ML19339B706

Responds to NRC 800924 Ltr Re Lessons Learned Task Force Short-Term Requirement 2.1.3.b.Existing Instrumentation Is Sufficient to Detect Inadequate Core Cooling.Reactor Vessel Level Indication Is Unwarranted

ML19339B706
Person / Time
Site:	Arkansas Nuclear
Issue date:	10/29/1980
From:	Trimble D ARKANSAS POWER & LIGHT CO.
To:	Eisenhut D Office of Nuclear Reactor Regulation
References
RTR-NUREG-0578, RTR-NUREG-578, TASK-2.F.2, TASK-TM 1-100-24, NUDOCS 8011070509
Download: ML19339B706 (3)

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ARKANSAS POWER & LIGHT COMPANY POST OFRCE BOX 551 UTTLE ROCK. ARKANSAS 72203 (501) 371-4000 October 29, 1980 1-100-24 g ;U

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. cs Mr. Darrell G. Eisenhut, Director _

kl, Division of Licensing , CB 3

Office of Nuclear Reactor Regulation $7g' N

U. S. Nuclear Regulatory Comm. 3 dj Washington, D.C. 20555 g ,, hg

SUBJECT:

Arkansas Nuclear One - Unit 1 $7 2 Docket No. 50-313 License No. DPR-51 Lessons Learned Short-Term Requirement 2.1.3.b. " Instrumentation for Detection of Inadequate Core Cooling (ICC) - Additional Infonna ti on" (File: 1510.3)

Gentlemen:

AP&L has reviewed your letter dated September 24, 1980, regarding the subject requirement. We feel that NRC staff interaction with AP&L and the other B&W Owners is a necessary part of resolution of this issue in a manner suitable to all parties involved, and, therefore, would like to provide a further clarification of our position.

Cirst, it should be pointed out that AP&L has met the requirements of NJREG-0578 and the October 30, 1979 clarnication letter for the subject item. An evaluation has been performed by AP&L, with assistance from B&W, which determined that no additional instrumentation was needed.

This conclusion was reached after performance of an evaluation of the ability of existing instrumentation (i.e., incore thermocouples and core outlet thennoccuples) to predict and indicate ICC. AP&L determined that the existing instrumentation could detect inadequate core cooling, and that additional instrumentation would not cause any operator actions beyond those actions taken as a result of ICC indication from existing instrumentation. -

Your letter indicates that AP&L has not met NRC requirements because "there has been insufficient effort to develop a level measurement system which is sufficiently accurate to provide valuable advance warning of the approach to inadequate core cooling". Because AP&L has determined that there is no need for additional instrumentation, it is

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O' . Mr. Darrell;G'. Eisenhut, Director October 29, 1980 irrelevant-whether or not_we have expended effort to develop a level measurement system. Because we have determined that RV level is not 4 needed, our efforts have been concentrated on providing appropriate guidelines to the operators for determination than an ICC condition exists and on appropriate actions to be taken if it does.

-It should be noted, however, that AP&L has evaluated other methods for detection of ICC. This evaluation has included reactor water level indication as required. Our letter to R. W. Reid of your staff dated August 26,31980, discussed the capabilities and evaluations of several different methods of ICC indication. In each case it was found that use of existing epipment provided the best and most direct method of determining that ICC had occurred. It was also determined that the combination of incore thermocouples and core o":let thermocouples pro-vides an accurate indication of ICC, while at tie same time meeting a majority of the NRC criteria.

AP&L therefore believes that we have made an appropriate effort to resolve this issue. Our technical arguments for acceptance by NRC of existing instrumentation for ICC indication have been presented to NRC. We have presented arguments which show that additional instrumentation, and reactor vessel water level in particular, provides information which cannot be used by the operators and could, in fact, provi4 ambiguous indication which could cause operator error. Even after a determination that existing instrumentation provided an adequate indication of ICC, AP&L undertook a study to determine what, if any, additional instrumentation could be added which would supplement, or at least not interfere with, existing instrumentation. We found no instrumentation which was superior to that which is already installed.

AP&L also notes that there is apparent variance of NRC staff cpinion on this issue. In paragraph 190 of the NRC Staff's proposed findings before the ASLB in the matter of SMUD (Rancho Seco), dated August 22, 1980, the staff states ". . . there is no evidence to indicate that the operators need such information (water level in the core) to undertake the required imediate actions. These actions are dictated by the presence or absence of.subcooling, and not by vessel level." Additionally, an NRC ~ staff witness testified before the ASLB during the SMUD nearings (see transcript, pa9c 3877, 3906 - 3907) that vessel level indication is not required and that it .aight even induce inappropriate operator action.

Similar staff positions have been voiced at the TMI-1 restart hearings Even the Proposed Rule (see Federal Register page before the ASLB.

65473 dated October 2,1980) does not mandate additional instrumentation, as it states ". . . each boiling and pressurized light-water nuclear power reactor shall be provided with instrumentation such as a reactor vessel water level indicator which supplies to the control room a recorded,

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un-ambiguous, direct indication of inadequate core coolir.g". The words "such as a reactor vessel water level indicator" indicates that this is not the only instrumentation which will meet the requirement.

9' Mr. Darrell- G. Eisenhut, Di rector October 29,'1980 The confusion which AP&L-faces in attempting to resolve this issue is, therefore, apparent. W e have met NRC requirements by our determination that no additional instrumentation is needed. A study has been under-taken which showed that existing instrumentation is superior to _any-thing which could be added. .We see conflicting staff positions as to the need for additional instrumentation. It should not be surprising .

that AP&L has not proceeded with an extensive research and development

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program to produce something which has not been determined to be necessary by either AP&L or NRC.

AP&L hopes that these comments have shed some light on the confusion we have faced in attempting to resolve this issue. Until further investi-gations determine otherwise, AP&L retains its position that additional instrumentation to indicate ICC is not needed. We will be happy _to discuss these issues with you in an effort to resolve our differences.

, Very truly yours, 0&f.Y0 David C. Trimble Manager, Licensing DCT: MAS:1p M

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