Search - OECD Nuclear Energy Agency

containing FA with B 4
C cladding is equal to -2.0%, and in the core with FA with zirconium hydride
cladding -2.3%. In the hybrid two-zones reactor core the transmutation rate is equal to -2.2%.
In Table 6 the mass of actinides at the BOC and after 1 FPY of fuel irradiation, as well as the
burn-up rate B Pu
(kg/FPY) for 239 Pu, are presented for different compositions of the reactor core:
Table 6. Mass of actinides in the BOC and after 1 FPY of fuel irradiation
in the reference core, in the core containing FA with B 4
C, and FA with HZr.
Time T = 0 (BOC) T = 360 days
Core
(Enr., %)
Reference
(23.2%)
B 4
C
(43.7%)
HZr
(24%)
Hybrid
(23.2%)
Reference
(23.2%)
B 4
C
(43.7%)
HZr
(24%)
Hybrid
(23.2)
239
Pu, kg 519.7 908.2 539.1 560.7 506.7 884.3 513.8 539.4
B Pu
, kg 0 0 0 0 -13.0 -23.9 -25.3 -21.3
241
Pu, kg 19.6 34.2 20.3 21.2 19.5 32.8 25.3 23.5
241
Am, kg 17.4 30.4 18.1 18.8 17.6 31.6 16.5 18.5
Pu, Am, Cu, kg 750.0 1311.3 778.0 809.3 739.8 1284.8 759.9 791.3
The burn-up rate of 239 Pu in FA with 10 B 4
C or HZr is about two times higher than in the reference
core. It should be noted that the burn-up rates of 239 Pu calculated using the MCNP-4b reaction rates
(see Table 4) are slightly different from results in the above table, because we supposed that reaction
rates remain constant during the time of irradiation. In the core with 10 B 4
C the burn-up rate of 241 Pu is
about -1.4 kg/FPY, while in the core with HZr the mass of 241 Pu is increased by 5 kg/FPY. The amount
of 241 Am in the reference core is increased by 0.2 kg/FPY, in the core with 10 B 4
C is increased by
1.2 kg/FPY, while in the core with HZr the amount is reduced by -1.6 kg/FPY, or by -0.3 kg/FPY in
the hybrid core.
It should be noted that the effective cross-section of 10 B in FA with 10 B 4
C is about 1.6 barn, and
the maximum of the neutron spectrum is located in the energy region higher then 0.1 MeV. So, the
burning of 10 B 4
C cladding in the fuel element during fuel cycle is small. Nevertheless, the burning of
10
B 4
C cladding was taken into account in the MCNP calculations. Production of fission fragments is
comparable in all considered schemes of the reactor core: 0.002 kg of 135 Xe, 0.1 kg of 149 Sm, 1.0 kg of
137
Cs, 0.7 kg of 99 Tc, 0.2 kg of 129 I per 1 FPY. The effective absorption cross-section of 135 Xe in fuel
elements with HZr is three orders of magnitude lower than in the thermal power reactors and is about
1 800 barns, and samarium 149 Sm has effective cross-section of absorption equal to 80 barns. In
calculations of reactivity loss during the fuel cycle the presence of all fission fragments were taken
into account. Reactivity calculations were performed using the MCNP-4b code. In the reference core
the reactivity loss ∆ρ during 1 FPY is equal to ∆ρ = -1.6%/FPY, in the core with HZr zone
∆ρ = -2.0%/FPY, in the hybrid core with HZr ∆ρ = -1.8%/FPY, while in the core with
10
B 4
C ∆ρ = –1.1 %/FPY.
The dependence of proton beam current on k eff
may be estimated using the simple formula:
P
r
= I
p
k
eff
M
( 1 − k )
eff
n , xn
ν
f
× N
n / p
ε
f
,
819