Accelerated tests on gamma compensated boron lined ionisation chamber for reactor safety and control applications

Accelerated tests have been conducted on a gamma compensated boron lined ionization chamber developed for reactor safety and control applications. In this detector, 40.5% enriched 10B has been coated on the electrode using multiple dip coating technique. Polyether ether ketone (PEEK) has been used as insulating spacer instead of alumina ceramic. These detectors have to withstand integrated neutron fluence of 3×1019nvt over a period of 3.8 years. The requirement of detector reliability demands the appropriate choice of materials, coating techniques and detector design. The paper discusses these issues and also selection of accelerated test parameters for long term performance evaluation of the detector. The details of the test results are presented. The accelerated tests were conducted on the neutron chamber at 4×1011nv neutron flux for 10 months at the Radial beam hole position 3001 of Dhruva Research Reactor. A special aluminum assembly with shielding plug was developed for testing the detector at the Beam Hole. The objective of the experiment was to determine the Voltage/Current (V/I) characteristics and the detector linearity response at higher values of neutron flux for required neutron fluence. This experiment also aided in evaluation of new materials used in detector design. During irradiation the performance was monitored periodically. A fall of 10% in signal response was observed due to the burn up of boron. The detector response was measured at reactor shutdown and also at different power levels. The detector linearity response was found to be within 10% and it has successfully withstood the life test.