Atomic analysis of the (n;t)−(n;t)-reaction of the helium-3 atoms with slow neutrons

Probabilties of formation of various hydrogenic species during the exothermic nuclear $(n,{}^3$He$;t,p)-$reaction of atomic helium-3 with slow neutrons are determined. In particular, we have found that the probability to form the tritium atom ${}^3$H in its ground state is $\approx$ 55.19287 %, while analogous probability to form the protium atom ${}^1$H is $\approx$ 1.02363 %. Analogous probabilities of formation of the negatively charged hydrogen ions, i.e. the ${}^3$H$^{-}$ and ${}^1$H$^{-}$ ions, in the nuclear $(n,{}^3$He$; t,p)-$reaction with slow neutrons, are $\approx$ 7.8680 % and $\approx$ 0.06583 %, respectively. We also consider bremsstrahlung from fast fission-type reactions in atomic systems. The spectrum of emitted radiation is analyzed

Ionoluminescent response of several phosphor screens to keV ions of different masses

We have characterized the ionoluminescent response of several phosphor powder materials when irradiated with ions of different masses H+ ,He+ ,Ar+ accelerated to keV energies. In particular, we have determined the absolute luminosity in terms of the number of photons per incident ion emitted by luminescent screens of Y2O2S:Tb P45, Y3Al5O12 :Ce P46, Y2SiO5 :Ce P47, Y2O3 :Eu P56, and SrGa2S4 :Eu TG-green. Their ionoluminescence has been studied as a function of ion beam energy and current and ion fluency. The energy trend and mass dependence of selected experimental results are compared relative to stopping and range of ions in matter SRIM code predictions.Ministerio de Educación y Ciencia FTN2003-090

Parameter uncertainty and sensitivity in a liquid-effluent dose model

Radioactive materials which are released into streams on the Savannah River Site (SRS) eventually flow into the Savannah River. Tritium, 90 Sr, 137 Cs, and 239 Pu account for the majority of the radiation dose received by users of the Savannah River. This paper focuses on the dose uncertainties originating from variability in parameters describing the transport and uptake of these nuclides. Parameter sensitivity has also been determined for each liquid pathway exposure model. The models used here to estimate radiation dose to an exposed individual provide a range of possible dose estimates that span approximately one order of magnitude. A pathway analysis reveals that aquatic food and water consumption account for more than 95% of the total dose to an individual.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42692/1/10661_2004_Article_BF00547126.pd

Exposure buildup factors of UO2 using the Monte Carlo method

When the gamma dose rate around an irradiated nuclear reactor fuel element is calculated, it is important to know the attenuating characteristics of the fuel element itself, one of them being the buildup factor. Exposure buildup factors of uranium dioxide (UO2) for ten gamma-ray energies (0.050 to 10.0 MeV) have been computed for ten material thicknesses (0.5 to 10.0 mean free paths) using the MCNP code. The accuracy of the MCNP model was checked by computing the buildup factors of oxygen and uranium and comparing these results with the data given in the literature for these elements. The results indicate that the UO2 exposure buildup factors, for the energies and distances studied, are close to those of uranium

Modeling gamma-ray dose rate from a spent pressurized water reactor fuel assembly

Gamma-ray dose rate distribution around a pressurized water reactor spent-fuel assembly is studied using the Monte Carlo N-particle transport code (MCNP) version 4a. A detailed rod-by-rod modeling of the assembly is utilized, showing explicitly the fuel, cladding, control rod channels, and the instrumentation tube. A cylindrically distributed source of gamma rays, within every fuel rod, is considered with a seven-group energy spectrum. Dose rates are obtained by tallying the gamma rays at several axial and radial positions outside the assembly. The results indicate that the radial distribution of the dose rate can be represented by a power relationship of the form r-n, where r is the radial distance from the assembly center. Another important conclusion from this study is that the dose rate close to the assembly surface is overestimated if a homogeneous assembly model is used