ML20147A686

Forwards Tech Ltr Rept Pacific Northwest Laboratory Review of Maine Yankee In-Situ Pressure Test Assessment, Rev 2 & Requests Copy Be Provided to Licensee to Inform of Staff Conclusions Re Assessment

ML20147A686
Person / Time
Site:	Maine Yankee
Issue date:	01/24/1997
From:	Sullivan E NRC (Affiliation Not Assigned)
To:	Dan Dorman NRC (Affiliation Not Assigned)
Shared Package
ML20147A693	List: ML20147A686 ML20147A710
References
CON-FIN-E-2029 NUDOCS 9701280095
Download: ML20147A686 (1)

Text

January 24,1997 MEMORANDUM TO: Daniel H. Dorman, Maine Yankee Project Manager Division of Reactor Projects - 1/11 FROM: Edmund J. Sullivan, Section Chief Materials and Chemical Engineering Branch

SUBJECT:

STAFF EVALUATION OF MAINE YANKEE ATOMIC POWER COMPANY ENGINEERING ASSESSMENT OF IN-SITU PRESSURE TESTING OF DEFECTIVE STEAM GENERATOR TUBES During the forced outage for Maine Yankee that began on July 15,1994, the licensee completed in-situ pressure testing and analytical calculations to assess the structural integrity of defective steam generator tubes. The NRC staff raised some potential concerns dunng discussions with the licensee regarding the results of these tests and the licensee's conclusions from its assessment of the testing. In an attempt to resolve these issues, the staff contracted to have Pacific Northwest National Laboratory (PNNL) review the licensee's assessment of the in-situ pressure testing. PNNL has completed its review, and the final report is included as Attachment 1.

The Maine Yankee assessment assumed, on the basis of a limited set of tube burst data, that burst pressures can be predicted by considering the average crack depth and the ultimate strength of the tube material. The PNNL report concluded that the use of ultimate strength to assess structural integrity may lead to nonconservative results in some instances. Although this may have led to an underestimation of the limiting flaw size by the licensee, the PNNL report notes that cracks with average depths measured by eddy current in excess of the actual structural limit may have sufficient strength to resist burst due to the limitations in inspection technology and the morphology of circumferential cracking. Therefore, the current operability of the Maine Yankee steam generators '

unaffected by PNNL's conclusione The Materials and Chemical Engineering Branch cequests that the NRC Project Manager provide a copy of PNNL's report to the licensee for Maine Yankee to inform them of the staff's conclusions regarding their engineering assessment. In addition, please put a copy of the report in the Public Document Room as members of the public may have an interest in the NRC assessment.

Docket No.: 50-309

Attachment:

As Stated Distribution w/att:

Central Files EMCB\RF Glainas JStrosnider 3

EMurphy 280039 To receive a copy of this document, indicate in the box: "C" = Copy without attachment / enclosure "E" - Copy with attachment / enclosure "N" = No copy OFFICE DE:EMCB lC DE:EMCB lC l NAME PJRush g?@/[, EJSullivan DATE 01/n/97 " _01/n/97 9701280095 970124 :lCIAL RECORD COPY PDR ADOCK 05000309 P PDR