Abstract: Neutron dose is highly dependent on its energy. However, the energy spectrum of the calibration field is different from workplace, which could lead to a large deviation in the measurement of neutron dose at workplace. Using simulation workplace neutron spectrum for equipment calibration will improve the accuracy of neutron dose measurements. In this paper, the modular construction method of the simulated workplace neutron spectrum and the structural design method of the device were studied based on the DT neutron source, the simulated spectrum with the characteristics of workplace neutron spectrum at pressurized water reactors (PWR), and its fuel cycle. By analyzing the T(d, n)⁴He reaction emission neutron’s energy spectrum and angular distribution law, a point source with an average energy of 14.1 MeV Gaussian distribution and isotropic emission was used to approximate the DT neutron source. 14 alternative materials were selected according to the interaction cross-section of neutron and matter, the relative neutron fluence ratio and average neutron energy were analyzed. And the materials for constructing the simulation workplace neutron spectrum device were selected from the perspectives of neutron multiplication, energy attenuation, energy spectrum adjustment, and practicality. Two workplace neutron spectrum of the pump room and reactor hall were selected as target spectrum. Main moderation assembly, modulating layers and reflector assembly were designed. The simulated neutron spectrum and device structure for the two workplace target spectrum were constructed. The results show that the construction method of the simulated workplace neutron spectrum described in this paper is effective, and the modular design is highly expandable, which can be adapted to a variety of workplace target spectrum to construct the simulated spectrum.

Key words: simulated workplace neutron spectrum, Monte Carlo simulation, neutron moderation, Geant4