ML20211N821
| ML20211N821 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 09/03/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20211N819 | List: |
| References | |
| NUDOCS 9909130082 | |
| Download: ML20211N821 (4) | |
Text
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UNITED STATES g
j NUCLEAR REGULATORY COMMISSION n
WASHINGTON, D.C. 30e86 4001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 187 TO FACILITY OPERATING LICENSE NO. DPR-20 CONSUMERS ENERGY COMPANY PAllSADES PLANT DOCKET NO. 50-255 1.0 JNTRODUCTION By letter dated June 17,1998, as supplemented by letters dated June 23 and December 2, 1998, and March 18,1999, the Consumers Energy Company (the licensee) requested an amendment to the Technical Specifications (TSs) appended to Facility Operating License No. DPR-20 for the Palisades Plant. The proposed amendment requested a reduction in the minimum reactor vessel flow rate limiting condition for operation (LCO). Conforming changes to the Bases were also proposed.
The December 2,1998, letter provided additional clarifying information and the March 18,1999, letter requested a 60-day allowance for implementation of the amendment. The additional information and proposed change to the implementation period were within the scope of the original Federal Register notice and did not change the staff's initial proposed no significant hazards consideration determination.
2.0 BACKGROUND
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 percent less than previous venturi-based feedwater flow measurements. Since the reactor vessel flow rate measurement is determined using a primary system calorimetric (solving the equation Q=me,AT for m)', the measured reactor vessel flow rate has also been reduced by 2 percent.
The difference between measured reactor vessel flow rate and the associated TS requirement has been reduced to approximately 1 percent. This is due, primarily, to incorporation of the UFM into the calorimetric power calculation. However, steam generator tube piming levels of 3-4 percent and changes in fuel assembly design have also had small contributions.
The current and proposed TSs read as follows:
'Where Q is the core heat output, m is the core mass flow rate, c,is the coolant specific heat constant, and AT is the increase in reactor coolant temperature across the core, i
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f l Current TS 3.1.1c The measured four primary coolant pumps operating reactor Vessel flow shall be 140.7 x 10' lb/hr or greater, when corrected to i
532 'F.
Proposed TS 3.1.1c The measured four primary coolant pumps operating reactor vessel flow shall be 2 352,000 gpm.
The results of this proposed change will be to (1) reduce the minimum allowable reactor vessel flow rate requirement by approximately 4 percent, and (2) revise the units of the TS requirement from mass flow rate (Ib/hr) to vclumetric flow rate (gpm) for consistency with the flow measurement procedure.
3.0 EVALUATION Because of the small margin between the Palisades measured vessel flow and the TS requirement, a new minimum flow rate is proposed. Also, the units of the new flow rate would be revised from mass flow rate (Ib/hr) to volumetric flow rate (gpm).
The proposed TS minimum reactor vessel flow rate is reduced approximately 4 percent from 140.7 x 10' lb/hr to a new flow rate of 135 x 10 lb/hr at 532 *F. This corresponds respectively 8
to a change in volumetric flow rate from 366,623 gpm to 352,000 gpm at 532 *F. When adjusted for a 3 percent flow measurement uncertainty, this corresponds to the analytical limit of 341,400 gpm.
The licensee stated that each of the applicable Palisades Final Safety Analysis Report (FSAR)
Chapter 14 events were re-evaluated incorporating the new minimum flow rate. The licensee examined each event for the impact of changes for the cycle. Each event was assigned to one of the four following categories:
(1)
The event is not a part of the plant licensing basis and no analysis is required.
(2)
The factors which determine the sequence of events and consequences of the event are either unchanged or bounded by the existing analysis and no analysis is required.
(3)
The consequences of the event are bounded by another event with the same or more demanding acceptance criteria and no analysis is required.
(4)
The factors wb;ch determine the sequence of events and consequences of the event are changed in such a manner that the existing analysis is no longer bounding and a new analysis is required.
