Analysis of Flow Blockage of a Single Fuel Assembly in the JRR-3 20MW Research Reactor

Abstract

The case of flow blockage of a single fuel assembly in the JRR-3 20MW open-pool-type research reactor is investigated without taking into account the effect of the power regulation system. The coolant system and multi-channel reactor core are modeled in detail using thermal hydraulic system analysis code RELAP5/MOD3.4. MDNBR (Minimum Departure From Nucleate Boiling Ratio) and the maximum fuel central temperature are investigated to assess the integrity of fuels. The fuel plates in blocked assembly are not damaged until the blockage ratio exceeds 70%. In addition, the mitigative effect of the assumed 18 MW lower power emergency shutdown operation on the accident is also discussed qualitatively. Results indicate that although the assumed lower power emergency shutdown operation cannot avoid the most severe operating condition, it can obviously mitigate the consequences of the accident. The reactor eventually remains in the long-term safe state when natural circulation is established.

Effects of U-Mo Irradiation Creep Performance on the Thermo-Mechanical Coupling Behavior in U-Mo/Al Monolithic Fuel Assemblies

“…In the reactor cores, dozens of fuel assemblies will be placed into specified positions, and control rod channels are retained among the fuel assemblies (Wu et al, 2017). The coolant channels exist between the fuel plates to keep the normal coolant flow (Baek et al, 2015;Fan et al, 2016;Guo et al, 2018;Ma et al, 2018), with the fission heat transferred timely (Cheng et al, 2004;Baek et al, 2015;Woolstenhulme et al, 2015). Under the in-service environments, different mechanisms are involved in the deformations of fuel assemblies (Deng et al, 2017), which will result in the variations of control rod channels and coolant channels.…”

Transient Parameter Analysis of Non-scrammed Local Melting Accidents—A VVER 1000 Case Study

“…In blockages beyond 95% of the channel width, the damage is quite severe giving rise to rupture and fuel melting. They emphasize that local flow blockage cannot be diagnosed until significant changes occur in the reactor's major parameters (Guo et al, 2018). Thus, the accidents referred to above can bring about weaknesses to the point of creating initial conditions for severe accidents.…”