ML062650232
| ML062650232 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 03/22/1986 |
| From: | Lainas G Office of Nuclear Reactor Regulation |
| To: | Charnley J General Electric Co |
| Byrdsong A T | |
| References | |
| 50-271-OLA, Entergy-Staff-18, RAS 12305 | |
| Download: ML062650232 (4) | |
Text
.1 GtSTAR HI NEDE-2401 I-P-A-1 L-US 19 03O5 UNITED STATES NUCLEAR REGULATORY COMMISSION Washington, D. C. 20555 March 22,1986 MFN 029-086 Ms.J.S. Charnley Fuel Licensing Manager General Electric Company 175 Curtner Avenue SanJose, California 95125 Dear Ms. Chamley.
(i )
DOCKET NUMBER PROD. & UTIL FAC, 50- 7/-0L4 SUBJECFr:
Acceptance For Referencing Of licensing Topical Report NEDE-2401 1-P-A, "GE Generic Licensing Reload Report," Supplement To Amendment II We have completed our review of the subject topical report submitted by General Electric Company by letter dated October 9, 1985.
We find the report to be acceptable for referencing in license applications to the extent specified and under the limitations delineated in the report and the associated NRC evaluation, which is enclosed. The evaluation defines the basis for acceptance of the report.
We do not intend to repeat our review of the matters described in the report and found acceptable when the report appears as a reference in license applications, except to assure that the material presented is applicable to the specific plant involved. Our acceptance applies only to the matters described in the report.
In accordance with procedures established in NUREG-0390, it is requested that GE publish accepted versions of this report, proprietary and non-proprietary, within three months of receipt of this letter. The accepted versions shall incorporate this letter and the enclosed evaluation between the tide page and the abstract. The accepted versions shall include an -A (designating accepted) following the report identification symbol.
Should our criteria or regulations change such that our conclusions as to the acceptability of the report are Invalidated, GE and/or the applicants referencing the topical report will be expected to revise and resubmit their respective documentation, or submitjustification for the continued effective applicability of the topical report without revision of their respective documentation.
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NWD.-Y401J I-P-A-I l-US SAFETY EVALUATION REPORT FOR AMENDMENT 11 TO NEDE-24011 By letter from Cecil 0. Thomas (NRC) to Ms.J.S. Chariley (GE) dated November 5, 1985, the Nuclear Regulatory Commission found Amendment 11 to NEDE-24011 acceptable for referencing in license applications with qualifications. In particular, the evaluation noted:
Amendment 11 also revised the manner in which code uncertainties are handled in obtaining the Option A and Option B MCPR operating limits.
However insufficientjustification has been provided for this change and we conclude that the currently used treatment of uncertainties must continue to be used. This has been discussed with GE and they concur in this condition to the staff approval of this amendment.
General Electric provided supplementary information which supports the proposed method of treating unertainties in letterjSC-065-85 fromJ.S. Charnley to C.O. Thomas dated October 9,1985.
The October 9 letter was revised injSC-005-86 fromJ.S. Charnley to H.N. Berkow datedJanuary 16, 1986. The new application methodology is for the GEMINI/ODYN transient analysis methodology.
- The proposed approach is similar to the previously approved GENESIS/ODYN methodology. The revised amendment 11 describes the derhiation of statistical adjustment factors to be applied to GEMINI/ODYN results to determine plant operating limits for BWR/4 and BWR/5 plants operating without recirculation pump trip. Factors for other types of plants will be provided in future reports.
Background (GENESIS/ODYN Application)
The current licensing basis approved with the GENESIS/ODYN models for calculating the CPR for pressurization events is performed in accordance with either or both of two methods known as Option A and Option B. These currently used options are summarized below:
Option A This approach is comprised of the two-step calculation which follows:
- 1.
The pressurization transient is analyzed using the GENESIS/ODYN models to obtain the change in the criticil power ratio (ACPR) for the core. The initial CPR (ICPR&) is then determined such that ICPRC minus &CPR equals the MCPR Fuel Cladding Integrity Safety Limit. Coniernative input parameters are used in the analysis, e.g. the scram speed is per technical specifications, and a conservative Haling power shape, as well as other maximum equipment specifications, is used.
- 2.
The licensing basis ICPR is given as:
ICPR Licensing Basis = 1.044 ICPRc where ICPRk = value of ICPR calculated using GENESIS/ODYN models, i.e. ICPR = ACPR + MCPR Safety Limit
.Option B This procedure provides for a statistical determination of the pressurization transient ACPR/1CPR such that there is a 95% probability with 95% confidence (95/95) that the event will not cause the US.C-207
GES TAR fl NEDE-2401 1-P-A-I I-US critical power ratio to fall below the MCPR Fuel Cladding Integrity Safety Limit. This approach can be satisfied in one of two ways:
- 1.
