Use of Zero Power Plutonium Reactor Measurements as a Support of Criticality Prediction for the SNR-300

Evaluations of criticality measurements performed in various SNEAK and Zero Power Plutonium Reactor (ZPPR) cores are compared. The best available methods of calculations (including transport theory) are used. Typical calculation-to-experiment (C/E) ratios for k_eff are as follows:

	SNEAK	ZPPR
For a clean core	1.007	1.009
For a core with control rod followers	1.007	1.008
For a core with absorbers inserted	1.009	1.005

The ZPPR results support well the trend indicated by the SNEAK evaluations for clean cores and for cores with followers; for cores with absorbers partially inserted, the agreement is only rough. Evaluations of control rod worth measurements are therefore also compared, using the routine method of calculation for SNR-300 (diffusion theory). The control rod worths are largely underestimated in SNEAK (C/E = 0.89), but only slightly underestimated in the ZPPR (C/E = 0.97). The difference in the nature of core fuel (uranium in SNEAK, plutonium in the ZPPR) could be at the origin of this discrepancy.