DESIGN OF A SMALL-ANIMAL THERMAL-NEUTRON IRRADIATION FACILITY AT THE BROOKHAVEN MEDICAL-RESEARCH REACTOR

The broad beam facility (BBF) at the Brookhaven Medical Research React or (BMRR) can provide a thermal neutron beam with flux intensity and q uality comparable to the beam currently used for research on neutron c apture therapy using cell-culture and small-animal irradiations. Monte Carlo computations were made, first, to compare with the dosimetric m easurements at the existing BBF and, second, to calculate the neutron and gamma fluxes and doses expected at the proposed BBF. Multiple cell cultures or small animals could be irradiated simultaneously at the s o-modified BBF under conditions similar to or better than those indivi dual animals irradiated at the existing thermal neutron irradiation fa cility (TNIF) of the BMRR. The flux intensity of the collimated therma l neutron beam at the proposed BBF would be 1.7 x 10(10) n/cm(2) . s a t 3-MW reactor power, the same as at the TNIF. However, the proposed c ollimated beam would have much lower gamma (0.89 x 10(-11) cGy . cm(2) /n(th)) and fast neutron (0.58 x 10(-11) cGy . cm(2)/n(th)) contaminat ions, 64 and 18% of those at the TNIF, respectively. The feasibility o f remodeling the facility is discussed.