Transient experiments on fast reactor core thermal-hydraulics and its numerical analysis Inter-subassembly heat transfer and inter-wrapper flow undernatural circulation conditions
M. Nishimura et al., Transient experiments on fast reactor core thermal-hydraulics and its numerical analysis Inter-subassembly heat transfer and inter-wrapper flow undernatural circulation conditions, NUCL ENG DE, 200(1-2), 2000, pp. 157-175
Sodium experiments were conducted on core thermal-hydraulics simulating a s
cram transient of a large scale fast breeder reactor using the test facilit
y PLANDTL-DHX with seven fuel subassemblies. The influence of inter-subasse
mbly heat transfer on temperature distribution in the subassembly was revea
led via measurements. The flow in the gap between neighboring subassemblies
called inter-wrapper flow (IWF) was also studied in relation to its capabi
lity of cooling the subassemblies. A computational model is presented for p
redicting the transient without IWF. The multi-dimensional numerical analys
is model employs an empirical correlation to simulate mixing effects betwee
n adjacent subchannels. It was shown that the present computational method
could evaluate the transient behavior of thermal-hydraulics in the subassem
blies accurately from forced to natural circulation accompanied by inter-su
bassembly heat transfer and flow redistribution in the subassembly. The coo
ling effects of IWF on the fuel subassemblies were found in spite of natura
l circulation flow reduction in the primary loop attributable to temperatur
e decreases in the upper non-heated section in the core. The inter-wrapper
flow can effectively cool the core under extreme conditions of low flow rat
es through the core. (C) 2000 Elsevier Science S.A. All rights reserved.