N.M. Badiger

Comprehensive study of energy absorption and exposure build-up factors for concrete shielding in photon energy range 0.015–15 MeV up to 40 mfp penetration depth: dependency of density, chemical elements, photon energy

Gamma ray build-up factors of concrete shielding have been investigated by Geometrical Progression fitting formula for photon energy range 0.015–15 MeV up to 40 mfp penetration depth. The energy absorption build-up factors and Exposure Build-Up Factor (EBF) of concrete shielding have been studied as a function of photon energy, penetration depth, concrete density and chemical element compositions. The EBF of the concrete shielding having high equivalent atomic number increases rapidly beyond 3 MeV photon energy for high penetration depths. The build-up factors show that the heavy concretes (≥ 3.5 g cm–3) are good biological shielding. Steel-magnetite (5.11 g cm–3) is the best shielding concrete for reactor core for power operation as well as accidents. Present build-up factors are very useful for selection of shielding materials for reactor core in controlling the gamma exposure to the people involved and the public of photon energy abundance in the range of 0.10–10 MeV.

Shielding efficiency of lead borate and nickel borate glasses for gamma rays and neutrons

Gamma ray exposure buildup factor (EBF) and neutron shielding efficiency of borate glass systems in composition (100 − x − y) Na2B4O7−xPbO−yNiO (where x and y = 0, 2, 4, 6, 8 and 10 weight percentage) were investigated in the present study. Gamma ray EBF values were computed using Geometric Progression (G-P) method for photon energy 0.015 to 15 MeV up to penetration depths of 40 mfp (mean free path). The macroscopic effective removal cross-sections (ΣR) for fast neutron (2 to 12 MeV) were calculated. At low- and high-energy region, the EBF values were found minimum whereas maximum in the intermediate-energy regions with a sharp peak below 100 keV for oxide containing glass samples. The investigation was carried out for potential applications of borate glasses for radiation shielding.

A method for measuring K-shell fluorescence parameters in a 2π geometrical configuration

Abstract Adopting a 2π geometrical configuration, target criteria for measuring fluorescence X-rays have been established. These criteria satisfy the Bambynek et al. (Rev. Mod. Phys. 44 (4) (1972) 716) suggestion regarding the optimum thickness of the target, balancing the production and attenuation of the fluorescence X-rays. The K-shell fluorescence cross section or K X-ray production cross section, σK, the K-shell fluorescence yield, ωK, and the ratio between the widths of the radiative transition and the Auger transition, ΓRK/ΓAK, have been measured for some high-Z elements (62⩽Z⩽82). The results are compared with theoretical, fitted and experimental values corresponding to several geometries. Good agreement indicates that the present method is a suitable alternative for measuring K-shell fluorescence parameters.

Determination of Effective Atomic Numbers Using Different Methods for Some Low-Z Materials

In the present work, different methods were used to determine the effective atomic numbers of some low-Z materials, namely, polyethylene (PE), polystyrene (PS), polypropylene (PP), Perspex (PX), polycarbonate (PC), nylon 6-6 (PA-6), plaster of Paris (POP), and TH/L2. These methods are the direct method, the interpolation method, Auto- software, and single value XMuDat computer program. Some of the results obtained were compared with experimental data wherever possible. It can be concluded from this work that the effective atomic numbers calculated with the direct, the interpolation and Auto- methods demonstrate a good agreement in Compton scattering and pair production energy regions. A large difference in the effective atomic numbers calculated by the direct and the interpolation methods of low-Z materials was also observed in photoelectric and pair production regions. It was determined that PE, PS, PX, and PA-6 were equivalent to adipose and muscle; POP was equivalent to cortical bone; TH/L2 was equivalent to thyroid tissue; PP was equivalent to yellow bone marrow and adipose tissues; PC was equivalent to spongiosa.

Study on γ-ray exposure buildup factors and fast neutron-shielding properties of some building materials

We have computed γ-ray exposure buildup factors (EBF) of some building materials; glass, marble, flyash, cement, limestone, brick, plaster of paris (POP) and gypsum for energy 0.015–15 MeV up to 40 mfp (mfp, mean free path) penetration depth. Also, the macroscopic effective removal cross-sections (ΣR) for fast neutron were calculated. We discussed the dependency of EBF values on photon energy, penetration depth and chemical elements. The half-value layer and kinetic energy per unit mass relative to air of building materials were calculated for assessment of shielding effectiveness. Shielding thicknesses for glass, marble, flyash, cement, limestone and gypsum plaster (or Plaster of Paris, POP) were found comparable with ordinary concrete. Among the studied materials limestone and POP showed superior shielding properties for γ-ray and neutron, respectively. Radiation safety inside houses, schools and primary health centers for sheltering and annual dose can be assessed by the determination of shielding parameters of common building materials.

