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UM '' M COOPER NUCLEAR STATION,k j P.O. box 98, BRoWNVILLE. NEBR A$hA 68324i

J 'g-__ Nebraska Pubh.c Power Distr. t~ ic TE LEr o~ E i.o2> .2,.3. i i

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LQA8200026

January 11, 1982$1 *9

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8RUCQptyn,

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,( NmMll.l$ g [Mr. Thomas A. Ippolitc, Chief 1

Operating Reactors Branch #2 4 N% g$g%-

Division of Licensing rb 5U.S. Nuclear Regulatory Commission

Washington, D.C. 20555 y /q -

Subject: NUREG-0737. Item II.K.3.27Cooper Nuclear StationNRC Docket No. 50-298, DPR-46

* Reference: 1) Letter from T. A. Ippolito to J. M. Pilant, DatedOctober 15, 1981, "NUREG-0737, Item II.K.3.27"

2) Letter from J. M. Pilant to D. G. Eisenhut, Dated'

June 30, 1981, " Post TMI-Requirements /NUREG-073""

3) Letter from J. M. Pilant to D. G. Eisenhut, DatedFebruary 27, 1981, " Revised Response to NUREG-0737"

4) BWR Owners Group Evaluation of NUREG-0737, II.K.3.27

5) Letter from J. M. Pilant to D. G. Eisenhut, DatedJune 9, 1981, " Emergency Response Facilities"

Dear Mr. Ippolito:

Your letter of October 15, 1981 (reference 1) requests that NPPD provideby January 15, 1982 the following:

1. The District's commitment to install a modification thatprovides a common re.ference level;

2. A description of that modification, including proposed imple-mentation schedules, and;

3. The District's commitment to meet acceptance criteria 2 and 3of reference 1.

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8201190165 820111PDR ADOCK 05000290 i

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_ _________ _ -

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!! Mr. Thomas A. Ippolito

! January 11, 1982 .

| Page 2!

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|In reply, the District does not consider it appropriate to commit to

,

acrosplishing the above requests as it is our opinion that this modi-I ficction is not necessary to assure nuclear safety and that furthermore,I this modification is not a well thought out requirement with respect to

good human factors engineering concepts and does not really consider howthe operator actually utilizes level indication during a transient

,

condition. The District's arguments supporting this viewpoint are|

presented by the following paragraphs. i

|

The control room operator at CNS has available nine level indicators or |1recorders. They are as follows:

A. Level Instrumentation Referenced to the Bottom of the Steam DryerSkirt

There are seven level instruments that are referenced to the bottomcf the steam dryer skirt. Zero on these instruments corresponds to165 inches above the top of active fuel (TAF).

|- Operating and Transient Level Instruments

| 1

1. Three narrow range indicators (0 to 60 inches)..

2. One narrow range recorder (0 to 60 inches).

3. Two wide range indicators (-150 to 60 inches).

Shutdown Level Instrument

1. One wide range indicator (0 to 400 inches).

B. Level Instrumentation Referenced to TAF

LOCA or Fuel Zone Level Instruments

1. Two wide range indicators (-100 to 200 inches).

As can be seen, seven of the nine level instruments that are availablehave a common reference point. They cover the normal and shutdown levelranges and the setpoints for initiation of HPCI/RCIC, low pressure ECCS,ADS and Primary Contsinment isolation as discussed in reference 4. Ofthe seven only those classified as Operating and Transient Level Instru-ments would be used to determine water level during normal operation andtransients. The Shutdown Level Instrument is used for monitoring levelduring refueling s. hen the reactor is depressurized and flooded up.

.

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e

Mr. Thomas A. Ippolito,

January 11, 1982Page 3

The remaining two of the nine level instruments are not used duringnormal operation or transients. They are provided to indicate reactorwater level following a large break LOCA and to verify core reflood byECCS. They do not provide meaningful indication other than when theRecirculation (RR) or Residual Heat Removal (RRR) pumps are not runningand when the reactor is not pree~irized. At 0 psig, O inches on thesetwo indicators corresponds to TaF At 1000 ps;g, -80 inches correspondsto TAF. Thus, it can be seen that these two indicators cannot be useddirectly to determine reactor water level other than during very re-stricted conditions. As a result, no direct comparison can be made

between the LOCA or Fuel Zone Level Instruments and the rest of thelevel instruments other than when these very restricted conditions aresatisfied.

