Exposure Dose Calculation inside JEM Using PHITS and 3D ISS Geometry
Abstract
The International Space Exploration Coordination Group (ISECG), a forum set up by 14 space agencies including Japan Aerospace Exploration Agency (JAXA), is planning future human space missions following the International Space Station (ISS) mission, such as long-term stay onboard the lunar orbital station called "Deep Space Gateway" and exploration on the Moon and Mars. One of the problems to solve for realizing such missions is space radiation effects on human health. In space, high liner-energy-transfer (LET) radiation that causes significant biological damage flows from outside of the solar system and the sun. Especially, outside of the geomagnetic field where the future missions will be undertaken, the radiation flows at high dose rates. Establishment of radiation protection technology is required for conducting the future missions while ensuring astronauts safety. The radiation protection technology includes accurate estimation of exposure dose and optimization of shielding design. We expect computer simulation using a radiation transport code as a method to estimate exposure dose for the future missions. In order to perform the simulation for actual missions, it is needed to evaluate the accuracy of the transport code (including nuclear reaction models and nuclear data libraries) and the radiation environment models, and the appropriate setting of calculation geometry.This time, we calculated the exposure doses inside the ISS Japan Experiment Module (JEM, called "Kibo") using PHITS (Particle and Heavy Ion Transport Code System) code and the ISS 3D-CAD model. The ISS 3D-CAD model, that includes JEM 3D-CAD model, was created for these calculations. The ISS CAD model (except the JEM model) describes simplified geometry of the ISS. And, the JEM CAD model consists of the geometry of the Pressurized Module (PM), the Experiment Logistics Module Pressurized Section (ELM-PS), and the Exposed Facility (EF) model. The PM and the ELM-PS models reproduce the approximate geometry of the outer shell structure, the debris bumpers, the racks, and so on. This ISS 3D-CAD model was converted to PHITS input format by using SuperMC (Super Monte Carlo simulation program for nuclear and radiation process) software system. The radiation environment model developed by Mattiä et al was employed for calculating the galactic cosmic ray (GCR) fluxes, while AP8 and AP9 model was used for calculating the trapped proton fluxes in the geomagnetic field. The calculated doses were absorbed dose and dose equivalent of the virtual dosimeters placed inside JEM geometry.In this presentation, we show the calculation results of the exposure doses inside the JEM, and discuss the method to estimate dose based on the comparison between the calculated data and the flight data.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E1266G