Research Of Monitoring Method For Neutron Ambient Dose Equivalent(Rate)

At present, most of the developed neutron dosimeters that have a moderator with a single counter, applied in neutron radiation fields within large range energies, are not a satisfaction to energy response. It is inconvenience for the neutron energetic spectrometers to be used to measure in the workplace for purpose of the radiation protection monitor. The research purpose of the article that needs colligating the virtues of both the dosimeters and the energetic spectrometers that are at present used and overcoming both shortcomings is seek for a dependable neutron dose monitor method, based on the theory and technology in order to develop a suitable dosimeter for the radiation protection purpose.The research contents of the article are as follows,(1) Application the neutron position-sensitive counter to the dose monitoring.(2) Comparing to the several detector designs through Monte Carlo calculation method, the suitable diameter of the spherical moderator is chosen, and the detector of a single sphere with multi-counters is designed.(3) The detector of the counter regions is divided by the equally dividing method and the non-equally dividing method in the data processing, and both methods are compared.(4) The results of the experiment show that the summer counts of the counting regions are unfolded by the unfolding code, and the neutron spectrums are acquired, and the monitoring quantities are evaluated by the neutron spectrum.For the sake of absorbing the advantage of easy portability for a singlesphere moderator and of overcoming the disadvantage of the unideal energy response of the neutron dosimeters combined a single sphere with a single counter, the single sphere is combined with multi-counters for the detector design. Based on the difference of the moderated neutron in the sphere moderator, making use of the neutron position-sensitive counter with sensing the positions characteristic, the thermal neutron distributions of three thermal-neutron sensitive counters inserted into moderator according to each other perpendicular were measured in the sphere inner by incidence neutron . The sphere is divided into five spherical shells in the radial direction by means of the equally dividing method for data treatment in the international. Each spherical shell that is the same thickness has six counting segments (the most inner region has only three). The six counters are accumulated acting as a counting region, so five counting regions are acquired. To acquire ideal energy response function, the first propose is that the dividing sphere is the non-equally method in the radial direction, which thickness of each spherical shell is less with the more radius.Comparing to the several detector designs through Monte Carlo calculation method with MCNP4A program, it shows that the detector of spherical moderator is suitable for 25cm in diameter. Each counter region of the fluence energy response matrices is calculated, analysing the influence the angle response, the gas pressure of counter and the density of moderator on response function. Through analysis of response function for the equally dividing method and the non-equally dividing method, it indicates that the non-equally dividing method has some advantage.Based on the high of two output pulses of the neutron position-sensitive counter, the position where neutron reaction with 3He has been arisen by neutron incidence in the counter is estimated. The position signals in thisexperiment are obtained by connectors to NIM electronic modules which include the dual sum and the invert amplifier, the position-sensitivedetector analyzer, the timing single-channel analyzer and theanalog-to-digital converter (ADC). Three ADC output signals coming from the position-sensitive counters and five counting regions are processed by the multi-channel acquiring system.Utilizing the advantage of the acquiring energy spectrum information by means of the Bonner spheres and the five counting regions of neutron fluence response matrices, the neutron spectrum in the monitoring radiation...