ML19350B690

Notifies That SEP Topic III-4.B, Turbine Missiles, Made Generic.Low Pressure Turbine Disc Cracking Problem to Be Handled as Part of Solution to multi-plant Generic Cracking Problem Applicable to All Plants W/Westinghouse Turbines

ML19350B690
Person / Time
Site:	Yankee Rowe
Issue date:	03/16/1981
From:	Crutchfield D Office of Nuclear Reactor Regulation
To:	Kay J YANKEE ATOMIC ELECTRIC CO.
References
TASK-03-04.B, TASK-3-4.B, TASK-RR LSO5-81-03-036, LSO5-81-3-36, NUDOCS 8103230327
Download: ML19350B690 (4)

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March 16, 1981 Docket No. 50-29 L505-81-03-036 Mr. James A. Kay Senior Engineer - Licensing Yankee Atomic Electric Company 1671 Worcester Street Framingham, Mass. 01701

SUBJECT:

YANKEE R0WE - SEP TOPIC III-4.B. TURBINE MISSILES This letter is to advise you that Topic III-4.B. Turbine Missiles has been made generic for reasons given in the enclosure.

This matter will be handled as part of the solution to the multi-plant generic cracking problem applicable to all plants with Westinghouse low pressure turbines.

Sincerely, ennis M. Crutchfield, C ef Operating Reactors Branch No. 5 Division of Licensing

Enclosure:

As stated cc w/ enclosure:

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See next page.

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Mr. J a:es A. Kay March 16, 1981 cc w/ enclosure:

Mr. James E. Tribble, President Yankee Atomic Electric Company 25 Research Drive Westborough, Massachusetts 01531 Greenfield Cocrunity College 1 College Drive Greenfield, Massachusetts 01301 Chairman Board of Selectmen Town of Rowe Rcwe, Massachesetts 01367 Energy Facilities Siting Council 14th Floor One Ashburton Place Boston, Massachusetts 02108 Director, Criteria and Standards Divisica Office of Radiation Programs (ANR-450)

U. S. Environmental Protection Agency Washington, D. C.

20460 U. S. Environmental Protection Agency Region 1 Office ATTN: EIS C0ORDINATOR JFK Federal Building Boston, Massachusetts 02203

-Resident Inspector Yankee Rowe Nuclear Power Station c/o U.S. NRC Post Office Box 28 l

Monroe Bridge, Massachusetts 01350 1

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ENCLOSURE

,SEP TOPIC III-4.B TURBINE MISSILES The purpose of this topic is to assure that, with respect to potential turbine missiles, all structures, systems and components important to safety either have adequate protection by means of structural barriers or have an acceptably low probability of damage.

Regulatory Guide 1.115 and 1.117 and Standard Review Plan (SRP) 3.5.1.3 provide guidance on this subject.

As discussed in SRP 3.5.1.3, it is acceptable to perform a probability analysis of damage to safety related structures, systems and components by potential turbine missiles and compare the calculated probability of damage to an acceptable probability.

The analysi3 includes utilizing the following individual probabilities: (1) the probability of turbine failure leading to the ejection of turbine missiles due to design speed failures and destructive overspeed failures (PI), (2) the probability of strike (P ) and (3) the probability of damage (P ).

SRP 3.5.1.3 2

3 gives acceptable values of P1 based on historical turbine data.

During November 1979, tha NRC staff became aware of low pressure turbine disc cracking in Westinghouse turbines at several operating plants.

Additional inspections at other plants possessing Westinghouse turbines also indicated cracking thus implying a generic problem applicable to plants with Westinghouse turbines. Consequently, on February 25, 1980, the NRC issued 50.54(f) letters to utilities with Westinghouse low pressure turbines requesting information related to this problem.

As a result of the turbine cracking problem, Westinghouse is in the process of revising its probability of turbine failure leading to the ejection of turbine missiles (P ) and their exit energies. They 1

expect to submit details of these analyses to the Materials Engineering Branch of the NRC staff for review in April 1981.

To more efficiently utilize NRC staff manpower and because the cracking problem is a multi-plant problem generic to all plants with Westinghouse turbines and extending beyond those plants in the Systematic Evaluation Program, we are making generic Topic III-4.B'" Turbine Missiles" for those plants possessing Westinghouse. low pressure turbines.

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The turbine inspection program developed by the Materials Engineering Branch for Westinghouse turbines provides assurance that turbine missile risks will remain acceptably low. The reasoning is discussed in the staff's letter of February 19, 1980 to the Atenic Safety and Licensing Board concerning the fiorth Anna nuclear power station.

The staff has developed inspection schedules for those plants with Westinghouse turbines operating with cracks based on the staff's crack growth model, t

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