JAXA Supercomputer System Annual Report (April 2018-March 2019)

Research on Radiation Protection Technology
Report Number: R18EG3210
Subject Category: Research and Development
URL: https://www.jss.jaxa.jp/en/ar/e2018/9141/
Responsible Representative
Koji Yamanaka, Director, Research and Development Directorate, Research Unit I
Contact Information
Aki Goto, Research and Development Directorate, Research Unit I (goto.aki@jaxa.jp)
Members
Aki Goto, Kazunori Shimazaki
Abstract
In order to realize future human space mission while ensuring astronauts safety, space-radiation protection
technologies are required. Our goal is to establish the accurate estimation technology of space-radiation exposure
doses and the method to optimize shielding designs for spacecrafts.
Reasons for using JSS2
We use JSS2 for PHITS (Particle and Heavy Ion Transport code System) Monte Carlo simulations to estimate
shielding effects of materials against space radiations. PHITS Monte Carlo simulations take a large amount oftime when the computational system is large and complex, such as the system simulated manned-spaceshipstructure. Such simulations enable to be run at high speed with statistical accuracy by using JSS2.
Achievements of the Year
In order to establish exposure dose estimation technology based on numerical simulation using radiationtransport code for future human missions, it is needed to evaluate the validity of existing radiation environment
models and the appropriate setting of calculation geometry.
This time, we created the International Space Station (ISS) and Japan Experiment Module (JEM) 3D-CAD
models and calculated the doses inside JEM using PHITS code. And, the calculated doses were compared withexperimental doses obtained by Area PADLES (Passive Dosimeter for Lifescience Experiments in Space)
dosimeters, and we examined the validity of the used environment models and the appropriate setting of thespacecraft geometry.
The ISS 3D-CAD model includes JEM, some modules close to JEM (e.g. Columbus, Node 1-3), and trussstructures (Fig. 1a). JEM 3D-CAD model includes Pressurized Module (PM), Experiment Logistics Module
Pressurized Section (ELM-PS), Exposed Facility (EF), and Node 2 (Fig. 1b). Inside PM and ELM-PS models,seventeen virtual PADLES dosimeters are installed at the same positions as actual ones. The files of such CAD
models were converted to PHITS input format by SuperMC (Super Monte Carlo simulation program for nuclear－275－

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JAXA Special Publication JAXA-SP-19-003Eand radiation process) software. Each part of ISS and JEM models was composed of Al alloy or Al.
As trapped proton (TP) and galactic cosmic ray (GCR) models, AP8 and Matthia model were used, respectively(Fig. 2). East-west effect of TP, which is a bias that the number of incident TP from the ISS moving direction (+Xdirection) is larger than that from backward direction (-X direction), is set as 0.5 (considered) or 0 (not considered).
Absorbed dose (D) and dose equivalent (DE) in the virtual dosimeters were calculated using PHITS code byparallel computing (JSS2).
Fig. 3 and Fig. 4 show calculated and measured (experimental) doses and their ratios (C/E), respectively. As
shown in Fig. 4, the calculated D and DE are in agreement with measured data mostly within ~20% and ~30%,
respectively, regardless of the differences of used geometry and setting of east-west effect of TP. This result
suggests that the dose estimation using the combination of AP8, Matthia model, PHITS, and the ISS / JEM model
created this time has enough accuracy in terms of dose estimation. And, the mean C/E obtained by using the ISS
model is almost the same as that obtained by using JEM model. Therefore, considering time efficiency incalculation, detail geometry is not necessarily, and it is important to use a geometry reproducing the surrounding
shielding environment of the position where estimated an exposure dose for reasonable estimating. We plan toestablish dose estimation method which is applicable in actual space missions by using the outcome of this work.

Fig. 1: (a) The ISS and (b) JEM 3D-CAD models

Fig. 2: Particle energy spectra obtained from Matthia model and AP8 model.
(period: Area PADLES #14 (Mar 28, 2015 - Sep 12, 2015) ; Only p (proton, H), He,C, Ne, Ar, Fe, and Ni spectra are shown.)－276－This document is provided by JAXA.

JAXA Supercomputer System Annual Report (April 2018-March 2019)

Fig. 3: Calculated and measured (a) D and (b) DE in the period of Area PADLES #14(Mar 28, 2015 - Sep 12, 2015)

Fig. 4: Calculated and measured dose ( (a) D and (b) DE) ratios (C/E) in the period of
Area PADLES #14 (Mar 28, 2015 - Sep 12, 2015)－277－

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JAXA Special Publication JAXA-SP-19-003EPublications- Oral Presentations
1) Aki Goto, Kazunori Shimazaki, Tatsuhiko Sato, Exposure Dose Calculation inside JEM Using PHITS and 3D
ISS Geometry, 42nd COSPAR Scientific Assembly, 2018.
2) Aki Goto, Kazunori Shimazaki, Tatsuhiko Sato, Dose Calculation inside Kibo Using PHITS and ISS 3D-CAD
Geometry, WRMISS-23, 2018.
3) Aki Goto, Kazunori Shimazaki, Exposure Dose Estimation inside Kibo Using ISS 3D-CAD Model and PHITS,PHITS Workshop, 2018.
4) Aki Goto, Kazunori Shimazaki, Exposure Dose Estimation inside JEM Using ISS 3D-CAD Model and PHITS,
14th Space Environment Symposium, 2018.

Usage of JSS2


Computational Information
Process Parallelization Methods

MPI

Thread Parallelization Methods

OpenMP

Number of Processes

12 - 120

Elapsed Time per Case

60000 Second (s)Resources Used
Fraction of Usage in Total Resources*1 (%): 0.54
Details
Computational Resources
System Name

Amount of Core Time(core x hours)

Fraction of Usage*2 (%)

SORA-MA0.00

0.00

SORA-PP

910,385.36

7.28

SORA-LM

0.00

0.00

SORA-TPP

0.00

0.00

File System Resources
File System Name

Storage Assigned (GiB)

Fraction of Usage*2 (%)

/home

14.31

0.01/data

4,978.18

0.09/ltmp

2,929.69

0.25

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JAXA Supercomputer System Annual Report (April 2018-March 2019)

Archiver Resources
Archiver Name

Storage Used (TiB)

J-SPACE

Fraction of Usage*2 (%)
0.00

0.00

*1

: Fraction of Usage in Total Resources: Weighted average of three resource types (Computing, File System,and Archiver).
*2: Fraction of Usage: Percentage of usage relative to each resource used in one year.

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