ML20197G279

Forwards SER for Radiological Consequences of Accidents for Extended Burnup.Calculated Dose to Thyroid for Fuel Handling Accident Indicates Plant Design Adequate.Salp Also Encl

ML20197G279
Person / Time
Site:	Surry, North Anna, 05000000
Issue date:	03/07/1984
From:	Muller D Office of Nuclear Reactor Regulation
To:	Lainas G Office of Nuclear Reactor Regulation
Shared Package
ML20197F859	List: ML20197F854 ML20197G279 ML20197H750 ML20210P567 ML20210P638
References
FOIA-86-78 TAC-53260, TAC-53261, TAC-53262, TAC-53263, NUDOCS 8403160165
Download: ML20197G279 (6)

Text

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DISTRIBUTION

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MEMORANDUM FOR: Gus Laines, Assistant Director for Operating Reactors Division of Licensing FROM:

Daniel Muller, Assistant Director for Radiation Protection Division of Systems Integration

SUBJECT:

SAFETY EVALUATION OF THE RADIOLOGICAL CONSEQUENCES OF ACCIDENTS FOR EXTENDED BURNUP IN SURRY UNITS 1 AND 2 AN NORTH ANNA UNITS 1 AND 2 TACS #53260/1/2/3 Enclosed is the Safety Evaluation Report for the radiological consequences of accidents for operation of Surry Units 1 and 2 andFor North l Anna Units 1 and 2 to 45,000 mwd /MTU batch average at discharge.  ;

this evaluation, the calculated dose to the thyroid for the fuel j handling accident has been increased by 305 for the Surry plants to The account for the increased release of I-231 into the fuel-clad gap. '.

calculated dose still shows that the design of the plants is adequate to '

mitigate the consequences of this accident. i The Accident Evaluation Branch recomends that the licensee, Virginia ,

1 Electric and Power Ctmpany, be apprised of the burnup restriction of j

this Safety Evaluation Report and of the dependence of the evaluation on the fuel management scheme and the peak linear heat generation rate, as

! described in the enclosure. '

As required by office letter 44, a SALP evaluation is also enclosed.

Orig'n21s!rned by l

Daniel R. I.*ulier. .

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Daniel Muller, Assistant Director

.' for Radiation Protection .

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Division of Systems Integration 1

Enclosures:

as stated .

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SAFETY EVALUATION REPORT OF THE RADIOLOGICAL CONSEQUENCES OF ACCIDENTS FOR EXTENDED BURNUP 4

SURRY UNITS 1 AND 2 AND NORTH ANNA UNITS 1 AN i BACKGROUND 23,1983, the Licensee for Surry Units 1 and 2 By letter dated November

and North Anna Units I and 2 Virginia Electric and Power Company ,

I (VEPCO), requested that the burnup restriction in the staff's

Evaluations be removed.VEPC0 to increase 15, 1980 burnup was toto about 45,000 m; discharge.

The first proposal, by letter dated May 1 and  ;

i permit an increase in the enrichment By letter dated limit in fue j similar increase at North Anna Units 1 and 2.

l l DecemberBoth 4, proposals 1980,were VEPC0 accepted by the staff, subject submitted Anna, a gene .

s safety evaluation.

to burnup limits of 38,000 and 33,000 mwd /MTU 4.1% for Surry and North respectively (References 1 and 2), and permitted fuel of up toTh l enrichment to be loaded. analyses by the licensee as burnup approa VEPCO has provided no further analyses to support the to apresent req but is relying upon its past submittals and an additional reference Westinghouse document, WCAP-10125, July 1982, " Extended Burnup Evaluation of Westinghouse ,

Fuel".

DISCUSSION .

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The staff has performed a preliminary review of the radiological consequences of accidents,as discussed in the Westinghouse re

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l' has concluded that the analyses presented ar

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Therefore, the staff has perfor.jped.pn evaluation of As accidents.

accidents which does provide the required measure of conservatism <

discussed more fully in Reference 1,.there are five factors that m considered, sinceTheyare(1)changesinthefuelfailurerate,(2) they affect the radiologic'al consequences of a for extended burnup.

changes in the total inventory and mix of radioisotopes in th changes in the fraction of the isotopes accu l

l pressure on decontamination factors (DF) d assumedj accidents.

rods during accidents, is reviewed as part of theThe fuel behavior an analyses l thermal-hydraulic analyses and is addressed separately.

provided in Reference.(1) are still valid for this requested ch the second and the last two factors The final (thefactor, mix ofthe radioisotopes, the l

i iodine spiking behavior, and the DF). accumulation of vol i

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GAP INVENTORY In considering those accidents where the radioisotope content of the gap is important, the staff has evaluated whether or not the traditional assumption concerning the gap fraction of volatile radionuclides (10%,

The staff's evaluation except Kr-85 which is 30%) remains valid. utilizes two "best estimate" a i

product release model in the ANS 5.4 standard (Reference The scheme is based on locating higher burnup modules in non-limiting '

locations and filling limiting locations with either fresh fuel or fuel l .

