ML20204E917

Forwards Summary of 870120 Meeting W/Bwr Owners Group in Bethesda,Md Re Sys Used in Mark I Containment Plants for Combustible Gas Control.List of Participants & Meeting Handouts Encl

ML20204E917
Person / Time
Site:	Cooper
Issue date:	03/19/1987
From:	Long W Office of Nuclear Reactor Regulation
To:	Trevors G NEBRASKA PUBLIC POWER DISTRICT
References
NUDOCS 8703260102
Download: ML20204E917 (8)

Text

. - .

f 4

March 19_, 1987 Docket No. 50-298 Mr. George A. Trevors, Division Manager -

Nuclear Support

Nuclear Power Group Nebraska Poblic Power District P.O. Box 499 Columbus, Nebraska 68601

SUBJECT:

JANUARY 20, 1987, MINUTES OF MEETING WITH BWR OWNERS GROUP TO DISCUSS SYSTEMS FOR COMBUSTIBLE GAS CONTROL DURING A LOSS OF COOLANT ACCIDENT Re: Cooper Nuclear Station

Dear Mr. Trevors,

On Tuesday, January 20, 1987, a meeting was held at NRC, Bethesda, Maryland, with representatives from GPU Nuclear (GPUN), Commonwealth Edison, Northeast Utilities and Nebraska Pub'ic Power District (NPPD) on the systems used in their Mark I containment (Mark I) plants for combustible gas control. These licensees have the following boiling water reactor (BWR) plants: Dresden 2/3 and Quad Cities 1/2 (Commonwealth Edison), Cooper (NPPD), Millstone 1 (Northeast Utilities) and Oyster Creek (GPUN).

Attachment 1 is the meeting summary which describes the significant items discussed and the actions, if any, taken or proposed. Attachment 2 is the list of the participants that attended the meeting. Attachment 3 contains the handout from the licensees for their presentation. The handout is arranged.in the order of the licensees' presentation.

The staff requested that each licensee submit its plant-specific position on its compliance to 10 CFR 50.44(g). This submittal should include the assumptions made by the licensees to justify their position on 10 CFR 50.44. This submittal should also include the information discussed during the meeting on the reliability

~

and capability of the containment inerting system and the window of accident sequences for which this system would be effective in controlling combustible gases. The staff stated that a passive system, such as the inerted containment, is not sufficient to meet 10 CFR 50.44(g) and that an active system, such as the containment inerting system, is required. The staff further stated that the reliability and capability of the existing containmcrt inerting systems may be sufficient to meet, as a minimum, the intent of the GDC 41, 42 and 43 of 10 CFR 50.44(g). This is because the RG 1.7 hydrogen and oxygen source term indicative of large metal-water reactions may show that the licensee has sufficient time to respond with the existing system to the increasing combustible gas concentrations in the containment from radiolysis of water before the acceptable limits are exceeded.

i 8703260102 870319 PDR ADOCK 05000298 P PDR

=, i a ,

~  ;.

.e -

t The time available until unacceptable concentrations are reached would allow J the licensee to overcome the lack of redundancy in components and in providing power to the system. This time period for the plant and the actions taken by

[ 7,=the licensee should be discussed in the licensee's justification of-the reliability of its containment inerting system.

OrlatulS40'd'i William 0. Long, Project Manager BWR Project Directorate #2 Division of BWR Licensing Attachments:

1. Sumary

2. List of Attendees

3. Licensees' Handout for Meeting cc w/ attachments:

See next page DISTRIBUTION I25ii d etlif NRC PDR Local PDR PD#2 Reading File DMuller WLong OGC-Bethesda EJordan BGrimes ACRS(10)

TRotella JZwolinski RBernero Glainas JDonohew JStang JShea PHearn JKudrick JHulman

. OFFICIAL RECORD COPY L:B W DBL:BWD2 DE SN #1s WLong t# er D) 9//9/87 j/jp/87 87 f

i

- __ _____________________..______J

Mr. George A. Trevors Mehraska Public Power District Cooper Nuclear Station Cc:

Mr. G. D. Watson, General Counsel Nebraska Public Power District Post Office Box 4999 Columbus, Nebraska 68601 Cooper Nuclear Station ATTN: Pr. G. Horn, Division Manager of Nuclear Operations Post Office Box 98 Brownville, Nebraska 68321 Mr. M. Steffensmeier, Supervisor Harardous Waste Section Nebraska Department of Environmental Control Post Office Box 94877 l Lincoln, Nebraska 68509 l Mr. William Siebert, Commissioner Nemaha County Board of Commissioners Nemaha County Courthouse Auburn, Nebraska 68305 Senior Resident Inspector U.S. Nuclear Regulatory Commission Post Office Box 218 Brownville, Nebraska 68321 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011 Mr. Harold Borchart, Director Division of Radiological Health Department of Health 301 Centennial Mall, South Post Office Box 95007 Lincoln, Nebraska 68509 i

.. ATTACHMENT 1 4

SUMMAPY OF JANUARY 20, 1987 MEETING WITH BWR OWNERS GROUP INVOLVING COMBUSTIBLE GAS CONTROL The licensees began their presentation with a history of the licer. sing activity concerning combustible gas control systems. These are pages 1 through 5 in.the handout. The regulations governing the standards for these systems are contained in 10 CFR 50.44. These regulations are discussed below:

Paragraph 50.44(c)(3)(1) requires each Mark I containrrent be normally inerted during power operation. All these plants meet tnis reovirement and the containments are inerted for power operation except for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> during startup to inert and shutdown to deinert.

