ML19206B388
| ML19206B388 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 07/20/1978 |
| From: | Kniel K Office of Nuclear Reactor Regulation |
| To: | Varga S Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7905090418 | |
| Download: ML19206B388 (3) | |
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-:T JUL 2 0 '978 MEMORANDGt FOR:
S.A. Varga. Chief. LWR 3 ranch M. DPH FROM:
K. Kniel, Chidf, Core Perfomacca Branch, DSS S W ECT:
EVALUATION OF TECHNICAL SPECIFICAT*0M CHAl4GE 14 FOR THREE MILE ISUU40, UNIT 2
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Enclosed is the evaluation of' Technical Specification Change No.14 dated July 7,1378 for THI.2 by the Relictbr' Fuel's 'Sectiosi of"the Core ~ Perfomanc~e-'
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Branch.
The Reactor Physics Se~ tion Es~~r.o Tnput.~ rc~ ~st + arf,~we approve
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c the use of the proposed holddow6 retainers foY EPRAsTnd codified' ORAs'. '
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Also, the applied rod bow equat%n has'been veHffed'to confo~ in To the' ~ ~ ~ ~ ~ ~ ~ ~ ~
r NRC-approYcd rQd BOW equation for BMf pTants'_~ ~~~~ ~~~}~]]
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Karl Knial Chief
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~~~ Division of Systems Safety
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Ecclosure: As stated cc:
S. Hanauer
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R. Mattson
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- 9. Vassallo
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R. Boyd
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CENTRAL FILES H.. Silver f4RR RCG FILE D. Ross CPB RDG FILE D. Fieno R. Meyer
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M. Tou r
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W. Brooks
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D. Houston
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Contact:
W. Brooks, NRR, 27577
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E'/ALUATION OF TECHNICAL SPECIFICATION CHANGE 14 FOR TMI-2 REACTCR FUEL 3 SECTION A burnable poison rod assembly (BPRA) was ejected from the core at one of B&W's Mark B plants.
B&W analyzed the problem and determined it to be caused by levitation of the BPRAs during four-pumo coeration ar.2 subsequent fretting wear in the holddcwn latching mechanism.
After tne initial irsspection of fuel assemblies at the affected plant, B&W also observed visual indications of wear at other plants in the identical latching mechanisms of BPRAs, assemblies that held orifice rods (CRAs),
and source or modified orifice red assemblies (MORAs).
A retainer device was then designed and tested by B&W to msure positive holddown of BPPAs, CRAs and MORAs during reactor operation.
The design and the test results were reported to NRC in references I and 2.
We have re-viewed these references and have previously determined (Ref. 3) that the test results and design analyses provide reasonable assurance that the retainers will provide adequate positive holddown force on the BPRAs, CRAs, and MORAs and that the proposed use of the retainers poses no safety
- problem, cor continued operation of TMI-2, Metropolitan Edison Campany proposes to install the retainer devices on 68 BPRAs and 2 MORAs.
All regular ORAs (38) will be removed from the core.
These changes apply only for the remainder of the current cycle, Cycle 1, at which time, BPRAs are usually withdrawn from the core.
Based on our evaluation as referenced above, we fine the use of these retainers to be acceptable.
The potential consequences of a retainer failure have also been addressed (Ref. 2), although failure is considered unlikely.
The neutronic and thermal-hydraulic consequences are considered small.
Interference with control rod motion, for example, would not, according to analyses of stuck-out control rod transients for B&W 177-FA plants, prevent safe shut down of the plant.
The major concern associated with retainer failure is plant damage, primarily in the steam generators, and potential outages for repair.
This damage should be precluded by the Loose Parts Monitoring System (LPMS).
The LPMS is designed to detect a failed retainer in either the reactor vessel or steam generator.
Even though the retainer device is designed
,for only or.e cycle of operation, B&W has stated (Ref. 2) that it will recommend that surveillance inspections be made following retainer use.
This should provide additional confirmation of acceptable operation.
S&W has also stated that definite plans regarding surveillance will be provided to NRC as they are fortulated.
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In summation, based on (1) analyses and test results on tne retainer device, (2) analyses which indicate that failure of the retainers, however unlikely, would not prevent shutdown and (3) failure detection capability of the Loose Parts Monitoring System, we conclude that there is reascnable assurance that the retainers will provide adequate holddown force on the BPRAs and MORAs and that the proposed use of the retainer devices in TMI-2 will pose no significant safety concern.
One other change to the Technical Specifications involves the use of a revised fuel rod bowing model.
The original calculations for a rod bcwing penalty had been performed with a B&W rod bow model that we found unaccept-able. We have verified that the revised rod bow model as presented in the change request conforms with the NRC-approved rod bow equation for S&W plants.
Therefore, we find this change acceptable.
REFERENCES 1.
"BPRA Retainer Design Report," Ba'; cock and Wilcox Report, BAW-1496, May 1978.
2.
James H. Taylor (B&W) letter to Steven A. Varga (NRC), June 7,1978.
3.
K. Kniel memorandum to D.F. Ross, Jr., " Proposed use of Burnable Poison Rod Assembly Retainers to Holddown Modified Orifice Rod Assemblies in Davis Besse 1," June 19, 1978.
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