"JOYO" Special test report; Measurements of flow distribution in the core (2)

Muramatsu, Toshiharu; not registered; Tamura, Seiji*; not registered; not registered

Flowrate seasurement of subassemblies of the reactor core was conducted under zero power and 250C conditions for the final core configuration of MK-I operation (79 fuel core S/A). The purpose of the mesurement is to comfime the change of flow distribution in reactor core due to core volume enlargement, As consequences, (1)Flowlate measurement of Subassemblies under the high flowrate condition of the main loops brought up followings: (i)Flowrates for core fuel assemblies decreased about 6.3% than the 70 fuel S/A core measurement. (ii)Flowrates of inner blanket fuel assemblies increased about 4.0% than the 70 fuel S/A core. (iii)Flowrates of all outer blanket fuel assemblies decreased about 2.5% than the 70 fuel S/A core. (2)All subassemblies flowrate under the low flowrate condition of the main loops was measured lower than the estimated values. (3)The flowrate indication at the center channed increased about 3.0% after 115 hours after steeped in sodium. This change was compasated to evaluate the subassembly flowrate as flowmeter drift.