Fujita Technical Research
Report No.55 2019

A fundumental study on the establishment of calculation machine
structure for radiation shielding design of accelerator facilities

Ken-ichi Kimura
Abstract
The radiation shielding design for the accelerator facilities such as particle medical therapy, academic
science, and industrial application is the one of the most important issues for the operation, because
they are required to satisfy the limit of radiation exposure dose from these facilities legislated by eachregulatory authority. Monte Carlo method is widely used for the shielding design because of ease of
constructing three-dimensional geometry and lots of recent technological breakthroughs in computing
power. This kind of calculation, however, might require huge parallel machine environment forrequirement of evaluation about 1/1010 to radiation dose at the source term in the facility. The
comparison of calculation speed by selected five CPUs on the four assumed facility designs which werea spherical, a cylinder and a rectangular systems, were conducted in order to establish the parallel
computing environments. The results of the comparison introduced two CPUs (Intel Core i7-4790K andAMD Ryzen 7 2700x) as good performance for low energy incident radiation. Based on the investigation above,
280 cores, 54 CPUs (216 cores) for Core i7-4790K and 8 CPUs (64 cores) for Ryzen 7 2700x were prepared inparallel computing to establish of calculation machine structure for radiation shielding design for accelerator
facilities in order to estimate the doses with reasonable accuracy within a half day for the investigated models.

Keywords : accelerator facility, radiation shield, Monte Carlo calculation,parallel computing, comparison of CPU performance−43−㻙㻌 㻝㻌 㻙㻌Fujita Technical Research Report No.55§1. Introduction
as MPICH2 [2] for windows PCs. A PC cluster works
Radiation is a generic name of energetic particles

as a single high power computer from a user thanks

ionizing atoms and molecules. It has been employed

to these kinds of software. One of essential factors offor not only basic science but also medical treatment.

computing performance is CPU model and theIn particular, X-ray has been used for diagnosis sincenumber of CPUs.

more than a hundred years ago. Tumor therapy

In this article, we evaluate computing performance ofsystems using energetic particle as proton, heavy-ion

parallel computing environment on estimation of radiationand neutron have been developed and applied indose according to five CPU models which are generally

several decades. These particles are generated byavailable and the numbers of CPUs in two simple

accelerators and transported to treatment rooms.

geometries and two actual radiation shielding design cases.

The energetic particles interact with accelerator and§2. Conditions for comparisonstransport components, a patient body and otheritems in a treatment room and unwanted secondaryradiations like neutron and γ-ray are generated.

For the investigation of the proper calculation

Shielding these radiations is highly essential forconditions, five different CPU models and four

safety to workers and general public. However,typical calculation models were prepared for theoptimization of radiation shielding is needed incomparison of calculation. Consideration of shielding

design of it due to limited space and cost in actual

design is usually required a large number of incident

facilities. Huge calculation is required in order toparticles for accurate estimation of the shielding

obtain sufficient accuracy in case radiation dose atperformance, because leakage of radiation must be

the boundary of radiation control area is needed lessenough lower than the prescribed value. So thethan 1/1010 that at the radiation source.

comparison has been conducted by several types ofA three-dimensional Monte Carlo simulation

CPU and calculation models in different numbers ofprogram PHITS (Particle and Heavy Ion Transport

CPU cores in parallel computing.

code System) [1] has been used for estimation ofradiation dose and optimization of radiation shield in

2.1 Prepared CPUs

accelerator and medical treatment facilities. This

Seven kinds of CPU were prepared for theprogram simulates behavior of each particle in anycomparison. Table 1 shows the specification of eachgeometry and give radiation dose and related

CPU with abbreviation. The number of cores for each

information. Estimation of radiation dose by PHITS

CPU also listed in the table, and that is one of theneeds just an affordable laptop PC to a simple

important for parallel computing as well as thegeometry but much higher computing power than acalculation speed, which should have positive

usual laptop PC for estimation in actual buildings

correlation to clock frequency of each CPU. There arewith acceptable accuracy in reasonable calculation

two manufacturers for CPUs which are AMD andtime.

Intel, and the CPU by AMD generally tends to be

As one of techniques to improve computing

more affordable than that by Intel. Numbers of cores

performance, a parallel computing environment

in our possession are also listed in the table, those ofusing a PC cluster is employed. It consists of multiple

C08 and C47 are more than forty because they werePCs connected with local area network

andcontrolled by MPI (Message Passing Interface) andjob schedule software. Rocks [2] is a Linux
distribution to organize PC clusters with ease as well−44−2

A fundumental study on the establishment of calculation machine structure for radiation shielding design of accelerator facilities

Table 1 Description of prepared CPU

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used for different calculation of finite elements
methods. C09 and CD6 were excluded from the25cm

comparison because CD6 was very old CPU with only
two cores, and we only owned two CPUs of C09 model
which was enough old.

