ML19325E118

Application for Amends to Licenses NPF-76 & NPF-80,revising Tech Spec Table 4.3-1 Re Monthly & Quarterly Channel Calibr (Incore to Excore Axial Flux Difference Single Point Comparison & Incore to Excore Calibr)

ML19325E118
Person / Time
Site:	South Texas
Issue date:	10/25/1989
From:	Chewning R HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML19325E119	List: ML19325E118 ML19325E120
References
ST-HL-AE-3078, NUDOCS 8911020016
Download: ML19325E118 (9)

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October 25, 1989 j ST-HL-AE-3078 l File No. 02.06, 020.01 j 10CFR50.90 t

i U. S. Nuclear Regulatory Commission j Attention: Document Control Desk i Washington, DC 20555 1 1

South Texas Project Electric Generating Station  !

Units 1 E 2 ,

f Docket Nos. STN 50-498, STN-50-499 j Proposed Amondment to the i Unit 1 and Unit 2 Technical specificatieng J l

l Pursuant to 10CFR50.90, Houston Lighting & Power Company (HL&P) hereby ,

I proposes to amend its operating Licenses NPF-76 and NPF-PO, by incorporating I the attached proposed changes to the Technical Specifications, for the South j Texas Project Electric Generating Station (STPEGS) Units 1 and 2. -]

The proposed changes consist of a revision to the Technical Specification Table 4.3-1, Functional Unit 2.a., monthly and quarterly channel calibration (incore to excore axial flux difference single point comparison

! and the incore to excore calibration). Attachment I contains the significant i hazards evaluation and Attachment 2 provides the proposed change. These {

proposed changes were discussed with members of the NRC staff on l April 14, 1989. j HL&P has reviewed the attached proposed amendment pursuant to 10CFR50.92 and determined that it does not involve a significant hazards consideration, j The basis for this determination is provided in the Attachments. In addition, l based on the information contained in this submittal and the NRC Final i Environmental Assessment for STPEGS Units 1 and 2, HL&P has concluded that, [

pursuant to 10CFR$1, there are no significant radiological or non radiological  ;

impacts associated with the proposed action and the proposed license amendment ]

will not have a significant effect on the quality of the environment. 1

The STPEGS Nuclear Safety Review Board has reviewed and approved the proposed changes.  ;

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In accordance with 20CFR50.91(b), HL&P is providing the State of Texas  !

l with a copy of this proposed amendment.

8911020016 891025 PDR P

ADOCK 05000498 PDC 6

A1/021.NL3 A Subsidiary of Ilouston Industries incorporated 1

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lloubon 1 ighting k l'ourt Cornpany ST-HL-AE-3078 ,

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If the MRC should have any questions concerning this matter, please I contact Mr. M. A. McBurnett at ($12) 972-8530.

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R. W. Chewning Vice President, '

Nuclear Operations RWC/GCS/n1 ,

i Attachments: 1. Significant Hazards Evaluation for l

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Proposed Modifications of the Incore to Excore Single Point Comparison and ,

Calibration, i I

2. Proposed change

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Regional Administrator, Region IV Rufus S. Scott '

Nuclear Regulatory Commission Associato General Counsel 611 Ryan Plaza Drive, Suite 1000 Houston Lighting & Power company Arlington, TX 76011 P. o. Box 1700  ;

i Houston, TX 77001

• l Coorge Dick, Project Manager U. S. Nuclear Regulatory Commission INPO Washington, DC 20555 Records Center .

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1100 Circle 75 Parkway

• J. 2. Tapia Atlanta, GA 30319-3064 ,

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Senior Resident Inspector  ;

c/o U. S. Nuclear Regulatory Commission Dr. Joseph M. Her.drie l P. O. Box 910 50 Bellport Lane f Bay City, TX 77414 Be11 port, NY 11713 J. R. Newman D. K. Lacker Newman & Holtzinger, P. C. Bureau of Radiation Control 1615 L Street, N. W. Texas Department of Health Washington, DC 20036 1100 West 49th Street ,

Austin, TX 78756-3189 '

R. L. Range /R. P. Verret

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Central Power & Light Company  :

P. O. Box 2121  !

Corpus Christi, TX 78403 l R. John Miner (2 Copies)

Chief Operating officer  :

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City of Austin Electric Utility 721 Barton Springs Road  :

Austin, TX 78704 R. J. Costello/M. T. Hardt I City Public Service Board P. O. Box 1771 San Antonio, TX 78296 ,

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, UNITED STATER OF AMERICA

!- NUCLEAR REGUIJ. TORY COMMIS$20N l

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In the Matter ) l

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[- Houstor. Lighting & Power ) Docket Nos. 50-498 l

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Company, et al., ) 50-499 i l

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South Texas Project ) i Units 1 and 2 )

