Impact of nuclear data libraries for criticality calculation of HTGR

This work examines how variations among evaluated nuclear data libraries affect criticality calculation for High-Temperature Gas-cooled Reactors (HTGR). Accurate nuclear data is essential for reactor safety analysis. However, previous studies have reported significant differences in calculated keff for HTGR systems when different nuclear data libraries are employed. This discrepancy can be attributed to a lack of applicable benchmark experiments for biasing the nuclear data for HTGR. To assist nuclear data evaluators in improving the accuracy of nuclear data, this thesis quantifies the reaction channels, isotopes, and energy range that have the largest contribution towards uncertainty in keff. It is also important to quantify the Δk caused by differences in nuclear data between nuclear libraries by specific reaction channels and isotopes. This research is based on the High Temperature engineering Test Reactor (HTTR) and HTR-10 reactor models. Serpent 2 was used to calculate criticality and its uncertainty due to nuclear data, using data from evaluated nuclear data libraries ENDF/B-VIII.1 and JENDL-5. Uncertainty quantification demonstrates that for both HTTR and HTR-10, keff uncertainty due to ENDF/B-VIII.1 data is larger than uncertainty due to JENDL-5 data because of larger thermal covariance of U-235 ̅_ data in ENDF/B-VIII.1. In addition, HTR-10 uncertainty is larger than HTTR uncertainty for both libraries. This could be attributed to smaller fuel volume ratio in the active core (V_fule/V_active core) of the HTR-10, therefore softer spectrum, causing its criticality to be more sensitive to C-12 capture and elastic scattering cross section. For criticality calculations, using JENDL-5 instead of ENDF/B-VIII.1 leads to a Δk≈−200 pcm for the HTTR and a Δk≈−360 pcm for HTR-10. The most significant contributors are the C-12 capture cross section, C-12 elastic scattering cross section, and angular distribution of C-12 elastic scattering. For the HTTR, compared with the nominal case (all ENDF/B-VIII.1), using C-12 capture cross section data from JENDL-5 causes Δk≈−180 pcm. The difference in thermal region dominates criticality variation for the C-12 capture cross section. For the C-12 elastic scattering cross section, Δk≈−140 pcm. For the C-12 elastic scattering angular distribution, Δk≈150 pcm. The fast region dominates criticality variation for both the C-12 elastic scattering cross section and its angular distribution. For the HTR-10, the C-12 capture cross section causes Δk≈−200 pcm. For the C-12 elastic scattering cross section, Δk≈−320 pcm. For the C-12 elastic scattering angular distribution, Δk≈320.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Nuclear, Plasma, Radiolgc Engr

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Wen, Runxia

Contributors dc:contributor

• Kozlowski, Tomasz
• Huff, Kathryn

• Uncertainty analysis
• Serpent 2
• HTGR
• HTR-10
• HTTR
• ENDF/B-VIII.1
• JENDL-5

Statement dc:rights

• Copyright 2025 Runxia Wen

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/132601

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/132601