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Docket No.: 50-359

MEMORANDUM FOR: The Atomic Safety and Licensing Board for the McGuireNuclear Station, Unit 1

FROM: Robert L. Tedesco, Assistant Director for Licensing, DL

SUBJECT: BOARD NOTIFICATION - HYDROGEN CONTROL MEASURES FOR SE000YAH(BN 81-02)

We are forwarding the following documents for your information:

1. Memorandum, T. E. Murley to D. Eisenhut, February 10, 1981,with rough draft - Sandia Report " Analysis of HydrogenMitigation for Degraded Core Accident in the SequoyahNuclear Power Plant (Dec.1,1980),

2. Memorandum, E. J. Hanrahan to the Comission, Jan. 22, 1981,with a report entitled " Evaluation of the Glow Plug IgniterConcept for use in the Sequoyah Nuclear Plant."

Both documents present singular views regarding :the use of specific hydrogencontrol maasures for the Sequoyah Nuclear Plant which utilizes a similar icecondenser containment design as in the McGuire Nuclear Station. The staff inits current review and evaluation of the Interim Distribution Ignition Systemwill consider the views presented in these documents. We will continue to keepyou infonred on this matter.

E'S%cu~--

Robert L. Tedesco, Assistant Directerfor Licensing

Division of Licensing

! Enclosures:As stated

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OISTRIBUTION FOR BOARD NOTIFICATION DATED II MI

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MEMORANDUM FOR:f-YTisenhut, DirectorDivision of Licensing ._

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Office of t'uclear Reactor Regulation

FROM: Thomas E. Murley, DirectorDivision of Safety TechnologyOffice of Nuclear Reactor Regulation

SUBJECT: SUCMITTAL OF ROUGH DRAFT-SANDIA REPORT"At;ALYSIS OF

HYDROGEN MITIGATION FOR DEGRADED CORE ACCIDENTS IrlTHE SEQUOYAH NUCLEAR POWER PLANT (DECEMBER 1, 1980)FOR ASLB NOTIFICATION CONSIDERATION

.

Discussion

The interim distributed ignition system (IDIS) proposed by TVA and foundacceptable by the staff for operation is the interim solution to theissue of hydrogen control for degraded core accidents. TVA in the designand installation of the IDIS has located 4 glow plug igniters in theupper plenum of the ice condenser sectton of the containment.

Sandia National Laboratory in the rough draf t report entitled, " Analysis ofHydrogen Mitigatiun for Degraded Core Accidents in the Sequoyah NuclearPower Plant," December 1,1980, has recommended that the igniters locatedin the upper plenum be removed. Their basis for the recommendation is thatthere may be accident scenarios where the lower' compartment atmosphereis steam inerted or oxygen deficient. Thus, the flow through the ice bedmay exit with highly enriched hydrogen concentrations, concentrations highenough to be detonable (Sandia considers 18% as the lower limit ofdetonability). Sandia is concerned about the effects of detonations inthe upper plenum region.

The staff previously considered this issue of igniter location and concludedthat 1) typical small break analysis has not shown the lower compartment tobe steam inerted or oxygen deficient; 2) TVA has considered the effects ofdetonations in the upper plenum and concluded that the effects are minimaland would not result in breach of containment; and 3) locating ignitersin the upper plenum is beneficial for reducing the hydrogen accumulationin the upper compartment. -

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D. Eisenhut -2-

However, as a result of my review of the draft Sandia report, I have recozmendedof ice condenser plants be evaluated in more detail in the coming raonths.to DSI (See enclosure) that the staff position on the igniters in the upper plenumSince this rough draft document recommends an action suggesting the staff positionon the upper plenum igniters may be unconservative, we recommend it be consideredfor submittal to any ASL Boards presently hearing operating license proceedingsor those hearing operating license amendments considering Hydrogen Control andMitigation.

This is in conformance with NRR Office Letter 19, Revision 1-Procedures for Notification to Licensing Boards of Relevant and Material NewInformation.

TVThomas 2. Murley, rectorDivision of Safety TechnologyOffice of Nuclear Reactor Regulation

Enclosure:Memorandum T. Murley .

to D. Ross dtd Feb. 9,19e

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1 l Docket Nos. 50,327/325ti

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MEMORANDUM FOR: Denwood F. Ross, Jr., Director*

Division of Systems Integrationa

tFROM: Thomas E. Murley, Director-

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Division of Safety Technology

SUBJECT:LCCATION OF IGNITERS IN ICE CONDENSER PLANTS

I believe that further analysis is needed to deal with Sandia's concerns on .

i the location of igniters in ice condenser plants. Specifically, tney state inNUREG/CR-1762,, Rough Draf t dated December 1,1980, the following:

''Under certain accident conditions, the lower compartmentcould be inerted either by high' concentrations of steam,;

j or by-low concentrations of oxygen. If this should occur,the interim deliberate ignition system (IDIS) as presently,

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planned for Sequoyah has a serious shortcoming. The inertedgas mixture e1tering the bottom of the ice condensers will..

I emerge as an extremely rich mixture at the top. Concentrationsi

could approaca or exceed the detonability limits in a toroidalI

region around the periphery at the top of the ice condensers.Four igniters are presently planned for this region. ge,strongly recommend that those igniters be removed. Instead,

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we suggest tnat upper compartment deliverage ignition strategy!

should attempt to burn lean mixt'.::es high in the upper ccmpartment."(emphasisadded)

If Sandia is correct that igniters are intended to be placed at the top ofi

the ice condensers, then I believe their recommendation should be evaluated| in more detail . In my judgment, it is unlikely that we will be able to show| that inerted conditions cannot exist in the lower compartment. Sandia states'

that steam inerting can occur with steam fractions of 30-56 percent, dependingon hydrogen concentration. Under these circumstances, we would have to con-*

sider the possibility of a detonation in the upper plenum. *

I don't believe this accident sequence is sufficiently probable that we need.

to modify ur- position regarding Sequoyah at this time. However, I believe

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Denwood F. Ross, Jr.2 FEB 9 TAl

we should evaluate the pros and cons of igniters in the ice condenser upperplenum in more detail over the coming months, taking into account the resultsof further testing and analysis we are planning. |

Please keep me informed of your progress ortthis issue.,

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Thomas E. Murit y, DirectorDivision of Safity Technology

cc: H. DentonD. Eisenhut

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