ML20207G497
| ML20207G497 | |
| Person / Time | |
|---|---|
| Issue date: | 06/08/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20207G482 | List: |
| References | |
| NUDOCS 9906110187 | |
| Download: ML20207G497 (3) | |
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UNITED STATES j
NUCLEAR REGULATORY COMMISSION t
WASHINGTON, D.C. 20665-4001
'+9.....,o Attachment SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO MODIFICATIONS TO TOPICAL REPORT CENPD-266-P-A THE ROCS & DIT COMPUTER CODES FOR NUCLEAR DESIGN ABB-COMBUSTION ENGINEERING NUCLEAR POWER
1.0 INTRODUCTION
in a letter of March 11,1999 (LD-99-016), ABB Combustion Engineering Nuclear Power (ABB-CENP) requested approval of modifications made relative to the DlT computer code. These specific modifications are described in Enclosure 1-P to the referenced letter, " Application of a DIT Cross Section Library Based on ENDF/B-VI," and include the generation of a new fine-group DIT neutron cross section library based on data from ENDF/B-VI as well as a change in the number of fine-mesh groups employed and in the number of isotopes explicitly modeled.
2.0 EVALUATION The NRC review of topical report CENPD-266-P, "The ROCS & DIT Computer Codes for Nuclear Design," was based on the use of neutron cross section data from ENDF/B-IV, as specifically stated in the Safety Evaluation Report (SER). Therefore, the staff has reviewed the proposed changes which would allow use of a newer version of the ENDF data based on ENDF/B-VI.
The use of ENDF/B-VI offers severalimprovements in PWR applications. These include:
1)
The use of new and significant!y different measured data in the energy dependence of the thermal U-235 nu-fission / absorption ratio 2)
A reevaluation of the epithermal U-238 capture to fission ratio 3)
New and revised evaluations for actinides 4)
New and revised evaluations of fission product data 5)
Comprehensive fission yield and decay data 6) improved Pu-239 data Our review focused on the comparisons of biases and uncertainties in reactivity, moderator temperature coefficient, power coefficient, Doppler coefficient, boron worth, control rod shutdown worth, and dropped and ejected control rod worth, based on ROCS calculations with 9906110187 990608 PDR TOPRP EMVC-E C
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DIT cross sections generated from ENDF/B-IV data and from ENDF/8-VI data. The I-comparisons included data for plants containing fuel assemblies with both 14x14 and 16x16 fuel rod arrays. In general, the uncertainties are consistent between the two calculations. The
~ ENDF/B-VI biases are generally smaller than those reported for the ENDF/B-IV based library due largely to the improvements in the ENDF/B-VI data, the increased parameter data base and the increase in the number of fine-mesh groups employea in DlT from 85 to 89.
Based on these comparisons, we conclude that the use of the ENDF/B-VI library for the generation of DIT cross sections is adequate for licensing work for Combustion Engineering I
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PWR plants.
3.0 CONCLUSION
We have reviewed the proposed use of data from ENDF/B-VI for the generation of DIT neutron cross sections presented in enclosure 3 to LD-99-016. Based on our review, we conclude that the ENDF/B-VI library is adequate for licensing work for Combustion Engineering PWR plants.
These cross sections can be utilized in the ROCS code as well as in the HERMITE space-time code, the MC fine-mesh code, and supporting boundary condition constant processing codes.
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- ABB-Combustion Engineering,Inc.
cc:
Mr. Charles B. Brinkman, Director -
Washington Operations ABB-Combustion Engineering, Inc.
1 12300 Twinbrook Parkway, Suite 330 Rockville, Maryland 20852 Mr. Ian C. Rickard, Director Nuclear Licensing ABB-Combustion Engineering, Inc.
Post Office Box 500 2000 Day Hill Road Windsor, Connecticut 06095-0500
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