Design of an in-pile device for testing of WCLL double wall tubes

The present paper describes irradiation devices proposed by SCK CEN to test segments of water cooled lithium–lead blankets (WCLL), and in particular their double-wall tubes (DWT), under irradiation in the BR2 reactor. The purpose of the first experiment is to assess the efficiency of a tritium permeation barrier (TPB) coating at the outer surface of the DWT. Hence, two DWT segments are plunged in a lithium–lead pool. The inside of the DWT is flushed by helium and collects the tritium permeating through the wall. One of the DWTs has received a TPB coating, the other not, so that comparative measurements are possible. For the second experiment, a DWT segment is heated by the gamma flux of BR2 and cooled at the inside by pressurised water. Hence, the temperature gradient tends to separate the two tubes. The purpose is to verify how the brazing agent performs at doses up to 3 dpa. The irradiation device is installed inside the central hole of a BR2 fuel element, in order to maximise the fast neutron component of the flux received by the target. As an attractive alternative, the utilisation of the PWR loop Callisto is also proposed.