J. Plasma Fusion Res. SERIES, Vol. 9 (2010)

Activation analysis for the HCSB-DEMO reactor in China
Zaixin Li, Kaiming Feng, Guoshu Zhang, Guoyao Zheng and Tao Yuan
Southwestern Institute of Physics, Chengdu, P.R. China(Received: 20 November 2009 / Accepted: 12 April 2010)

The Neutron induced activity and decay heat are very important for the nuclear design of fusion reactor. In thispaper, activation analysis of DEMO reactor with helium-cooled solid blanket (HCSB-DEMO) was performed.
Ceramics Li4SiO4 and Beryllium options were considered as tritium breeding material and neutron multiplier,respectively. Chinese low-activation ferritic steel (CLF-1) developed in South Western Institute of Physics (SWIP)
was applied as structural materials of blanket. Activation analysis was performed using FDKR code with activation
cross section data file FENDL/A-2.0. Neutron fluxes as the input of FDKR were calculated with MCNP Monte
Carlo code and FENDL/MC-2.1 neutron cross section data. The activity inventories and decay heat in
HCSB-DEMO were examined. The contributions of radionuclides of structural materials, Li4SiO4 and Beryllium inblanket were discussed, respectively.
Keywords: Activation analysis, DEMO, Solid breeder blanket, CLF-1, Impurity.

FDKR code was used for activation analysis [6]. FDKR
code is based on DKR code which originated at theUniversity of Wisconsin in 1976 [6, 7]. With thesupplements of decay chain of fission products andactinides and related libraries, FDKR code can performthe activation calculation for fission, fusion and hybrid
reactors. In this analysis, the recent activation crosssection data file FENDL/A-2.0 was used [8].

1. Introduction

In recent 50 years, China has made an effort todevelop the fusion energy. China DEMO (CN DEMO)
study is the important aspect of long-term national
program [1]. DEMO reactor with Helium-cooled solid
breeder (HCSB) blanket (HCSB-DEMO) concept is an
option of China DEMO design study [1, 2]. Tritium
breeding blanket is one of the key components of fusion
reactor. The main requirements for DEMO blankets are
tritium self-sufficiency and extraction of high-grade heat.
Some of HCSB-DEMO related blanket technologies will
be tested with ITER [2].
In HCSB-DEMO design, the low activation
ferritic/martensitic steel of CLF-1, which was developed
in SWIP of China, was chosen as structure material.
Beryllium was used for neutron multiplication. Li4SiO4
ceramic tritium was chosen as tritium breeder due to its
high lithium content and good thermal stability. Li4SiO4
ceramic pebble bed was adopted in blanket to improve
the tritium release and to reduce the thermal stress due tolow conductivity of Li4SiO4.
The radioactivity of fusion materials induced in D-T
neutron field is very important in terms of maintenanceand radioactive waste management. In this paper, we
report the investigation of the induced radioactivity anddecay afterheat in the components of HCSB-DEMO.

Table 1 Radial build of HCSB-DEMO
Thickness Composition
(cm)
FW
3.0
CLF-1, 54%; He, 46%
37.0 (IB) CLF-1, 12.2%; He,Blanket
38.0%; Be, 18.7%;
47.0 (OB) Li4SiO4, 31.1%
Shield

45.0

V.V

20.0

CLF-1, 70%; B4C,20%; H2O, 10%
CLF-1, 90%; H2O, 10%Major radius and minor radius of HCSB-DEMO
are 7.2 m and 2.1 m respectively. Fusion power is 2550
MW. The neutron wall loading is 2.3 MW/m2. A torus
model was used in the activation analysis. Table 1 shows
the radial build of HCSB-DEMO. The inboard andoutboard total thicknesses of First Wall (FW), blanket andshield are 85 cm and 95 cm, respectively. Vacuum Vessel(V.V) in 20 cm thickness is consisting of CLF-1 structure
and water. The water in shield and V.V was used as bothof coolant and shield material. Activation analysis wasassumed for a full power continuous operation 4 years,
which is the predicted life of blanket. The chemical

2. Calculation procedure

The neutron transport calculation was performed
using MCNP Monte Carlo code and FENDL/MC-2.1
neutron cross section data [4, 5]. The calculated neutron
fluxes were used as input file for activation analysis.

author’s e-mail: lizx@swip.ac.cn348©2010 by The Japan Society of Plasma
Science and Nuclear Fusion Research

Z. Li et al., Activation Analysis for the HCSB-DEMO Reactor in China

activation of CLF-1. The FW activity is dominated by55
Fe (T1/2=2.72 y) up to 10 years as shown in Fig. 2. 55Feis mainly produced through 56Fe(n, 2n)55Fe reaction.
After about 100 years cooling, the dominant radionuclide

composition of CLF-1 is: 8.3 Cr, 1.5 W, 0.3 V, 0.11 C, 0.5Mn, 0.08 Ta, 0.001 O, 0.007 N (wt. %) and Fe for balance[3]. The impurities in CLF-1 were considered inactivation analysis.

3. Results and discussion
3.1 Radioactivity inventoryRadioactive inventories in HCSB-DEMO include
the bred tritium and activated materials. Figure 1 shows
the activity generated in the component of FW, blanket,
shield and V.V. The results are given as a function ofcooling time after shutdown. First, the activity fromblanket dominates for about 60 s. Then the activity
generated in FW is dominant up to about 10 years. Finally,the activity from blanket dominates up to 1000 years. The
activity in V.V is one order lower than that in othercomponents. The decay curves of FW and V.V activity
are very close.
The radioactivity in FW is responded by theFig. 1 Total activity generated in FW, blanket, shield
and V.VFig.2

Major radionuclides contributing to FW
activity

349

Fig.3

Total activity generated in CLF-1 structure,
Li4SiO4 breeder and Be neutron multiplier ofblanket.

