ML18066A198

Application for Amend to License DPR-20,updating TS to Reflect Reduced Min Reactor Vessel Flow Rate Assumption in Accident Analyses

ML18066A198
Person / Time
Site:	Palisades
Issue date:	06/17/1998
From:	Haskell N CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML18066A199	List: ML18066A198 ML18066A201
References
NUDOCS 9806230096
Download: ML18066A198 (8)

Text

A CMS Energy Company Palisades Nuclear Plant Tel: 616 164 2216 21780 Blue Star Memorial Highway Fax: 616 764 2490 Covert, Ml 49043 Nathan L. Haskell Director, Licensing June 17, 1998 U S Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT TECHNICAL SPECIFICATIONS CHANGE REQUEST - PRIMARY COOLANT SYSTEM FLOW A request for a change to the Palisades Technical Specifications (TS), which revises the reactor vessel flow rate requirement, LCO 3.1.lc, is enclosed.

This change is desired to update the TS to reflect a reduced minimum reactor vessel flow rate assumption in the accident analyses.

Palisades primary coolant flow rate was initially determined to be 140 x 10 6 lb/hr during post core loading hot functional testing in 1971. During subsequent operation, steam generator tube plugging necessitated TS amendments to the minimum flow rate requirement. In 1988, the minimum flow rate requirement was reduced to its lowest value of 124.3 x 10 6 lb/hr by Amendment 118. Following steam generator replacement in 1991, the minimum flow rate requirement was raised to the current value of 140.7 x 10 6 lb/hr by Amendment 137.

In September of 1997, Palisades installed ultra-sonic flow measurement (UFM) devices on the steam generator feedwater piping and incorporated use of them into the secondary system calorimetric-based reactor power calculation.

Calorimetric heat balance calculations since installation of UFM indicate that actual reactor power was approximately 2% less than previous venturi-based feedwater flow measurements. Since the vessel flow rate measurement relies on measured reactor power, the use of the more accurate secondary flow measurements has resulted in a corresponding reduction in measured reactor vessel flow rate. The difference between measured reactor vessel flow rate and the associated TS requirement has been reduced to approxim_ately 1%. This

- - - - - - - - r 9806230096 980617 j~*t) ;,

PDR AoocK osooo255 p PDR 1

r\ uiv I

2 is due, primarily, to incorporation of the UFM into the calorimetric power calculation, however, steam generator tube plugging levels of 3-4% and changes in fuel assembly design have also had small contributions.

Because of the small difference between measured vessel flow and the TS requirement, applicable FSAR Chapter 14 events have been re-analyzed incorporating a new minimum flow. The proposed TS minimum reactor vessel flow requirement is 352,000 gpm (135 x 10 6 lb/hr at 532°F - a 4% reduction), which corresponds to the analytical limit of 341,400 gpm when adjusted for flow measurement uncertainty. The utilization of the proposed minimum reactor vessel flow rate in the accident analyses serves as the basis for this TS change request.

The proposed change would revise TS 3.3.lc: 11 The measured four primary coolant pumps operating reactor vessel flow shall be 140.7 x 10 6 lb/hr or greater, when corrected to 532°F. 11 to state: 11 The measured four primary coolant pumps operating reactor vessel flow shall be ~ 352,000 gpm. 11 The results of this proposed change will be to: 1) reduce the minimum allowable reactor vessel flow rate requirement by approximately 4%, and 2) revise the units of the TS requirement from mass flow rate (lb/hr) to volumetric flow rate (gpm) for consistency with the flow measurement procedure.

It is requested that the license amendment associated with this change request be effective upon approval. A copy of this letter has been sent to the appropriate official of the State of Michigan.

SUMMARY

OF COMMITMENTS This letter establishes no new commitments and makes no revisions to existing commitments.

Fi\AllllIUIJI ~

Administrator, Region III, USNRC Project Manager, NRR, USNRC NRC Resident Inspector - Palisades Dennis R. Hahn, Michigan Department of Environmental Quality Enclosures

ENCLOSURE CONSUMERS ENERGY COMPANY PALISADES PLANT DOCKET 50-255 TECHNICAL SPECIFICATIONS CHANGE REQUEST PRIMARY COOLANT SYSTEM FLOW

e e CONSUMERS POWER COMPANY Docket 50-255 Technical Specifications Change Request License DPR-20 It is requested that the Tethnical Specifications contained in the Facility Operating License DPR-20, Docket 50-255, for the Palisades Plant be changed as described below. to this change request contains the proposed TS pages. The changed areas are marked with a vertical line in the margin. Attachment 2 contains the current TS and Bases pages marked to show the proposed changes.

