Small, long-life high temperature gas-cooled reactor free from prompt supercritical accidents by particle-type burnable poisons

Figures & data

Table 1 Design specification of the 100-MW_th prismatic HTGR

Thermal power	100 MW
Equivalent core diameter	2.8 m
Effective core height	2.9 m
Average power density	5.7 MW/m^3
Number of fuel blocks	270 blocks
Number of fuel block layers	5 layers
Number of fuel blocks per layer	54 blocks
Number of fuel rods in a block	33 rods
Coolant	Helium
Coolant temperature inlet/outlet	395°C / 850°C
Fuel	UO2 in TRISO&break;particles
Uranium enrichment	20.0 wt%
Packing fraction of TRISO particles in&break;fuel compact	30%

Figure 1 The arrangement of fuel blocks and control rod blocks in the 100-MW_th prismatic HTGR

Figure 2 A loading of fuel particles and BP particles in a fuel rod

Figure 3 Cross sections of a fuel-coated particle and a BP particle

Table 2 The properties of burnable poisons [6,11]

Material	B4C	Gd2O3	CdO
Main absorbing isotope	^10B	^155Gd, ^157Gd	^113Cd
Density (g/cm^3)	2.52	7.4	8.15
Content of main absorbing isotope (%)	90	14.8, 15.65	12.22
Thermal neutron mean free path* (μm)	25	8.3	101.6
Thermal neutron capture cross sections* (barn)	3,837	60,740 and 253,700	20,760

Figure 4 Microscopic absorption cross section of main absorbing isotopes [11]

Figure 5 The sensitivity of the parameters obtained using the combination of B₄C + Gd₂O₃ particles loading

Table 3 Summary of the burnup characteristics of a reactor without BP particles and with the appropriate loading of BP particles

	BPP #1: B4C		BPP #2: Gd2O3 or CdO
	D (μm)	V F/V BP	D (μm)	V F/V BP	(% error)	ρ max&break; (% Δk/k)	Δρ&break; (% Δk/k)	Discharge burnup (GWd/t)
No BP	–	–	–	–	1.430 (0.029%)	30.08	30.08	102.8
B4C + Gd2O3	202	160	1,200	99	1.010 (0.034%)	0.98	0.98	82.2
B4C + CdO	200	146	1,000	309	1.013 (0.040%)	1.32	1.32	80.7

Figure 6 The effective multiplication factor (k _eff) of the reactor without and with BP particles insertion at 1200 K

Table 4 The change in reactivity achieved by decreasing the parameters by 1% in the appropriate loading of B₄C + Gd₂O₃ particles

B4C		Gd2O3		The results			Deviation from ref. (%)
D (μm)	V F/V BP	D (μm)	V F/V BP	ρ max	ρ min	Δρ	ρ max	ρ min	Δρ
202^**	160	1200	99	0.984	0.096	0.887	–	–	–
202	160	1200	98	0.990	0.076	0.913	−0.006	−0.020	−0.026
202	158	1200	99	0.831	−0.156	0.987	−0.152	−0.252	0.100
202	160	1188	99	0.969	0.042	0.928	−0.015	−0.055	0.041
200	160	1200	99	1.021	0.004	1.017	0.037	−0.092	0.130

Figure 7 The change in the k _eff by decreasing the diameter and the V _F/V _BP by 1% for the appropriate loading of B₄C + Gd₂O₃ particles

Table 5 Summary of the burnup characteristics of a reactor without BP particles and with the appropriate loading of BP particles to avoid a prompt supercritical accident

	BPP #1: (B4C)		BPP #2: (Gd2O3 or CdO)
	D(μm)	V F/V BP	D (μm)	V F/V BP	ρ max&break; (% Δk/k)	ρ min&break; (% Δk/k)	Δρ (% Δk/k)	Discharge burnup (GWd/t)
B4C+ Gd2O3	210	155	1200	95	0.52	−0.51	1.03	78.2
B4C+ CdO	200	140	1100	293	0.46	−0.77	1.23	75.0

Figure 8 Change in the number densities of ²³⁹ Pu, ²⁴⁰Pu, ²⁴¹Pu, and ²⁴²Pu isotopes in the fuel kernels for the appropriate loading of B₄C + Gd₂O₃ particles

