ML20198A576

Final NSHC Determination & Noticing Action Re Util Application to Amend License DPR-61 to Permit Cycle 14 Operation W/O Removing Tube 37-73.Amend Involves NSHC

ML20198A576
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	05/14/1986
From:	Miraglia F Office of Nuclear Reactor Regulation
To:
Shared Package
ML20198A523	List: ML20198A520 ML20198A541 ML20198A553 ML20198A576
References
NUDOCS 8605210134
Download: ML20198A576 (4)

Text

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FINAL NO SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION Docket No. 50-213 Facility Haddam Neck Plant Licensee: Connecticut Yankee Atomic Date of application 5/9/86 Power Company

1. Surinary of State telephone consultation:

See Section 3.2 of attached.

2. Sumary of any public coments received by telephone:

. None solicited.

3 Attach any written State or public coments regarding NSHC.

4 Final determination (X ) The amendment request involves no significant hazards consideration.

( ) The amendment request involves a significant hazards consideration.

5 Basis for determination and response to comments received. .(Attach additional sheets, if necessary).

See Section 3.1 of attached. ,

6. Concurrences: Date

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7. Approved: '

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3.0 EMERGENCY CIRCUMSTANCES On May 6, 1986, during preparation of the Haddam Neck Steam Generator Tube Inservice Final Report, the licensee discovered that tube 37-73 of the No. 2 steam generator should have been plugged during the recently completed refueling outage. As discussed earlier, a transcription error during the evaluation of the eddy-current test data for this tube resulted in the tube at row 37, column 33 (tube 37-33) being plugged by mistake.

A temporary waiver of compliance was issued by NRC letter dated May 8, 1986. If NRC authorization is not received for this proposed license amendment by May 14, 1986, then the temporary waiver of compliance will expire. CYAPC0 will isolate Loop 2 of the reactor coolant system to maintain technical specification compliance for an inoperable steam generator. The net effect of this action is to derate the plant to 65% power in three-loop operation. Long-term operation with three loops will adversely affect cycle length and very likely result in a forced shutdown to repair tube 37-73 in the No. 2 steam generator.

The staff has determined that the above circumstances constitute an emergency situation since, if no action were taken, plant operation would be derated and limited to only 65% of rated power.

3.1 No Significant Hazards Consideration Determination In accordance with 10 CFR 50.92, the Commission may make a final determination that a license amendment involves no significant hazards considerations if operation of the facility in accordance with the amendment would not:

(1) Involve a significant increase in the probability or consequences of an accident previously evaluated; or (2) Create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) Involve a significant reduction in a margin of safety.

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The information in this section provides the staff's evaluation of this e

license amendment against these criteria:

A. Involve a significant increase in the probability or consequences of an accident previously evaluated.

The accident analysis potentially affected by this proposed change is the steam generator tube rupture. The progression rate of pit defects is bounded by 18% and structural integrity is ensured if the most limiting type defects do not exceed 89% through-wall during the cycle. Since the 55% tube defect (olus a' 10% allowance for

, measurement uncertainty) is not expected to exceed 83% through-wall by the next refueling outage and pit-type defects are not expected to result in structural failure until well beyond 89% through-wall, the probability or consequence of an accident previously evaluated is not increased by the proposed change.

B. Create the possibility of a new or different kind of accident from any accident previously evaluated.

Since the proposed change to the technical specification does not affect plant operating conditions, does not affect the way in which any equipment is operated, and does not create any new failure modes, no accidents would be created of a new or different kind from any previously analyzed.

C. Involve a significant reduction in a margin of safety.

Steam generator tubes form a part of the RCS pressure boundary and are manufactured with a wall thickness much greater than the minimum wall thickness necessary to withstand the stresses due to normal operation and design basis accidents. The 50% technical specification plugging limit is chosen to ensure that, assuming a conservative progression rate, defects do not degrade to the minimum thickness i before the next tube inspection. Using the guidance of Regulatory Guide 1.121, CYAPC0 calculated the allowable through-wall pit defect to be 89% through-wall degradation.

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' Based on burst testing and structural analysis, a single large pit up to 92% through-wall has a greater margin to burst than 50%

through-wall uniformily thinned tubes.

In addition, the progression rate of defects in the Haddam Neck steam generator tubes has been shown to be conservatively bounded by 18% per cycle. As a result, the 55% through-wall defect (plus a 10%

allowance for measurement uncertainty) is not expected to increase beyond a maximum of 83% through-wall before the next refueling outage.

Because of the conservative progression rate, and the structural integrity of the tube material, the margin of safety that is the basis of this technical specification will not be significantly reduced during one cycle of operation.

3.2 State Consultation Mr. K. McCarthy, Director, Radiation Control Unit, Department of Environmental Protection, State of Connecticut, was contacted concerning the waiver of compliance issued on May 8,1986. The issue of plant operation with an unplugged defective steam generator tube was discussed at that time. Mr. McCarthy expressed no concern about the waiver of compliance from the standpoint of plant safety at that time. On May 14, 1986, an attempt was made to notify Mr. McCarthy of our intent to issue an emergency license amendment following the licensee's formal application.

However, he was unavailable due to official state business.

.