at the beginning of the second cycle.

j The increase to 45,000 in the batch average at discharge burnup

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represents an increase in the burnup of the limiting Thislocations value has at the been i

limiting time in cycle, to about .16,000 mwd /MTU. g assumed in this analysis,

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Suitable conservatism has been maintained by assuming 11.4 the plant-specific kW/ft at maximum linear heat generation rate (LHGR) at the plants:

These values are based on the F

North Anna and 13.5 kW/ft at Surry.ation maxima for peaking factors.

respective Technical Specifics  :

1 For North Anna, the results of the annalysis show that the traditional

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4 assumptions concerning gap content are not exceeded for any radionuclide.

4 For Surry, however, the analysis shows that more than 10% of the 1-131 5

is predicted to be contained in the gap, but significantly less than 10%

is predicted for all'other radiciodines.and for the noble gases (except Kr-85, which remains less than 30%). .This is important only for the fuel handling accident,~ because for fuel failures taking place during

- accidents occurring during core operations the assumption of 10% of each

' ' ' radiciodine nuclide in the gap will still provide a limiting 1 calculation. (1-131 contributes For the only about half'of the dose to the fuel handling accident, which is

' ~ thyroid in these cases.)

postulated to occur 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> after shutdown, the thyroid dose is i

dominated by the I-131 release because the other radiciodines of.

importance have decayed significantly from their levels during operation. The ANS 5.4 model,- combined with Surry's peak LHGR, burnup.

i' of the limiting module,~and axial power shape, predicts about 13% of the '

rod's iodine inventnry in the gap.

The staff evaluated the fuel handling accident in Refer'ence (4) and determined that the thyroid dose at the Exclusion Area Boundary (EAB) w.s 34 rem. Correcting this value to account for the increased release i

} of I-131 relative to the traditional assumption yleids a thyroid dose at the EAB of 44 rem, This value is less than the guideline value of 75 rem in the Standard Review Plan and shows that the design of the plant is adequate to mitioate the consequences of this accident.

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CONCLUSIONS The staff has concluded that operation of Surry Units 1 and 2 and North Anna Units 1 and 2 to 45,000 mwd /MTU batch average at discharge using 4.1 w/o enriched fuel is acceptable. Implicit in this evaluation are the assumptions that there will be no increase in the peak linear heat generation rate and that the fuel management scheme continues to provide the limiting location in fuel at the beginning of the second cycle of irradiation. .

REFERENCES (1) Memorandum from R. Wayne Houston to S.A. Varga and R.A. Clark, December 18, 1981.

23,1981.

(2) Memorandum from William E. kreger to Thomas Novak, April (3) "American National Standard Method for Calculating the Release of Fission Products from Oxide Fuel", ANSI /ANS-5.4, 1982.

(4) Safety Evaluation by the Division of Reactor Licensing, U.S. Atomic  ;

Energy Commission in the Matter of Virginia Electric and Power

- Company Surry Power Station Units 1 and 2. February,1972. .

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" ENCLOSURE 2

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SALP INPUT FROM THE ACCIDENT EVALUATION BRANCH l

.. plant: Surry Units 1 & 2 and North Anna Units 1 and 2 A. Functional Areas: Licensing Activities

1. Management involvement in Assuring Quality. ,

i No licensee management involvement occurred during our discussions with the licensee. Therefore, no conclusion can be made.

2. Approach to Resolution of Technical Issues from a Safety -

Standpoint.

The licensee provided no technical discussion of the  ;

requested change. The technical memorandum referenced by the licensee, which was prepared by Westinghouse, was not suitably conservative as appropriate for accident evaluations. An extenuating circumstance .is the proprietary nature of the matters addressed. Because no licensee '

submittal in response to staff's concerns was made, no staff conclusion can be made in this area.

3. Responsive to NRC Initiatives. ,

The licensee did not respond to the staff question on

. the submi.ttal, but relied upon their fuel supplier. ,

Rating: Category 3 i

4. Staffing (includingManagement) ,,

This section is not applicable for this staff effort. No

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staff conclusion can be made in this area'.

5. Reporting and Analysis of Riportable Events.'

- T5is section is not applicable for this staff effort.

No staff conclusion can be made in this area.

r 7, 6. Training and Qualification Effectiveness.

l This section is not applicable for this effort. ik) staff conclusion can be made in this area. .

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7. Overall Rating for Licensing Activity Functional Area:

As noted above under activity 3, the licensee We relied havealmost exclusively no infonnation by upon Westinghouse to support their proposal.

which to judge whether this reliance was due to lack of technical It competence, or due to other contractual or proprietary constraints.

is clear, however, that the licensee did not respond to staff c.oncerns -

over assessing changes in accident consequences as a result of higher burnup levels.

Overall Rating: Category 3 8 e

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