Determination of mass attenuation coefficient of low-Z dosimetric materials

The mass attenuation coefficients of some low-Z dosimetric materials with potential applications in dosimetry, medical and radiation protection have been investigated using the Monte Carlo simulation code Monte Carlo N-Particle (MCNP). Appreciable variations are noted for the mass attenuation coefficient by changing the photon energy. The MCNP-simulated parameters are compared with the experimental data wherever possible and theoretical values through the WinXcom program. The simulated results obtained by MCNP generally agree well with the experiment and WinXcom predictions for various low-Z dosimetric and tissue substitute materials. In addition, the mass attenuation coefficients around the k-edges for low-Z dosimetric materials estimated from the MCNP code agree very well with WinXcom prediction. Finally, the results indicate that this simulation process can be followed to determine the interaction parameters of gamma rays in such low-Z materials for which there are no satisfactory experimental values available.

Effective atomic numbers of some tissue substitutes by different methods: A comparative study

Effective atomic numbers of some human organ tissue substitutes such as polyethylene terephthalate, red articulation wax, paraffin 1, paraffin 2, bolus, pitch, polyphenylene sulfide, polysulfone, polyvinylchloride, and modeling clay have been calculated by four different methods like Auto-Zeff, direct, interpolation, and power law. It was found that the effective atomic numbers computed by Auto-Zeff, direct and interpolation methods were in good agreement for intermediate energy region (0.1 MeV < E < 5 MeV) where the Compton interaction dominates. A large difference in effective atomic numbers by direct method and Auto-Zeff was observed in photo-electric and pair-production regions. Effective atomic numbers computed by power law were found to be close to direct method in photo-electric absorption region. The Auto-Zeff, direct and interpolation methods were found to be in good agreement for computation of effective atomic numbers in intermediate energy region (100 keV < E < 10 MeV). The direct method was found to be appropriate method for computation of effective atomic numbers in photo-electric region (10 keV < E < 100 keV). The tissue equivalence of the tissue substitutes is possible to represent by any method for computation of effective atomic number mentioned in the present study. An accurate estimation of Rayleigh scattering is required to eliminate effect of molecular, chemical, or crystalline environment of the atom for estimation of gamma interaction parameters.

Investigation of Gamma and Neutron Shielding Parameters for Borate Glasses Containing NiO and PbO

The mass attenuation coefficients, , half-value layer, HVL, tenth-value layer, TVL, effective atomic numbers, , and effective electron densities, , of borate glass sample systems of (100--) Na2B4O7 : PbO : NiO (where and , and 10 weight percentage) containing PbO and NiO, with potential gamma ray and neutron shielding applications, have been investigated. The gamma ray interaction parameters, , HVL, TVL, , and , were computed for photon energy range 1 keV–100 GeV. The macroscopic fast neutron removal cross-sections () have also been calculated. Appreciable variations were noted for all the interaction parameters by varying the photon energy and the chemical composition of the glass samples. The better shielding properties of borate glass samples containing PbO were found. These results indicated that borate glass samples are a good radiation shielding material.

A Comprehensive Study on Gamma-Ray Exposure Build-Up Factors and Fast Neutron Removal Cross Sections of Fly-Ash Bricks

Geometric progression (GP) method was utilized to investigate gamma-ray exposure build-up factors of fly-ash bricks for energies from 0.015 to 15 MeV up to 40 mfp penetration depth. The EBFs of the fly-ash bricks are dependent upon the photon energy, penetration depths, and the chemical compositions of the elements. Appreciable variations in exposure build-up factor (EBF) are noted for the fly-ash bricks. The EBFs were found to be small in low and high photon energy regions whereas very large in medium energy region. EBF of the bricks is inversely proportional to equivalent atomic number below 10 mfp for entire energy region of interest 0.015 to 15 MeV. The EBFs of fly-ash, brick of mud, and common brick were similar at 1.5 MeV photon energy. The EBF of the fly-ash bricks was found to be higher than that of the brick of mud, and common brick. The fast neutron removal cross sections of the fly-ash bricks, brick of mud, and common bricks were also calculated which were found to be in the same order. It is expected that this study should be very directly useful for shielding effectiveness of fly-ash brick materials and dose estimation.

L X-ray fluorescence cross sections experimentally determined for elements with 45<Z<50 at 9 keV

Experimental determination of L fluorescence cross-sections for elements with 45<Z<50 have been determined at 9 keV using Synchrotron radiation. This work is part of an investigation we did at low energies in the same group of elements. The individual L X-ray photons, Ll, Lα, Lβ(I), Lβ(II), Lγ(Ι) and Lγ(ΙΙ) produced in the target were measured using a Si(Li) detector. The experimental set-up provided a low background by using linearly polarized monoenergetic photon beam, improving the signal-to-noise ratio. The experimental cross sections obtained in this work were compared with data calculated using coefficients from Scofield (1973), Krause et al., (1978), Krause (1979) and Scofield and Puri et al. (1993, 1995).