Electron Accelerator Shielding Design of KIPT Neutron Source Facility

다국어 초록 (Multilingual Abstract)

The Argonne National Laboratory of the United States and the Kharkov Institute of Physicsand Technology of the Ukraine have been collaborating on the design, development andconstruction of a neutron source facility at Kharkov Institute of Physics and Technologyutilizing an electron-accelerator-driven subcritical assembly. The electron beam power is100 kW using 100-MeV electrons. The facility was designed to perform basic and appliednuclear research, produce medical isotopes, and train nuclear specialists. Thebiological shield of the accelerator building was designed to reduce the biological dose to lessthan 5.0e-03 mSv/h during operation. The main source of the biological dose for the acceleratorbuilding is the photons and neutrons generated from different interactions of leakedelectrons from the electron gun and the accelerator sections with the surrounding componentsand materials. The Monte Carlo N-particle extended code (MCNPX) was used for theshielding calculations because of its capability to perform electron-, photon-, and neutroncoupledtransport simulations. The photon dose was tallied using the MCNPX calculation,starting with the leaked electrons. However, it is difficult to accurately tally the neutron dosedirectly from the leaked electrons. The neutron yield per electron from the interactions withthe surrounding components is very small, ~0.01 neutron for 100-MeV electron and evensmaller for lower-energy electrons. This causes difficulties for the Monte Carlo analyses andconsumes tremendous computation resources for tallying the neutron dose outside theshield boundary with an acceptable accuracy. To avoid these difficulties, the SOURCE andTALLYXuser subroutines ofMCNPXwere utilized for this study.The generated neutrons werebanked, together with all related parameters, for a subsequent MCNPX calculation to obtainthe neutron dose. The weight windows variance reduction technique was also utilized forboth neutron and photon dose calculations. Two shielding materials, heavy concrete andordinary concrete, were considered for the shield design. The main goal is to maintain thetotal dose outside the shield boundary less than 5.0e-03 mSv/h during operation. The shieldconfiguration and parameters of the accelerator building were determined and are presentedin this paper.

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