ML19323G701

Forwards Main Steam Line Rupture Analyses for Yankee Rowe, in Response to IE Bulletin 80-04.Overall Conservatism of Design to Main Steam Line Ruptures Has Not Been Lessened. Second Level Review Underway

ML19323G701
Person / Time
Site:	Yankee Rowe
Issue date:	05/08/1980
From:	Moody D YANKEE ATOMIC ELECTRIC CO.
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19323G702	List: ML19323G701 ML19323G703
References
IEB-80-04, IEB-80-4, WYR-80-50, NUDOCS 8006060503
Download: ML19323G701 (2)

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Tclephone 617 366-9011 rwx 750 = 3 9 0-0 73 9 YANKEE ATOMIC ELECTRIC COMPANY g.a.1.1 WYR 80-50 2

20 Turnpike Road Westborough, Massachusetts 01581

.YAN KEE May 8, 1980 United States Nuclear Regulatory Commission Of fice of Inspection and Enforcement Region I 631 Park Ave.

King of Prussia, PA 19406 Attention:

Mr. Boyce H. Grier, Director Ref e rences :

(a) License No. DPR-3 (Docket 50-29)

(b) USNRC Letter to YAEC, dated February 8,1980

Subject:

Response to IE Bulletin No. 80-04

Dear Sir:

Reference (b) requested a review of the main steam line rupture analyses supporting plant operation to determine if the assumptions made in the analyses regarding feedwater system operation were appropriate. Reference (b) specifies four basic concerns. These four concerns are the following:

1) Containment pressure response,

2) Feedwater system pump (main, condensate, auxiliary) operability,

3) Ability to detect and isolate a damaged steam generator, and

4) The potential f or core return-to power.

Attachment A provides the results of our review atid response to each of the items specified in Reference (b).

Reference (b) requires a proposed corrective action and a schedule for completion cf the corrective action, if any are required, as a result of the review. Yankee has identified two of the concerns identified in Reference (b) as possible concerns at Yankee Rowe. At this time it is not clear that these concerns require a design change. However, Yankee will

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be implementing two design changes that address the concerns of containment overpressurization and potential for return-to power. These two design 8006060$ O '

J United States Nuclear Regulatory Commission May 8, 1980 Attention:

Mr. Boyce H. Grier Page 2 changes are auto tripping of condensate pumps on coincidence high containment pressure and low steam line pressure, and ensured boiler feed pump auto trip at power levels greater than 15 MWe. These two design daanges will be implemented during the next refueling outage and before the plant goes back on line, respectively.

It is important to note that the design change regarding containment response to a main steam line rupture may not be required to ensure acceptable consequences and the second design change is not necessary to prevent a core return to power transient. However, in both cases, Yankee feels these design changes are prudent since the changes would lessen the severity of a main steam line rupture.

Additionally, emergency procedures will be modified to provide additional assur me of feedwater termination to a damaged steam generator.

A significant amount of the content of safety analyses contained in more recent LWR license applications were not required when Yankee Rowe was lice ns ed.

However, Yankee has taken additional s teps to ensure that the concerns expressed in Reference (b), which are beyond those events considered or analyzed during the Yankee Rowe licensing process, have been addressed as part of our continuing obligation to ensure the health and safety of the public. We believe the information presented herein is both accurate and responsive to your request. A second level review of the supporting analyses is in progress and will be completed shortly.

If our continued review identifies any items that alter our conclusions, we will inform you of the findints. Additionally, the main steam line rupture analyses, both core response and containment response, are being addressed by NRC under the Systematic Evaluation Program (SEP). The SEP topics are VI-2.D, VI-3 and XV-2.

We trust you will find this response satisfactory. However, if you have any questions please contact us.

Yours truly, YANKEE ATOMIC ELECTRIC COMPANY

.O.

D. E. Mookh I

Manager of Operations JRC/wpc Attach me nt i

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