A plant-speoific statistical analysis can be performed per the approved statistical methodology procedures to determine the 95/95 ACPR/ICPR; or
- 2.
Generic ACPR/ICPR statistical adjustment factors (SAF) for groupings of similar type plants can be applied to plant-specific calculations to derive the 95/95 ACPR/ICPR value. This procedure is characterized by the following expression:
(ACPR)
(4CPR c ICPR )95/95
where ( I-'RCP
= ACPR/ICPR calculated for the pressurization event per the assumptions of Step I in Option A By substituting into the above expression the relationship:
ACPR95/ 95 - ICPR95/93 MCPR Safety Limit, it follows that the (ICFR) 95/ 95 is determined from the following expression:
9 MCPR Safety Limit PR9S/9 -c This statistical Option B uses a GENESIS/ODYN model uncertainty of 37% of ACPR/ICPR at the 2c level to determine the 95/95 ICPR. This uncertainty was determined by the staff when the GENESIS/ODYN model predictions were compared to the full scale turbine trip qualification data.
Utilities using Option B must demonstrate that their plant's scram speed distribution is consistent with that used in the statistical analysis. This is accomplished through an approved technical specification which consists of testing at the 5% significance level and allows adjustment of the operating limit MCPR if the scram speed is outside the assumed distribution.
GEMINI/ODYN Application The GEMINI/ODYN set ofnmethods has been compared against actual test data. The results of the comparison indicate an improvement in prediction accuracy with GEMINI/ODYN. The true 95/95 ACPR/ICPRwill be determined using the same fundamental approach established for the current GENESIS/ODYN Option B and accounting for the improvement in prediction accuracy. The resulting procedure, which will be used with the GEMINI/ODYN models, simplifies the current two option approach (Option A and Option B) into one. The GEMINI/ODYN licensing bases are discussed in the following sections.
Licensing Analysis Licensing analyses accomplised with the GEMINI/ODYN models will permit plants to operate under a single set of MCPR limits if scram speed compliance procedures identical to those in current plant Technical Specifications are followed. If scram speed compliance is not demonstrated, more conseivative MCPR operating limits must be met. The licensing analysis with the GEMINI/ODYN models will be calculated in a similar manner as with the GENESIS/ODYN US.C-208
1"
-'T vw models. The statistical determination of the transient ACPR/ICPR adjustment factor for the pressurization event will continue to assure a 95% probability with 95% confidence that the critical power will not fall below the MCPR Fuel Cladding Integrity Safety Limit. The ODYN model uncertainty used in statistical analysis will be revised from the 57% ACPR/ICPR used for the GENESIS/ODYN methods to a value to reflect the improved accuracy of the GEMINI/ODYN set of methods demonstrated by comparison to data.
GEM*NI/ODYN Technical Specification Limits The technical specification limit will be determined from the following general equation:
OLMCPRTcch Spec = OLPMCPR9 5,95 + A-B (AOLMCPR) where &OLMCPR = factors derived by the new methodology and OLMCPR95 /9 5 =ACPRg 9/95 + MCPR Safety limit.
The definitions of tA, rB and tave remain the same as those currently appearing in Technical Specifications. for plants that demonstrate scram speed compliance (i.e. Tave < -rB) using the NRC approved procedures, the Technical Specification limit becomes:
OLMCPRTech Spc = OLMCPR95/95 (for ra,: _ iB.)
If scram speed compliance is not demonstrated by a plant (i.e. tav,, > TB) or if a plant chooses not to perform the scram speed compliance procedures (i.e. T,,, = rA), then a more conservative operating limit must be used.
The cycle-specific reload submittal will contain results for both the case where scram speed compliance is demonstrated (;ave:
B, OLMCPRTech Spec = OLMCPR9,*J/95), and for the case where xave = -A (OLMCPRTch Sp= = OLMCPR95/ 95 + AOLMCPR).
As is the case today, the actual operating limitwill be a straight-line interpolation between these two values dependent on the results of'scram speed testing. We have reviewed the new methodology to be used with the GEMINI/ODYN codes and find it to be acceptable.
General Electric also requested approval for use of the statistical methodology for GEMINI/ODYN with GENESIS/ODYN. Because the GENESIS/ODYN methodology is more conservative than the GEMINI/ODYN methodology, we find this application to also be acceptable. In addition, continued use of the GENESIS/ODYN methodology and its statistical factors is also acceptable.
US.C-209