ML20195J019

Discusses Util 880617 Request for Temporary Waiver of Tech Spec 3/4.6.5 Re Ice Condenser Bed Inoperability Time to Avoid Unnecessary Entrance Into Mode 5.Safety Evaluation Concluded No Unreviewed Safety Questions Exist

ML20195J019
Person / Time
Site:	Catawba
Issue date:	06/20/1988
From:	Tucker H DUKE POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
NUDOCS 8806290036
Download: ML20195J019 (2)

Text

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ENCLOSURE I DtncE POWER COMPANY P.O. box 33180 cxAxLoTTm. x.c. sages MAL B. 7 ticker vet.apisown (fo4) om 4 set v.es reasement June 20, 1988 U. S. Nuclear Regulatory Comm!ssion Attention: Document Control Desk Washington, D. C. 20555

Subject:

Catawba Nuclear Station, Unit 1 Docket No. 50-413 Discretionary Inforcement Relief from Technical Specification 3.6.5.1 Gentlemen:

This letter constitutes written follow-up of a request for temporary waiver of Technical Specification 3/4.6.5 requirements via a telecon between Duke Power Company personnel and members of the NRC/ Region II Staff on June 17, 1988.

This temporary emergency relief from compliance with Technical Specification Limiting Conditions f or Operation (LCO) Action Statement was requested to avoid unnecessarily forcing Catawba Unit i to Mode 5 (Cold Shutdown).

The requested emergency relief allowed for a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> extension of the Technical Specification 3.6.5.1 Action Statement ice condenser bed inoperability time.

The proposed relief request was the result of frost accumulation in flow passages between ice baskets in the ice condenser in sixcess of the r.aximum amount allowed by Surveillance Requirement 4.6.5.1.b.3.

The Action Statement for Technical Specification 3.6.5.1 ended at 1430 hours0.0166 days <br />0.397 hours <br />0.00236 weeks <br />5.44115e-4 months <br /> on June 17, 1988.

Unit 1 was operating in Mode 1 at 100% power when the Action Statement ended.

Continued inoperability of the ice condenser bed without Discretionary Enforcement would have required I

the Unit to enter Mode 3 Hot Standby, by 2030 hours0.0235 days <br />0.564 hours <br />0.00336 weeks <br />7.72415e-4 months <br /> on June 17, 1988 and to enter Mode 5, Cold shutdown, within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

Duke Power personnel initiated appropriate action to remove excess frost accumulation upon discovery of the situation. The ice bed was declared operable at 1710 hours0.0198 days <br />0.475 hours <br />0.00283 weeks <br />6.50655e-4 months <br /> on June 17, 1988.

j It should be noted that the discovered frost accumulation in flow passages between ice baskets in the ice condenser would have resulted in less than 15%

flow blockage of steam through the ice condenser in the event of a hypothetical i

LOCA. Duke Power personnel have evaluated the Westinghouse flow blockage analysis and determined that all affacted subcompartment walls and steel shell can withstand the differential pressures associated with a hypothetical LOCA with up to 15% blockage in the ice condenser bays.

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,'U, 5. Nuciaar Regulatory Comission Jui.ea$. 1988 Page Two A Safety Evaluation was completed in accordance with 10 CFR 50.59.

This Safety Evaluation concluded that no unreviewed safety question exists and that granting f

I this request has no affect on the health and safety of the public.

Very truly yours, 0

.br Hal B.

cher Ij JGT/33/sbn Attachment xc Dr. J. Nelson Grace, Regional Administrator U. S. Nuclear Regulatory Comission Region II 101 Marietta Street. NW, Suits 2900 Atlanta, Georgia 30323 Mr. P. K. Van Doorn NRC Resident Inspector Catawba Nuclear Station i

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P.1 JUN 17 '80 13:01 E-FAST 425t, Westlnshou$a Power Systems E/h'io,eceistneni Ehetric Corporation P

Mr. N. A. Rutherford Jr.

OCP 84-557 Ouke Power company June 17, 1984 PO Box 33149 Charlotte NC 18t42 Attention:

P.G. Leroy Duke Power Company Catawba Unit 1 611ewable fee condanner Flow Blockana Arat Dear Mr. Rutherfords Westinghouse was informally requested via telecon on 6/17/86 to assess the allowable percentage of ice condensor flow blockage at CattWbt Unit 1.

