ML20107L545

Provides Addl Info for Amend to License NPF-29 Re Fuel Handling Accident Operational Conditions

ML20107L545
Person / Time
Site:	Grand Gulf
Issue date:	04/24/1996
From:	Meisner M ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GNRO-96-00048, GNRO-96-48, NUDOCS 9604290350
Download: ML20107L545 (7)

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" ENTERGY %TJ!*'"""'""-

Port Gbun MS 33150 Tei 601437 6470 M. J. Meisner April 24,1996 [','[ my ,,

U.S. Nuclear Regulatory Commission Mail Station P1-37 Washington, D.C. 20555 Attention: Document Control Desk

SUBJECT:

Grand Gulf Nuclear Station  !

Docket No. 50-416 License No. NPF-29 Fuel Handling Accident Operational Conditions Proposed Amendment to the Operating License Additional information

Reference:

1. GNRO-95/00090, Fuel Handling Accident Operational Conditions, Proposed Amendment to the Operating License (PCOL-93/08 Revision 1), dated August 4,1995.

2. GNRO-94/00131, Fuel Handling Accident Operational Conditions, Proposed Amendment to the Operating License (PCOL-93/08), dated November 9,1994.

GNRO-96/00048 Gentlemen:

Entergy Operations, Inc. (EOl) is submitting by this letter additional information concerning a proposed amendment to the Grand Gulf Nuclear Station (GGNS) Operating License.

Reference 1 transmitted requested Technical Specification changes which would remove the requirements for secondary containment during shutdown when no credit is taken for it in mitigating the dose consequences of any accident. This letter provides additional information concerning the need for the timely approval of the requested changes and  ;

requests a meeting with the Staff to discuss the resolution of any issues associated with the requested change.

This letter was prompted by two factors.

1) As discussed below, GGNS will shortly need to perform significant work on the secondary containment boundary due to degradation of the enclosure building roofing materials.

2) We understand that tha Staff's delay in processing the requested change was due to a lack of Staff consensus concerning the role of containment integrity during shutdown conditions. Since we last met on January 4,1996, the Staff has published a draft shutdowri rule and regulatory guide which address the need for 9604290350 960424 - 0 0\

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GNRo-93/ooo48 page 2 of 7 i

containment integrity during shutdown. During the recent Regulatory Information i Conference session on the draft shutdown rulemaking Mr. Gary Holohan confirmed that the time seemed appropriate to revisit the requested Technical Specification  ;

changes in light of the Staff positions on containment contained in the draft  ;

rulemaking.  ;

A. STATUS OF REQUEST EOi has been working with the Staff for an extended period of time to resolve issues associated with the proposed change. The following summarizes the history of the requested change:  ;

l 1. GGNS originally proposed the requested changes on November 4,1994, i

! approximately 41/2 months prior to the last refueling outage. Due to other priorities the Staff was unable to complete their review in time to stoport the April 1995 refueling outage.

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2. Tc miuce Staff resource demands, and at the request of the NRC, GGNS collaborated e r ". the other BWR 6's (Clinton Power Station, Perry Nuclear Power i Plant, and Rivt Bend Station) in developing a joint approach. The group met with the Staff on July 20,1995 and discussed the basis for the proposed changes and the generic aspects of the proposed changes to the Technical Specifications, in this meeting GGNS discussed the dose analyses that had been performed and why the requested change did not have a significant imp:.ct on shutdown risk. Following this meeting GGNS updated the' request (Reference 1) to reflect the information provided in the meeting.

l 3. With approval of the change imminent, the BWR 6s were notified in November,  ;

1995 that NRC management felt additional work was necessary to clarify the role of j containment during shutdown conditions.

4. The BWR 6's again met with the Staff and NRR management on January 4,1996.

In this meeting the Technical Specification improvement rule was reviewed with the Staff to demonstrate that removal of these requirements was in accordancs with the rule. In this meeting we reiterated why the change doe 9 not have a ognificant impact on shutdown risk and reviewed our intentions with respect to containment closure. A!:,o, during this meeting the Staff expressed a desire for the issue to be resolved more genetically than just the BWR 6's.

5. In response the Staff's desire for the issue to be resolved more generically than just the BWR 6 s, EOl has voluntarily worked with the Nuclear Energy Institute's (NEl's)

Technical Specification Task Force to propose the appropriate Technical

. Specifications for all reactor types. The results of this effort were transmitted to j the Staff via letter from NEl on March 28,1996. The generic changes proposed are j consistent with GGNS's requested changes.

