This paper presents an integrated study regarding the feasibility of using {sup 4}H-SiC semiconductor neutron diode detectors in the GT-MHR core. The goal of the study is to introduce a method to identify locations in the GT-MHR, where the detector count rate is acceptably high and the detector life-time may be acceptably long. The modeling methods that we have used to determine the neutron count rate and the rate of displacement damage are discussed. (authors)

This paper presents an integrated study regarding the feasibility of using {sup 4}H-SiC semiconductor neutron diode detectors in the GT-MHR core. The goal of the study is to introduce a method to identify locations in the GT-MHR, where the detector count rate is acceptably high and the detector life-time may be acceptably long. The modeling methods that we have used to determine the neutron count rate and the rate of displacement damage are discussed. (authors)

Silicon carbide (SiC) semiconductor diode detectors may be useful as neutron power monitors in the International Reactor Innovative and Secure (IRIS) nuclear reactor, due to their very high band-gap (which allows high temperature operation and also mitigates many of the effects of radiation damage) and their small volume (which allows high fluence rate operation and detector redundancy). Pulse mode operation is envisioned in order to discriminate gamma-ray events from neutron events, in which case operation at high count rates is necessary to quickly sense and respond to fast transients. We are designing a power monitoring system for IRIS based on SiC diode detectors. This paper discusses the choice of locations for the SiC detectors in IRIS considering accessibility of the location, detector count rate and radiation damage rate. The IRIS reactor was modeled in 3-dimensions in MCNP, accounting for radial and axial variations of the core power distribution. The neutron flux distribution was calculated as functions of axial location for four radii in the downcomer region (155 cm, 170 cm, 185 cm, and 200 cm). We used these data to predict the detector count rate and the 1 MeV equivalent neutron flux in SiC. We predict that the 1 MeVmore » equivalent neutron flux in SiC varies from 9.2 E+10 to 4.6 E+08 cm{sup -2}s{sup -1}, and the triton count rate varies from 1.8 E+05 cps to 5.0 E+02 cps, as the detector radial location is varied from 155 cm to 200 cm. (authors)« less

As a part of a U.S. Department of Energy Nuclear Engineering Research Initiative (NERI) project, we are evaluating the potential for using silicon carbide (SiC) semiconductor radiation detectors, operating in the pulse mode, as power monitors for gas turbine modular helium reactor (GT-MHR) [1]. Locations for the power monitors will be selected considering acceptable detector count rates and lifetimes. We have characterized the radiation environment at various locations in the GT-MHR, where detectors may be placed, in terms of the 1 MeV equivalent neutron flux in SiC (φeq,1 MeV, SiCTotal). Also, we have characterized the radiation field in beam part 1 (BP1) of the Ohio State University Research Reactor (OSURR) in these same terms, with the intent of correlating observed degradation of the SiC detectors in the OSURR to the degradation that can be expected for various detector locations in the GT-MHR. Comparing φeq,1 MeV, SiCTotal for the GT-MHR and for the OSURR, we conclude that SiC devices cannot be adequately tested in the characterization vessel in OSURR BP1 for the radiation damage that would be incurred over a refueling cycle for detectors placed in-core. Also, we note that the radiation environment in the OSURR BP1 is harder than the radiation environment in the GT-MHR.