ML20009B630

Forwards Draft Evaluation of SEP Topic XV-16, Radiological Consequences of Failure of Small Lines Carrying Primary Coolant Outside Containment. Evaluation Will Be Basic Input to Integrated Safety Assessment If No Mods Are Identified

ML20009B630
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	07/10/1981
From:	Crutchfield D Office of Nuclear Reactor Regulation
To:	Counsil W CONNECTICUT YANKEE ATOMIC POWER CO.
References
TASK-15-16, TASK-RR LSO5-81-07-032, LSO5-81-7-32, NUDOCS 8107160468
Download: ML20009B630 (7)

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July 10,1981 Docket No. 50-213 fe@%g'-

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JUL 15 NI A j Mr. W. G. Ccunsil, Vice President g} u,%

Nuclear Engineering and Operations Connecticut '. nkee Atomic Power Corp.

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Q Hartford, Connecticut 06101 9

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SUBJECT:

SEP TOPIC XV-16, RADIOLOGICAL C0kSEQijENCES OF FAILUBE OF SMALL LINES CARRYING PRIMARY COOLANT OUTSIDE CONTAIN-MENT (HADDAM NECK)

Enclosed is our draft evaluation of SEP Topic XV-16 for the Haddam Neck plant. This evaluation compares your facility as described in Docket No. 50-213 with the criteria currently used for licensing new facilities.

The evaluation utilizes information contained in your June 20, 1980 submittal. Please respond within 30 days if your as-built facility differs from the licensing basis assumed in our assessment.

If no response is received within 30 days we will assume the evaluation is correct.

You will note that the ovaluation assumes that the primary coolant activity is limited to a value consistent with the Standard Technical Specification (STS) values.

It is our understanding that you intend to implement STS in the future. Since you intend to convert to STS which include provisions for limiting the primary coolant activity, no action is required until the plant integrated safety assessment. If the STS are not implemented by that time, this item will be evaluated during the integrated assessment.

This evaluation will Le a basic input to the intcgrated safety assessment for your facility unless you identify changes needed to reflect the as-built conditions at your facility. This topic assessment may be revised in the future if your facility design is changed or if NRC criteria relat-ing to this topic are n:dified before the integrated assessnent is completed.

Sincerely,

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0 PDR Dennis H. C.utchfield, Chief I

Operating Reactors Branch No. 5 Division of Licensing

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July 10,1981 Docket No. 50-213 LS05 07-032 Mr. W. G. Counsil, Vice President Nuclear Engineering and Operations Connecticut Yankee Atomic Power Corp.

Pest Office Box 270 Hartford, Connecticut 06101

SUBJECT:

SEP TOPIC XV-16, RADIOLOGICAL CONSEQUENCES OF FAILURE OF SMALL LINES CARRYING PRIMARY COOLANT OUTSIDE C0NTAIN-MENT (HADDAM NECK)

Enclosed is our draft evaluation of SEP Topic XV-16 for the Haddam Neck plant. This evaluation compares your facility as described in Docket No. 50-213 with the criteria currently used for licensing new facilities.

The evaluation utilizes information contained in your June 20, 1980 submi ttal. Please respond within 30 days if your as-built facility. differs from the licensing basis assumed in our assessment. If no response is received within 30 days we will assume the evaluation is correct.

You will note that the evaluation assumes that the primary coolant activity is limited to a value consistent with the Standard Technical Specification (STS) values. It is our understanding thet you intend to implement STS in the futu m.

Since you intend to convert to STS which include provisions l

for limiting the primary coolant activity, no action is required until the l

plant integrated safety assessment.

If the STS are not implemented by that time, this item will be evaluated during the integrated assessment.

This evaluation will be a basic input to the integrated safety assessment for your facility unless you identify changes needed to reflect the as-built conditions at your facility. This topic assessment may be revised in the future if your facility design is changed or if NRC criteria relat-ing to this topic are modified before the integrated assessment is completed.

Sincerely, f)dt k. a6

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/tv Dennis M. Crutchfield, Chief

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Operating Reat. tors Braich No. 5 l

Division of Licensing

Enclosure:

As stated cc w/ enclosure:

See next page.

Mr. W. G. Counsil cc Day, Berry & Howard Counselors at Law One Constitution Plaza Hartford, Connecticut 06103 Superintendent Haddam Neck Plant RFD #1 Post Office Box 127E East Hampton, Connecticut 06424 Mr. James R. Himmelwright Northeast Utilities Service Company P. O. Box 270 Hartford, Connecticut 06101 Russell Library 119 Broad Street Middletown, Connecticut 06457 Board of Selectmen Town Hall Haddam, Connecticut 06103 Connecticut Energy Agency ATTN: Assistant Director Research and Policy Developmer.t Departaent of Planning and Energy Policy 20 Grand Street Hartford, Connecticut 06106 U. S. Environmental Protection Agency Region I Office ATTN: EIS C0ORDINATOR JFK Federal Building Boston, Massachusetts 02203 Resident Inspector Haddam Neck Nuclear Power Station c/o U. S. NRC East Haddam Post Office East Haddam, Connecticut 06423

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D HADDAM NECK PLANT (CONNECTICUT YANKEE)

SYSTEMATIC EVALUATION PROGRAM XV-16 RADIOLOGICAL CONSEQUENCES OF FAILURE OF SMALL LINES CARRYING PRIMARY C0OLANT OUTSIDE CONTAINMENT I.