The minimum departure from nucleate boiling ratio (MDNBR) was recalculated for all limiting events using a reduced primary flow, since they fall in category 4 above. Hydraulic compatibility and melt limits were evaluated and found to be unaffected by the reduced flow. The trip setpoint
3-confirmation for Cycle 14 was reviewed and margin was demonstrated for the TM/LP trip and the T. LCO.
A listing entitled " Standard Review Plan Events Reanalyzed or Dispositioned with Revised Reactor Vessel Flow Rate" was provided in Attachment 3 of the June 17,1998, letter. The licensee indicated that the 4 percent reduction in reactor vessel flow rate was incorporated in the re-evaluation or reanalysis of the listed items. The licensee provided a correlation between the Standard Review Plan (SRP) listed items and the corresponding FSAR items.
The licensee stated that all Palisades FSAR Chapter 14 events were analyzed or dispositioned using (1) approved codes and methodologies and (2) appropriate conservative inputs consistent with the applicable approved methodologies. Details of these analyses were provided in the Siemens Power Corporation reports EMF-98-013. " Palisades Cycle 14:
Disposition and Analysis of Standard Review Plan Chapter 15 Events," and EMF-98-042,
" Palisades Cycle 14: Disposition and Analysis of Standard Review Plan Chapter 15 Events for Reduced Primary Coolant Flow." These reports were provided by the licensee in its June 23 and December 2,1998, submittals.
The large and small break loss-of-coolant accident (LOCA) reanalyses were examined by the licensee for the effect of the proposed reduction in minimum primary coolant system flow rate.
The licensee stated that this will cause the Tm temperature to increase by at most 1 - 2 *F. A small change in this value is within a typical uncertainty range and does not represent a significant change to the overall LOCA mass and energy and accompanying containment pressure / temperature response.
The licensee reported in a June 1,1998, letter that a reanalysis of the large break LOCA for fuel Cycle 14 resulted in a new peak clad temperature (PCT) of 1869 *F. This is a 23 'F drop in calculated PCT between Cycle 13 and Cycle 14. This change was due primarily to revised core fuel design (pellet diameter and clad thickness) and neutronics values (radial peaking factors), which were used to reflect the Cycle 14 core design and reload "R" fuel. The results of confirmatory calculations for Cycle 14 indicate that when the RELAP4 model is corrected for excessive variability, the predicted PCT will be lower by about 70 'F. This is greater than 50
- F, which constitutes a significant change in accordance with Section 50.46 of Title 10 of the Code of Federal Regulations (10 CFR 50.46). However, the resulting changes in the PCT for i
fuel Cycles 13 and 14 will be in the conservative direction and are acceptable.
The licensee reported that the reanalysis for the small break LOCA resulted in a new PCT of 2,025.8 *F. This is acceptable in accordance with 10 CFR 50.46.
The limiting MDNBR event was found to be the Single Rod Withdrawal event for which the MDNBR value is 1.17. This is an acceptable value as it is equal to or greater than the MDNBR correlation limit of 1.164. The limiting pressure event was found to be the Loss of External Load event for which the pressure is 2,614.9 psia. This is acceptable as it is less than 110 percent of the design limit of 2,500 psia, which is equoi to 2,750 psia.
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7 The results of the reanalyses showed that the reduction of the assumed minimum reactor vessel flow rate did not result in:
(1) unacceptable values in peak clad temperature in the results of the Loss Of Coolant Accident Emergency Core Cooling System analyses for the large and small break LOCAs (2) penetration of TS DNB limits or additional fuel failures for non-LOCA events (3) exceeding the pressure limits (4) a change in the results of the LOCA or Main Steamline Break containment response analyses (5) a change to the radiological consequences of the SRP events with respect to 10 CFR Part 100 offsite dose or SRP 6.4 control room habitability requirements As a result of the above evaluation, the reanalyses were found to be acceptable. Therefore, the staff finds the proposed reduction of the minimum reactor vessel flow rate to be acceptable.
4.0 STATE CONSULTATION
in accordance with the Commission's regulations, the Michigan State official was notified of the proposed issuance of the amendment. The Michigan State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding (63 FR 36271). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
6.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: H. Balukjian 1
Date: September 3, 1999 l
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