Paragraph 50.44(c)(3)(ii) requires plants relying on a purge /repressurization system as the primary means of combustible gas control shall have an installed recombiner capability. The Commission determined in Generic Letter 84-09 dated May 8, 1984, that Mark I plants did not have to have this capability if the plant met the 3 technical criteria listed in the letter. The 3 criteria are given on page 3 of the handout.

Paragraph 50.44(g) requires all combustible gas control systems to meet General Design Criteria (GDC) 41, 42 and 43. This regulation applies only to those plants which have the notice of hearing on its application for the construction permit published on or before December 22, 1968. All of the plants involved in this meeting meet this condition and paragraph 50.44(g) applies to them.

The GDC are in Appendix A to 10 CFR Part 50.

The licensees stated that their plants comply with the above regulations. The containments are inerted during power operation except briefly (24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) during startup and shutdown. This is allowed by the plant Technical Specifi-cations (TS). It is the licensees' position that the primary means of combustible gas control is the inerted containment and not a purge /repressurization system, and one licensees have addressed in submittals to NRC how the 3 criteria in GL 84-09 are met at their plants. Therefore, the licensees stated that a hydrogen recombiner capability is not required, the combustible gas control system of Paragraph 50.44(g) is the inerted containment and it meets GDC 41 to

43. The basis for the licensees' conclusion that the inerted containment is sufficient to assure peak combustible gas concentrations are below acceptable limits without the need to take any action to purge, repressurize or provide e recombiner is General Electric Report NED0-22155, " Generation and Mitigation of Combustible Gas Mixtures in Inerted BWR Mark I Containments" dated 1982.

The licensees stated that the NRC has identified some concerns in its review of NED0-22155. This report was part of the NRC staff's basis for and was indirectly addressed in GL 84-09. The licensees explained that these concerns, listed in page 5 of the handout were addressed in a submittal dated November 5, 1982, from Millstone 1 which had additional information not given in NED0-22155.

This additional information was not discussed in this meeting.

7 6

The licenseet discussed the typical system used to inert or de-inert the containmer.t at their plants. The figure on page 6 is a typical containcert inerting system for these plants. This system is operated during startup to inert the containment with nitrogen. This is through the nitrogen (N2) makeup line and purging the containment through the ventilation exhaust line.

The containment atmosphere is reduced to less than 4% oxycen for power operation. During shutdown, the containnent atmosphere is increased to atmospheric conditions using the nitrogen purge line and the ventilation exhaust line. The containment is inerted during startup and de-inerted during shutdown to alluw personnel to be in containment with a breathable atmosphere and conduct needed surveillance of the reactor coolant system while the reactor is at high temperature and pressure. This period of time is restricted by TS to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> for startup and 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> for shutdown.

The licensees explained that this containment inerting system is a backup to the inerted containment for controlling combustible gases during a LOCA. This system could be used to purge the containment of such gases or to pressurize the containment to dilute the concentration of the -gases. The licensees presented page 8 of the handout which compares the inerted containment and the containment _inerting system to GDC 41, 42 and 43 of 10 CFR 50.44(g). The licensees concluded that the containment inerting system almost meets these GDC except for loss of power to the system and lack of some redundancy in components.

The " features" referred to on page 8 are the plant-specific features in the systems at each plant. These features might be different for each plant. The licensees explained that the containment inerting system is used continually during power operation. Besides startup and shutdown, these systems are used during power operation to maintain pressure in the atmosphere at about 1 psi gauge and to reduce containment pressure for the monthly tests of the torus-to-drywell vacuum breakers. The licensees stated that no additional surveillance should be needed for these systems to meet GDC 42 and 43.

The licensees further explained that the difference between the existing inerting system and a system meeting GDC 41 is the lack of redundancy in components and in supMying power. The existing incrting systems do not meet GDC 41 on single failure.

The staff stated that it did not consider the containment inerting system as a backup to the incrted containment. This system could not itself deal with the metal water reaction which generates large quantities of hydrogen at a high rate at the beginning of an accident. The production rate of hydrogen is too high for the current inerting system alone to keep combustible gases within acceptable limits. The inerted coatainment is the safety system to keep the hydrogen from the metal water reaction within acceptable limits. For the duration of an accident, an active combustible gas control system is required to maintain the hydrogen and oxygen cuncentrations from the radiolysis of water within acceptable limits.