The attached includes the results of our svaluttion.

Sincerely, WE5TINtH00$

ICTR!C CORPORAT!0N i

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3. 3. Kilborn 1ectManager Duke PcWer Pro, cci P. 4. Leroy R. W. Fritz M. J. Lee R. C. Futrell K. 5. Canady H. R. Gibson

8. E. Lawson T. R. Puryone

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',.JUN 17 800 13:01 WCC-Cost 4054 8tJPp0RT FOR 15% ICE CCNDENSER FLOW SI4CKAGE Introduction And Backcreuhd Frost or ice acounulation in flow passages between ice baskets may momentarily restrict the flow of steam through the ice This condenser in the event of a hypothetical LOCA.

restriction will only be momentary, as the high energy steam Hence, the only design will quiox1y esit any accumulation.

basis nocident that may be appreciably affected by such accumulation is the Containment 8ubcompartment Analysis of the loop coopartments presented in 8setion 6.2.1.2 of the Catawba This analysla is performed to ensure the subcompartoont F8AR.

walls and the steel shell of the containment structure can maintain their structural integrity during the short pressure pulse (generally less than 3 seconds) which accompanies the A

rupture of a high energy line within the icver compartment. f in a momentary pressure build-up in the icwor compartment or lower plenum of the ice condenser bays and challenge the integrity of the operating deck, the upper or lower craneA detailed analysis wall, or the contalnment's steel shell.

has shown that up to ist flow blockage in the los condenser bays is acceptable for the Catawba Nucisar Plant.

184 Flev Bleekaan Analvmin An allowable ice condenser flow blockage level of 154 for the catawba Huolaar plant is supported by a conservative detailed subcompartnent pressuritation analysis of a similar ice A comparison of the key parameters between condenser plant.

thase plants shows that the plants are virtually identical.

The similar ice condenser plant contained more restrictive flow passages in the lower compartment than those in the the similar plants Catawba Nuolear Plant.

Consequently,t is expected that a I

results are applicable to Catawba.

detailed Catawba specific analysis would demonstrate that the allowable flow blookage level would be greater than 15%.

The detailed analysis for the similar plant was performed with The TMD code was the tJBNRC approved TMD code (Reference 1).

employed to perform the subcompartment pressurisation This calculations of Section 6.2.1.2 of the Catawba TSAR.

conservative analysis utilised experimentally determined loss coefficients for flow through the ice condenser flow paths.

The corresponding average flow area employed in the analysis was assumed to be est of the total flow area (15% blooxage This assumption) which occurs at a lattice frame elevation This passage length, and throughout the ice condenser Days.

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. AN 17 'CS 13:03 LEC-EAST 423A P.3 reduced flow area was assumed to be permanent throughout the duration of the acoident, conservatively neglecting the fact that much of the blockage would be blown out by the high As a result energy's one hrough the ice condenser passages. dimensional ice condenser the flow t of TMD code conservatively neglects the benefits that cross-flow will provide in venting the steam and air around actual blockages in the ice bed.

In addition, the TND analysis contains many other The hypothetical accident Was conservatively conservatisms, assumed to be initiated by the instantaneous double-ended The break plane was rupture of one of the main coolant pipse.

assumed to be oor.pletely displaced instantaneously, such that the effective break flow area is twice the main coolant pipe Mechanistic pipe break technology has demonstrated i

flow area.

that a double-ended guillotine break of the reactor coolant In addition, the analysis piping is hichly unlikely.

conservatively naglected the heat removal capabillty of the structural heat sinks.

Hence, this 154 blockage analysis provides a conservative basis for defining an acceptable limit of effective flow blookage in the ice condenser.

Table 1 contains the percent changes in the peak differential pressures for a 15% blockage assumption.

fatD21usiana Application of the results from Table 1 to the peak pressures reported in Tables 6.2.1-11, 6.2.1-12, and Table 6.2.1-13 of the CataVba T8AR are reported in Table 2.

Assuming that the subcompartment valls and steel shall can withstand the differential pressures reported in Table 2, then 154 blockage i

L per ice condenser bay will be acceptable.

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change In Maximum Peak Differential Pressure For 154 Flow Blockage l

t chanda Differential Pressure

+4 Maximum Peak Pressure In The IC Compartment' 1

+2 operating Deck dr Lower Crans Wall

+6 Upper crane Wall l

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