KFFIDAVIT ,

t F-R. W. Chewning being duly sworn,'hereby deposes and says that he is Vice President, Nuclear Operations, of Houston Lighting & Power Company; that he is  ;

W duly.authorimod to sign and file with the Nuclear Regulatory Commission the attached proposed changes to the south Texas Project Electric Generating station i

l Technical Specification Table 4.3-1, relative to Incore to Excore single Point '

Comparison and Calibration; is familiar with the content thereof; and that the .

matters set forth therein are true and correct to the best of his knowledge and [

belief. {

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R. W. Chewning i Vice Presidents Nuclear o tiene i

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Subscribed and sworn to before me, a Notary Public in and for The Stata  ?

of Texas this.25M day of 864.f.cA) , 1989. i

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A1/021.NL3

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ATTACHMENT 1.

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ATTACHMENT 1 SIGNIFICANT HAEARDS EVALUATION FOR THE INCORE.TO ,

O- EXCORE SINGLE POINT COMPARISON AND CALIBRATION ,

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ATTACHMENT 1 l l

SIGNIFICANT HAEARDS CONSIDERATION FOR PROPOSED  !

CHANGES TO THE INCORE TO EXCORE SINGLE POINT l COMPARISON AND CALIBRATION I l

i SACKGROUND l

Table 4.3-1, runctional Unit 2a, High setpoint, note 3 requires a single point comparison of incore to excore axial flux difference above 15% of rated thermal power (RTP). South Texas Project Electric Generating Station has ,

interpreted this note to mean that a single point comparison is required after i l overy thirty one calendar days of operation above 15% RTP. If the unit goes below 15% during a 31 day surveillance interval, this period is not counted as part of the 31 days. Note 6 is interpreted to mean that after every 92 calendar ,

days of operation above 75% a calibration is required. If the unit goes below '

75% during a surveillance interval, this period of time is not counted in the 92 i day period. The basis of this interpretation is that the single point J comparison and calibration are based upon changes in flux profile associated i i with core burnup, not calendar time. The excore neutron flux detectors are in a 3

! fixed location on the exterior of the core. As core burnup progresses, the j calibration and single point comparison respectively adjust and verify that the {

excore detectors accurately reflect the changes in flux profile associated with [

core burnup.

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23. a telephone conversation with the NRC staff on April 14, 1959 members ,

I of the HL&P staff discussed basing these surveillance tests on effective full power days (EFPD) instead of calendar days. The NRC staff agreed that EFPDs (

were more appropriate and requested that HL&P submit a Technical Specification I change request to base these surveillance tests on EFPDs instead of calendar j time.

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PROPOSED CHANGE e

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In Table 4.3-1, Punctional Unit 2a, High Setpoint, Notes 3 and 6, the

reference to monthly and quarterly should be changed to effective full power f days (EFPD). [

t JUSTIFICATION FOR THE USE OF EFPD f

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An EFPD frequency for the single peint comparison and calibration is l

more representative of core burnup and flux distribution when compared to a l calendar based frequency. The flux profiles chango with core burnup, not l calendar time. As the fiux profile changes the excore detectors output will i change, creating the need for a single point comparison or a calibration. The .

f quantity of neutrona detected by the excore detectors is proportional to reactor power and will change with the flux profile change. The execre detectors are in  ;

a fixed location on the outside of the core and as the flux profile changes the  !

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output of the excore detectors will change proportionally. As the flux profile j' changes with core burnup the excore detectors must be compared at a single point ,

to the incore detectors and calibrated to the incore detectors. EFPD is more representative of core burnup because a EFPD is equal to one day at full power.  !

A day at full power is more representative of core burnup than a calendar day

! becauoe on any given day the reactor may not be at full power. Therefore the ,

single point comparison and calibration of the excore detectors should be  :

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b. performed on the bases of EFPD.  ;

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. Currently days below 15% RTP for the single point comparison and days j below 75% RTP do not count towarde the single point comparison or the

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. calibration. However, as a conservatism and to provide consistency with the single point comparison, STPEGS.has used days above 15% to schedule the next required calibration. With the proposed change, time at power will count g towards the'ocheduling of the next surveillance and will be representative of j core burnup.

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The Power Range High Neutron Flux Reactor Trip (High Setting) is ,

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actuated when two out of four power rLage channels indicate a power level above

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I' a preset setpoint._ The Power Range High Neutron Flux Reactor Trip is actuated c by the output of the excore detectors. The setpoint on the Power Range High

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Neutron Flux Reactor Trip (High Setting) will not bo changed with this proposal.

F: The frequency of the single point comparison and the calibration will be >

chan0ed. The change in the single point comparison and calibration will allow l these surveillances to be performed on a bases that is representative of core ,", c burnup and flux distribution. Therefore the proposed change will not affect the .i Power Range High Neutron Flux Reactor Trip.

