24P115-P
Performance of high temperature gas-cooled reactor as an outer tritium source
for fusion reactors
核融合炉用外部トリチウム供給源としての高温ガス炉の特徴
Shohei Kochi1, Hideaki Matsuura1, Hiroyuki Nakaya1, Satoshi Shimakawa2, Yasuyuki Nakao1,Minoru Goto2, Shigeaki Nakagawa2, Masabumi Nishikawa3
河内昌平, 松浦秀明，中屋裕行，島川聡司，中尾安幸，後藤実，中川繁昭，西川正史
1

Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University,744, Motooka, Nishi-ku, Fukuoka 819-0395, Japan1
九州大学大学院工学府 〒819-0395 福岡市西区元岡744
2Japan Atomic Energy Agency, 4002, Oarai, Ibaraki 311-1393, Japan2
日本原子力研究開発機構 〒311-1393 茨城県東茨城郡大洗町成田町4002
3Interdisciplinary Graduate School of Engineering Sciences, Kyushu University,
6-10-1 Hakozaki, Fukuoka 812-8581, Japan3
九州大学大学院総合理工学研究院 〒812-8581 福岡市東区箱崎6-10-1

The performance of a gas turbine high-temperature reactor of 300 MWe nominal capacity (GTHTR300)
as a tritium production device was examined by using LiAlO2 compound. It was shown that if 6Li wasenriched between 7.5 wt% and 30 wt%, gas-cooled reactors with thermal output power of 3 GW in all canproduce 2.5-7.5 kg of tritium in a year.

1. Introduction
To secure tritium supply to the first andsubsequent fusion power-generation reactors at an
early stage, it is important to prepare the plan tostably supply an adequate amount of tritium.[1] To
solve this problem, we have proposed the use of ahigh-temperature gas-cooled reactor as a tritium
producing device.[2] By assuming Li2O, Li2SiO3,and Li4TiO4 compounds without 6Li enrichment,
the performance of the gas turbine high-temperature
reactor of 300 MWe nominal capacity(GTHTR300)[3] was estimated.
To reduce the produced-tritium diffusive leakage
from the device, LiAlO2 is one of the mostpromising compounds.[4] Because this compound
has Li density almost one-third by compared withLi2O, however, enough amounts of Li cannot beloaded into the core region and the amount oftritium produced decreases regardless of remaining
large excess reactivity.
In this study, we examine the performance ofgas-cooled reactor as a tritium production device byusing LiAlO2 compound with 6Li enrichment.
2. Analysis modelOn the basis of the continuous-energy MonteCarlo transport code MVP-BURN[5], burn-up
calculations for the entire-core region ofGTHTR300 were carried out considering its unique
double heterogeneity structure. Fig.1 presents thehorizontal cross section of the GTHTR300 core andFig.1 Horizontal cross section of GTHTR300 coreFig.2 Schematic views of (a) fuel block (b) fuelrod and (c) Li compound pellet
LiAlO2 kernel
Low density PyC
0.55mm

PyC
SiC
PyC

Fig.3 Schematic views of a ceramic-coated
LiAlO2 particle. 4 types of 6Li enrichment isassumed for Li compounds in the calculations.

800

1.35

700

6

1.30

keff

1.25

600
500

1.20

400

1.15300

1.10

200

1.05

100

1.00

050100Time [days]

1500Fig.4 Time evolutions of the effective multiplication
factor and the time-integrated weight of the tritium
produced in the gas-cooled reactor for several 6Li
enrichments of LiAlO2. Thermal output power isassumed to be 600 MW.

Fig.2 presents its schematic views of each fuelblocks. We can see that there is a large space nearby the fuel regions and in fuel blocks. For example,
removable reflector columns, control-rods andburnable poison (BP) holes are expected as aLi-compound loading space. In this paper, all BP
compacts in the reactor are assumed to be replacedwith Li-compound pellet which contains
ceramic-coated LiAlO2 particles (Fig.3). The
operation parameters of the GTHTR300 assumed inthis study are indicated in Table I.
Table I. Typical calculation parameters in thepresent system of gas-cooled reactor
Thermal Output power
600[MW]
235
U Enrichment
14[wt%]
Fuel Temperature
1360[K]
Moderator Temperature
1190[K]
3. Numerical result and conclusion remarks
We carried out the 180-day burn-up simulation of
the gas-cooled reactor with 600 MW thermal output
power by changing the 6Li enrichment contained in
Li compounds pellets.
The time evolutions of the effective multiplication
factor and the time-integrated weight of the tritium
produced in the gas-cooled reactor are shown in
Fig.4 for several 6Li enrichments. It was shown thatthe total amount of tritium produced in 180-day
operation increases and excess reactivity decreases
with increasing 6Li enrichment. When 30 (7.5) wt%
enrichment of 6Li is assumed, the amount of tritium
produced in 180-day operation is estimated as 750(260) g. Although the loaded 6Li weight increases

1.050.9

40.8

30.7

20.6

10.5

R/R0Li 7.5wt%
6Li 15wt%
6Li 22.5wt%
6Li 30wt%

Tritium Production [g]600MW thermal output assumed

Normalized neutron flux

1.40

15wt%
7.5wt%
22.5wt%30wt%
6Li enrichment [wt%]0Fig.5 Normalized neutron flux averaged over theLiAlO2 particles and relative 6Li(n,T)4He reaction rate
R R0 for several 6Li enrichments. Here R0 is thereaction rate when 7.5 wt% 6Li enrichment is assumed.

almost 4 times, the amount of tritium produced in
180–day operation increases only 3 times. The
reason can be seen in Fig.5. The normalized neutron
flux averaged over the total volume of the LiAlO2
particles and the ratio of 6Li(n,t)4He reaction rate R
to the one when 7.5 wt% enrichment is assumed R0
are shown in Fig.5 as a function of 6Li enrichment.
As 6Li concentration in the particles increases, theneutron absorption at the outside layers in theLi-compound pellet increases. Because of theself-shielding effect, the neutron flux averaged overthe volume of the LiAlO2 particles decreases withincreasing the enrichment.
It is shown that when LiAlO2 compound is used in
the gas-cooled reactors with 3 GW thermal output
power, 2.5-7.5 kg of tritium can be produced in ayear. This study was performed under the condition
not to change the original structural design ofGTHTR300. In this study, we loaded Li compoundin the original space prepared for BP insertion. At
the presentation, the different Li loading patternse.g., use of the control rod regions, will also beshown.

References[1] M.Nishikawa, Fusion Sci. Technol., 57, 120 (2010).
[2] H.Matsuura, et al., “Study of Tritium Production forFusion
Reactors
Using
High-Temperature
Gas-Cooled Reactors”, presented at 15th Int. Conf.
Emerging Nuclear Energy Systems (San Francisco,May, 2011).
[3] X.Yan, et al., Nucl. Eng. Des., 222, 247 (2003).
[4] K.Yamashita, et al., J. Atomic Energy Society ofJapan, 40, 65 (1998). (in Japanese)[5] Y.Nagaya, et al., JAERI-1348 (2005).