Emission Of. Gamma. Rays from Various Materials Pulsed with 14-MeV Neutrons


Book Description

We have performed a number of experiments at LLNL recently to investigate the leakage of gamma rays from spheres of selected materials pulsed centrally with 14-MeV neutrons. Such spectral information may be carefully compared to calculational results to validate the transport models, particularly the nuclear cross section data base. In the present case, the TART code and SANDYL codes are used to explicitly calculate the observable, the recoil electron spectrum. The materials studied were H2O, 6LiD, Be, C, 14N, CF2, Al, Si, Ti, Fe, Cu, Ta, W, Au, Pb, Th, and 238U. Generally, agreement was good between experiment and calculation. However, for some, the calculations significantly underestimated or overestimated experiment. For oxygen (i.e., H2O), the ENDL cross section set led to a sizeable calculational overestimate. Re-examination led to a large improvement. For tungsten, the calculated output was approx. 30% below experiment. A re-evaluation led to closer agreement. 16 refs., 10 figs., 1 tab.




Gamma Rays Resulting from Interactions of 14.7 Mev Neutrons with Magnesium, Aluminum, Calcium, Titanium and Iron


Book Description

The prompt gamma rays resulting from the interaction of 14.7 MeV neutrons with the nuclei of the elements magnesium, aluminum, calcium, titanium and iron have been investigated. Cross sections for the production of many of these gamma rays have been measured by observing them with a carefully shielded detector during neutron bombardment of a given elemental sample. It is found that the n, n'-gamma process predominates and that gamma rays resulting from the deexcitation of the lowest energy levels, with one or two notable exceptions, are generally most prominent. Other processes including n, p-gamma, n, alpha-gamma, and n, d-gamma are also observed. Some of the most improtant gamma rays are found to have the following elemental production cross sections (in millibarns per steradian at 90 deg): 1:37 Mev gamma ray from Mg, 30. 9= 3.1; 1.81 MeV gamma ray from Al, 13.7= 2.0; 3.73 Mev gamma ray from Ca, 9.0= 1.4; 0.99 Mev gamma ray from Ti, 51.9= 5.2; and 0.85 MeV gamma ray from Fe, 57.6= 5.8. (Author).







The Effect of Nuclear Radiation on Structural Metals


Book Description

The effect of fast-neutron (>1 Mev) irradiation on the mechanical properties of structural metals and alloys was studied. Although the yield strengths and ultimate tensile strengths are increased su stantially for most materials, the ductility suffers severe decreases. This report presents these changes in properties of several structural metals for a number of neutron exposures within the 1.0 x 10 to the 18th power to 5.0 x 10 to the 21st power n/sq cm range. Data summarizing these effects on several classes of materials such as carbon steels, low-alloy steels, stainless steels, Zr-base alloys, ni-base alloys, Al-base alloys, and Ta are given. Additional data which show the influence f irradiation temperatures and of post-irradiation annealing on the radiation-induced property changes are also given and discussed. Increases as great as 175% in yield strength, 100% in ultimate strength, and decreases of 80% in total elongation are reported for fast-neutron exposures as great as 5 10 to the 21st power n/sq cm. (Author).




Gamma Rays Resulting from Interactions of 14.7 Mev Neutrons with Sodium, Sulfur, Chlorine, Potassium and Lead


Book Description

The prompt gamma rays resulting from the interaction of 14.7 MeV neutrons with the nuclei of the elements sodium, sulfur, chlorine, potassium and lead, were investigated. Cross sections for the production of many of these gamma rays were measured by observing them with a carefull shielded detector during neutron bombardment of a given elemental sample. It was found that the n, n'-gamma process generally predominates and that gamma rays resulting from the deexcitation of the lowest energy levels, with one or two notable exceptions, are usually most prominent. Gamma rys attributable to n, p-gamma, n, alpha-gamma, and n, d-gamma process were also observed. In chlorine and potassium, gamma rays attributable to the n, d-gamma process are unusually preponderant. Some of the most important gamma rays were found to have the following elemental production cross sections (in millibarns per steradian at 90 deg): 0.44 MeV gamma ray from Na, 39.5 plus or minus 4.5; 2.24 MeV gamma ray from S, 15.3 plus or minus 1.7; 2.15 MeV gamma ray from Cl, 17.1 plus or minus 2.0; 2.17 MeV gamma ray from K, 19.3 plus or minus 2.5; 2.62 MeV gamma ray from Pb, 20.3 plus or minus 2.7. (Author).













14 MeV Neutrons


Book Description

Despite the often difficult and time-consuming effort of performing experiments with fast (14 MeV) neutrons, these neutrons can offer special insight into nucleus and other materials because of the absence of charge. 14 MeV Neutrons: Physics and Applications explores fast neutrons in basic science and applications to problems in medicine, the envir