OSIRIS REACTOR - Centre de Cadarache - CEA

MORE ABOUT IRRADIATIONNUCLEAR ENERGY AUTHORITY ••• CEA33Damage dosimetryDamage dosimetry is designed to experimentally evaluate the fluence of damage, or the displacement per atom (dpa),of irradiated materials. It requires detectors such as G.A.M.I.N dosimeter, comprising a graphite rod, or a tungsten detector.The technique is based on the use of ultra-pure materials and the change in electricalresistance under irradiation.Based on the “integral” spectrum indices provided by these dosimeters and inconnection with activation dosimeters ( 58 Ni), the neutron spectrum is characterisedby the spectrum indices in order to deduce the damage flux of the considered object.Damage dosimetry is carried out before the irradiation itself, using a model irradiatedwith low fluence. This model simulates the real irradiation and therefore respectsthe quantities and proportions of the various materials present in the irradiation experiment.The operation of damage detectors requires: A thermometry laboratory equipped with a thermostated bath at ± 0.001°C to measureDetectors used indamage dosimetry.the electrical resistance, before and after irradiation, as well as G.A.M.I.N and tungstendetectors, An activation-based dosimetry laboratory to measure the 58 Ni dosimeters.Water chemistryA conditioning plant provides water for the irradiation loops under the conditionsrequired for demineralisation, degasification, hydrogenation and additivecontents. The installation comprises: The demineralised water purification unit,• the processing plant,• degassers to eliminate dissolved oxygen,• tanks to prepare and control the injection of chemical additives(boron, lithium oxide etc.),• hydrogenation tanks,• the slaved sampling circuit for the control and adjustmentof water quality, The analysis equipment: U.V. spectrophotometer for metal titration,liquid/ionic chromatographs to measure the anion, cation and metal contents,conductimeter and pH-meter, and calcination apparatus.The chemicalconditioning of water.Data processingReal-time data acquisition and processingDepending on the type of experiment to be realized, two types of systems are available to acquire data from all the sensorsand to carry out the real-time calculations required to control them. The first, highly integrated with the control-command facilitiesis used, via a supervision network, to carry out all the calculations. It is dedicated to experiments not implementing fasttransients. The second system communicates with the control-command facilities, but in addition has its own acquisition chains,enabling it to process fast transients, in particular during the control of power ramps.