ML19260E913
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QUESTION 14 With respect to the proposed new instrumentation for the detection of inadequate core cooling, the staff has concluded that the licensee is not in compliance with this part of the Order because "no additional -instrumentation has yet been com-mitted to, scheduled, or conceptually addressed..." (lines 22-24 on p. C8-21).
Explain precisely what the staff will require on this issue prior to restart and for the long-term modification.
RESPONSE
The staff requirements for new instrumentation to detect inadequate core cooling are presented in NUREG-0578 (l_) and supporting documents (2_, 3_) and are reite ated in our evaluation (4) of the Till-l Restart Report.
These documents state that the licensee shall provide a description of any a(ditional instrumenta:icn or ccntrols pecposed for the plant to supplement tnose devices cited in the preceding section of the requirement (2.1.3.5).;hich give an unambiguous, easy-to-in:erpret indication of inadequate ccre c cling. A ccnceptual descripticn of the method of ccToliance, including an acceptable schedule for procurement, testing, installation, calibra-tion, and implementaticn, ";ould be judged sufficient to demonstrate reasonable prcgress in satisfying this requirement prior to restart.
Metropolitan Edison and Babcock & Wilcox have proposed the use of existing instru-Tents (that is, no additicnal instrumenta:icn) to provice an incicaticn of inadequate core cooling. The basis for this proposal is that there is no need for additional instrumentation, particularly a reactor vessel water level measure-ment, to determine inadequate core cooling. We have reviewed the justification for no additional instrumentation and find it unacceptable (5) for all B&W plants.
We agree that the as-designed and field-modified instrucents at Ti1I-2 provided sufficient information to indicate reduced reactor vessel coolant level, core voiding, and deteriorated core thermal conditions.
'le have concluded, hcwever, that this detemination was not nade quickly and unambiguously.
The NRC Lesscns Learned Task Force recognized this instrumentation deficiency at TMI-2 and also recognized the variety of instrumentation concepts available to it; rove the cperator's understanding of core thermal ccnditions. The inadequate core cooling instrumentation requirement in NUREG-0578 was an attempt to provide the licensee with the flexibility to select those instrument (s) or data processing schemes which would substantially improve the operator's ability to detect these conditions in the future.
As it 8008080 b
, now stands, the instrumentation at IMI-l remains fundamentally unchanged and is still similar to that at TMI-2 at the time of the accident.
Prior to restart of TMI-1, we will require a commitment en the part of the licensee to substantially improve the operator's ability to detect inadequate core cooling.
We will require a conceptual description of, and implementation schedule for, the instrument (s) proposed to accomplish this task. We will not accept a discussion of the desirability of such instruments.
In the long term, possibly after restart, we will require design and testing details, implementation, and verification of installation of these instruments.
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4 REFERENCES
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TMI-2 Lessons Learned Task Force Status Report and Short-Tern 1
Recommendations, NUREG-0578, July 1979.
2 D. Eisenhut (NRC) letter to All Operating Nuclear Power Plants on " Followup Actions Resulting from the NRC Staff Reviews Regarding the Three Mile Island Unit 2 Accident," dated September 13, 1979.
3 H. Denton (NRC) letter to All Operating *:uclear Power Plants on
" Discussion of Lessons Learned Short-Term Requirements," dated Oct:ber 20, 1979.
4 TMI-l Restart:
Evaluation of Licensee's Conoliance with the
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inort-and Lcng-Term Items of Section II of ' he NRC Order dated t
August 9,1979, Metropolitan Edison Company, et al., Three Mile Island Nuclear Staticn Unit 1, Occket 50-239, NUREG-0680, June 1983.
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L. Rubenstein (NRC/DSI) memorandum to T. Novak (NRC/DL) on " Position 5
cn Inadecuate Core Cooling (ICC) Recuirements for B&W Plants," dated June 17, 1930 (attached).
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