ML17332A825
| ML17332A825 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 06/29/1995 |
| From: | Fitzpatrick E INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| AEP:NRC:1168B, NUDOCS 9507060110 | |
| Download: ML17332A825 (9) | |
Text
PRIORITY 1 (ACCELERATED RZDS PROCESSING)
P'EGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)
ACCESSION NBR:9507060110 DOC.DATE: 95/06/29 NOTARIZED: YES DOCKET g
FACIL:50-316 Donald C.
Cook Nuclear Power Plant, Unit 2, Indiana M
05000316 AUTH.NAME AUTHOR AFFILIATION FITZPATRICK,E.
Indiana Michigan Power Co. (formerly Indiana
& Michigan Ele RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)
SUBJECT:
Provides addi info re review of submittal to delete plant TS 3/4.3.4 that concerns turbine overspeed protection requirements.
N
'ISTRIBUTION CODE:
A001D COPIES RECEIVED LTR ENCL SIZE TITLE: OR Submittal:
General Distribution NOTES RECIPIENT ID CODE/NAME PD3-1 LA HICKMAN,J INTERNAL.
KTZ 1
NRR/DRCH/HICB NRR/DSSA/SRXB OGC/HDS2 EXTERNAL: NOAC COPIES LTTR ENCL RECIPIENT ID CODE/NAME PD3-1 PD NRR/DE/EMCB NRR/DSSA/SPLB NUDOCS-ABSTRACT NRC PDR COPIES LTTR ENCL NOTE,TO ALL "RZDS" RECIPIENTS:
PLEASE HELP US TO REDUCE WASTE!
CONTACT THE DOCUMENT CONTROL
- DESK, ROOM OWFN 5DS (415-2083)
TO ELIMINATE YOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!
TOTAL NUMBER OF COPIES REQUIRED:
LTTR 12 ENCL
Indiana Michigan Power Company P.O. Box 16631 Columbus, OH 43216 Nl June 29, 1995 Docket Nos.:
50-316 AEP:NRC:1168B U. S. Nuclear Regulatory Commission ATTN:
Document Control Desk Washington, D.
C.
20555 Gentlemen:
Donald C.
Cook Nuclear Plant Unit 2 TECHNICAL SPECIFICATIONS CHANGE REQUEST TO DELETE TURBINE OVERSPEED PROTECTION REQUIREMENTS ADDITIONALINFORMATION 2.
Donald C. Cook Nuclear Plant, Individual Plant Examination of External
- Events, submitted to the NRC in letter AEP:NRC:1082E, dated May 1, 1992.
"Review Insights on the Probabilities Risk Assessment for the Limerick Generating Station,"
NUREG-1068, 1984
'his letter is in response to the request for additional information as a result of the review of our submittal to delete Donald C.
Cook Nuclear Plant unit 2 technical specification (T/S) 3/4.3.4, which concerns the turbine overspeed protection requirements.
The additional information requested concerns the following specific issues:
the turbine manufacturer's recommendation for maintenance and testing; the plant specific maintenance and test results for the associated valves; and the potential for missiles to affect safety-related equipment.
The Cook Nuclear Plant unit 2 turbine is equipped with several turbine valves, which control turbine speed and load during normal plant operations and protect it from overspeed during abnormal conditions.
These valves are the high pressure turbine control valves and main stop valves, and the low pressure turbine reheat stop valves and reheat intercept valves.
The turbine overspeed protection system consists of two.independent mechanical sensing
- devices, which are capable of initiating fast closure of the
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U. S. Nuclear Regulatory Commission Page 2
AEP:NRC:1168B turbine valves through two independent trip circuits.
Each of these circuits are exercised weekly to verify their operability.
The proposed change to delete T/S 3/4.3.4 will not change the intention to test the turbine overspeed protection system at Cook Nuclear Plant.
The surveillance for the turbine overspeed protection on unit 2 willbe performed as a plant procedure as part of our Preventive Maintenance
- Program, outside of the T/Ss and in accord with operating experience at Cook Nuclear Plant, applicable industry experience, and consideration of the turbine manufacturer's recommendations.
Changes to the plant procedure will receive a technical review in accord with T/S 6.5.3.1.
