ML20137Z507
| ML20137Z507 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/22/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20137Z496 | List: |
| References | |
| NUDOCS 9704240209 | |
| Download: ML20137Z507 (4) | |
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j NUCLEAR REGULATORY COMMISSION 2
WASHINGTON, D.C. 30666 4 001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO THE REVIEW OF TOPICAL REPORT TR-092 i
RELOAD DESIGN AND SETPOINT METHODOLOGY FOR THREE MILE ISLAND NUCLEAR STATION UNIT NO 1 DOCKET NO 50-289 L
1 INTRODUCTION By letter dated February 27, 1996, GPU the licensee for Three Mile Island, Unit 1 (TMI-1) submitted topical report TR-092, Revision 0, "TMI-I Reload Design and Setpoint Methodology (Reference 1)."
The submittal was supplemented by a response to a request for additional information dated October 28, 1996 (Reference 2). This report describes the GPU Nuclear reload design methodology applied to nuclear, thermal-hydraulic and safety analyses, and presents setpoint methodology including safety and acceptance criteria to 2
determine various safety limits, reactor trip setpoints and alarm limits for future TMI-1 fuel cycles.
The major areas of the reload design process are the nuclear design, the core thermal-hydraulic design, maneuvering analysis and setpoint methodology.
1 Within each of these areas the licensee proposes to use various staff approved analytical codes to simulate core loading, transi_nt analysis and the resultant system response. During the staff trip to GPU (Referente 3), the licensee indicated that the proposed GPUN methodology is the same approved j
methodology that was used by B&W, the vendor for previous THI-l reload analyses.
2 EVALUATION The primary goals of the fuel cycle design are to determine (1) the number of fuel assemblies and their enrichments for the feed batch, and (2) an efficient core loading pattern that will meet the energy requirement for the reload.
Using this process the licensee will determine the pattern of the fuel assemblies and the core components in such a manner as to ensure that the power distribution, energy production, fuel burnup and control rod worth acceptance criteria are met.
The GPUN reload analysis uses three analytical codes, CASM0-3/ SIMULATE-3 for nuclear analysis, RETRAN-02 for system transient analysis and VIPRE-02 for core thermal hydraulic analysis. Although these codes have been submitted separately and approved by the staff, GPUN utilizes TR-092 to describes how these three codes will be used in the reload analytical methodology.
9704240209 970422 ENCLOSURE PDR ADOCK 05000289 P
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. 2.1 Codes Review In a letter dated February 21, 1996, the staff approved TR-091
" Steady State Reactor Physics for TMI-1".
This document demonstrated GPU's ability to use CA5MO-3/ SIMULATE-3. The licensee conducted extensive benchmarking using the computer codes CASMO-3/ SIMULATE-3 methodology and performed comparisons between predicted (calcuiated) and measured key physics data.
The results of these comparisons were then used to determine the 95/95 tolerance limits for calculating the pertinent physics parameters, and also demonstrating the ability of the licensee to use the various computer codes for application to i
TMI Unit 1.
The staff reviewed various core physics parameters used in the safety analysis of TMI Unit 1.
The primary core parameters of interest were the integrated 1
radial and planar peaking factors, the moderator temperature Nefficient of reactivity, control element assembly (CEA) rod drop data, irshidual group rod worth, rod ejection data, and CEA scram reactivity worth. Core flux symmetry, incore flux measurement, steamline break cooldown reactivity insertion, power distributions, critical boron and differential boron worth (boron reactivity coefficient), were also reviewed.
The above derived parameters and their associated uncertainties were found to be within the licensee's plant <M eif'c acceptance criteria.
The staff has determined that the ratults of ue revbw are acceptable.
"TMI-1 Core Thermal-Hydraulic Methodology Using the VIPRE-01 Computer Code" was approved by the staff in a letter dated, December 19, 1996. The copical presented the methods for performing steady-state and transieret thermal-hydraulic analyses of the nuclear reactor core for normal operating conditions and several accident conditions.
Specifically, the licensee demonstrated their ability to use VIPRE-01 in conjunction with the BWC correlation to determine the design DUBR limit.
GPU Nuclear Corporation (GPUN) submitted for NRC veview and approval the GPUN topical report TR-0is, Revision 0, "TMI-1 Transient Analyses Using the RETRAN Computer Code," which describes the transienf. analysis methodology it intends to use to perform licensing basis non-loss-of-coolant-accident (non-LOCA) transient and accider.t analyses for the Three Mile Island Unit No.1 (TMI-1) plant.
This topical,et approved by the staff in a letter dated February 10, 1997.
GPUN plant to use RETRAN in conjunction with VIPRE.
