Analysis of the start-up test of experimental fast reactor "JOYO"; The analysis of core nuclear characteristics (part-1)

Kawashima, Masatoshi*; not registered; not registered; not registered

This report describes the analysis of core nuclear characteristics of "Joyo" which were measured at the start up test. This report includes the following analyses; (1)Minimum Critical (2)Control Rod Worth (3)Sodium Void Reactivity (4)Fuel Subassembly Worth (5)Reaction Rate Distributions. The calculations were done by using JAERI-FAST-2 set (70 group). One of the purposes of this analysis was to confirm the validity of the 3-D Hex-Z model with diffusion theory. Followings are main results; (1)C/E value for K was 1.0044 in the minimum critical core. (2)C/E values of control rods worth were 0.971.03. (3)The analysis of sodium void effect for single channel showed that the C/E values were 0.81.0 in the core region and 1.3 at the blanket-core boundary with homogeneous model. The diffusion calculations with JFS-2 set showed good agreement between measured and calculated data. (4)The calculated substitution reactivity worth between core S/A and blanket S/A at the core periphery agreed well with the measured ones (C/E = 0.951.05). The calculated substitution worth between Na channel and various S/A's generally overestimated the measured ones. (core fuel Na at the center C/E = 1.1 1.2, blanket fuel Na at 5F1 C/E - 1.31.5) (5)The analyses of the reaction rate traverses were done by the 3-D Hex-Z model with 8 group diffusion theory. C/E values of the central spectral indices for F/F, F/F were 0.99 and 0.95 respectively. It was confirmed that 3D Hex-Z model was very useful to calculate whole core power distributions including the flux-tilt by the control rod insertion.