The licensees continued their presentation with a discussion on when the inerting systems would be effective during accidents. This is pages 9 to 15 of the handout. The licensees stated that these systems are effective only for accident sequences where the metal water reaction is between 1% and 10% of the fuel cladding and char.nels in the core. The licensees explained that this is based on the report HEDO-22155 which shows that for above 10% the amount of hydrogen in containment will suppress the generation of oxygen and hydrogen generated from the radiolysis of water. This would be through the recombination of oxygen and hydrogen.

The licensees' conclusions of this discussion are on pages 14 and 15 of the handout. Page 14 is the accident event tree for the containmen+. inerting system for Millstone Unit 1. The system is effective for only 1.77. of all core damage accident sequences. For this 1.7%, the system is effective 99.5% of the time. The existing system failure rate with core damage is only 2.6 x 10-8 events / year.

The licensees stated that requiring the existing containment inerting system to meet 10 CFR 50.44(g) could at best only raise the effectiveness of the system by 0.5% from 99.5% to 100.0%.

The licensees concluded their presentation with the following: (1) the Mark I plants meet 10 CFR 50.44(g) with the inerted containment and (2) the existing non-safety containment inerting systems are sufficient for addressing those accident sequences where the metal water reaction is between 1% and 10%. This is page 16 of the handout.

The staff stated that the window of accident sequences where the containment inerting system is effective may be too small. It further stated that the arguments presented had been reviewed when the staff reviewed NED0-22155 prior to issuing GL 84-09.' The staff did not agree with the report conclusion that above 10% metal water reaction the hydrogen generated suppressed the further generation of oxygen and hydrogen from the radiolysis of water. It stated that the uncertainties listed on page 5 of the handout were the basis for the staff's position that Regulatory Guide (RG) 1.7 should be used to calculate the generstion of combustible gases during an LOCA.

In response to the staff, the licensees stated that if RG 1.7 were used, the number of accident sequences in which the inerting system could be used does increase. The licensee further stated that the existing system should be sufficiently reliable to handle these additional sequences; however, if this increase in accident sequences is high enough, it would be the justification for having the system meet GDC 41, 42 and 43.

The staff requested that each licensee submit its plant-specific position on its compliance to 10 CFR 50.44(g). This submittal should include the assumptions made by the licensees to justify their position on 10 CFR 50.44.

This submittal should also include the information discussed during the meeting on the reliability and capability of the containment inerting system and the window of accident sequences for which this system would be effective in controlling combustible gases. The staff stated that a passive system, such as the inerted containment, is not sufficient to meet 10 CFR 50.44(g) and

that en active system, sucr as the containrent inertirg system, is requirec.

The staff further statea that the reliability and capebility of the existir,9 containrent inerting systens may be sufficient to reet, as a minimum, the

' intent of the GDC 41, 42 anc 43 of 1G CFF 50.44(g). This is because the RC !.'

! hydrogen and oxygen source terms indicative of large metal-water reactiers ra;.

I short that the licensee has sufficient tir:e to respor,d with the existing syster to the increasing combustible gasses concer,trations ir, the containnent fror rediolysis cf water before the accepte51e limits are exceeced. The tire available until unacceptable concentrations are reached would allow the licerset j to overcone the lack of reduncar.cy in components anc ir. providinc power to the j syster. This tir.;e period for the plant and the actions taken by the licensee

should be discussed in the licensee's justificatior cf the reliability of its i contdinment irierting system.

t

}

}

(

i i

I i

l l

A

- _ _ _ _ . . _ . _ _ . . _ _ - . _ . _ _ _ _ _ _ _ _ _ _ _ _ . . _ _ = - - - - -

l.TTACHMD,T ?

MINI r.t:f ERS MEETINC TO DISCL'S5 MSTEM F0F COMEbilICLE GAS CONTROL

.1ANUA0v 20, 1987 i

. NAME CRGANIZATION 4 .. Rotelle NRC/NRR/ DBL / eld 1 l I. Johnson CECO-huclear Licensing J. Zwolinski NRC/NRR/ DBL /Bt;Di D. Fa r ra r CECO-Nuclear Licnesinc E. Rowley CECO-Engineering R. Senero NRC/NRR/ DBL G. Lainas hPC/NRR/DSL J. Donohew NRC/NRR/DCL/BWD1 T. Pickens NSP-Licensing L. Nexbitt GE San Jose Engineering I J. Lachenmayer GPUN I G. Snith NPPD Licensing C. Griraes NRC/NRR/DPLB/ISAPC P. Blasioli NU-Licensing J. Stang NPC/NRR/ DBL /BWD1

{

3 J. Shea NRC/NPP/DPLB C. Wright GE-Licensing l

i P. Hearn NRC/NRR/ DBL /PSB i'

J. Kudrick NRC/NRR/ DBL /PSB J. Fulmon NRC/NRP/ DBL /PSC L. Giffora GE-Licensing M. Laggort GPUN Conmenwealth Edison (CECO)

General Electric (GE)

GPU Nuclear (GPUN)

Nebraska Public Power District (NPPD)

Northern States Power (NSP)

Northeast Utilities (NU)

>