ML19339A051

Submits Further Technical Support for Util Position Re Asymmetric LOCA Loads & Appropriateness of Evaluating Issue within Scope of SEP Program

ML19339A051
Person / Time
Site:	Yankee Rowe
Issue date:	06/21/1978
From:	Moody D YANKEE ATOMIC ELECTRIC CO.
To:	Office of Nuclear Reactor Regulation
References
TASK-03-07.B, TASK-03-08.D, TASK-3-7.B, TASK-3-8.D, TASK-RR WYR-78-56, NUDOCS 8010310682
Download: ML19339A051 (2)

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7 o-330 0733 YANKEE ATOMIC ELECTRIC COMPANY ura 78-5s em, k,a 20 Turnpike Koad Westborough, Massachusetts 01581

,YAN KEE June 21, 1978 United States Fuclear Regulatory Commission uashington, D.C. 20555 Attention: Of fice of Nuclear Reactor Regulation

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References:

(a) License No. DPR-3 (Docke t No. 50-29.

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(b) NRC letter to YAEC dated June 7, 49

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(c) YAEC letter to NRC dated February 2 /19f8'/

(d) NRC letter to YAEC dated January 25, if7~8".d,>[f S,w, U t ;/; s

Dear Sir:

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Subject:

LOCA Loading on Primary System Components and Structures

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This letter will serve to respond to Reference (b) and provide further technical support for Yankee's position regarding asymmetric LOCA loads and the appropriateness of evaluating that issue within the scope of the SEP program.

The design criteria established for the Yankee Nuclear Power Station did not require that direct consideration be given to the effects of main coolant system ruptures on components and structures.

As described in Section 400 of the Final Hazards Summary Report, the effects of certain postulated a:cidents were assessed for their consequences to the health and safety of the public. These were bounding analyses and not considered credible accidents.

The defanse in depth concept was utilized, i.e., a conservatively designed system that is highly resistant to failure backed up by an analysis that showed even if the unexpected were to occur no undue risk would result.

Since the design of Yankee Nuclear Power Station was completed technical evolutions have occurred which serve to reinforce the approach utilized in the original design.

The ANSI B31.1 Power Piping Code has been revised and allowable stresses for the materials utilized in the design of Yankee have been increased, in ef fect increasing the conservatism of the Yankee design.

For later generation plants, ANSI B31.7 or ASME Section III are utilized for the design of the reactor coolant system.

Yankee has reviewed several designs where both ANSI B31.1 and AS'1E Section III were utilized 8010320g m.1 m e-(tP

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• United States Nuclear Regulatory Commission Page Two

• Attention: Office of Ntclear Reactor Regulation June 21, 1978 for piping design and in all instances the ASME Section III design approach resulted in thinner required pipe wall thicknesses.

The NDE utilized during the construction of Yankee is comparable i

to that currently required by ASME Section III.

i Since 1978 Yankee has been involved in an inservice inspection program on portions of the reactor coolant system intended to detect service related defects, thus further ensuring that potentially serious defects can be detected and repaired.

1 Also, as is the case in most designs, the actual operating and transient conditions are less severe than the design conditions. The plant has reached approximately half of its design life and experienced far fewer transients than the design assumed.

Since the transients are the cause for crack development and propagation further conservatism is gained.

1 In summary, i t is Yankee's position that the original design bases were appropriate, did not require specific analysis of LOCA related effects on structures and components and that events occurring since plant startup support even further conservatism in the plant design.

For these reasons, Yankee restates its position that the SEP is the appropriate forum for considering the need for the analyses requested by Reference (c).

In order to assist the NRC in its review of this matter, Yankee.

has initiated a program to reanalyze the reactor coolant system utilizing ASME Section III Class 1 criteria.

We will inform you of the schedule for this effort as soon as it is available.

We 'shall be glad to discuss this issue further with your staff should you desire.

r Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY D.E. Moody"-b'

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Manager of Operations JRH/wpc cc:

Mr. Victor Stello - USNRC

j MN REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

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OEC:

ORG: MOODY D E ATE: 06/21/78 NRC YANKEE ATOMIC ELEC DATE RCVD: 06/26/78 DOCTYPE: LETTER NOTARIZED: NO COPIES RECEIVED 3UBJECT:

LTR 3 ENCL 0 NESPONSE TO NRC LTR OF 06/07/78..PROVIDING FURTHER TECHNICAL SUPPORT FOR iPPLICANT"S POSITION RE ASYMMETRIC LOCA LOADS AND THE APPROPRIATENESS OF

.IVALUATING THAT ISSUE WITHIN SCOPE OF THE SEP PROGRAM.

oLANT NAME: YANKEE ROWE REVIEWER INITIAL:

XJM DISTRIBUTOR INITIAL: y

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