ML20055A363
| ML20055A363 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 07/13/1982 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Counsil W CONNECTICUT YANKEE ATOMIC POWER CO. |
| References | |
| TASK-03-04.B, TASK-3-4.B, TASK-RR LSO5-82-07-023, LSO5-82-7-23, NUDOCS 8207160213 | |
| Download: ML20055A363 (6) | |
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July 13,1982 Docket No. 50-213 LS05 07-023 Mr. W.G. Counsil. Vice President Nuclear Engineering and Operations Connecticut Yankee Atomic Power Company Post Office Box 270 l' rtford, Connecticut 06101 a
Dear Mr. Counsil:
SUBJECT:
SYSTEMATIC EVALUATION PROGRAll TOPIC III-4.B.
TURBINE MISSILES - HADDAM NECK Enclosed is a copy of our evaluation of Systematic Evaluation Program Topic III-4.B.
You are requested to examine the facts upon which the staff has based its evaluation and respond either by confirming that the facts are correct, or by identifying errors and supplying the corrected information.
We encourage you to supply any other material that might affect the staff's evaluation of this topic or be significant in the integrated assessment of your facility.
Your response is requested as soon as possible. If no response is received by the time the next phase of the integrated assessment of your facility begins, we will assume that you have no comments or SGCI corrections and will consider the topic complete.
usGh Sincerely, 054 Dennis il Crutchfield, Chief Operating Reactors Branch #5 Division of Licensing
Enclosure:
As stated cc w/ enclosure:
See next page 8207160213 820713 PDR ADOCK 05000213
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7 Mr. W. G. Counsil i
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Day, Berry & Howard Counselors at Law One Constitution Plaza Hartford, Connecticut 06103 Superintendent Haddam Neck Plant RFD #1' Post Office Box 127E j
East Hampton, Connecticut 06424
. Mr. Richard R. Laudenat Manager, Generation Facilities Licensing
. I Northeast Utilities Service Company P. O. Box 270 Hartford, Connecticut 06101 Board of Selectmen Town Hall Haddam, Connecticut 06103 State of Connecticut 0Ffice of Policy and Management ATTN:
Under Secretary Energy Division 80 Washington Street Hartford, Connecticut 06115 U. S. Environmental Protection Agency Region I Office ATTN:
Regional Radiation Representative JFK Federal Building Boston, Massachusetts 02203 Resident Inspector Haddam Neck Nuclear Power Station c/o'U. S..NRC East Haddam Post Office l
East Haddam, Connecticut 06423 1
Ronald C. Haynes, Regional Administrator Nuclear Regulatory Commission, Region I 631 Park Avenue King of Prussia, Pennsylvania 19406 O
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SYSTEMATIC EVALUATION PROGRAM h
TOPIC III-4.B HADDAM NECK Topic III-4.B TURBINE MISSILES I. 8 INTRODUCTION The purpose of this topic is to assure that, with respect to potential turbine missiles, all structures, systems and com'ponents important to safety either have adequate protection by means of structural barriers or have an acceptably low probability of damage.
II.
REVIEW CRITERI_A 10 CFR 50, Appendix A, GDC 4.
III.
RELATED SAFETY TOPICS AND INTERFACES III-4.C Internally Generated Missiles IV.
REVIEW GUIDELINES Standard Review Plan (SRP) Section 3.5.1.3, Regulatory Guides (R.G. ) 1.115 and 1.117.
V.
EVALUATION During November 1979, the 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 indicatedcracking 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. Both Westinghouse and the NRC staff have been following this problem closely and have developed independent crack growth models.
The findings of multi-plant action, B-46, " Turbine Missiles,"
concluded that an inspection schedule based on an approach developed by Westinghouse for their turbines provides an acceptably high degree of assurance that discs will be inspected before cracks can grow to one-half of a size that could cause disc failure at speeds up to design speed.
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The Connecticut Yankee Atomic Power Company was provided with a safety evaluation report of this approach and was requested to commit to use the four criteria listed on page 3 of the safety evaluation report (Reference 1).
Connecticut Yankee Atomic Power Company responded to this request (Reference 2) and committed to the use of the four criteria with the exception of criterion 4's inspection schedule. Also, the turbine is protected from over-speed conditions by two independent systems. The overspeed 8
protection controller (electrical) which senses loss of load, and the turbine generator overspeed trip (mechanical) set at 102% (1836 RPM). As a result of both this commitment and the design of the overspeed protection systems, an acceptably high degree of assurance is provided, that disc failures at design speed will not occur.
The following tabulation is a listing of turbine trips and over-speed since the initial operation date of July 18, 1976 for the new LP rotors (Reference 3). The maximum design overspeed for this turbine is 134%.
Overspeed Date Description
(% Above 1800 RPM) 7/18/76 Turbine Overspeed Trip Test (No load) 2%
8/1/76 Turbine Trip from 76% Load 15.6%
9/10/76 Plant Trip from Full Load N,o Overspeed 9/18/77 Turbine Trip from Full Load 24.4%
10/9/77 Plant Trip from Full Load No Overspeed 12/1/77 Reactor Trip from 10% Load No Overspeed 12/2/77 Turbine Overspeed Trip Test (No Load) 2%
12/3/77 Turbine Trip from 70% Load 20.8%
1/1/78 Reactor Trip from 80% Load No Overspeed 4/30/78 Plant Trip from 50% Load No Overspeea 5/4/78 Plant Trip from 100% Load No Overspeed j
11/2/78 Reactor Trip at 100% Load No Overspeed 3/12/79 Turbine Overspeed Trip Test 2%
. l As a result of the turbine cracking problen. Westinghouse has revised its probability analysis of damage to safety related struc'
', systems and components of damage to an acceptable pro ba bil i ty.
The analysis 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 (pl),
(2) the probability of strike (P2) and (3) the probability of damage (P3).
Since the evaluation of the latest Westinghouse g
probability analyses has not been completed by the staff, criteria, considering turbine cracking and the implemented inservice inspection program, has not been established for determining Pl.
The staff upon completion of the Westinghouse review, will determine what actions, if any, are required.
The staff determined that the licensee performs a testing program for the overspeed protection system.
Specifically, there are three different tests perfonned on a routine basis as follows:
Every time the turbine is returned to operation the following two tests are performed:
1.
Overspeed protective test - simulated overspeed turbine to trip set point to close stop and governing valves.
2.
As turbine is brought up to speed, stop and control valves are tested to verify system operability.
Every 30 days, while the plant is operating, power is reduced and each of the control and stop valve combination (there are 2) is sequentially exercised.
VI.
CONCLUSION The inspection program committed to by Connecticut Yankee Atomic Power Company (References 1 and 2) provides an acceptably high degree of assurance that turbine discs will not fail at speeds up to design speed. The testing program of the overspeed protection system, including the stops and control valves at Haddam Neck, provides reasonable assurance that the overspeed protection systen will remain operable and, thereby, limit the likelihood that overspeed past the design conditions would occur.
, The staff concludes, for an interim period until a decision is reached regarding the need for updated probabilistic analysis of the turbine missile hazard, the probability of damage from turbine missiles is acceptably low.
Should further reviews of operating plants and/or additional requirements be deemed necessary, the Haddam Neck plant will be included with that operating plant action.
s REFERENCES 1.
Letter from D. Crutchfield (NRC) to W.G. Counsil (CYAPCo),
August 28, 1981.
2.
Letter from W.G. Counsil (CYAPCo) to D. Crutchfield (NRC),
October 20, 1981.
3.
Letter from W.G. Counsil (CYAPCo) to D. Crutchfield (NRC),
July 8,1980.
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