Delayed gamma power measurement for sodium-cooled fast reactors

Previous works on pressurized water reactors show that the nitrogen 16 activation product can be used to measure thermal power. Power monitoring using a more stable indicator than ex-core neutron measurements is required for operational sodium-cooled fast reactors, in order to improve their economic efficiency at the nominal operating point. The fluorine 20 and neon 23 produced by (n,α) and (n,p) capture in the sodium coolant have this type of convenient characteristic, suitable for power measurements with low build-up effects and a potentially limited temperature, flow rate, burn-up and breeding dependence.This method was tested for the first time during the final tests program of the French Phénix sodium-cooled fast reactor at CEA Marcoule, using the ADONIS gamma pulse analyzer. Despite a non-optimal experimental configuration for this application, the delayed gamma power measurement was pre-validated, and found to provide promising results.

Figure optionsDownload as PowerPoint slideResearch highlights▶ 20F and 23Ne tagging agents are produced by fast neutron flux. ▶ 20F signal has been measured at the SFR Phénix prototype. ▶ A random error of only 3% for an integration time of 2 s could be achieved. ▶ 20F and 23Ne power measurement has a reduced temperature influence. ▶ Burn-up impact could be limited by simultaneous 20F and 23Ne measurement.