ML20054K906
| ML20054K906 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 06/25/1982 |
| From: | Tedesco R Office of Nuclear Reactor Regulation |
| To: | Jackie Cook CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| References | |
| NUDOCS 8207060270 | |
| Download: ML20054K906 (7) | |
Text
Qc L WG JUN 2 51982 Docket Hos: 50-329
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and 50-330 Mr. James W. Cook Vice President Consumers Power Company 1945 West Parnall Road Jackson, Michigan 49201
Dear fir. Cook:
Subject:
Request for Turbine Missile Generation Probability Data During the June 4,1982, ACRS neeting to review the flidland Plant operating license a;, plication, the staff made a presentation on the status of the Midland turbine missile protection evaluation. During the presentation, the staff noted that a new review procedure in this area was being developed which would lessen the efforts required to establish strike and danage probabilities while craphasizing rare substantial efforts in the determination of missile generation probability. Attached for your information are the staff's position on turbine missiles which was given to ACRS subcomittee on June 2 as well as the handouts used for the June 4 presentation.
The turbine missile risk evaluation provided by Consumers Power uses ^ values for turbine missile generation probabilities which were supplied by General Electric Company. These values were 8.7 x 10 -9 and 5.0 x 10 -9 er year for p
missiles from design failure and destructive overspeed failure, respectively.
in its evaluation used Standard Review Plan recomended values The staff,5 and 4 x 10 -5 er, year.
of 6 x 10-p Ve understand your position to be that, since the turbine inspection and test programs are explicitly or implicitly incorporated in the Consumers Power evaluation, use of the General Electric probability figures are justified.
In order for the staff to evaluate whether or not the vendor-supplied probabilities can be used, you are requested to supply to the staff the relevant General Electric analyses and any supporting information relevant to 8207060270 920625 PDR ADOCK 05000329 A
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2-Mr. James W. Cook your planned turbine inspection and test program. This information should be stbnitted within two weeks of receipt of this letter. If a meeting between your staff and the NRC appears warranted following our review of the infomation supplied, the Licensing Project Manager will schedule such a meeting.
The reporting and/or recordkeeping requirements contained in this letter affect fewer than ten respondents; therefore, OMB clearance is not required under P.L.96-511.
Sincerely,
, Robert L. Tedesco, Assistant Director for Licensing Division of Licensing
Enclosures:
As stated cc: See next page DISTRIBUTION Docket Nos. 50-329/330 NRC PDR L PDR TERA NSIC LB#4 r/f EAdensam RHernan MDuncan DHond RTedesco WJohnston Attorney, OELD DEisenhut/RPurple ACRS (16)
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MIDLAND Mr. J. W. Cook Vice President Consumers Power Company 1945 West Parnall Road Jackson, Michigan 49201 cc:
Michael I. Miller, Esq.
Mr. Don van Farrowe, Chief Ronald G. Zamarin, Esq.
Division of Radiological Health Alan S. Farnell, Esq.
Department of Public Health Isham, Lincoln & Beale P.O. Box 33035 Suite 4200 Lansing, Michigan 48909 1 First National Plaza
- Chicago, Illinois 60603 William J. Scanlon, Esq.
2034 Pauline Boulevard James E. Brunner, Esq.
Ann Arbor, Michigan 48103 Consumers Power Company 212 West Michigan Avenue U.S. Nuclear Regulatory Commission Jackson, Michigan 49201 Resident Inspectors Office Route 7 Ms. Mary Sinclair Midland, Michigan 48640 5711 Summerset Drive Midland, Michigan 48640 Ms. Barbara Stamiris 5795 N. River Stewart H. Freeman Freeland, Michigan 48623 Assistant Attorney General l
State of Michigan Environmental Mr. Paul A. Perry, Secretary Protection Division Consumers Power Conpany 720 Law Building 212 W. Michigan Avenue Lansing, Michigan 48913 Jackson, Michigan 49201 Mr. Wendell Marshall Mr. Walt Apley Route 10 c/o Mr. Max Clausen l
Midland, Michigan 48640 Battelle Pacific North West Labs (PNWL)
Battelle Blvd.
