Fluence Profiling at JSI Triga Reactor Irradiation V

Fluence Profiling at JSI Triga Reactor Irradiation V. Sola

Container gets into the core through a tube and it is in vertical position during irradiation, parallel with fuel rods Our samples are irradiated in channel F 19 Rotation of the irradiation container around the axis of the cylinder is not controlled → we don’t know the angle during irradiation Location of irradiation More detail of the reactor in e. g. : L. Snoj et al. , Applied Radiation and Isotopes 70 (2012) 483– 488 channel (doi: 10. 1016/j. apradiso. 2011. 042) Photo of reactor core when reactor is on power (photo taken through 5 m of water from the platform) V. Sola FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 2

Irradiation Strategy - Sensor Placement Up B-16 -4 B-16 -6 Down B-16 -5 73 ± 1 mm B-22 -5 19 ± 1 mm B-19 -6 B-13 -5 B-22 -3 B-22 -6 V. Sola FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 3

Flux Simulation - From Igor Calculated flux of fast neutrons (E > 100 ke. V) in location of F 19 in the reactor Calculations were made with resolution 2 x 2 x 2 mm 3 ➣ horizontal direction is towards the centre of the core ➣ factor 2 variations peak to peak in this volume V. Sola FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 4

Radial Flux - From Igor In F 19 1 Me. V equivalent flux: 1. 54 E 12 n/cm 2/s → ϕ(E > 100 ke. V) = 1. 71 E 12 n/cm 2/s Irrad. Container (2 cm) ± 20% Gradient within irradiation container ± 20% peak-to-peak V. Sola FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 5

Perpendicular Flux - From Igor Gradient much smaller in perpendicular (phi) direction < ± 10% V. Sola FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 6

Irradiation Strategy - Support Structure Samples ready for irradiation V. Sola FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 7

2 D Flux Simulation - Fixed z z = -4. 595 cm [z = 2. 6 cm → row 1 of lower 5 x 5 array] V. Sola z = 0. 805 cm [z = 8 cm → row 1 of upper 5 x 5 array] FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 8

2 D Fluence Simulation - Fixed z z = -4. 595 cm [z = 2. 6 cm → row 1 of lower 5 x 5 array] V. Sola z = 0. 805 cm [z = 8 cm → row 1 of upper 5 x 5 array] FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 9

B-19 -6 Fluence from Data - UP B-16 -5 B-16 -6 V. Sola B-22 -3 FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 10

Compare Data & Simulation - UP Idea: Take the minimum and maximum fluence for each sensor and try to find those fluence values on the simulated surface, to extrapolate the sensor position inside the channel V. Sola 19 -6 22 -3 16 -6 16 -5 FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 11

Compare Data & Simulation - UP ▼ 19 -6 lowest fluence ▲ 19 -6 highest fluence All ▼ 22 -3 lowest fluence ▲ 22 -3 highest fluence ▼ 16 -5 lowest fluence ▲ 16 -5 highest fluence ▼ 16 -6 lowest fluence ▲ 16 -6 highest fluence ➣ Try to interpolate the data points with the support structure to estimate the structure orientation V. Sola FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 12

Compare Data & Simulation - DOWN Idea: Take the minimum and maximum fluence for each sensor and try to find those fluence values on the simulated surface, to extrapolate the sensor position inside the channel V. Sola 22 -5 13 -5 16 -4 22 -6 FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 13

Compare Data & Simulation - DOWN ▼ 19 -6 lowest fluence ▲ 19 -6 highest fluence All ▼ 22 -3 lowest fluence ▲ 22 -3 highest fluence ▼ 16 -5 lowest fluence ▲ 16 -5 highest fluence ▼ 16 -6 lowest fluence ▲ 16 -6 highest fluence ➣ Try to interpolate the data points with the support structure to estimate the structure orientation V. Sola FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 14

Error Propagation d. V = 0. 1 V d. C = ? → can we assume 10 p. F? Made for row 1 - column 1 of sensor 22 -6: VGL new = 22, 2 V ± 9, 3% VGL irr = 12, 3 V ± 9, 5% ratio = 0, 55 ± 13. 3% V. Sola FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 15

Additional Material FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020

CV on W 1 13 -5 - IRR Horizontal uniformity Average: 13, 064 V Sigma: 0, 072 V (0. 5%) Vertical uniformity [column] V. Sola FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 [row] 17

CV on W 1 13 -5 - RATIO Vertical uniformity Horizontal uniformity There is a clear horizontal trend No particular vertical trend [column] V. Sola FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 [row] 18

Vertical Trend 73 +-1 mm // neutron flux 19 +-1 mm 0 V. Sola … 5 55 60 65 [mm] No vertical trend observed FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 19

Conversion into Fluence Using M. Ferrero parametrisation presented at TREDI 2019(Trento, Italy) y = e-3, 85 E-16 x Maximum spread in fluence is 10% Delivered F = (1. 50 ± 0. 15)E 15 neq/cm 2 V. Sola FLUENCE PROFILING AT JSI TRIGA REACTOR - 29. 05. 2020 20