Sensitivity Analysis of Transient Critical Heat Flux by RIA Under High-Pressure Flow Boiling Conditions in TRTL

Abstract

A reactivity-initiated accident (RIA) is a design-basis accident under which critical heat flux (CHF) is likely to be exceeded. The operational margin for RIAs is currently determined using steady-state CHF lookup tables, which provide conservative estimates relative to transient CHF phenomena. The Transient Reactor Test Loop (TRTL) facility at Oregon State University is capable of performing out-of-pile rapid heating experiments representative of a RIA at conditions representative of a pressurized water reactor (PWR). To further our understanding of and ability to predict transient CHF under PWR conditions, we performed a sensitivity analysis on a RELAP5-3D model of the TRTL facility coupled to the RAVEN code framework to define a proposed experimental test matrix to be performed at the TRTL facility. We then implemented a flow boiling CHF correlation into RELAP5-3D and performed a secondary sensitivity analysis inspecting the impact of the built-in RELAP5-3D CHF and heat transfer multipliers on both the prediction of CHF and key safety parameters, such as peak cladding temperature and heat flux. The results show that the multiplier with the highest influence toward the prediction of CHF occurrence and the safety parameters is the transient CHF multiplier. Operational performance envelopes have been developed for each of the test matrix cases and will be used for validation once the experiments are performed. The TRTL facility is currently performing shakedown testing to verify system performance prior to proceeding with the experimental campaign. Restart testing results include pump curve restart testing, pressure tests, and heater rod thermocouple transients.

Keywords:

• Transient boiling
• transient critical heat flux
• reactivity-initiated accident
• TRTL
• RELAP5-3D

Acknowledgments

The aid and technical insights of Charlie Folsom (INL), Christina Jones (Framatome), and Colby Jensen (INL) have been essential to the success of this project so far. Additional vital contributions to this work from our group at UTK include those of Quang Phung in developing and testing the RELAP5-3D and TRACE models, Soon Lee in assisting with transient CHF models, and Isabelle Lindsay for additional development of the RELAP5-3D/BISON coupling framework. Further important contributions to this work from the group at OSU include those of Wade Marcum, Jaden Miller, Musa Moussaoui, and Allison Wilson for assisting with shakedown testing activities.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was funded by a U.S. Department of Energy (DOE) Nuclear Energy University Program Project (grant DENE0009213).