These pages show shading for proposed additions and a line drawn through deleted text. Attachment 3 contains a list of those Standard Review Plan (SRP) events which have been reanalyzed using the reduced reactor vessel flow rate. The proposed changes are described below.

I. The following Changes are Proposed:

It is proposed that TS 3.1.lc be revised as follows:

Currently TS 3.1.lc states:

The measured four primary coolant pumps operating reactor vessel flow shall be 140.7 x 106 lb/hr or greater, when corrected to 532°F.

It is proposed that TS 3.1.lc be revised to state:_

The measured four primary coolant pumps operating reactor vessel flow shall be ~ 352,000 gpm.

The bases have been revised accordingly.

II. Discussion of Changes:

The results of this proposed change would be to:

1) Reduce the minimum allowable reactor vessel mass flow rate requirement from 140.7 x 10 6 lb/hr (which corresponds to a volumetric flow rate of 366,623 gpm at 532°F) by approximately 4%.

The proposed flow limit is 96% of 366,623 gpm rounded up to the nearest thousand gpm, and corresponds to approximately 135 x 10 6 lb/hr at 532°F.

2) Revise the units of the vessel flow requirement from a mass flow rate (lb/hr) to a volumetric flow rate (gpm).

This change is desired to update the TS to reflect a lower minimum reactor vessel flow rate assumption in the accident analyses. The change from a requirement expressed in mass flow rate (lb/hr) to one expressed in volumetric flow rate will eliminate the need to correct for specific PCS operating conditions. The words "when corrected to 532°F" have, therefore, been omitted.

2

!he i~itial Palisades post core loading flow testing resulted in a measured primary coolant volumetric flow rate of 376,000 gpm (140 x 106 lb/hr when corrected to 555°F). During subsequent operation, steam generator tube plugging necessitated TS amendments to the reactor vessel flow rate requirement. On November 23, 1988, the TS required reactor vessel flow was reduced to its lowest value of "124.3 x 106 lb/hr or greater, when corrected to 532°F" by TS Amendment 118.

Following Steam Generator Replacement (SGRP) in 1991, the TS reactor vessel flow rate requirement was raised to "140.7 x 106 lb/hr or greater, when corrected to 532°F" by Amendment 137. The*equivalent volumetric flow rate is 366,623 gpm. That TS flow requirement was based on calculations performed by Consumers and ABB/CE which predicted that the actual reactor vessel flow rate would be 146.6 x 106 lb/hr at 532°F. Those calculations assumed no S/G tube plugging and correspond to a volumetric flow rate of approximately 382,000 gpm.

Reactor vessel flow rate measurements subsequent to SGRP and prior to September 1997 range between 376,000 and 381,000 gpm. These venturi-based measurements were consistent with both the original 1971 flow measurements and the SGRP calculations, and indicate a difference of approximately 3% between measured flow and the TS flow limit. The variability in the measurements is roughly 5,000 gpm (-1.4%) and is well within the 3% reactor vessel flow measurement uncertainty assumed by the accident analyses.

In September of *1997, Palisades installed ultra-sonic flow measurement (UFM) devices on the steam generator feedwater piping and incorporated use of them into the secondary heat balance based reactor power calculation. Calorimetric heat balance calculations since installation of UFM indicate, due to a reduction in the instrument error allowance necessary when using venturi-based flow measurements, that actual reactor power was approximately 2% less than previously thought. Since the reactor vessel flow rate measurement is determined using a primary system calorimetric (solving the equation Q=rhcP~T for rh), the measured vessel flow rate has also been reduced by 2%. The difference between measured reactor vessel flow rate and the TS minimum limit has reduced to approximately 1%. This reduction is due primarily to incorporation of the UFM flow measurement into the heat balance power calculation, however, actual steam generator tube plugging levels of 3-4% and changes in fuel assembly spacer grid and lower tie plate design have also had small contributions.

Because of the reduction in the difference between measured vessel flow and the TS minimum limit, applicable SRP events have been re-analyzed incorporating a new TS minimum flow limit which is approximately 4% less than the previous limit. The proposed TS minimum reactor vessel flow requirement is 352,000 gpm (135 x 106 lb/hr at 532°F - a 4% reduction from 366,623 gpm),

which corresponds to the safety analyses analytical limit of 341,400 gpm when adjusted by 3% to account for flow measurement uncertainty. For those calculations which utilize a minimum core flow rate, the analytical limit is reduced by an additional 3% to account for core bypass, to 331,200 gpm.

