Nuclear Operations Core Elements Improvements for Optimization of Radioisotopes Production in an MTR-type Core T. Makmal 1,2 , M. Alqahtani 2 , A. Buijs 2 , J. Luxat 2 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 • The primary purpose of Research Reactors is to provide a neutron source for research in natural sciences, industrial processing and nuclear medicine. • The most common method for isotopes production is by the neutron activation process. • Due to the cosine shape of the flux in every axis, the maximal flux length is located around the center of the active length of the Fuel Assembly (FA). • This limited area of maximal flux makes the activation process of large or multiple samples less efficient. Core Elements Improvements 2
Nuclear Operations PART II: THE OBJECTIVE OF THIS STUDY • Analyzing the main components in isotope production process in order to optimize the production by uniform and flat thermal flux. • Re-design components: Standard MTR FA • Irradiation Position (IP) body material. • FA linear fuel distribution loading. Inner cylinder for irradiation samples • Carry out a production rate comparison between MNR FA to the modified FA. IP “ Body Material ” THE METHODOLOGY • 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. Core Elements Improvements 3
Nuclear Operations PART II: FLUX IMPROVEMENTS (1/4) xy-plot of the mini-core. xy-plot of the mini-core – mesh image. yz-plot Core Elements Improvements 4
Nuclear Operations PART II: FLUX IMPROVEMENTS (1/4) Changes in the IP body material • Five principal materials simulated to analyse the change in flux shape. 2,10E+13 9,3E+13 Thermal Flux [n/cm2/sec] 2,05E+13 9,2E+13 Thermal Flux [n/cm2/sec] 2,00E+13 9,1E+13 1,95E+13 9,0E+13 1,90E+13 8,9E+13 1,85E+13 8,8E+13 1,80E+13 8,7E+13 1,75E+13 Case#4 IP - Be Case#4 IP - HWT Case#4 IP - GRA Case#4 IP - He Case#4 IP - LWT 1,70E+13 8,6E+13 0 10 20 30 40 50 60 Active length [cm] Core Elements Improvements 5
Nuclear Operations PART II: FLUX IMPROVEMENTS Changes in the linear atom density • The U-235 atom density change will be achieved by increasing the number of U 235 mass in Total U 235 mass U 235 density in a plate Card U density in a plate Thermal Conductivity U 3 Si 2 molecules per cc without changing the enrichment of the. [gU 235 /cc] # each plate [gr] in a FA [gr] [gU/cc] [W*m/K] • Different cards were built with Uranium densities between 3.735 to 5.478 gU/cc. 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 • At very high loadings the aluminum ceases to play a significant role, and the thermal conductivity approaches that of the fuel (15 [W/mK] ), which indicates stopping criteria for additional high density card. Core Elements Improvements 6
Nuclear Operations PART II: FLUX IMPROVEMENTS Case#7 Changes in the linear atom density: • Using the different loadings Cards, a new fuel (Case) was built. Card5# • Each FA was split into seven sub segments (8.5714cm each). Card3# • Eight different Cases were simulated. All analysed and compared. Card2# • The most efficient cases, in terms of high and flat flux, were chosen. Card1# Card2# Fuel atom Thermal Fuel atom Thermal density Conductivity density Conductivity Card3# Sub-segment [grU/cc] [w*m/K] [grU/cc] [w*m/K] # Card5# Case #4 Case #7 (MNR standard FA) 1 3.735 77.70 4.731 37.06 2 3.735 77.70 4.233 55.68 3 3.735 77.70 3.984 66.39 4 3.735 77.70 3.735 77.70 5 3.735 77.70 3.984 66.39 6 3.735 77.70 4.233 55.68 7 3.735 77.70 4.731 37.06 Core Elements Improvements 7
Nuclear Operations PART II: FLUX IMPROVEMENTS Changes in the linear atom density and the IP body material: 9,3E+13 Thermal Flux [n/cm2/sec] 9,2E+13 9,1E+13 9,0E+13 Case#4 IP - LWT Case#7 IP - LWT 8,9E+13 8,8E+13 8,7E+13 8,6E+13 0 10 20 30 40 50 60 Active length [cm] 1,96E+13 Thermal Flux [n/cm2/sec] 1,94E+13 1,92E+13 1,90E+13 Case#4 IP - Be Case#7 IP - Be 1,88E+13 1,86E+13 1,84E+13 1,82E+13 1,80E+13 0 10 20 30 40 50 60 Active length [cm] Core Elements Improvements 8
Nuclear Operations PART III: PRODUCTION RATE COMPARISON 70 • To present the benfit of the suggested FA in comparison to the known MTR 60 60 60 # of accepted seeds in 24 hr 60 FA, calculation of Iridium-192 seeds production carry out. 50 • The objective is to evaluate, by calculations, the productions of uniform 40 shift activity Ir-192 seeds. 30 25 24 23 • Using the well known activation equation, the activity of 60 seeds calculated. 20 • The irradiation time set according to the center seed approaching to the 10 activity target (200mCi). 0 Case#4 Case#7 Case#4 Case#7 Case#4 Case#7 • A strict quality check disqualifies seeds if their activity is outside of 1% from GRA GRA Be Be HWT HWT 400 the activity target . # of accepted seeds in 24 hr 334 350 300 250 shift 200 150 118 100 50 𝐵 𝐷𝑗 = Ν ∙ 𝜏 ∙ 𝜚 ∙ (1 − 𝑓 −𝜇𝑢 0 ൯ Case#4 Case#7 LWT LWT Core Elements Improvements 9
Nuclear Operations PART IV: THERMAL-HYDRAULIC CALCULATION • Calculations of lower thermal conductivity (higher fuel atom density) show not much difference in the temperatures profile along an axial fuel plate. (~3.7grU/cc) 𝑒 • Explained by the Biot number, Bi = h ∙ 𝑙 , the fuel thickness is not thick enough to get heated. (~4.7grU/cc) • 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 U 3 Si 2 are very similar. • Safety analysis calculations for Onset Nucleate Boiling and Pump Failure show no significant difference comparing to MNR standard FA calculations values. Core Elements Improvements 10
Nuclear Operations PART IV: K EFF AND BURNUP CALCULATIONS • For reliable running, each simulation done with 50000 particles, 5000 active and 250 inactive cycles. • The absolute error in the Keff was found to be <0.07mK and therefore neglected. 1,58 1,571 55days 1,60 1,564 1,567 1,56 2500 1,546 1,540 # of acceepted seeds in cycle 1,542 2207 1,54 1,50 1,52 2000 1,40 1,5 25days 1,482 IMP keff Keff 1,48 1500 1,30 1,457 1,46 65days 1,44 1,20 1000 676 1,42 558 1,10 1,4 500 • 1,38 In terms of the successful continuity operation, 16 cycles of five days each 1,00 Be GRA HWT LWT Be GRA HWT LWT 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 0 were preformed. Operating Days Case#7 Case#4 Case#7 4 4 4 4 7 7 7 7 • The core become sub-critical only after 50 days of operation. Case#7_Be Case#7_LWT Case#4_LWT Be Different Cases LWT LWT Core Elements Improvements 11
Nuclear Operations PART IV: SUMMARY AND CONCLUSIONS • 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 K eff . • 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. Core Elements Improvements 12
Nuclear Operations Questions? THANK YOU! Core Elements Improvments 14
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