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Nuclear Operations
Core Elements Improvements for Optimization of Radioisotopes
Production in an MTR-type Core
T. Makmal1,2, M. Alqahtani2, A. Buijs2, J. Luxat2
1) Nuclear Physics and Engineering Division, Soreq Nuclear Research Center, Yavne, Israel
2) Engineering and physics department, McMaster University, Ontario, Canada
Nuclear Operations
PART I: INTRODUCTION
2Core Elements Improvements
• The primary purpose of Research Reactors is to provide a neutron source forresearch in natural sciences, industrial processing and nuclear medicine.
• The most common method for isotopes production is by the neutronactivation process.
• Due to the cosine shape of the flux in every axis, the maximal flux length islocated around the center of the active length of the Fuel Assembly (FA).
• This limited area of maximal flux makes the activation process of large ormultiple samples less efficient.
Nuclear Operations
PART II: THE OBJECTIVE OF THIS STUDY
3Core Elements Improvements
• Analyzing the main components in isotope production process in order to optimize the production by uniform and flat thermal flux.
• Re-design components:
• Irradiation Position (IP) body material.
• FA linear fuel distribution loading.
• Carry out a production rate comparisonbetween MNR FA to the modified FA. IP “Body Material”
Inner cylinder for irradiation samples
Standard MTR FA
• 3-D, Monta-Carlo Simulations of MTR fuel-type mini-core.
• The thermal flux, along the active length, of the inner cylinder was detected. The
values were analysed and compared.
THE METHODOLOGY
Nuclear Operations
PART II: FLUX IMPROVEMENTS (1/4)
4Core Elements Improvements
xy-plot of the mini-core. xy-plot of the mini-core – mesh image. yz-plot
Nuclear Operations
PART II: FLUX IMPROVEMENTS (1/4)
5Core Elements Improvements
Changes in the IP body material
• Five principal materials simulated to analyse the change in flux shape.
8,6E+13
8,7E+13
8,8E+13
8,9E+13
9,0E+13
9,1E+13
9,2E+13
9,3E+13
1,70E+13
1,75E+13
1,80E+13
1,85E+13
1,90E+13
1,95E+13
2,00E+13
2,05E+13
2,10E+13
0 10 20 30 40 50 60
Ther
mal
Flu
x [n
/cm
2/s
ec]
Ther
mal
Flu
x [n
/cm
2/s
ec]
Active length [cm]
Case#4 IP - Be Case#4 IP - HWT Case#4 IP - GRA Case#4 IP - He Case#4 IP - LWT
Nuclear Operations
PART II: FLUX IMPROVEMENTS
6Core Elements Improvements
Changes in the linear atom density
• The U-235 atom density change will be achieved by increasing the number of
U3Si2 molecules per cc without changing the enrichment of the.
• Different cards were built with Uranium densities between 3.735 to 5.478 gU/cc.
• At very high loadings the aluminum ceases to play a significant role, andthe thermal conductivity approaches that of the fuel (15[W/mK]), whichindicates stopping criteria for additional high density card.
Card
#
U235 mass in
each plate [gr]
Total U235 mass
in a FA [gr]
U235 density in a plate
[gU235/cc]
U density in a plate
[gU/cc]
Thermal Conductivity
[W*m/K]
1 14.0625 225 0.737 3.735 77.70
2 15.0000 240 0.786 3.984 66.39
3 15.9375 255 0.836 4.233 55.68
4 16.8750 270 0.885 4.482 45.81
5 17.8125 285 0.934 4.731 37.06
6 18.7500 300 0.983 4.980 29.81
7 19.6875 315 1.032 5.229 24.48
8 20.6250 330 1.081 5.478 21.60
Nuclear Operations
PART II: FLUX IMPROVEMENTS
7Core Elements Improvements
Changes in the linear atom density:
• Using the different loadings Cards, a new fuel (Case) was built.
• Each FA was split into seven sub segments (8.5714cm each).
• Eight different Cases were simulated. All analysed and compared.
• The most efficient cases, in terms of high and flat flux, were chosen.
