Monitoring neutrons from spent reactor fuel by bubble detectors

In order to eliminate the strong temperature-dependence of bubble detectors used for spent fuel assay, a simple way could be to keep them in the water pond but far from fuel assemblies before exposure for about 20 min, until the detectors warm up. Fast neutrons from fuel assemblies in the Paks Nuclear Power Plant, Hungary, were detected by BD-100R type detectors at 28 deg. C (in winter) and at 35 deg. C in summer). Calibration was performed by a standard 252Cf source in borated water. Burnup monitoring inside fuel assemblies can be provided by smaller diameter detectors prepared from BD-100R type ones