Fig.4

Major radionuclides contributing to Li4SiO4breeder activity in blanket.

Fig.5

Major radionuclides contributing to Be
neutron multiplier activity in blanket

Z. Li et al., Activation Analysis for the HCSB-DEMO Reactor in China

is 63Ni (T1/2=92 y) which is produced by 63Cu(n, p)63Ni,62
Ni(n, Ȗ)63Ni and 64Ni(n, 2n)63Ni reactions. The
long-term radioactivity in FW is determined by thelong-lived radionuclides of 93Mo (T1/2=3.5 x 103 y) and94
Nb (T1/2=2.0 x 104 y, product of 93Nb (n, Ȗ) reaction).
93
Mo is form through 92Mo(n, Ȗ)93Mo and 94Mo(n,2n)93Mo reactions.
The total activity generated in blanket materials isshown in Fig. 3 as a function of cooling time following
shutdown. After a few seconds, the activity from CLF-1
structure dominates up to 10 years. During 10-100 years,
the activity from Li4SiO4 breeder and Be neutron
multiplier is higher than the activity from CLF-1 becauseof the bred tritium (T1/2=12.33 y) as shown in Fig. 4 and5.
Induced radioactivities in Li4SiO4 breeder are
dominated by 28Al(T1/2= 2.27 m) and by tritium,respectively. 28Al is the activation production of 28Si (n,Fig.6

Total decay heat generated in FW, blanket,
shield and V.V.

Fig.7

Major radionuclides contributing to FW
decay heat.

p)28Al reaction.
The short and intermediate radioactivity in Be
neutron multiplier is dominated by 8Be (T1/2=7 x 10-17 s,
product of 9Be(n, 2n)8Be reaction) and by tritium.
Long-term activity in Be is due to 10Be (T1/2=1.51 x 106y), which is produced by 9Be(n, Ȗ)10Be reaction.

3. 2 Decay heat

The total decay heat generated in the component ofFW, blanket, shield and V.V is shown in Fig. 6 as afunction of cooling time after shutdown. The decay heatgenerated in FW, blanket and shield are comparable up to10 years following shutdown. The decay heat fromblanket dominates during the period of 10-1000 years.
The decay heat generated in V.V is about one order lower.
The FW decay heat is dominated by 56Mn
(T1/2=2.578 h) up to several hours after shutdown asshown in Fig. 7. 56Mn is mainly produced through 56Fe(n,p)56Mn reaction. Then 54Mn (T1/2=312.12 d), which isformed by 54Fe(n, p)54Mn reaction, dominates up to 1year. During 1 year to several tens years after shutdown,
the dominant nuclide is 55Fe. Long-term decay heat is due
to 94Nb.
Figure 8 give the total decay heat generated inblanket materials as a function of cooling time after
shutdown. The decay heat from CLF-1 structure
dominates up to 1000 years. The decay heat from Li4SiO4breeder and Be neutron multiplier are very low comparedwith that from CLF-1 structure.
Figures 9 and 10 show the major radionuclides
contributing to the decay heat in Li4SiO4 breeder and Be
neutron multiplier, respectively. For Li4SiO4, thedominant decay heat contributions are due to 28Al, 29Al
(T1/2=6.5 m, production of 29Si (n, p)29Al reaction) andbred tritium, respectively. The decay heat in Be neutron
multiplier is dominated by 6He (T1/2=7 x 10-17 s, productFig.8 Total decay heat generated in CLF-1 structure,
Li4SiO4 breeder and Be neutron multiplier ofblanket.

350

Z. Li et al., Activation Analysis for the HCSB-DEMO Reactor in Chinaof 9Be(n, a)6He reaction) , by tritium and by 10Be,respectively.

lower. The radionulides of 54Mn, 56Mn, 55Fe, 63Ni, 94Nband 93Mo dominate the radioactivity and decay heat levelof CLF-1 FW. The long-lived rodionuclides of 63Ni, 94Nband 93Mo are the activation product of the impurities ofCu, Ni, Nb and Mo in CLF-1. Long-term activity in Be isdue to 10Be.
For Li4SiO4 and Be, the bred tritium contributes
most of radioactivity and decay heat from several hours
to hundreds years following shutdown. The activation ofLi4SiO4 and Be are negligible if the tritium is removed.

Acknowledgements
This work was supported by the Major State Basic
Research Development Program of China (grant No.
2009GB108000).
Fig.9

Major radionuclides contributing to Li4SiO4breeder decay heat in blanket.

5. References

[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]

Fig.10 Major radionuclides contributing to Be
neutron multiplier decay heat in blanket.
For Li4SiO4 and Be, the bred tritium contributes
most of decay heat from several hours to hundreds years
following shutdown. The decay heat from Li4SiO4 and Be
are negligible if the tritium is removed.

4. Summary and conclusion

In this paper, the preliminary design ofHCSB-DEMO was introduced. The neutron induced
radioactivity inventories and decay heat in HCSB-DEMO
were investigated. The contributions of radionuclides ofstructural materials, Li4SiO4 and Beryllium werediscussed, respectively.
After several minutes cooling, the radioactivity anddecay heat of FW, blanket and shield are comparable up
to about 10 years following shutdown. On the other hand,
the radioactivity and decay heat of V.V is bout one order351

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