Sub-segment #
Fuel atom density [grU/cc]
Thermal Conductivity
[w*m/K]
Fuel atom density [grU/cc]
Thermal Conductivity
[w*m/K]
Case #4 (MNR standard FA)
Case #7
1 3.735 77.70 4.731 37.062 3.735 77.70 4.233 55.683 3.735 77.70 3.984 66.394 3.735 77.70 3.735 77.705 3.735 77.70 3.984 66.396 3.735 77.70 4.233 55.687 3.735 77.70 4.731 37.06
Card5#
Card5#
Card3#
Card3#
Card2#
Card2#
Card1#
Case#7
Nuclear Operations
PART II: FLUX IMPROVEMENTS
8Core Elements Improvements
Changes in the linear atom density and the IP body material:
8,6E+13
8,7E+13
8,8E+13
8,9E+13
9,0E+13
9,1E+13
9,2E+13
9,3E+13
0 10 20 30 40 50 60
Ther
mal
Flu
x [n
/cm
2/s
ec]
Active length [cm]
Case#4 IP - LWT Case#7 IP - LWT
1,80E+13
1,82E+13
1,84E+13
1,86E+13
1,88E+13
1,90E+13
1,92E+13
1,94E+13
1,96E+13
0 10 20 30 40 50 60
Ther
mal
Flu
x [n
/cm
2/s
ec]
Active length [cm]
Case#4 IP - Be Case#7 IP - Be
Nuclear Operations
PART III: PRODUCTION RATE COMPARISON
9Core Elements Improvements
• To present the benfit of the suggested FA in comparison to the known MTR FA, calculation of Iridium-192 seeds production carry out.
• The objective is to evaluate, by calculations, the productions of uniform activity Ir-192 seeds.
• Using the well known activation equation, the activity of 60 seeds calculated.
• The irradiation time set according to the center seed approaching to the activity target (200mCi).
• A strict quality check disqualifies seeds if their activity is outside of 1% from the activity target .
൯𝐴 𝐶𝑖 = Ν ∙ 𝜎 ∙ 𝜙 ∙ (1 − 𝑒−𝜆𝑡
25
60
24
60
23
60
0
10
20
30
40
50
60
70
Case#4 Case#7 Case#4 Case#7 Case#4 Case#7
GRA GRA Be Be HWT HWT
# o
f ac
cep
ted
see
ds
in 2
4 h
r sh
ift
118
334
0
50
100
150
200
250
300
350
400
Case#4 Case#7
LWT LWT
# o
f ac
cep
ted
see
ds
in 2
4 h
r sh
ift
Nuclear Operations
PART IV: THERMAL-HYDRAULIC CALCULATION
10Core Elements Improvements
• Calculations of lower thermal conductivity (higher fuel atom density) show not much difference in the temperatures profile along an axial fuel plate.
• Explained by the Biot number, Bi = h ∙𝑑
𝑘, the fuel thickness is not thick enough
to get heated.• The heat capacity of the fuel meat decreases from 2.44 to 2.13 [MJ/m*K] as the
fuel volume fraction (fuel+voids) increases from 0 to 0.5. The decrease is a result of the increase in porosity as the fuel volume fraction increases, since the volumetric heat capacities of aluminum and U3Si2 are very similar.
• Safety analysis calculations for Onset Nucleate Boiling and Pump Failure show no significant difference comparing to MNR standard FA calculations values.
(~3.7grU/cc)
(~4.7grU/cc)
Nuclear Operations
PART IV: KEFF AND BURNUP CALCULATIONS
11Core Elements Improvements
• For reliable running, each simulation done with 50000 particles, 5000 activeand 250 inactive cycles.
• The absolute error in the Keff was found to be <0.07mK and therefore neglected.
• In terms of the successful continuity operation, 16 cycles of five days each were preformed.
• The core become sub-critical only after 50 days of operation.
1,546 1,540 1,542
1,457
1,571 1,564 1,567
1,482
1,38
1,4
1,42
1,44
1,46
1,48
1,5
1,52
1,54
1,56
1,58
Be GRA HWT LWT Be GRA HWT LWT
4 4 4 4 7 7 7 7
Kef
f
Different Cases
1,00
1,10
1,20
1,30
1,40
1,50
1,60
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70
IMP
kef
f
Operating Days
Case#7_Be Case#7_LWT Case#4_LWT
558676
2207
0
500
1000
1500
2000
2500
Case#7 Case#4 Case#7
Be LWT LWT
# o
f ac
cee
pte
d s
eed
s in
cyc
le
25days
55days
65days
Nuclear Operations
PART IV: SUMMARY AND CONCLUSIONS
12Core Elements Improvements
• In this scoping study a new design of MTR FA analyse in order to optimize isotope production at MTR type RRs.
• Components impact:
• IP body material changes the flux amplitude.
• Linear fuel distribution changes the flux shape.
• In comparison a full cycle, by using the re-design models, the cycle length increases by 120% and the radioisotopes production increases by 230%
• Except LWT, no significant different found between the IP body materials, in terms of production rate and the Keff .
• Thermal-Hydraulic calculations and a safety analysis for the selected cases shows safe operations comparing to an MNR safety analysis report.
• This new design can be cost effective in terms of radioisotopes production and fuel.
Nuclear Operations
THANK YOU!
14Core Elements Improvments
Questions?
