104
M. Yamanaka
Table 4.11 Subcriticality variation and pulsed-neutron frequency of 14 MeV neutrons and
spallation neutrons (Ref. [15])
(a) Cases I-1 to I-5
Case
# of fuel plates
Rod insertion
pattern
Pulsed frequency (Hz)
14 MeV neutrons
Spallation neutrons
I-1
4560
C1
20
20
I-2
4560
C1, C3
20
20
I-3
4560
C1, C2, C3
20
20
I-4
4560
C1, C3, S5
–
20
I-5
4560
C1, C3, S4, S5
–
20
(b) Cases II to VII
Case
# of fuel plates
Rod insertion * Pulsed frequency [Hz]
14 MeV neutrons
Spallation neutrons
II
4440
–
20
20
III
4200
–
20
20
IV
4080
–
50
20
V
3960
–
20
20
VI
3840
–
50
20
VII
3600
–
20
20
*Full withdrawal of all control (C1, C2, and C3) and safety (S4, S5, and S6) rods
described in Ref. [19] with the SCALE6.2 code system [20], as shown in Fig. 4.6.
The validation of the numerical analyses was confirmed through comparison between
measured reactivity and calculated reactivity. Here, excess reactivity and control rod
worth (C1, C2, and C3) were measured by the positive period method and the rod
drop method, respectively, and calculated as follows:
ρ
cal
excess =
1 −
1
k
clean
eff
−
1 −
1
k
critical
eff
=
1
k
critical
eff
−
1
k
clean
eff
,
(4.42)
ρ
cal
rod =
1 −
1
k
critical
eff
−
1 −
1
k
rod
eff
− =
1
k
rod
eff
−
1
k
critical
eff
,
(4.43)
where ρ
cal
excess and ρ
cal
rod are the calculated excess reactivity and control rod worth,
respectively, k
critical
eff
the value of the effective multiplication factor at the critical state
so as to reduce the calculation bias induced by the nuclear data, k
clean
eff
the value of
effective multiplication factor at the withdrawal of all control rods, and k
rod
eff the value
of effective multiplication factor at the insertion of control rod C1, C2, or C3 at the
critical state. The difference was confirmed at less than 5% in control rod worth by
MCNP6.1, as shown in Table 4.12, although large uncertainty was observed in excess
reactivity attributed to estimating small reactivity, considering valid for subsequent
analyses. For PARTISN calculations, while the C/E (calculation/experiment) ratio
M. Yamanaka
Table 4.11 Subcriticality variation and pulsed-neutron frequency of 14 MeV neutrons and
spallation neutrons (Ref. [15])
(a) Cases I-1 to I-5
Case
# of fuel plates
Rod insertion
pattern
Pulsed frequency (Hz)
14 MeV neutrons
Spallation neutrons
I-1
4560
C1
20
20
I-2
4560
C1, C3
20
20
I-3
4560
C1, C2, C3
20
20
I-4
4560
C1, C3, S5
–
20
I-5
4560
C1, C3, S4, S5
–
20
(b) Cases II to VII
Case
# of fuel plates
Rod insertion * Pulsed frequency [Hz]
14 MeV neutrons
Spallation neutrons
II
4440
–
20
20
III
4200
–
20
20
IV
4080
–
50
20
V
3960
–
20
20
VI
3840
–
50
20
VII
3600
–
20
20
*Full withdrawal of all control (C1, C2, and C3) and safety (S4, S5, and S6) rods
described in Ref. [19] with the SCALE6.2 code system [20], as shown in Fig. 4.6.
The validation of the numerical analyses was confirmed through comparison between
measured reactivity and calculated reactivity. Here, excess reactivity and control rod
worth (C1, C2, and C3) were measured by the positive period method and the rod
drop method, respectively, and calculated as follows:
ρ
cal
excess =
1 −
1
k
clean
eff
−
1 −
1
k
critical
eff
=
1
k
critical
eff
−
1
k
clean
eff
,
(4.42)
ρ
cal
rod =
1 −
1
k
critical
eff
−
1 −
1
k
rod
eff
− =
1
k
rod
eff
−
1
k
critical
eff
,
(4.43)
where ρ
cal
excess and ρ
cal
rod are the calculated excess reactivity and control rod worth,
respectively, k
critical
eff
the value of the effective multiplication factor at the critical state
so as to reduce the calculation bias induced by the nuclear data, k
clean
eff
the value of
effective multiplication factor at the withdrawal of all control rods, and k
rod
eff the value
of effective multiplication factor at the insertion of control rod C1, C2, or C3 at the
critical state. The difference was confirmed at less than 5% in control rod worth by
MCNP6.1, as shown in Table 4.12, although large uncertainty was observed in excess
reactivity attributed to estimating small reactivity, considering valid for subsequent
analyses. For PARTISN calculations, while the C/E (calculation/experiment) ratio