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y, The ion chambers (excore detectors) that input the Power-Range High L Neutron Flux Trip (high setpoint) also input the Power-Range High Positive

' Neutron Flux Rate Trip and the Power Range High Negative Neutron Flux Rate Trip.

L These trips are not affected by the proposed change because they trip on rate of I f signal increase or decrease. The rate of signal change is not affected because i l the single point comparison and calibration surveillances do not change the rate L of signal change setpoints.

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The Overtemperature and Overpower delta T trips have inputs from the ,

excore ion chambers, although in the overpower delta T trip the excore ion s

. chamber input is zeroed as defined in Technical Specification Table 2.2-1.

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These inputs use the difference between top and bottom detector of the power l l range ion chambers. The trip setpoints for the overtemperature and overpower delta T trips are not changed with this proposal. The frequency of the single

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peint comparioon and the calibration will be based on EFPD with the proposed change which is indicative of the change in the flux profile.

Additionally, changing from calendar based frequency to burnup based frequency for the single point comparison and calibration is consistent with industry practice. The VOGTLE Technical Specifications have been approved using EFPD and the Westinghouse proposed revised Standard Technical Specifications (MERITS) contain EFPD as represented in this proposed change.

As with any instrument loop the excore neutron dete: tors do experience

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instrument drift. The single point comparison and the calibration ensure that instrument drift is within the acceptance criteria. However, the effect of the flux profile change is much greater than the effect of instrument drift.

Instrument loops affected by drift are routinely calibrated on a 18 month

frequency. In the case of the excore neutron detectors, the calibration frequency is chosen to account for the flux profile change. While it is possible that operation at low power levels for a long period of time would allow the single point comparison and calibration to be performed infrequently, Technical Specification 4.3-1, Functional Unit 2a, requires a compariton of calorimetric to excore power indication above 15% rated thermal power which would correct or account for most of the effects of drift.

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Based on the above discussion, the setpoints for the various reactor

j. trips remain unchanged.' The single point comparisons and calibrations will be 1 4 performed on the bases ~of core burnup and flux profile change. Performing the-

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single point comparison and calibration on the bases of flux profile. change will i provide a surveillance frequency based on the change in parameters that are

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affecting the excore neutron detectors, instead of calendar time.

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An analysis of the proposed change has.been performed in accordance with 10CFR50.91(a)(1) regarding significant hazards considerations using the criteria  !

established ~in 10CFR50.93(c). This analysis has determined thatt i

1. The proposed change does not involve a significant increase in the i probability or consequences of an accident previously evaluated.

The proposed change involves the frequency of the single point comparison and calibration. With the proposed change tra single c ,

point comparison and calibration would be performed on the basis of: l

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l days at effective full power versus calendar days above 15% RTP or.

75%.RTP. EPPD are representative of core burnup and changes in the flux profile, and it is the change in the flux profile that

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primarily effects calibration and dictates when the excore neutron detector single point comparison and calibration should be I L performed. Since this change in frequency is a more accurate

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indication of core burnup and when the comparison and calibration should be performed, the consequences of an accident are not o significantly increased. Therefore, the proposed change does not i involve a significant increase in the probability or consequences I

l4 of an accident previously evaluated.

i l 2. The proposed change does not create the possibility of a new or different kind of accident from any previously evaluated. The only accident possible involves a reactivity anomaly and the resulting

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detection of this anomaly by the excore detectors. The proposed change can not create a reactivity anomaly. The proposed change ,

does not involve a change in any setpoints for the trips generated i l from the excore neutron detectors. This proposal changes the l

frequency of performing the single point comparison and the calibration for the excore detectors. This change will result in -

i. the single point comparison and the calibration boing performed on

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a frequency more closely related to core burnup and the resulting i

flux profile change. The single point comparison and calibration

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should be performed on a frequency determined by the change in flux h profile because the quantity of neutrons detocted is proportional to reactor power and will change with the flux profile change.

L Therefore a reactivity anomaly can be detected with the proposed L change and the proposed change does not create the possibility of c new or different kind of accident.

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3.- The proposed change does not involve a significant reduction in the margin of safety. This proposed change will allow the single point  :

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comparison and the calibration to be performed on a basis of EFPD which is related to core burnup and the change in flux profile..

This will allow the excore. neutron detectors single point comparison and calibration frequency-to be based on the relation to ll core burnup and the change in flux profile which are the effects that actually change the calibration. Basing the surveillance on core burnup is more reflective of the changes occurring and there are no setpoint changes _ associated with.the proposed change.

Therefore the proposed change does not involve a significant reduction in the margin of safety.

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.-The proposed change will allow the surveillance frequency,to be based

,  ; upon the_ change in flux profile and core burnup. The proposed change does not l ' change any:setpoints on a reactor trip and does not involve a hardware change. g, _.

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HL&P has reviewed the proposed' change and determined that there are no significant hazards considerations involved with the proposed changed. ,

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