3 Reducing the assumed minimum reactor vessel flow did not result in a

'significant change (per 10 CFR 50.46) in the results of the Loss Of Coolant Accident (LOCA) Emergency Core Cooling System (ECCS) analyses. Reducing the assumed minimum reactor vessel flow did not result in penetration of TS DNB limits or additional fuel failures for non-LOCA events. Reducing the assumed minimum reactor vessel flow did not result in a change in the results of the LOCA or Main Steam Line Break containment response analyses. Reducing the assumed minimum reactor vessel flow did not result in a change to the radiological consequences of the SRP events with respect to 10 CFR 100 offsite dose or SRP 6.4 control room habitability requirements. The revised accident analysis minimum reactor vessel flow rates are the basis for this TS change request.

III. Analysis of No Significant Hazards Consideration

a. Involve a significant increase in the probability or consequences of an accident previously evaluated.

The proposed change to the minimum reactor vessel flow does not alter the assumed initiators to any analyzed event. Rather, specification of a minimum reactor vessel flow provides assurance that sufficient cooling will take place during normal and accident operating conditions of the reactor.

Therefore the probability of an accident previously evaluated has not been increased by this proposed change.

Each of the applicable Palisades FSAR Chapter 14 accident analyses have been evaluated with respect to the proposed reduction in minimum reactor vessel flow rate. The results of these analyses, which have been incorporated into the Palisades Cycle 14 Disposition and Analysis of Standard Review Plan (SRP) Events, demonstrate that the acceptance criteria for each of the events continues to be met.

Therefore, operation of the facility in accordance with the proposed change to TS section 3.1.lc would not involve a significant increase in the probability or consequences of an accident previously evaluated.

b. Create the possibility of a new or different kind of accident from any previously evaluated.

The proposed changes provide a reduced requirement for PCS flow through the reactor vessel than currently exists in the TS. The change does not, however, involve any alteration in the plant configuration (no new or different type of equipment will be installed) or make changes in the methods governing normal plant operation. However, these changes are consistent with the assumptions in the safety analyses and licensing basis.

Therefore, the changes do not create the possibility of a new or different kind of accident from any accident previously evaluated.

Therefore, operation of the facility in accordance with the proposed change to TS section 3.1.lc would not create the possibility of a new or different kind of accident from any previously evaluated.

4

c. Involve a significant reduction in a margin of safety.

The proposed change to the minimum reactor vessel flow has been evaluated

,against each of the applicable Palisades FSAR Chapter 14 accident analyses.

Reducing the assumed minimum reactor vessel flow did not result in a significant change (per 10 CFR 50.46) in the results of the Loss Of Coolant Accident (LOCA) Emergency Core Cooling System (ECCS) analyses. Reducing the assumed minimum reactor vessel flow did not result in penetration of TS DNB limits or additional fuel failures for non-LOCA events. Reducing the

. assumed minimum reactor vessel flow did. not result in a change in the results of the LOCA or Main Steam Line Break containment response analyses.

Reducing the assumed minimum reactor vessel flow did not result in a change to the radiological consequences of the SRP events with respect to 10 CFR 100 offsite dose or SRP 6.4 control room habitability requirements.

Therefore, operation of the facility in accordance with the proposed change to TS 3.1.lc does not involve a significant reduction in the margin of safety.

III. Conclusion The Palisades Plant Review Committee has reviewed this TS Change Request and has determined that proposing this change does not involve an unreviewed safety question. Further, the change involves no significant hazards consideration. This change has been reviewed by the Nuclear Performance Assessment Department.

CONSUMERS ENERGY COMPANY TECHNICAL SPECIFICATIONS CHANGE REQUEST To the best of my knowledge, the content of this Technical Specifications change request, which revises the minimum allowable Primary Coolant System flow through the reactor vessel, is truthful and complete.

Licensing Sworn and subscribed to before me this /7tll, day of ~l~ 1998.

~'M-~

Alora M. Davis, Notary Public Berrien County, Michigan (Acting in Van Buren County, Michigan)

My commission expires August 26, 1999

,.,* :. *~ ' I

'~. '*'1 1*1_

' '.