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The Cherenkov power meter developed at the Jožef Stefan Institute (JSI) is an independent, reliable and cost-effective measurement system based on Cherenkov radiation detection, used to measure fast power transients during pulse operation at the JSI TRIGA research reactor. It is based on a closed tube in order to avoid interference from external light sources and radiation damage experienced by optical fibers. The tube is placed in the reactor core periphery, the bottom part of the tube is filled with water, serving as the source of Cherenkov light. The measurements obtained in the framework of an extensive experimental campaign in collaboration with the French Atomic and Alternative Energy Commission (CEA) focused on reactor pulse operation using the Cherenkov power meter show excellent agreement with existing nuclear instrumentation (TRIGA pulse recorder), especially for high peak power pulses. However, the Cherenkov power meter outperforms the TRIGA pulse recorder in accurately recording low peak power pulses. The power vs. time behavior measured with the Cherenkov power meter is in accordance with measurements using miniature fission and ionization chambers developed at the CEA. The possibility of reactor pulse characterization based on measurements with the Cherenkov power meter combined with neutron dosimetry measurements sets the basis for enabling irradiation during pulse operation at JSI TRIGA research reactor in the future.

The Fission Track Thermal Ionization Mass Spectrometry (FT-TIMS) method is considered as the reference method for particle analysis in the field of nuclear Safeguards for measurements of isotopic compositions (fissile material enrichment levels) in micrometer-sized uranium particles collected in nuclear facilities. An integral phase in the method is the irradiation of samples in a very well thermalized neutron spectrum. A bilateral collaboration project was carried out between the Jožef Stefan Institute (JSI, Slovenia) and the Commissariat à l’Énergie Atomique et aux Énergies Alternatives (CEA, France) to determine whether the JSI TRIGA reactor could be used for irradiations of samples for the FT-TIMS method. This paper describes Monte Carlo simulations, experimental activation measurements and test irradiations performed in the JSI TRIGA reactor, firstly to determine the feasibility, and secondly to design and qualify a purpose-built heavy water based irradiation device for FT-TIMS samples. The final device design has been shown experimentally to meet all the required performance specifications. [ABSTRACT FROM AUTHOR]

Recently a series of test irradiations was performed at the JSI TRIGA Mark II reactor for the Fission Track-Thermoionization Mass Spectrometry (FT-TIMS) method, which requires a well thermalized neutron spectrum for sample irradiation. For this purpose the Monte Carlo N-Particle Transport Code (MCNP5) was used to computationally support the design of an irradiation device inside the TRIGA model and to support the actual measurements by calculating the neutron fluxes inside the major ex-core irradiation facilities. The irradiation device, filled with heavy water, was designed and optimized inside the Thermal Column and the additional moderation was placed inside the Elevated Piercing Port. The use of the device improves the ratio of thermal neutron flux to the sum of epithermal and fast neutron flux inside the Thermal Column Port by 390% and achieves the desired thermal neutron fluence of 10 15 neutrons/cm 2 in irradiation time of 20 h. [ABSTRACT FROM AUTHOR]

ABSTRACT: Ionizing radiation has been identified as an option for sterilization of disposable filtering facepiece respirators in situations where the production of the respirators cannot keep up with demand. Gamma radiation and high energy electrons penetrate deeply into the material and can be used to sterilize large batches of masks within a short time period. In relation to reports that sterilization by ionizing radiation reduces filtration efficiency of polypropylene membrane filters on account of static charge loss, we have demonstrated that both gamma and electron beam irradiation can be used for sterilization, provided that the respirators are recharged afterwards. Image 1 • Gamma irradiation and electron beam irradiation have comparable effects on filtration efficiency of the respirators. • Sterilization with gamma and e-beam irradiation doesn't cause chemical changes in polypropylene membranes used in respirators. • The respirators can be reused after sterilization if charge is re-applied. [ABSTRACT FROM AUTHOR]