ML20154H594

Summary of ACRS Subcommittee on Core Performance 860129 Meeting W/Util & NRC in Washington,Dc to Review Potential for Recriticality at TMI-2 During Defueling Operations. Viewgraphs Encl

ML20154H594
Person / Time
Site:	Three Mile Island
Issue date:	02/15/1986
From:	Advisory Committee on Reactor Safeguards
To:	Advisory Committee on Reactor Safeguards
References
ACRS-2392, NUDOCS 8603100329
Download: ML20154H594 (24)

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ACRS SUSCCMMITTEE MEETING

SUMMARY

/itIfiUTES FOR CORE PERFORMANCE JANUARY 29, 1986 l WASH!flGTON, DC l

Purpose The ACRS Subcommittee on Core Performance met on January 29, 1986 at Washington, DC. The purpose of this meeting was to review the potential for recriticality at TMI-2 during the defueling operations. The Subcom-mittee heard presentations from the Itcensee, General Public Utilities (GPU),andNRRStaffmembers. Copies of the agenda and selected slides '

from the presentation are attached. The meeting began at 8:30 a.m. and '

adjourned at 12:35 p.m. and was held entirely in open session. The principal attendees were as follows:

l Attendees, ACRS GPU NRR W. Kerr, Chairman F. Standerfer, VP B. Travers M. Carbon, Member R. Knief H. Richings l C. Mark, Member D. Williams L. Thonus '

O. Ward, Member J. Curry C. Marotta >

W. Lipinski, Consultant W. Stratton, Consultant i

D. Houston, Staff M. Westphal, Consultant R. Murray, Consultant l

l Discussion i i .

GPU began their presentation with a status report on the cleanup activ- l

, ities at TMI-2 and a video segment showing the condition of the upper  !

core, lower vessel and loading debris into canisters. This was followed i with a discussion of their program to ensure sub-criticality of the damaged core during defueling operations.  ;

C o r..a nim 3r, l 0603100329 060215 Certiflod i ne [ g ,

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Care Perfor ance Meetin9 January 29, I?ES The GPU concept for ensuring sub-criticality utilizes a high baron content in the water that covers the core. The calculational medel with various conservatisms and analyses were discussed. The results showed that a boron concentration of 4350 ppm was sufficient to maintain k,ff

<0.99. The current boron level et TMI-2 is 5050 ppm. The operating procedures for maintaining the baron level at or above 4350 ppm were discussed and were concerned with sampling plans, dilution scenario's and addition of foreign materials. The neutron instrumentation associated with the core was also described. GPU concluded that the instrumentation would not observe suberitical multiplication changes but would see criticality if it occurred. The Subcomittee members and consultant discussed the possibilities of placing additional neutron detectors in the downcomer region and concluded it was not necessary.

Due to time constraints, GPU gave only a brief description of the criticality considerations in regard to the defueling canisters. The canisters used Boral sheets or B4 C rods to assure sub-criticality and the dimensions of the canisters precluded an infirite array configura-tion.

NRR Staff presented the results of their independent assessment per-formed at Brookhaven to consider the potential for recriticality at THI-2. Their results for a bounding calculation showed a boron concen-tration of 4350 ppm was sufficient to maintain k,7f at 0.99, in general agreement with GPU. The Staff had also reviewed the dilution scenarios, the introduction of foreign materials and the defueling canisters.

Their conclusions for assuring sub-criticality were in agreement with GPU.

W. Kerr asked the Subcommittee members and consultant to develop a recommendation on this matter and advise him as to the content of a draft Committee Report. GPU was requested to provide a 50-60 minute presentation to the full ACRS on February 13, 1986, and to bring sufficient members with them to answer inquiries. No formal NRC Staff presentation was requested for the Comittee meeting.

Cere Performan:1 vesting Jar.uary 19, 173 NOTE: Additional reeting details can be obtained from a transcript of this meeting available in the NRC Public Document Room, 1717 H Street, N.W., Washington, D.C., or can be purchased from Ace-Federal Reporters, 444 North Capitol Street, Wash-ington, DC 20001,(202)347-3700.