This technical review willbe conducted by an individual(s) qualified to ANSI N18.1-1971 and other than the individual(s) who prepared the procedure.
The turbine manufacturer's recommendation for maintenance and testing for the main stop valves and control valves has been followed.
Our maintenance and testing for the reheat stop and reheat intercept valves differs from the turbine manufacturer's recommendation.
Our maintenance intervals are longer than the turbine manufacturer's recommendation.
Our maintenance interval has been in accord with T/S 3/4.3.4.1.2 and as indicated below has proven sufficient to ensure the reliability of the turbine overspeed protection system.
Cook Nuclear Plant specific maintenance experience and test results of the main stop valves, control valves, reheat stop valves, and reheat intercept valves have been good.
The unit 2 turbine is now operating in its tenth operating cycle with over 90,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> of operation.
Turbine overspeed protection surveillance results have been satisfactory since unit startup in 1978.
In 1983, a wear problem was found with the overspeed plungers.
Replacement plungers were installed.
Then in 1988 these plungers were replaced with parts having stellited (hardened) surfaces.
There have been no subsequent problems.
As noted in our submittal
- 1168A, the Brown-Boveri low pressure turbine rotors are assembled from separate forgings that are welded together.
They are not assembled using a shrunk-on disk design.
The Brown-Boveri welded design is considered to be less susceptible to turbine burst.
The UFSAR section 14.1.13 "Turbine-Generator Safety Analysis,"
deals with the safety analysis of the main turbine-generator and presents the results of our study of the consequences of a failure.
This safety analysis has determined that the chance of a
turbine overspeeding out of control to destruction is extremely small.
U.
S. Nuclear Regulatory Commission Page 3
AEP:NRC:1168B The requested change will not change the potential for turbine missiles to affect safety related equipment.
The potential for.
turbine missiles is generally calculated as the product of three
- factors, the probability of missile generation, the probability of missile strike on a critical
- area, and the probability of penetration of the turbine missile through barriers into the critical area.
The latter two factors are clearly not impacted by this change.
The probability of turbine missile generation is comprised of the probability of failure during normal operations and the probability of an overspeed failure.
The Cook Nuclear Plant Individual Plant Examination of External Events (reference
- 1) examined the potential for turbine missile generation from normal operating conditions, and found the probability of turbine missile-induced core damage to be significantly less (better) than the individual plant safety objective of 10 ~/year (reference 2).
An analysis of the probability of failure of the turbine overspeed protection system has never been performed for the unit 2
Brown-Boveri turbine.
As described above, the overspeed protection system is considered to be highly reliable.
Removing the overspeed test from the T/Ss and performing the overspeed test with administrative controls will ensure that the potential for overspeed turbine missiles will not increase.
Therefore, the requested change willnot change the potential for turbine missiles to affect safety related equipment.
In summary, approval of the elimination of the T/S 3/4.3.4 is based upon:
turbine protection from excessive overspeed by two independent mechanical sensing devices, which are capable of initiating fast closure of the turbine valves through two independent trip circuits, 2.
testing frequencies based on manufacturer's recommendations of every two weeks, at present, maintenance inspection intervals for the main stop valves and the control valves in accordance with the OEM recommended intervals, 4,
maintenance inspection intervals for the reheat stop and reheat intercept valves longer than the OEM recommendation but in accord with the successful maintenance intervals outlined in T/S 3/4.3.4,
I a
U. S. Nuclear Regulatory Commission Page 4
AEP NRC:1168B 5.
the Brown-Boveri welded design is considered to be less susceptible to turbine burst, and 6.
the potential for overspeed turbine missiles will not increase as a result of removing T/S 3/4.3.4.
In compliance with the requirements of 10 CFR 50.91(b)(1),
copies of this letter and its attachments have been transmitted to the Michigan Public Service Commission and the Michigan Department of Public Health.
Sincerely, EE'.
E. Fitzpatrick Vice President SWORN TO AND SUBSCRIBED BEFORE ME
'HIS E
1995
.'Not ry b
c My. Commission Expires: 3 pit CC:
A. A. Blind G. Charnoff J.
B. Martin NFEM Section Chief NRC Resident Inspector
- Bridgman J.
R. Padgett
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