In discussing cod? inputs and assumptions, GPUN clarified that the current qualification anplyses and intended licensing analyses apply licensing basis assumptions which limit the scope of the revier. The current TMI-l analytical licensing tuis does not include loss of offsite power in several of the transients analyses, such as steamline break, steam generator tube rupture (SGTR), and locked rotor.
Feedwater line break analyses are not included in the present licensing basis, though GPUN does use RETRAN to perform non-licensing analyses of this event. Additionally, the analytical methods for baron dilution and SGTR events may differ from what would be included in the design basis for a newly licensed plant. The above derived parameters and
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, their associated uncertainties were found to be within the licensee's plant specific acceptance criteria. The staff has determined that the results of the review are acceptable.
At this time, GPUN does not expect to perform safety valve sizing / overpressure protection analyses using RETRAN, as per Standard Review Plan 5.2.2, because the existing design bases remain applicable under present operating conditions.
The scope of staff's review is limited to the present TMI-1 licensing basis; and the analysis would have to be reevaluated should there be any change to the THI-1 licensing basis, as conceivable in the case of a power uprate.
4 2.2 Setpoint Analyses The Technical Specifications (TS) include safety limits, RPS trip setpoints, LC0 alarms, surveillance requirements and design features, and administrative controls that were derived from applicable design evaluations and safety analyses.
The TS generally affected by reload design are the core safety j
limits, RPS trip setpoints, and LC0 alarms.
The licensee demonstrated their ability to successfully generate key setpcints by using Cycle 10 data and results to benchmark the.setpoint analysis. The axial power imbalance core protection safety limits establish the maximum
. allowable overpower as a function of the axial power imbalance for various pump operating conditions. GPUN based the imbalance protective limits on the i
maneuvering analysis for the operating parameter range of 0 to 75 effective i
full power days and 4-pump operation.
In a comparison of the GPUN results with the vendors results, the licensee found good agreement in the determination of the core protective safety limits and the axial power imbalance protective limits.
The plot of the GPUN results of the axial power imbalance protective limits bound both the vendor results and the Cycle 10 COLR values.
GPUN had similar benchmarking results with the LC0 alarm limits - power imbalance alarm limits, control rod index limits and core quadrant power tilt limits and the power / imbalance / flow trip setpoints, which were derived by I
applying the RPS instrument errors to the safety axial power imbalance protective limits.
The GPUN results for the flux / flow event indicated a DNBR slightly higher than the vendor results. However, the impact of this higher limit at the bottom portion of the fuel assembly on the setpoint analysis is insignificant. As illestrated in figure 5.5 of the submittal, the Maximum Allowable Peaking (MAP) limits, are not limiting in the determination of the negative core offset (or axial imbalance) limit, but are limiting for the positive core offset liinit. The GPUN MAP limits for the axial peak will result in a more conservative setpoint than the vendor MAP limits, since GPUN MAP limits are more conservative that those of the vendor in the upper half of the fuel assembly.
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d j i Furthermore, as the licensee indicated in the submittal and subsequent responses to the staff's RAls, the MAP limits are mathematically derived and r
i-require verification.
This verification analysis is a cycle specific analysis, performed during the reload design process by incorporating the i
calculated axial power distribution data directly into VIPRE-01, to determine i
the actual DNBR margin.
The acceptance criteria of this verification is that i
the DNBR results for the verification case are greater than the target DN8R limit.
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3 CONCLUSION f
The staff has reviewed the GPUN reload design process and based on the i
submittal, Reference 1, and the subsequent RAI and site visit, Reference 3, the staff has determined that the GPUN analytical methods acceptable. This l
methodology is acceptable with the limitation that:
I This approval is based on the current licensing basis of TMI-l any change to the current licensing basis requires that this methodology be j
reevaluated for applicability; t
i This approval is based on the use of the codes (CASMO, RETRAN and VIPRE) 1 subject to the limitations stated in the staff safety evaluations, and in the manner described in TR-092, any use beyond these descriptions
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requires reevaluation for applicability.
GPUN completed a setpoint analysis using Cycle 10 data to demonstrate the i
ability to accurately determine the cycle spacific safety limits. The staff reviewed the results' and agree that GPUN w:s able to accurately determine the setpoint values, t
4 REFERENCES i
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1.
Letter from J. Knubel to NRC, "TMI Unit 1 Reload Design and Setpoint Methodology," dated February 27, 1996, i
1 2.
Letter from J. Knubel to NRC, "TMI Unit 1 Response to Request for Additional Information - Core Reload Methodology," dated October 28, 1996.
3.
Memo from A. Attard, S. Brewer, F. Orr to T. Collins, " Trip / Audit / Meeting Summary - TMI-l Reload, VIPRE, and RELAP Methodologies," dated January 14, 1997.
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