Estimation
areaforFinally, five CPU, which are Ryzen 7 2700x [4],Vertical direction (cm)Ryzen 7 1700x [5], RyzenThreadripper1950x [6],Corei7-6800K [7], and Corei7-4790K [8] (symbols areR27, R17, THR, C68, and C47, respectively), were
picked up for the comparison.
2.2 Calculation models for radiation facilities
Table 2 shows calculation models assumed

Existing

8cm

radiation facilities for the comparison. Simple
spherical shape geometry was suitable to evaluate

ProtonNew
wall

Flexibleshieldingmateri
Collision

each CPU performance for the shielding calculation.
Neutron and γ-ray are generally main particles toevaluate for radiation shielding and reaction ofHorizontal (beam) direction

neutron with matter generates secondary γ-rays. OnFigure 1 Calculation model for the two

the other hand, radiation reaction processes byneutron and charged particle are quite different.
Thickness of shielding wall and size for the facilitybuildings.

As an example, Figure 1 shows the geometry ofAcH, which is assumed existing accelerator facility

are also important for the calculation. Table 2 shows

to be a cylindrical shape for reducing calculation

the typical wall thickness and size of the geometry

time.

for the models. Spherical shapes are very simple

Finally, five CPUs and four models were selectedgeometries, a cylindrical shape and a rectangular

for the comparison.

shape which are examples of actual existing facilities.

Table 2 Calculation models$EEUHYLDWLRQ

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20 m×40m

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Figure 2 Comparison of calculation speed for various
CPUs in simple models (SpL and SpH).

Figure 3 Comparison of calculation speed for various
CPUs in models assumed existing facilities (AcH andAcL).

Figure 4 Comparison of calculation time for various
CPUs in models assumed the existing facility (AcL).

Figure 5 Comparison of calculation time for various
CPUs in models assumed the existing facility (AcH).

§3.

Comparison of machine performance inwere performed by Ryzen Threadripper 1950x CPU, which

several facility models

had 16 cores in one CPU, with the simple sphericalgeometry in 3.6×108 histories, which were the number ofCalculations for the comparison of CPUs were assumed

incident particles, without any tallies. In the results,

to be conducted by PHITS program with parallel

calculation

computing techniques, which were distributed-memory

timebydistributed-memory

parallelcomputing (calculation time was 5172.88 seconds) was 4.5

parallel computing using the MPI protocol and shared-times faster than that by shared-memory parallel

memory parallel computing by OpenMP architecture. So,computing. (the time was 23323.43 seconds)

first investigation was focused on the comparison of theSecondly, comparisons of calculation speed for fourparallel computing between distributed-memory parallel

CPUs (R27, R17, C68, and C47) in simple models ( SpL

method and shared-memory parallel one. Calculationsand SpH) were conducted in 7.2×108 histories without any㻙㻌 㻠㻌 㻙㻌−46−

A fundumental study on the establishment of calculation machine structure for radiation shielding design of accelerator facilities

tallies in 4, 6, 8, 10, 12, 15, 16, 18, 20, 24, and 30 cores foreach CPU, respectively. Figure 2 shows histories per
second for each core number for the CPU, which wasdescribed as “node” with the meaning of calculation core ineach CPU for parallel computing. This figure introduced
that calculation speed for low energy incident particle (20MeV proton in SpL mode) was faster than that for highenergy particle (200 MeV proton in SpH mode).
Figure 3 shows the comparison of calculation speed forfour CPU in models assumed existing facilities.

AcHmodel was cylindrical geometry with 150 MeV proton asincident particles, and AcL model is assumed a BNCT
facility in rectangular shape with 20 m × 40 m in footprint
size. Incident particle for this model was neutron withFigure 6 Comparison of calculation time for Ryzen
2700x and Core i7-4790K assumed the existing facility(AcL).

certain energy distribution up to several MeV.
Figures 4 and 5 show the comparison of calculation timefor four CPUs in models assumed existing facilities (AcLand AcH). Figures 2 to 5 indicate the calculation speed by
C47 and R27 CPUs were obviously faster than those by
C68 and R17 CPUs. Therefore, the two CPUs, Intel Core 7 4790K with 4 cores and AMD Ryzen 7 2700x with 8 cores,
were selected to establish the machine environment forradiation shield calculation for accelerator facilities.

§4.

