Calculations to Support On-line Neutron Spectrum Adjustment by Measurements with Miniature Fission Chambers in the JSI TRIGA Reactor

Kaiba, Tanja; Radulović, Vladimir; Žerovnik, Gašper; Snoj, Luka; Fourmentel, D.; Barbot, L.; Destouches, C.

doi:10.1051/epjconf/201817004012

Cited by 4 publications

(2 citation statements)

References 12 publications

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“…Inspired by other work presented at this conference [9], a study was performed to determine the utility of thermal-neutron filters for providing additional responses given a fixed number of fissile nuclides. In particular, case 3 was revisited with the addition of 113 Cd and 155 Gd.…”

Section: Resultsmentioning

confidence: 99%

On Use of Multi-Chambered Fission Detectors for In-Core, Neutron Spectroscopy

Roberts

2018

EPJ Web Conf.

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Abstract-Presented is a short, computational study on the potential use of multichambered fission detectors for in-core, neutron spectroscopy. Motivated by the development of very small fission chambers at CEA in France and at Kansas State University in the U.S., it was assumed in this preliminary analysis that devices can be made small enough to avoid flux perturbations and that uncertainties related to measurements can be ignored. It was hypothesized that a sufficient number of chambers with unique reactants can act as a real-time, foilactivation experiment. An unfolding scheme based on maximizing (Shannon) entropy was used to produce a flux spectrum from detector signals that requires no prior information. To test the method, integral, detector responses were generated for singleisotope detectors of various Th, U, Np, Pu, Am, and Cs isotopes using a simplified, pressurized-water reactor spectrum and fluxweighted, microscopic, fission cross sections, in the WIMS-69 multigroup format. An unfolded spectrum was found from subsets of these responses that had a maximum entropy while reproducing the responses considered and summing to one (that is, they were normalized). Several nuclide subsets were studied, and, as expected, the results indicate inclusion of more nuclides leads to better spectra but with diminishing improvements, with the best-case spectrum having an average, relative, group-wise error of approximately 51%. Furthermore, spectra found from minimum-norm and Tihkonov-regularization inversion were of lower quality than the maximum entropy solutions. Finally, the addition of thermal-neutron filters (here, Cd and Gd) provided substantial improvement over unshielded responses alone. The results, as a whole, suggest that in-core, neutron spectroscopy is at least marginally feasible.

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Section: Resultsmentioning

confidence: 99%

On Use of Multi-Chambered Fission Detectors for In-Core, Neutron Spectroscopy

Roberts

2018

EPJ Web Conf.

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“…HE ability of a research reactor to perform precise irradiations (for electronic components, biological samples, sensors,…) lies with its neutron and gamma fields characterization. In steady state operating mode, the neutron field of various irradiation positions of the TRIGA Mark II reactor of the Jožef Stefan Institute has already been measured by means of neutron activation dosimetry and miniature fission chambers techniques [1]- [3].…”

Section: Introductionmentioning

confidence: 99%

Gamma-Heating and Gamma Flux Measurements in the JSI TRIGA Reactor: Results and Prospects

Gruel

Ambrožič

Destouches

et al. 2020

IEEE Trans. Nucl. Sci.

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The neutron field of various irradiation positions of the TRIGA Mark II reactor of the Jožef Stefan Institute has been thoroughly characterized by neutron activation dosimetry and miniature fission chambers techniques. In order to have a fully validated calculation scheme to analyze and plan experiments, the gamma field also has to be experimentally validated. The 10-year long collaboration between CEA and JSI is a perfect framework to carry out such a study, and measurements of the gamma field started in late 2016. Several measurement techniques were investigated in in-core and ex-core positions. On-line measurements were carried out using miniature ionization chambers manufactured by the CEA and PTW Farmer ionization chambers. Positional dependence was studied, showing a decrease in the delayed gamma contribution to the total gamma flux with increasing distance from the reactor core center. To characterize the gamma dose in the core, as well as in the periphery, thermo-and optically stimulated luminescent detectors were tested. These detectors are commonly used at CEA to measure the gamma dose in a given material in order to study the nuclear heating in various core elements (control rod, baffle, structural material). Different filters were used in order to assess an integrated dose ranging from a few Gy up to several kGy. The feasibility of such measurements demonstrates the complementarity between measurements with dosimetry and ionization chambers from low to very high gamma-dose environment, such as in material testing reactors.

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Gamma-heating and gamma flux measurements in the JSI TRIGA reactor, results and prospects

Gruel

Ambrožič²,

Destouches

et al. 2020

EPJ Web Conf.

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The neutron field of various irradiation positions of the TRIGA Mark II reactor of the Jožef Stefan Institute has been thoroughly characterized by neutron activation dosimetry and miniature fission chambers techniques. In order to have a fully validated calculation scheme to analyze and plan experiments, the gamma field also has to be experimentally validated. The 10-year long collaboration between CEA and JSI is a perfect framework to carry out such a study, and measurements of the gamma field started in late 2016. Several measurement techniques were investigated in in-core and ex-core positions. On-line measurements were carried out using miniature ionization chambers manufactured by the CEA and PTW Farmer ionization chambers. Positional dependence was studied, showing a decrease in the delayed gamma contribution to the total gamma flux with increasing distance from the reactor core center. To characterize the gamma dose in the core, as well as in the periphery, thermo- and optically stimulated luminescent detectors were tested. These detectors are commonly used at CEA to measure the gamma dose in a given material in order to study the nuclear heating in various core elements (control rod, baffle, structural material). Different filters were used in order to assess an integrated dose ranging from a few Gy up to several kGy. The feasibility of such measurements demonstrates the complementarity between measurements with dosimetry and ionization chambers from low to very high gamma-dose environment, such as in material testing reactors.

show abstract

Calculations to Support On-line Neutron Spectrum Adjustment by Measurements with Miniature Fission Chambers in the JSI TRIGA Reactor

Cited by 4 publications

References 12 publications

On Use of Multi-Chambered Fission Detectors for In-Core, Neutron Spectroscopy

On Use of Multi-Chambered Fission Detectors for In-Core, Neutron Spectroscopy

Gamma-Heating and Gamma Flux Measurements in the JSI TRIGA Reactor: Results and Prospects

Gamma-heating and gamma flux measurements in the JSI TRIGA reactor, results and prospects

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