INTRODUCTION

-Rupture of lines carrying primary coolant outside containment can allow primary coolant and the radioactivity contained therein to escape to the environment. SEP Topic XV-16 is intended to review the radiological consequences of such failures. The review of this to ic encompassed those lines which carry primary coolant outside containment during power operation. The scope included those lines that are not normally expected to be open to the primary system but can be opened during power operation (i.e., reactor coolant sample lines, instrument lines, etc.)

II.

REVIEW CRITERION All small lines carrying primary coolant outside containment were reviewed to ensure that; any release of radioactivity from their postulated failure was a small fraction of the 10 CFR Part 100 exposure guidelines. Small fraction is defined in the SRP to be no more than 10% of the 10 CFR Part 100 exposure guidelines.

III. RELATED SAFETY. TOPICS AND INTERFACES Lines which were excluded from this review included lines for which failure outside containment is not postulated, or lines for which interlocks prevent opening during power operation (e.g. the PWR residual heat removal lines).

The review also did not consider the release of radioisotopes from large pipes carrying primary system fluid prior to automatic isolation of such lines.

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• IV. REVIEW GUIDELINES TherehiewwasconductedinaccordancewithSRP15.6.2. The licensee was requested to provide plant specific information such as the identification of lines covered by this Topic, the size of these lines, break locations and flow, etc. The licensee responded to this request in a letter dated June 20, 1980.

V.

EVALUATION We. reviewed Connecticut Yankee's (licensee's) June 20, 1980, submittalreceihed, in response to the request for information regarding small lines carrying primary coolant outside the containment. The licensee indicated that the line fortheworst-casebreak(thatdidnothaveisolationhalhesinsideand outside coiltainment) of this type was the Loop #1 hot leg sample line, with an ID of 0.245 inch. An independent ehaluation of the maximum possible flow fromabreakinthisline,outsidecontainment,butupstreamofanyvalhes outside containment, was performed. Thisflowrate,basedonheryconserhative assumptions, is 100 pounds per minute.

(Neither this flow rate or the resulting dose is limiting for this analysis - the letdown line break, described later, is). The duration of the leak is dependent on the time required to manually isolate the instrument lines. The licensee has indicated that this~could be accomplished in 30 minutes, based on the following sign.al indications: area radiationmonitorsandholumecontroltanklevelrateofchangeindicators.

The total amount leaked, therefore,is 3000 pounds.

An iodine spike is assumed to occur at the time of the pipe break, resulting in a gradual increase in coolant iodine concentration. This iodine spike

9 is modelled by a 500-fold increase in the iodine release rate from the' fuel, as specified in SRP.15.6.2. The amount of iodine that could be released to the coolant is unacceptably high, unless the coolant iodine concentration is limited by technical specifications. The plant's current technical specifications do not contain a limit for iodine concentration in the reactor coolant.

Assuming that the Standard Technical Specifications for Westinghouse plants for coulant activity are implemented, the iodine release rate is based on an equilibrium concentration of 1.0 pCi/g Dose Equivalent I-131. The amount of iodine released to the environment is conservatively assumed to be all that is flashed after release out the break, based on the hot leg temperature.

Based on the above assumptions and parameter the 0-2 hour EAB thyroid dose is calculated to be 3.4 rem, and the 0-30 day LPZ dose is about 0.1 rem thyroid. The whole-body EAB and LPZ doses are small fractions of the thyroid doses. These doses are less than 10% of the dose guidelines in 10CFR100, and therefore comp'y with the SRP 15.6.2 dose criterion.

l A review of other lines carrying primary coolant and penetrating the containment was performed to determine the need for any.special technical specification limits for the isolation valves in these lines. The letdown line of the i

l Chemical and Volume Control System was identified to be the largest such l

line. This is a three inch line with inboard and outboard isolation valves, an'd three pressure reduction orifices (letdown orifices) in parallel upstream of the outboard isolation valve. The containment isolation. valves closure signals have been upgraded as a result of TMI Lessons Learned (Diverse Isolation Signals), so that either low pressurizer pressure, low pressurizer 1

level, or high containment pressure signals will cause the valves to close..

Based on these isolation signals,.it is assumed that a leak from a ruptured letdown line will be isolated within 30 minutes.

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The break is assumed to occur downstream of the outboard isolation valve, and the flow rate is limited by the letdown orifices to about 5% higher than the maximum flow rate during normal operation, which is 170 gpm. Thus, it is predicted that 5400 gallons (31,400 lbs) of coolant will be released before the leak is isolated. An iodine spike is assumed to occur as described above.

The flashing fraction is based on the cold leg temperature; no credit is taken for the regenerative heat exchanger.

The calculated 0-2 hour EAB dose resulting from the letdown line break is 29.8 rem thyroid, and the 0-30 day LPZ dose is 0.5 rem thyroid. The whole-body doses are small fractions of the thyroid doses. These doses are also within 10% of the dose guidelines of 10CFR100.

They therefore comply with the SRP 15.6.2 dose criterion, provided that Standard Technical Specifications on reactor coolant activity are implemented.

VI. CONCLUSIONS It is concluded that the radiological consequences of small line failures outside containment are a small fraction of,the 10 CFR 100 guidelines, provided thattheStandardTechnicalSpecificationsforcoolantactihityareimplemented in order to limit reactor water iodine concentrations.

Since the licensee is converting to STS which include provisions for limiting the primary coolant activity no action is required until the plant integrated safety assessment.

If the STS are not implemented by that time, this item will be evaluated du,ing the integrated assessment.

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