Dynamic simulation of a space gas-cooled reactor power system with a closed Brayton cycle

doi:10.1007/s11708-021-0757-9

Front. Energy

2021, Vol. 15

Issue (4) : 916-929 https://doi.org/10.1007/s11708-021-0757-9

RESEARCH ARTICLE

Dynamic simulation of a space gas-cooled reactor power system with a closed Brayton cycle

Chenglong WANG, Ran ZHANG, Kailun GUO, Dalin ZHANG, Wenxi TIAN(

), Suizheng QIU(

), Guanghui SU

Department of Nuclear Science and Technology, State Key Laboratory of Multiphase Flow in Power Engineering, Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology, Xi’an Jiaotong University, Xi’an 710049, China

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Abstract

Space nuclear reactor power (SNRP) using a gas-cooled reactor (GCR) and a closed Brayton cycle (CBC) is the ideal choice for future high-power space missions. To investigate the safety characteristics and develop the control strategies for gas-cooled SNRP, transient models for GCR, energy conversion unit, pipes, heat exchangers, pump and heat pipe radiator are established and a system analysis code is developed in this paper. Then, analyses of several operation conditions are performed using this code. In full-power steady-state operation, the core hot spot of 1293 K occurs near the upper part of the core. If 0.4 $ reactivity is introduced into the core, the maximum temperature that the fuel can reach is 2059 K, which is 914 K lower than the fuel melting point. The system finally has the ability to achieve a new steady-state with a higher reactor power. When the GCR is shut down in an emergency, the residual heat of the reactor can be removed through the conduction of the core and radiation heat transfer. The results indicate that the designed GCR is inherently safe owing to its negative reactivity feedback and passive decay heat removal. This paper may provide valuable references for safety design and analysis of the gas-cooled SNRP coupled with CBC.

Keywords gas-cooled space nuclear reactor power closed Brayton cycle system startup and shutdown positive reactivity insertion accident

Corresponding Author(s): Wenxi TIAN,Suizheng QIU

Online First Date: 26 July 2021 Issue Date: 04 January 2022

Cite this article:

Chenglong WANG,Ran ZHANG,Kailun GUO, et al. Dynamic simulation of a space gas-cooled reactor power system with a closed Brayton cycle[J]. Front. Energy, 2021, 15(4): 916-929.

URL:

https://academic.hep.com.cn/fie/EN/10.1007/s11708-021-0757-9
https://academic.hep.com.cn/fie/EN/Y2021/V15/I4/916

Fig.1 A schematic diagram of a gas-cooled SNRP with a direct gas Brayton cycle.

Fig.2 Cross-sectional views of GCR.

Fig.3 Fuel pin of GCR.

Tab.1 Design dimensions of GCR for SNRP system

Fig.4 Sub-models involved in reactor model.

Fig.5 Reactor thermal-hydraulic model.

Fig.6 Control volume division for one flow passage.

Fig.7 Principle of PID speed controller.

Fig.8 Recuperator model.

Fig.9 Building blocks of SAC-SPACE for SNRPS.

Fig.10 Reactor reactivity in startup transient.

Fig.11 Reactor power and average fuel temperature in startup transient.

Fig.12 TAC shaft speed and mass flow rate in startup transient.

Fig.13 System temperatures during the startup transient.

Fig.14 System pressure during the startup transient.

Tab.2 Steady-state parameters of the GCR SNRPS

Fig.15 Fuel temperature contour of GCR core.

Fig.16 Axial temperature profiles of fuel zone in first core region.

Fig.17 Reactor reactivity in PRIA.

Fig.18 Reactor power in PRIA.

Fig.19 Core temperatures during PRIA.

Fig.20 Brayton loop flow rate and turbine pressure ratio in PRIA.

Fig.21 Brayton component powers in PRIA.

Fig.22 Reactivity and reactor power in shutdown.

Fig.23 Reactor temperatures in shutdown.

A	Flow area/m²
C	Delayed neutron precursor concentration/m^–3
c_p	Specific heat capacity/(J·kg^–1·K^–1)
D	Hydraulic diameter/m
E	Effective energy fraction
f	Friction coefficient
H	Height/m
h	Heat transfer coefficient/(W·m^–2·K^–1)
I	Moment of inertia/(kg·m²)
k	Thermal conductivity (W·m^?1·K^?1)
m	Mass/kg
M	Number
N	Shaft speed (r·s^–1)
Nu	Nusselt number
P	Power/W
Pr	Prandtl number
p	Pressure/Pa
Q	Volumetric heat generation/(W·m^?3)
R	Radius/m
R_g	Gas constant/(J·kg^–1·K^–1)
Re	Reynolds number
r	Radial coordinate/m
S	Area/m²
T	Temperature/K
t	Time/s
V	Volume/m³
W	Mass flow rate/(kg·s^?1)
z	Axial coordinate/m
ρ	Reactivity (Δk·k^?1); Density/(kg·m^?3)
λ	Decay constant/s^?1
Λ	Neutron generation time/s
β	Delayed neutron fraction
ε	Emissivity
α	Reactivity feedback coefficient/(Δk·k^–1·K^–1)
σ	Stefan-Boltzmann constant/(5.67 × 10⁻⁸ W·m^?2·K^?4)
Subscripts
alt	Alternator
b	Core block
bin	Core block inner surface
bout	Core block outer surface
bv	Core block and pressure vessel
com	Compressor
Cin	Compressor inlet
Cout	Compressor outlet
d	Downcomer
db	Downcomer and core block
decay	Decay
din	Downcomer inner
dout	Downcomer outer
dv	Downcomer and pressure vessel
eff	Effective
f	Fuel pin
fb	Fuel pin and core block
fiss	Fission
fout	Fuel pin outer surface
g	He-Xe gas
gb	Gas and core block
gf	Gas and fuel pin
i	delayed neutron group
iavg	Average
in	External reactivity
inner	Inner surface
iref	Reference
j	Fission product group
n	Component
outer	Outer surface
p	Annular gas passage
pin	Gas passage inner
pout	Gas passage outer
pv	Pressure vessel
pvin	Pressure vessel inner surface
pw	Plate wall
pwH	Plate wall high-pressure side
pwL	Plate wall low-pressure side
r	Radial reflector
rout	Radial reflector outer surface
RCH	Recuperator high-pressure side
RCL	Recuperator low-pressure side
RCP	Recuperator passage
s	Solid
shaft	TAC shaft
sp	Space environment
Tin	Turbine inlet
Tout	Turbine outlet
tur	Turbine
x	Core block ring

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