coming from drain lines connected to the drywell vessel sand cushion. In 1986, during refueling, water was again observed coming from the sand cushion drains. Due to concern about the potential for corrosion of the drywell caused by moisture in the sand cushion, the licensee removed sec-tions of the drywell concrete curb and floor to permit ultrasonic testing of the steel drywell in the area abutting the sand cushion. (Removalofsections of the concrete interior curb area and floor was necessary in order to permit placement of ultrasonic transducers against the drywell shell interior at lo-cations where the exterior rests on the sand.) It was determined that consid-erable corrosion and reduction of drywell shell thickness had occurred.

Analyses indicated that sufficient thickness remained to meet ASME Code requirements. .

STATUS On December 8, 1986 the staff issued INFORMATION NOTICE 86-99 informing Mark I owners of the Oyster Creek event. On March 12, 1987, the staff issued j

Generic Letter 87-05 to these licensees requesting their plans for (1) assuring sand cushions are properly drained, (2) assuring water leakage into the sand cushion (during refueling) is minimized, and l

(3) performing ultrasonic testing of the drywell shell. ,)[

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CONTACT:

]d'p W. Long, NRR/PDSNP 492-1103 Of03 .d h  !

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Mr.: Frank P. Gillespie- March.17, 1989 MPA B-94 was established to provide project management and. tracking of the GL 87-05 responses. . It was subsequently found that other facilities had wet sand cushions. At Dresden (both units) the drain lines are found to be capped.

When the caps were removed a large amount.of water was~ released (1900 gallons from Unit 2.and 1100 gallons from Unit 3). During the ensuing inspections-

involving drilling of large permanent holes in the concrete interior floor of the drywell for UT transducers,- it was found that the interior side of the drywell shell under the poured concrete floor was also wet (water appeared in the drilled holes)!

Since reviewing the licensees' GL 87-05 responses, the staff has determined that new generic requirements for augumented periodic inservice. inspection related to the sand cushion area of Mark I steel containments are necessary.

Note: Brunswick is a Mark I but not a steel containment and is therefore not a .

concern for this issue. WNP-2 has a Mark II containment, but does have a steel drywell and sand cushion and therefore is subject to this concern.

ACTION / RECOMMENDATIONS The staff is presently planning to issue a new generic letter outTining new periodic augumented inservice inspection requirements aimed at the GL 87-05 sand cushion corrosion problem. However, we note that there are other concerns and pending actions related to steel containment deterioration and degradation. . In addition to corrosion in the sand cushion area, there.is evidence that corrosion may be taking place at other. locations in Mark I's. Information Notice 88-82 describes concerns relating to torus corrosion resulting from coating deterioration. Also, corrosion may be taking -

place in tendons of concrete containments.

It is our recommendation that any future requirements for additional contain-ment inspections not only encompass the sand cushion problem, but also any other necessary new ISI needs for steel and concrete containments. In addition we recommend a review of the potential adverse effects on severe accident vulnerability of the. permanent removal of drywell floor concrete from

'the area opposite the sand cushion in Mark I's. We note that EPRI currently has a research project to investigate use of electromagnetic acoustic trans-ducers to enable the drywell shell thickness to be measured without removal of ,

concrete. The EPRI effort is being pursued in support of future license ex- I~

tension needs, but is directly applicable to the B-94 concern and should be evaluated by the staff as a potential surveillance or ISI requirement. As an initial action, we recomend that Task Action Plan / Issue B-49 be redesignated  ;

_ Generic Issue B-49 and be subjected to prioritization by RES. j l

N N t-Gary M. Holahan, Acting Director Division of Reactor Projects III, IV, V and Special Projects, NRR t

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Mr. Frank P. Gillespie March 17, 1989 MPA 8-94 was established to provide project management and tracking of the GL 87-05 responses. It was subsequently i sand cushions. At Dresden (both units)y found the drainthat other lines facilities are found had to be wet capped. {

When the caps were removed a large amount of water was released (1900 gallons i from Unit 2 and 1100 gallons from Unit 3). During the ensuing inspections J involving drilling of large permanent holes in the concrete interior floor of )

the drywell for UT transducers, it was found that the interior side of the drywell shell under the poured concrete floor was also wet (water appeared in J the drilled holes)!

Since reviewing the licensees' GL 87-05 responses, the staff has determined that new generic requirements for augumented periodic inservice inspection related to the sand cushion area of Mark I steel containments are necessary.

Note: Brunswick is a Mark I but not a steel containment and is therefore not a concern for this issue. WNP-2 has a Mark II containment, but does have a steel drywell and sand cushion and therefore is subject to this concern.

ACTION / RECOMMENDATIONS The staff is presently planning to issue a new generic letter outlining new periodic augumented inservice inspection requirements aimed at the GL 87-05 sand cushion corrosion problem. However, we note that there are other concerns and pending actions related to steel containment deterioration and degradation. In addition to corrosion in the sand cushion area, there is evidence that corrosion may be taking place at other locations in Mark I's. Information Notice 88-82 describes concerns relating to torus corrosion resulting from coating deterioration. Also, corrosion may be taking place in tendons of concrete containments.

It is our recommendation that any future requirements for additional contain-ment inspections not only encompass the sand cushion problem, but also any other necessary new ISI needs for steel and concrete containments. In addition, we recommend a review of the potential adverse effects on severe accident vulnerability of the permanent removal of drywell floor concrete from the area opposite the sand cushion in Mark I's. We note that EPRI currently has a research project to investigate use of electromagnetic acoustic trans-ducers to enable the drywell shell thickness to be measured without removal of concrete. The EPRI effort is being pursued in support of future license ex-tension needs, but is directly applicable to the B-94 concern and should be evaluated by the staff as a potential surveillance or ISI requirement. As an initial action, we recomend that Task Action Plan / Issue B-49 be redesignated Generic Issue B-49 and be subjected to prioritization by RES.

Original sicaed by r Gary M. Holahan, Acting Director Division of Reactor Projects III, IV, Y and Special Projects ,

(MPA B-94 RECOMMENDATIONS) ,

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