Method of H∗(10) evaluation using a spherical-type energy-independent neutron dose monitor

A spherical-type neutron dose monitor has been developed for the use of area monitoring around the neutron producing fields. Considering the practical fields that neutrons coming from multiple directions, the study has been performed using MCNP simulation, in order to estimate the resultant direction of the sources and to find a suitable method of H∗(10) evaluation. This was done by irradiating the monitor using two neutron sources of different energies and intensities; placed at an angle between them. A parallel neutron beam of 50 cm radius with wide energy was used for the irradiation. The direction of the neutron sources was determined comparing the responses of 12 thermo-luminescent detectors (TLDs) of first layer between single and two directional sources. It was found that in most of the cases, the direction of the source was estimated to be the average angle or near the average angle of single sources. Using a linear combinational equation the method has been developed for evaluating the dose from the mean values of selected detectors of two consecutive depths of TLDs and the TLD of core depth. It was found that the ratio of the calculated to the expected dose was almost close to unity which indicates that the method can be used for evaluating the dose with good accuracy.