Characterization of the gamma flux in a tangential channel of the CENM TRIGA MARK II research reactor

The CNESTEN (National Center for Energy Sciences and Nuclear Technology, Morocco) operates a TRIGA Mark II reactor, which can reach a thermal maximum power at steady state of 2 MW. In reactors devoted to research and experiments, it is mandatory to characterize the neutron and photon fields in the irradiation positions. Together with a computational model of the core, it ensures the ability to reach the requested uncertainties when performing experiments, such as detectors testing, irradiation for hardening or nuclear data measurements. The neutron field of different irradiation positions has been characterized by dosimetry techniques and compared to the MCNP full model of the reactor. Preliminary photon propagation calculations are also performed with this model, but up to now, no experimental validation of the results exists. The aim of the newly set collaboration between CEA and CNESTEN is to characterize the gamma field of these positions. The first position investigated is the part of the NB1 tangential channel closest to the core. Among gamma measurements techniques, and according to the constraints arising from using this channel, it was chosen to use thermos- and optically stimulated luminescent detectors. This paper presents the experiments carried out in September 2018 as well as their results. Three detectors types were used: TLD400 (CaF2:Mn), TLD700 (7LiF:Mg,Ti) and OSLD (Al2O3:C). Measurements were performed in several steps: background measurements, transient measurements (divergence phase + SCRAM), and irradiation at steady state. In the end, these measurements will provide a dose as well as a gamma flux value for this position.

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The CANDELLE experiment for characterization of neutron sensitivity of LiF TLDs

EPJ Web of Conferences ◽

10.1051/epjconf/201817004014 ◽

2018 ◽

Vol 170 ◽

pp. 04014 ◽

Cited By ~ 2

Author(s):

M.Le Guillou ◽

A. Billebaud ◽

A. Gruel ◽

G. Kessedjian ◽

O. Méplan ◽

...

Keyword(s):

Neutron Field ◽

Early Assessment ◽

Power Flux ◽

Design Studies ◽

Thermoluminescent Dosimeters ◽

Highly Sensitive ◽

Gamma Field ◽

Nuclear Heating

As part of the design studies conducted at CEA for future power and research nuclear reactors, the validation of neutron and photon calculation schemes related to nuclear heating prediction are strongly dependent on the implementation of nuclear heating measurements. Such measurements are usually performed in low-power reactors, whose core dimensions are accurately known and where irradiation conditions (power, flux and temperature) are entirely controlled. Due to the very low operating power of such reactors (of the order of 100 W), nuclear heating is assessed by using dosimetry techniques such as thermoluminescent dosimeters (TLDs). However, although they are highly sensitive to gamma radiation, such dosimeters are also, to a lesser extent, sensitive to neutrons. The neutron dose depends strongly on the TLD composition, typically contributing to 10-30% of the total measured dose in a mixed neutron/gamma field. The experimental determination of the neutron correction appears therefore to be crucial to a better interpretation of doses measured in reactor with reduced uncertainties. A promising approach based on the use of two types of LiF TLDs respectively enriched with lithium-6 and lithium-7, precalibrated both in photon and neutron fields, has been recently developed at INFN (Milan, Italy) for medical purposes. The CANDELLE experiment is dedicated to the implementation of a pure neutron field “calibration” of TLDs by using the GENEPI-2 neutron source of LPSC (Grenoble, France). Those irradiation conditions allowed providing an early assessment of the neutron components of doses measured in EOLE reactor at CEA Cadarache with 10% uncertainty at 1σ.

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Characterization of the TRIGA Mark II reactor full-power steady state

Nuclear Engineering and Design ◽

10.1016/j.nucengdes.2016.01.026 ◽

2016 ◽

Vol 300 ◽

pp. 308-321 ◽

Cited By ~ 8

Author(s):

Antonio Cammi ◽

Matteo Zanetti ◽

Davide Chiesa ◽

Massimiliano Clemenza ◽

Stefano Pozzi ◽

...

Keyword(s):

Steady State ◽

Full Power ◽

Triga Mark Ii

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

EPJ Web of Conferences ◽

10.1051/epjconf/202022504029 ◽

2020 ◽

Vol 225 ◽

pp. 04029 ◽

Cited By ~ 1

Author(s):

A. Gruel ◽

K. Ambrožič ◽

C. Destouches ◽

V. Radulović ◽

A. Sardet ◽

...

Keyword(s):

Measurement Techniques ◽

Reactor Core ◽

Neutron Field ◽

Gamma Dose ◽

Ionization Chambers ◽

Control Rod ◽

Stefan Institute ◽

Core Elements ◽

Gamma Field ◽

Gamma Flux

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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Characterization of a DNA polymerase from the hyperthermophile archaea Thermococcus litoralis. Vent DNA polymerase, steady state kinetics, thermal stability, processivity, strand displacement, and exonuclease activities.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(18)53949-1 ◽

1993 ◽

Vol 268 (3) ◽

pp. 1965-1975

Author(s):

H. Kong ◽

R.B. Kucera ◽

W.E. Jack

Keyword(s):

Thermal Stability ◽

Steady State ◽

Dna Polymerase ◽

Strand Displacement ◽

Thermococcus Litoralis ◽

Steady State Kinetics

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Characterization of a polyphenyl ether oil irradiated at high doses in a TRIGA Mark II nuclear reactor

Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms ◽

10.1016/j.nimb.2021.03.021 ◽

2021 ◽

Vol 497 ◽

pp. 1-9

Author(s):

Matteo Ferrari ◽

Aldo Zenoni ◽

Yongjoong Lee ◽

Yoshikazu Hayashi

Keyword(s):

Nuclear Reactor ◽

Polyphenyl Ether ◽

Triga Mark Ii ◽

High Doses

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Isolation and Molecular Characterization of the Romaine Lettuce Phylloplane Mycobiome

Journal of Fungi ◽

10.3390/jof7040277 ◽

2021 ◽

Vol 7 (4) ◽

pp. 277

Author(s):

Danny Haelewaters ◽

Hector Urbina ◽

Samuel Brown ◽

Shannon Newerth-Henson ◽

M. Catherine Aime

Keyword(s):

Lactuca Sativa ◽

New Combinations ◽

Food Spoilage ◽

Human Pathogens ◽

Plant Leaves ◽

Romaine Lettuce ◽

Future Studies ◽

The Core ◽

American Agriculture

Romaine lettuce (Lactuca sativa) is an important staple of American agriculture. Unlike many vegetables, romaine lettuce is typically consumed raw. Phylloplane microbes occur naturally on plant leaves; consumption of uncooked leaves includes consumption of phylloplane microbes. Despite this fact, the microbes that naturally occur on produce such as romaine lettuce are for the most part uncharacterized. In this study, we conducted culture-based studies of the fungal romaine lettuce phylloplane community from organic and conventionally grown samples. In addition to an enumeration of all such microbes, we define and provide a discussion of the genera that form the “core” romaine lettuce mycobiome, which represent 85.5% of all obtained isolates: Alternaria, Aureobasidium, Cladosporium, Filobasidium, Naganishia, Papiliotrema, Rhodotorula, Sampaiozyma, Sporobolomyces, Symmetrospora and Vishniacozyma. We highlight the need for additional mycological expertise in that 23% of species in these core genera appear to be new to science and resolve some taxonomic issues we encountered during our work with new combinations for Aureobasidiumbupleuri and Curvibasidium nothofagi. Finally, our work lays the ground for future studies that seek to understand the effect these communities may have on preventing or facilitating establishment of exogenous microbes, such as food spoilage microbes and plant or human pathogens.

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