Discussion and requirement for thecalculation
For the selected two CPUs based on fundamental
investigation shown in Figures 2-5 in the last chapter, next
calculations were conducted in order to establish
calculation machine structure for radiation shielding
design of accelerator facilities. Because these kinds ofFigure 7 Comparison of calculation time for Ryzen
2700x and Core i7-4790K assumed the existing facility(AcH).

calculation might be required huge computing resources,
another set of comparisons were investigated with up to216 cores consisted by 54 CPUs of Core i7-4970K (C47) andC47, and C47 and R27 might be used as a node in same

32 cores by 8 CPUs of AMD Ryzen 7 2700x(R27) for

huge parallel calculation. These results introduced thatassumed calculation models for existing accelerator

huge parallel computing machine structure can befacilities (AcL and AcH).

consisted C47 with four cores and R27 with 8 cores

Figure 6 shows the calculation time per 108 histories for

simultaneously. On the other hands, Figure 7 shows

various cores (nodes) for C47 and R27 in AcL model incalculation performance for R27 and C47 CPUs in AcH,logarithmic axis. The calculation points by R27 describing

which were cylindrical geometry with high energy proton

as blue circulars were very similar to those by C47 as a

as incident sources, while AcL in Figure 6 were largediamond shape. These results indicated calculation

rectangular geometry with low energy neutron as incident

performance per core (node) of R27 was similar to that ofsources.
㻙㻌 㻡㻌 㻙㻌−47−

Fujita Technical Research Report No.55

CPUs on the four assumed facility designs which area spherical, a cylinder and a rectangular systems
were conducted in order to establish the parallel
computingenvironments.

Theresultsof

thecomparison introduced two CPUs (Intel Core i7-4790K
and AMD Ryzen 2700x) as good performance for low
energy incident radiation. Based on the investigation
above, 280 cores with 54 CPUs (216 cores) for Core i74790K and 8 CPUs (64 cores) for Ryzen 7 2700x wereprepared in parallel to establish of calculation machine
structure for radiation shielding design for accelerator
facilities in order to calculate within a half day for theinvestigated models.
Acknowledgements
The author wishes to acknowledge Prof. Nobuhiro Shigyoof Kyushu University

Figure 8 Established calculation machine structure
for radiation shielding design of accelerator facilities

References

Appropriate estimation of numbers of histories for[1] T. Sato et al., “Features of Particle and Heavy Ion

shielding calculation required further investigational

Transport code System (PHITS) version 3.02”, J. Nucl. Sci.

calculation with simple tally for AcL and AcH models.

Technol., 55, 684-690, 2018.

Neutron and γ-ray fluence and/or their dose rates at the[2] http://www.rocksclusters.org

just outside of the facilities’ boundary were calculated by[3] http://www.mpich.org/static/downloads/1.4/

C47 and R27 with 200 cores (nodes) for AcH and with 280[4] https://www.amd.com/en/products/cpu/amd-ryzen-7-cores for AcH, respectively. Static errors of neutron and γ-

2700x

ray fluence by the calculation with AcH model were 0.016[5] https://www.amd.com/en/products/cpu/amd-ryzen-7-

and 0.011 in 2.0E9 histories, respectively, which took

1700x
[6]

16078.92 seconds. This result introduces that the parallel

https://www.amd.com/en/products/cpu/amd-ryzen-

threadripper-1950x

computing machine structure with 200 cores by 50 of C47[7]https://ark.intel.com/content/www/us/en/ark/products/

CPU can be used for the shieling design of this type of

94189/intel-core-i7-6800k-processor-15m-cache-up-to-3-

facility within 4.5 hours.

60-ghz.html

On the other hand, the static error of summation both of[8]https://ark.intel.com//www/us/en/ark/products/80807/i

neutron and γ-ray dose rate with AcL model was 0.22 in

ntel-core-i7-4790k-processor-8m-cache-up-to-4-40-

5.6E9 histories with 42085.71 seconds as calculation time.

ghz.html

Even 0.22 as calculation static error is not enough low, it
might indicate rough decision of good or need to improvefor the object in the design phase. In this meaning, theShort comment
Radiation shielding calculation is
one of the key technologies for thedesign of radiation facilities as well
as low-activation materials. The
way of machine setup is described.

parallel computing machine structure with 280 cores by 54
of C47 CPU and 8 of R27 CPU might be able to investigate
shielding design within 12 hours even for large scalebuildings assuming existing facilities.

§5. Conclusion

Ken-ichiKimuraThe comparison of calculation speed by selected five㻙㻌 㻢㻌 㻙㻌−48−