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GNRo-90/00048 page 3 of 7 B. ENCI.OSURE BUILDING CONDITION Over 1he years as leaks have developed in the enclosure building roof the affected areas have i.een patched to stop tha leakage. As the roof has aged the frequency of the leaks and thus the remired repairs has increased. Also, in the past year GGNS has experienced severe weather which included significant hail. These two factors have resulted in multiple leaks through the roofing. To date, the leakage has not adversely affected the function of any sEfety equipment within the enclosure building nor has the leakage adversely affected the ab;!ity of the enclosure building to perform its safety function.

GGNS currently plans to repair the enclosure building deck roofing overlay materials during the Fall 1996 refueling outage. This repair introduces the possibility of causing l secondary containment inoperability especially while the old roofing is being removed and during the initial reinstallation work.

C. DESIGN DESCRIPTION The secondary containment at Grand Gulf Nuclear Station (GGNS) consists of the auxiliary building and the enclosure building. The auxiliary building is a reinforced concrete structure which completely surrounds the lower portion of the containment, and the enclosure building is a metal-siding structure which completely surrounds the containment above the auxiliary building roof line. The enclosure building has a metal decking roof which by design was sealed sufficiently to support the inteakage j requirements of the secondary containment. To protect the metal decking and i associated sealant (e.g., caulking) the roof decking was overlaid with approximately 2  ;

inches of insulation, severa!!arers of fiberglass felt, gravel, and asphalt.

The fuel handlirsg area and the auxiliary building ventilation systems maintain the secondary containment at a slightly negative pressure during normal operation. These nonsafety systems assure that no ambient air escapes from the fuel-handling area during fuel handMg operations without first being monitored and treated for airborne radioactivity. Upon detection of high radioactivity, the standby gas treatment system is initiated and these systems are isolated.

The standby gas treatment system (SGTS) maintains the secondary containment at a negative pressure and provides cleanup of the potentially contaminated secondary containment volume following a design basis accident. Following actuation, the system draws air from the auxiliary building, mixes this air with air drawn from the enclosure

! building, and returns the mixed air to the enclosure building. A portion of the mixed air

! is exhausted via a charcoal filter assembly to maintain the SGTS boundary region at a j negative pressure.

Adequate leaktightness of the secondary containment is demonstrated every 18 months

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by running one of the two SGTS subsystems and verifying that the secondary

. containment reaches (within 120 seconds) and maintains the design differential j pressure with respect to the environment. These tests have always been performed i with the protective layers installed over the metal decking thereby contributing to the l leaktightness of the building.

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/ , i GNRo-96/o0048 page 4 of 7 D. OPTIONS As a result of the age and hail induced degradation of the roofing material the enclosure j building is in need of major repair to stop the leaks and the resulting degradation of the j enclosure building. This repair can be performed one of two ways:

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l 1. patching the current roofing material, or I l

2. replacing the roofing material.

i Each of these options have specific benefits and drawbacks. An overview of the options is discussed in more detail below.

1. Patching the current roofing material

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Patching the current roof would include activities such as adding additional asphalt to damaged areas of the esting roofing, covering the current roofing material with another layer of roofing material, and removing the most damaged areas of the roofing and building the roofing back up. Patching the current roof would be an j ongoing process with leaks being patched as they are identified and the source of the leak located. Since the roofing will continue to rely on the current degraded roofing as the base materialit is expected that the frequency of the leaks occurring l will continue to increase as the roofing ages further.

l' Patching the current roofing in the short term is the cheapest, easiest, and fastest way to stop the leaks in the enclosure building roof. Additionally while patching the roof the operability of the secondary containment should not be affected; therefore, the repair work can easily be performed in any plant condition. But patching the current roofing is also the least effective of the options available since the new roofing material will continue to rely on the current degraded roofing material.

2. Replacing the roofing material i The longest term solution is to remove and replace the current degraded roofing l material. This will allow the fewest number of seams in the material to be left as sites of future degradation and will allow for the most comprehensive inspection for degradation of the underlying roofing material. Unfortunately, this method may also result in inoperability of the enclosure building. ,

As discussed above, the enclosure building metal decking and associated sealant is  !

! by design sufficient to support the leaktightness requirements of the secondary l

, containment. But the inleakage tests have always been performed with the roofing l l protective layers installed over the metal ciecking thereby contributing to the i

! leaktightness of the buildmg. Although unlikely, the possibility exists that removing I i tne roofing material may result in an unacceptable increase in air leakage and

j. consequent inoperability of the enclosure building. But removing the material is not j the only reason secondary containment could become inoperable during the activity, i The metal decking could be damaged by the sepair activities or when the roofing

{ material is removed it may be identified that the metal decking is degraded.