Figure 9 Change in the number densities of ¹⁵⁵Gd and ¹⁵⁷Gd in Gd₂O₃ particles and ¹⁰B in B₄C particles for the appropriate loading of B₄C + Gd₂O₃ particles

Figure 10 Change in the number densities of ¹¹³Cd in CdO particles and ¹⁰B in B₄C particles for the loading of B₄C + CdO particles

Figure 11 The change in the k _eff when the core temperature decreases from 1200 K for the appropriate loading of B₄C + Gd₂O₃ particles

Figure 12 The change in the k _eff when the core temperature decreases from 1200 K for the appropriate loading of B₄C + CdO particles

Table 6 Compensation for the reactivity worth by decreasing the core temperature for reactors with the appropriate loading of BP particles to avoid a prompt supercritical accident

BP particles	k eff	At burnup	α T,avg* (% Δk/k/K)	Maximum temperature reduction	Drop of thermal efficiency
B4C + Gd2O3	0.996 ± 0.0003	30 GWd/t	−0.0024	164 K	5.74%
B4C + CdO	0.992 ± 0.0003	25 GWd/t	−0.0043	178 K	6.23%

Figure 13 The neutron flux in fuel kernels at energy level 0.01–100 eV in various burnup periods: 10 GWd/t, 30 GWd/t, and 42.5 GWd/t

Figure 14 Diagram of the direct Brayton cycle [12]

Figure 15 The thermal efficiency of a gas turbine direct Brayton cycle in GT-MHR as a function of turbine inlet temperature [13]

Table 7 Summary of the burnup characteristics of a reactor without BP particles and with the appropriate loading of BP particles to avoid any supercritical accident during operation

	BPP #1: (B4C)		BPP #2: (Gd2O3 or CdO)
	D (μm)	V F/V BP	D (μm)	V F/V BP	ρ max (% Δk/k)	ρ min (% Δk/k)	Δρ (% Δk/k)
B4C + Gd2O3	215	148	1200	96	−0.094	−1.25	1.16
B4C + CdO	205	136	1100	292	−0.06	−1.35	1.30

Table 8 Compensation for the reactivity worth by decreasing the core temperature for subcritical reactors with the appropriate loading of BP particles to avoid any supercritical accident during operation

BP particles	k eff	At burnup	α T,avg* (% Δk/k/K)	Maximum temperature reduction	Drop of thermal efficiency
B4C + Gd2O3	0.989 ± 0.0004	35 GWd/t	−0.00318	347 K	12.1%
B4C + CdO	0.987 ± 0.0003	25 GWd/t	−0.00479	280 K	9.8%

Figure 16 The change in the k _eff when the core temperature decreases from 1200 K for the appropriate loading of B₄C + Gd₂O₃ particles

Figure 17 The change in the k _eff when the core temperature decreases from 1200 K for the appropriate loading of B₄C + CdO particles

Tran , H N and Kato , Y . 2009 . An optimal loading principle of burnable poison for an OTTO refueling scheme in pebble bed HTGR cores . Nucl Eng Des , 239 : 2357 – 2364 .

 Web of Science ®Google Scholar

Shibata , K , Iwamoto , O , Nakagawa , T , Iwamoto , N , Ichihara , A , Kunieda , S , Chiba , S , Furukawa , K , Otuka , N , Ohsawa , T , Murata , T , Matsunobu , H , Zukaran , A , Kameda , S and Katakura , J . 2011 Jan . JENDL-4.0: a new library for nuclear science and technology . J Nucl Sci Tech , 48 : 1 – 30 .

 Web of Science ®Google Scholar

LaBar , M P . 2002 . The gas turbine–modular helium reactor: a promising option for near term deployment . ANS 2002 Annual Meeting . June 9–13 2002 , Hollywood , FL . GA-A23952

 Google Scholar

Juhasz , A J , Rarick , R A and Ranggarajan , R . 2009 . High efficiency nuclear power plants using liquid fluoride thorium reactor technology . AIAA Paper 2009-4565 presented at: 7th IECEC . Aug 2–5 2009 , Denver , CO .

 Google Scholar