ML20004C654
| ML20004C654 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 05/29/1981 |
| From: | Tramm T COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-CR-0660, RTR-NUREG-CR-660 NUDOCS 8106040409 | |
| Download: ML20004C654 (5) | |
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May 29, 1981 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Zion Station Units 1 and 2 l
Diesel Generator Reliability NRC Docket Nos. 50-295 and 50-304 Reference (a):
March 27, 1981 letter from S. A.
Varga to J. S. Abel
Dear Mr. Denton:
This letter will provide information requested in reference (a) regarding our plans for improving the reliability of Zion's emergency oiesel generators.
It also provides our comments on the suggestions and summary of NRC's review of Zion LER's contained in reference (a).
LER Review Table 4 of Reference (a) lists aiesel generator LER's which the NRC has attributea to human factor causes.
The following events do not belong in this category:
1.
The 1/16/78 failure of lA DG was due to an oil cooler tube leak.
This war not a failure of IB DG due to a faulty bearing high temperature trip as listed.
The cause for the tube leak was excessive service water velocity.
Flow restricting orifice plates are being installed to correct this problem.
2.
The 7/17/78 failure of 1A DG was also due to an oil cooler tube leak.
The orifice plate solution to the erosion problem had not been engineered at that time.
3.
The 3/10/79, 5/17/78, 1/06/78 failures of the 2A DG voltage regulator were not related.
There was no reason to replace the entire voltage regulator until 3/10/79.
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The 3/15/79 event involving 1A DG required an LER because of reauced auxiliary power redundancy.
This was not a failure as defined in Reg. Guiae 1.108.
5.
The 5/11/79 failure of 0 DG starting air valve involved a defective part.
The capscrews which hold the valve seat to the seat retainer are inside the valve and should have been properly lockwired by the manufacturer.
Historical Reliability We also feel the statement made in regard to the 18 diesel generator's reliability was unjustified.
In order to determine reliability, the number of valid failures and attempts must be known.
The 1/16/78 failure listed in Table 4 of Reference (a) should not be included because no such failure occurred.
The number of attempts is not readily available to the NRC.
It appears an arbitrary number of attempts was assigned to arrive at a reliability figure.
The reliability of the IB DG for 1/1/78-5/21/81 is 97.6%
compared with the overall station DG reliability of 97.9% for that period.
Station reliability has improved from 96.9% in 1978 to 98.4% in 1980.
NUREG/CR-0660 The recommendations made in NUREG/CR-0660 were reviewed by our engineering department in January, 1980.
The resulting recommendations have been addressed as follows:
1.
Personnel training should be established to insure adequate maintenance and operation of the diesel generators.
At the present, all equipment operators and licensed reactor operators receive training on the diesel generator system.
A program is being developed to have
" hands on" training given by a Cooper-Bessemer instructor.
This training would be given to operating, maintenance, and technical staff personnel responsible for the diesel generators.
2.
No load and light load operation should be minimized to prevent fouling of engine components due to incomplete combustion.
The policy at Zion is not to run any engine unloaded for more than 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
In some instances this is unavoidable, but the point has been empharized with operating personnel.
All periodic testing is at 100%
of full load for a minimum of one hour.
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. 3.
Instrumentation and control devices should be mounted such that engine vibration will not induce damage.
Engine vibration has caused numerous failures due to loose or leaking pneumatic tubing fittings.
This problem has been corrected by using a locking compound on controi air system fittings.
This is completed on four engines.
The last one is to be done in the near future.
Since application of the locking compound, no failures hive been attributed to bad fittings.
Other improvements in this area include use of stainless steel tubing in place of copper, use of liquid filled pressure gauges, and periodic tightening of electrical connections.
Manufacturer's Recommendations Manufacturer's recommendations are under constant consideration by engineers and maintenance personnel at Zion.
A diesel' generator task force committee was formed in May, 1980 to discuss problem areas, evaluate recommendations, and propose solutions.
Cooper-Bessemer's District Service Manager attended such a meeting and gave his recommendations.
The initiation of an engine analysis program, design of a jacket water heating system, and use of' proper materials for repair are examples of his recommendations that were acted on.
Rjtliability Improvement A schedule of planned diesel generator improvements is listed in Attachment A.
There improvements can have a significant effect on diesel generator reliability.
The training of operators, mechanics, and engineers in diesel fundamentals should reduce the human factor failures of the diesel generatces.
Training the system engineers in engine analysis techniques will promote better engine condition through preventative maintenance.
Implementation of a periodic analysis program can be used to detect degradation of the engine components.
Completion of the locking compound application to air system fittings should lessen the number of failures from leaks which have plagued Zion for years.
Installation of flow limiting orifices in the' service water piping from the lube oil coolers should eliminate oil cooler tube
- leaks.
The lifetime of engine components will be lengthened through l
use of uncontaminated oil.
Engine downtime will also be lessened.
The installation of a circulating jacket water heating system will allow engine temperatures to remain nearer their
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'. operating values.
The effects of thermal cycling on power heads, cylincur liners, and turbocharger casings will be greatly reduced.
Crankcase components will have longer lifetimes from less rust formation.
Availability will increase because there will be fewer repairs of-gaskets that have aged from thermal cycling.
Regulatory Relief It is Zion's goal to attain the highest diesel generator reliability and availability possible to provide a depencable source of emergency power.
This goal is not achievable within the regulatory constraints imposed.
The NRC's philosophy of repeated testing of diesel genertors is adverse to system reliability.
The overtesting of diesel generator will shorten the life of engine components and necessitate more frequent repairs.
The allowable outage time stipulation of the Zion Confirmatory Order limits the amount of maintenance possible and can result in quick fixes versus quality repairs.
Unnecessary cycling of the nuclear unit will occur if repairs cannot be made in the required time.
Zion has logged over 1400 engine starts and 1247 valid tests since January 1978.
Based on this and an increasing trend in diesel generator reliability, we feel increased testing requirements are not necessary.
The requirements that we feel are sufficient to maintain reliability are being included in an Auxiliary Electrt-cal
~ Power Technic.nl Specification change (Section 3.15/4.15).
This letter constitues our complete reply to the requests of reference (a).
Please contact me if there are other questions.
One (1) original and thirty-nine (39) topies of this letter are being provided.
Very truly yours, f i k f : -- __
T. R. Tramm Nuclear Licensing Administrator Pressurized Water Reactors Attachment cc:
Zion Resident Inspector 2077N l
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O Attachment A SCHEDULE OF-DIESEL GENERATOR IMPROVEMENTS SCHEDULED AC T),0N COMPLETION DATE 1.
Training of maintenance, operating, and technical staff personnel by Cooper-Bessemer.
1/01/82 2.-
Training of engineers on diesel engine analysis techniques by Cooper-Bessemer.
1/01/82 3.
Application of locking compound to control air system fittings.
(IB, 0, 2A, 2B diesel generators 8/01/81 completed) 4.
Installation of flow limiting orifices in service water piping from lube oil and jacket water coolers.
(lB, 0, 2A diesel generators completed) 9/01/81 5.
Installation of first out annunciator on protective trip system.
(lA, IB, O diesel generators completed) 8/01/81 6.
Performance analysis of all diesel generators.
(IA partially complete) 1/01/83 7.
Installation of a jacket water heating system.
1/01/83 2077N