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GNRo-96/00o48 page,5 of 7 If the enclosure building cannot achieve (within 120 seconds) and maintain a 1/4" inch negative pressure then it cannot be assured that radioactive materials are not leaking unfiltered to the environment. The effect of this unfiltered leakage is exacerbated by the design of the SGTS. The design of the SGTS, as discussed above, is to draw air from the potentially centaminated areas in the auxiliary ,

building, mix it with air drawn from the anclosure building, filter and discharge =

25% of the resulting mixture, and return the rest of the mixture to the enclosure building. In effect, should the enclosure building leaking excessively, operation of the SGTS could result in the increased release of unfiltered contaminated air into the environment, in this case SGTS operation is undesirable.

Replacing all of the roofing material is the best and longest term solution to the current degraded condition of the roofing. But this option introduces the possibility of enclosure building inoperability and operation of SGTS in a manner adverse to safety. However, as demonstrated in our referenced submittals, the proper scheduling of work during shutdown conditions obviates the need for secondary containment and SGTS operability.

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i E. TECHNICAL SPECIFICATION CHANGES REQUESTED j The requested changes remove the OPERABILITY requirements for the secondary j containment and control room and the associated support systems for the 1 OPERABILITY of the secondary cor.tainment and control room when no credit is taken for these structures to mitigate t'ie consequencas of any accident. The details of the requested changes and the asso.:iated justification can be found in GGNS's letter dated August 4,1995 (Reference 1).

Also identified in Reference 1 is a commitment by GGNS concerning the ability to l restore the containment function. In addition to preexisting commitments concerning the containment function, this commitment reflects GGNS's intention to control radioactive releas'.ss following an accident and work with the Staff to satisfy any concerns in this area.

F. WHY THE REQUESTED CHANGES SHOULD BE REVISITED The requested changes are needed for the upcoming outage to support full removal and replacement of the roofing material for the following reasons:

1. The repair option of patching the roof is only a short-term expedient and it provides little opportunity to identify and repair any degradation to the underlying roofing.

2. The option of replacing the roofing material is the best option for precluding future degradation of the secondary containment boundary and identifying and r3 placing any current degradation. Because the enclosure building metal decking and associated sealant is by design sufficient to support the leaktightness requirements of the secondary containment, this option could be performed durirv) operation or shutdown conditions. But this option does introduce the possibility of causing

GNRo-96/ooo48 page 6 of 7 secondary containment inoperability especially while the old roofing is being removed and during the initial reinstallation werk.

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3. Removal and replacement of roofing material will require a period of time comparable to a significant fraction of the upcoming refueling outage schedule.

, Given the potential for creating a condition where secondary containment is l inoperable, roofing work with the highest risk of causing secondary containment l I

inoperability could not be scheduled when secondary containment was required. As a consequence, the enclosure building roofing repairs may lead to a significant outage extension without improving safety, in addition to the urgency associated with the refueling outage repairs, we believe it is appropriate to revisit this issue because the Staff has crystallized its thinking on the role ,

of containment during shutdown conditions. The recently published draft shutdown I rulemaking and regulatory guide discuss the need fer contair. ment integrity in terms of a j core damage event. We believe that the rulemaking approach bounds the requested change and that this change provides a convenient opportunity to extend the rulemaking concepts to a fuel handling accident.

i in summary, approval of the requested TS change will allow EOl to perform a long-term

repair of the enclosure building roof without incurring either a significant economic impact through an extended refueling outage, or delaying the repair in favor of localized repairs.

Consequently, we request your timely review to support the Fall 1996 refueling outage and would be happy to meet with the Staff to respond to questions.

The information presented in this submittal does not affect the bases or conclusions of Reference 2.

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Your ruly, 1 -

F cc: Mr. R. B. McGehee Mr. N. S. Reynolds Mr. J. Tedrow ,

i Mr. H. L. Thomas

Mr. J. W. Yelverton Mr. L. J. Callan

Regional Administrator 5

U.S. Nuclear Regulatory Commission Suite 400  !

611 Ryan Plaza Drive Arlington, TX 76011 l

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B GNRo-96/00o48 page 7 of 7 cc: (continued)

Mr. J. N. Donohew, Project Manager Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop 13H3 Washington, D.C. 20555 Mr. Warren C. Lyon Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop 8E23 Washington, D.C. 20555 Dr. Eddie F. Thompson State Health Officer j State Board of Health P.O. Box 1700 l Jackson, Mississippi 39205 l I

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