Simulation of Neptunium Extraction in an Advanced PUREX Process—Model Improvement

Figures & data

Figure 1. Neptunium extraction flowsheet being simulated (primary extract-scrub section of an advanced PUREX process)^[11].

Table 1. Experimental nitrous acid distribution coefficients data.

Author	CHNO3,aq mol·L^–1	CU,aq g·L^–1	CU,or g·L^–1	CHNO2,or mmol·L^–1	Temperature, °C	No. of data points
Uchiyama, G., et al. ^[Citation23]	0–4	0–14.5	0–80	1.4	25	11
French, E.S. ^[Citation45]	0.1–4	none	none	2–71	22	43
Jenkins, L., ^[Citation46,Citation47]	0.1–2	0–110	0–91.2	0.6–92.3	22–35	186
Zhu, L., et al. ^[Citation44]	0.433–4.355	none	none	0.165–4.174	25	20
Burger, L.L and Money M.D. ^[Citation48]	0–8		0–116	<10	25–50	22
Biddle, P. and Miles, J.H. ^[Citation49]	0.95–2.91		0–71.4	2.4–12.5	20	11

Figure 2. Evaluation of various nitrous acid distribution coefficient models.

Table 2. Parameters of equation (13) ^[35].

a93	28.526	a94	0.01869	a95	0.11958	a96	1.8174	a97	0.009986
a98	4.5326	a99	0.9194	a100	0.000507	a101	0	a102	1
a103	0.24621	a104	1.0622	a105	0.5977	a106	3	a107	0.02016
a108	2.6322	a109	0	a110	1	a111	0.2962	a112	0.5822

Table 3. Specific output powers.

Isotope	Specific output power (W/g),α-radiation	Specific output power (W/g),β- and γ-radiation
^234U	0.000179023
^235U	5.99346 × 10^−8
^236U	1.75418 × 10^−6
^238U	8.51157 × 10^−9
^237Np	0.000704728
^238Pu	0.56771
^239Pu	0.0019283
^240Pu	0.00706947
^241Pu		0.00327218
^242Pu	0.000116829
Reference spent fuel Pu (40 GWd/te, 5 year cooled)	0.01207
Reference spent fuel (40 GWd/te, 5 year cooled)	2.53 × 10^−4	0.001929
Total U*	5.77 × 10^−8	0
Total Pu**	0.01207	6 × 10^−4
FP and inextractable minor actinides***	0.01317	0.1923

*calculated based on the fuel of 98%U, 1%Pu and 1%FPs, the uranium isotope is 0.022% ²³⁴U, 1.09% ²³⁵U, 0.53% ²³⁶U, and 98.35% ²³⁸U;

**suppose the radiation power of plutonium is about 95% α-radiation and 5% β- and γ-radiation.

*** all other isotopes’ output radiation powers are counted in this item.

Figure 3. Single-stage test flowsheet^[11].

Figure 4. Simulation of single-stage experiments with new developed redox kinetics.

Figure 5. Deviations of simulations to experiments with variable neptunium redox kinetics.

Figure 6. Deviations of simulations to experiments with and without disproportionation reactions.

Figure 7. Calculated concentrations of neptunium species present in aqueous and organic phases, based on simulation of single-stage experiment 12 in ref. ^[11].

Figure 8. Deviations of simulations to experiments with and without radiolysis.

Figure 9. Flowsheet simulation results using various descriptions of Np(V) oxidation kinetics.

Figure 10. Aqueous HNO₂ profiles with different HNO₂ distribution coefficient models compared to experimental results.

Figure 11. Organic HNO₂ profiles with different HNO₂ distribution coefficient models.

Figure 12. Simulated neptunium aqueous profiles with different HNO₂ distribution coefficient models.

Figure 13. Simulated neptunium organic profiles with different HNO₂ distribution coefficient models.

Table 4. Hot test feeds.

	A1	F1	F2	A2	S1
U(VI), g·L^–1	0	277	0	0	0
Pu(IV), g·L^–1	0	2.77	0	0	0
Np(V), mg·L^–1	0	166	0	0	0
Np(VI), mg·L^–1	0	0	0	0	0
FPs, mg·L^–1	0	2.77	0	0	0
HNO2,mol·L^–1	0	0	0.073	0	0
HNO3,mol·L^–1	4.5	5	0	0	0.05
TBP, %					30
Flow rate (mL·min^–1)	0.45	0.9	0.1	0	3

Figure 14. Radiation output power in hot test simulation results.

Figure 15. Hot test simulation results, (a) nitrous acid profile and (b) neptunium profile.

Table

Symbols	Unit	Definition
a		Distribution coefficients model parameter
C	mol·L^–1 or g·L^–1	Concentration
G	mol·J^–1	G value
m	g·mol^–1	Atomic weight
N	moles	Moles
P	W·g^–1	Specific output power
t	s or minute	Time
T	°C	Temperature
v	mol·L^–1·s^–1	Reaction rate
V	L	Volume
W	Watt	Radiation power
Subscripts
abs	Absorbed
aq	Aqueous phase
emit	Emitted radiation
or	Organic phase
α	α irradiation
β	β irradiation
γ	γ irradiation

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