Therefore, the staff's argument that the operator would have to performa mental interpolation to understand what a. reading on one water levelindicator means relative to a reading on another water level indicatoris not a valid argument. Those ther. would be used during normal opera-tion or transients have the same reference point. The LOCA or Fuel ZoneLevel Instruments would not be used for a direct comparison to the

Operating and Transient Level Instruments, not because of the difficultyof performing a mental interpolation to understand what a reading on onewater level indicator means relative to a reading on another water levelindicator, but because they do not read accurately other than in veryrestricted conditions. At reactor pressures other than atmosphericpressure, with the RR and RHR pumps not running, an adjustment must beapplied to the reference point that is dependent upon the actual reactorpressure (temperature). With the RR and RHR pumps running, these twoinstruments cannot be used to determine level as there is no way toascertain the variable effects of the pumps on these levsl instruments.Based upon the above, it is the District's opinion that there is littleto be gained by requiring the LOCA or Fuel Zone Level Instrumentation

Iand the Operating and Transient Level Instrumentation to have the samereference point.

In the staff's letter (reference 1) to the District, it is stated that

the operator should not have to perform mental interpolations to under-stand what a reading on one water level indicator means relative to areading on another water level indicator. The staff further states thatthe District's modification makes information readily available that the

operator needs to perform a mental interpolation, but it doca noteliminate the need for performing the interpolation. The Districtconcurs that if the operator had to make such a mental interpolation,then our modification does not eliminate the need for performing theinterpolation. However, it is the District's view that this does notreflect how an operator actually uses the water level instrumentation

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Mr. Thomas A. IppolitoJanuary 11, 1982Page 4

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during a transient or accident situation. The District's modificacion,

! (reference 3) informs the operator how far above TAF the water level isat a minimum at any time. It is the District's opinion that the operator

'is interested in knowing only whether water level is at least 15 inchesor 165 inches above TAF and whether it is increasing or decreasing. Thestaff's view that the operator will have to make a mental interpolation,

; to determine whether the water level is for example 17 inches or 172inches above TAF is not realistic. The operator will look at the in-dicators and only be interested in knowing whether water level is atleast 15 inches or 165 inches atove TAF or whether it is increasing,

decreasing or holding steady. Even in the very restricted conditionswhen the LOCA or Fuel Zone Level Instruments are responding correctly,this type of direct comparison can still be made. All indicators can becompared to determine whether the core is adequately covered or not and

4

| whether level is increasing or decreasing. This is consistent with the

| viewpoint of the symptom oriented Emergency Procedure Guidelines beingdeveloped by the BWR Owners Group which emphasize that the primaryindication of nuclear safety during a transient or accident situation isan indication of adequate core coverage. Knowledge of the exact waterlevel is not as important as knowledge of how tne water level is varyingrelative to TAF.

Based upon the above, the District is firml/ convinced that the modi-fication that we have made provides sufficient information (see enclosedphctographs) to the operator to adequately adjudge adequate core coolingduring a transient or accident situation.

Regarding human factors engineering considerations for action itemII.K.3.27 of NUREG-0737, the District believen there are two aspectsrelative to the desirability of changing to a common reference level and'

that the staff has focused on only one of these aspects without ade-

quately determining if there is a positive benefit to be gained. These'

aspects are the positive side of the requirement which would permit theoperator to more easily determine reactor water level and the negative

| side which must weigh the desirability of retrofitting this requirementto an operating plant versus the benefits to be gained. The Districtdoes not believe the staff has properly weighed the two aspects for anoperating plant. The staff's argument in NUREG-0737 is that this modi-

1

i fication will help eliminate operator confusion regarding water level.As stated above, the District is of the opinion that the staff has notI

correctly considered how the operator actually utilizes water levelindication during a transient or accident situation and as a result, hasincorrectly assessed the potential for operator confusion. Furthermore,the District is of the opinion that this modification quite probably

will contribute more confusion than it will alleviate (see reference 3).For this reason, we do not believe that modifications other than thosewe have already implemented are appropriate.

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Mr. Thomas A. IppolitoJanuary 11, 1982Page 5

As part of the District's plans regarding the NRC requirements ofNUREG-0696, we are considering implementing a fuel zone water levelmonitoring package on the proposed computer system (reference 5). Thispackage would utilize all level sensors discussed above and would com-bine them to develop or.e composed 1.evel indication that would bepressure (temperature) compensated as necessary to provide accuratelevel indication under all conditions. This would provide ona indi-cation available via the SPDS, that would be validated as necessary toprovide reliable indication from 100 inches below TAF to vessel top.Enclosed is an example of the type of display that is being considered.This display would be available on a color CRT in the Control Room andwould be color coded for various operating conditions. The Districtbelieves this modification is preferable to changing existing equipmentand would provide better information to the operator.

If you have any questions concerning this response, please contact me.Sincerely,

k

.i. Pilant'

Division Manager ofLicensing 6 yuality Assurance

JMP: ROP:1bEnclosures

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