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1/24/86 ACRS SUSCC.'St:TTEE MEETING ON CCPE PERFORMANCE JANUARY 29, 1986 WASHINGTON, DC

- Tentative Presentation Schedule -

Potential for Recriticality at THI-2 During Defueling 1

A. Subcommittee Chairman Remarks W. Kerr 10 min 8:30am B. Introduction and Overview of GPU - 15 min 8:40am Cleanup Activities and Current E. Kintner Status of Core F. Standerfer r C. Potential for In-Vessel GPU - 60 min 8:55am Criticality R. Knief et. al.

- Boron Dilution Hazards Analysis

- Introduction of Other Moderator Material

• • • Break *** 10 min 9:55am D. Staff Independent Review of NRR - 30 min 10:05am In-Vessel Criticality B. Travers H. Richings L. Thonus E. Criticality Safety During Fuel GPU - 30 min 10:35am Removal D. Williams

- Defueling Operations

- Canister Considerations <

F. Staff Review of Fuel Removal NRR - 30 min 11:05am Safety C. Marotta ,

G. Subcommittee Remarks W. Kerr 10 min 11:35am

• • • Adjourn *** 11:45am ACRS

Contact:

Dean Houston 634-3267

AORS AGDCA I Introductory Remarks F. R. Standerfer II Overview - Potential for Criticality Dr. R. A. Knief III Criticality Analyses D. Williams IV Maintenance of Subcriticality J. J. Curry V Neutron Monitoring Dr. R. A. Knief VI Sumary Assessment of TMI-2 Criticality Program Dr. W. Stratton NRC STAFF PRESENTATION AND BREAK VII Assuring Subcriticality During Canister Leading D. Williams and Fuel Transfer from Reactor Vessel to Fuel Pool A i

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AND OPEN HEAD D. b!EW OF PLANT CONFIGURATION INDICATES MAXIMM DILUTIONRATEOF15GPM E. thBCRATED WATER IS MSS DENSE THAN BORATED WATER (TO AT OF=@B

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Operability Verification Procedural Requirements 5

.; PRESENTATION TO THE ADVISORY C0&ilTTEE ON REACTOR SAFEGUARDS SU3-COMMITTEE ON CORE PERFORMANCE OVERVIEW OF THE CRITICALITY EVALUATIONS PERFORMED F DEFUELING CANISTERS s.

PRESENTED BY D. S. WILLIAMS JANUARY 29, 1986

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Canister Design Features a

Fael Filter Inockomt F. .ture Canister Canister Canister Ovar 11 Lausth 150.0 inches 150.0 inches 150.0 laches (maximan)

Ostor Diameter 14.00 laches 14.00 inches 14.00 inches (nominal)

Canister Contents Up to partial Small fines Rabble fuel assemblies (0.5 to 840 g) (140 p to pellet size (.375 in.

dia x .600 in.))

Criticality Control Boral TM sheets 34C rod B4C rods Load:d Canister Yeight 2,940 posads 2,940 posads 2,940 pounds ,

(maximas, devatored La air)

Empty Canister Yeight 1,230 posads 1,440 pounds 1,046 posads (toelmal, la sir)

Bottom Need Design Reversed dish Reversed dish Reversed dish T p Esad Design Flat plate with Plat plate with Plat plate with skirt (bolted skirt (welded skirt (welded closure) olosure) slosare)

Fittings 2.5 inch inlet 2.0 inch talet 2.5 inch outlet 2.0 inch outlet 0.38 inch draia 0.38 inch drain 0.38 inch drain 0.25 inch fill 0.25 inch fill 0.25 inch fill 8

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3 CANISTER

SUMMARY

SINGLE CANISTERS (DAMAGED OR UNDAMAGED) IN UNE0 RATE K < 0.95 i EFF CANISTER IN STORAGE RACKS WITH MINIMUM CENTER-TO-CEN

< 0.95 SPACING OF 17.3" - KEFF i

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