Mr. Roger W. Huston SIGMA IV Building Suite 220 Richland, Washington 99352 7910 Woodmont Avenue Bethesda, Maryland 20814 Mr. I. Charak, Manager NRC Assistance Project Mr. R. B. Borsum Argonne National Laboratory Nuclear Power Generation Division 9700 South Cass Avenue Babcock & Wilcox Argonne, II.linois 60439 7910 Woodmont Avenue, Suite 220 Bethesda, Maryland 20814 James G. Keppler, Regional Administrator U.S. Nuclear Regulatory Commission, Cherry & Flynn Region III l
799 Roosevelt Road Suite 3700 Three First National Plaza Glen Ellyn, Illinois 60137 l
Chicago, Illinois 60602 Mr. Steve Gadler 2120 Carter Avenue St. Paul, Minnesota 55108 l
EMCLoSu.Rc la. What is the staff's criterion for turbine missiles?
Answer The SRP Section 2.2.3 risk acceptance guidelines that are used for potential accident situations in the vicinity of the plant are and will continue to be used in determining the sufficiency of protection against turbine missiles.
During the past several years the results of turbine inspections at operating nuclear facilities indicate that cracking to various degrees has occurred at the inner radius of turbine disks, particularly those of Westinghouse design. Within this time period, there has actually been a hestinghouse turbine disk failure at one facility - Yankee Atomic Electric Company.
Furthermore, recent inspections of General Electric turbines have also resulted in the identification of disk bore cracks.
In view of current experience and NRC safety objectives, the NRC staff intends to emphasize the turbine missile generation probability (i.e. turbine system integrity) in its reviews of the turbine missile issue and eliminate the need for elaborate and somewhat ambiguous analyses of strike and damage probabilities given an assumed turbine failure rate. Although straightforward in principle, the latter calculations have to be based on detailed facility infonnation and assumptions as to missile shape and size, missile energies, barrier penetration potential and ultimately to the likelihood of damaging a facility safety system. Generally, there are significant differences between licensees or applicants submittals and the final evaluation by the staff. Nevertheless, the staff concludes, based on our reviews of many facilities, that the probability of a turbine missile striking and damaging a safety system is in a relatively narrow range depending on turbine orientation. More refined analyses or additional calculations for other facilities are unlikely to change this conclusion. Therefore, expensive and time consuming strike probability analyses on the part of applicants / licensees and/or the NRC staff are judged to be unwarranted.
This shift of emphasis requires all nuclear steam turbine manufacturers to develop volumetric (ultrasonic) examination techniques suitable for inservice inspection of turbine disks and shaft, and to prepare reports for NRC review which describe their methods for determining turbine missile generation probabilities. These methods are to relate disk design, materials properties, and inservice volumetric inspection interval to the design overspeed missile generation probability, and to relate overspeed protection system characteristics, and stop and control valve design and inservice test interval to the destructive overspeed missile generation probability.
It should be noted that although evaluations of strike and damage orcDabilities are not involved in following the proposed new procedures, the effect of these probabilities are taken into account in these procedures. The new procedures
. are related to the NRC safety goal for turbine missiles (SRP Section 3.5.1.3) by taking the P2 P3 product (i.e.$ the strike and damage probability) to b roughly in the range 10 -4 to 10 -
for favorably oriented turbines and 10 to 10-Z for unfavorably oriented turbines, for all plants in each category, and specifying degrees of unacceptable damage in terms of missile generation probability ranges and corresponding appropriate responses required of the applicant or licensee.
Ib. What is the status of the Midland Turbine Missile Protection Evaluation?
Answer The applicant has made an evaluation of the turbine missile risk for Midland Plant Units 1 and 2.
Based on their analysis, which uses General Electric calculated probabilities fo, the generatiog of missiles from design gnd destructive overspeed failure of 8.7 x 10-per year and 5.0 x 10-per y respectively, the probability of unacceptable damage for Unit 1 is 1.4 x 10 gar, per year and that for Unit 2 is 1.5 x 10-9 per year. However, based on the SRP Section 3.5.1.3 recomended missile generation probabiligies for missiles from design and destructive overspeed failure of 6 x 10-per year and 4 x 10-5 per year, respectively, the probability of unacceptable damage for both Units 1 and 2 are about 1 x 10-5 per.
These are two orders of magnitude above the NRC safety objective of 10 ', year.per year.
The applicant contends that their turbine inspection and test programs are either explicitly or implicitly incorporated in their evaluation and justify their use of the General Electric missile generation probabilities.
It is the staff's position that the relevant General Electric analyses be submitted to the staff for review and acceptance in order to verify the adequacy of the applicant's turbine inspection and test programs.
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