Evaluation of Control Rod Interaction Measurement in the Prototype Fast Reactor Monju

For evaluating control rod (CR) interaction, CR worth values with and without the insertion of interaction CRs were measured in six CR interaction patterns by the continuous period method and the compensation method in the prototype fast breeder reactor Monju. The measured CR worth was evaluated in detail by conducting corrections, such as the thermal contraction of CR drive shafts, and compared with calculations to examine the reliability. The calculation-to-experiment values (C/Es) of examined CR worths with and without the interaction were 0.96 to 0.98 ± 0.03. The values of the measured CR interactions were obtained from those examined CR worth measurements as a change in target CR worth by the insertion of interaction CRs: 5.0 ± 0.6% to 10.1 ± 0.1%. The C/Es of the interaction in those cases were 0.78 to 0.93 within 5% to 27% uncertainty. Through this study, the consistency and reliability of the measurements and the calculations of the CR interaction were confirmed, and the measurements were judged useful.