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DT fusion neutron radiation strengthening of copper and niobium

Description: The initial results of a comparative study of the radiation strengthening and damage structures produced in Cu and Nb by D-T fusion and fission reactor neutrons are described. The radiation strengthening produced by a given fluence of fusion neutrons above about 10$sup 17$n/cm$sup 2$ is equal to that produced by a fluence of fission reactor neutrons (E greater than 0.1 MeV) ten times as great. This difference is about twice as large as would be expected if the strengthening scaled with damage energy or dpa. Initial transmission electron microscopy observations of the damage structures in fusion and fission reactor neutron irradiated copper indicate that the same type of primary structural defects, vacancy and interstitial point defect clusters and small dislocation loops with a/3 (111) and a/2 (110) Burgers vectors, are produced in both cases. The difference in the radiation strengthening produced by fusion and fission reactor neutrons in Cu appears to result from a substantially greater rate of accumulation of damage, in the form of point defect clusters, during irradiation with fusion neutrons than during irradiation with fission reactor neutrons plus a significant difference in the size and spatial distributions of the damage clusters. (auth)
Date: October 30, 1975
Creator: Mitchell, J.B.; Van Konynenburg, R.A.; Echer, C.J. & Parkin, D.M.
Partner: UNT Libraries Government Documents Department

Radiation damage by $sup 252$Cf fission fragments and alpha particles

Description: Rates of atom displacement and helium injection in materials exposed to $sup 252$Cf fission fragments and alpha particles were calculated to establish the potential for use of $sup 252$Cf sources for radiation damage studies. Maximum displacement rates of about 10$sup -6$ dpa/sec at the surface of typical targets exposed to a $sup 252$Cf fission fragment source were comparable to those experienced by materials in a fast breeder reactor or in a controlled thermonuclear reactor (CTR) first wall, though much lower than the displacement rates achieved using particle accelerators. Helium was concurrently accumulated at a rate of 3 x 10$sup -4$ atom ppM/sec at the target surface, yielding a He/ displacement ratio 10$sup 3$ times that produced in the fast breeder reactor materials, but only about 20 times that produced in the CTR materials. These comparisons suggest that $sup 252$Cf fission fragment sources may find useful applications in studies of effects of high-He content on radiation damage in CTR materials. (auth)
Date: January 1, 1975
Creator: Gould, T. H., Jr. & McDonell, W. R.
Partner: UNT Libraries Government Documents Department

Analysis of radiation damage in fusion-simulation neutron spectra

Description: Various parameters which are relevant to an understanding of radiation effects in metals have been evaluated utilizing available neutron spectrum information for several existing sources, e.g., EBRII, HFIR, and LAMPF, as well as the hypothetical spectrum at a fusion reactor first wall, and measured Li(d,n) spectra. Recoil energy distributions were calculated for several metals including Al, Cu, and Nb. The recoil energy range was divided into groups, and the fraction of recoils occurring in each energy group was compared with the fraction of the damage energy contributed by that group. From this comparison it was possible to conclude that the significant recoil range differs by about an order of magnitude between fission and fusion sources. The analysis further confirms that basic defect production characteristics depend upon the neutron spectrum, and that integral calculations of radiation-effect parameters do not provide a complete description of the dependence. This is equally true for comparisons between fusion-related spectra or fission-reactor spectra independently. Four recoil-dependent parameter functions which describe different aspects of radiation damage were used in the calculations. The relative effectiveness of neutron sources was found to depend upon the choice of parameter function. Fission-reactor spectra comparisons are relatively insensitive to the parameter functions used whereas spectra with an appreciable component of high-energy neutrons are much more sensitive. (auth)
Date: January 1, 1975
Creator: Parkin, D.M. & Goland, A.N.
Partner: UNT Libraries Government Documents Department

Irradiation of graphite cloth at various temperatures with deutrons and helium ions

Description: Graphite cloth samples were irradiated with 100 keV deuterons and $sup 4$He$sup +$ ions at room temperature and at elevated temperatures. Scanning electron microscopy was used to examine the surfaces of irradiated and unirradiated graphite fibers. Irradiation at room temperature with $sup 4$He$sup +$ to a total dose of 3.1 x 10$sup 18$ ions cm$sup -2$ produces considerable flaking of individual fibers, which is not observed on unirradiated fibers. Identical irradiations at 400$sup 0$ and 800$sup 0$ with $sup 4$He$sup +$ did not produce any detectable flaking or other surface damage. The elevated temperatures apparently prevent an accumulation of helium in localized areas which in turn could cause flaking in near surface regions. Results obtained for deuteron bombardment of graphite cloth at room temperature and at 600$sup 0$C are also discussed. (auth)
Date: January 1, 1975
Creator: Ekern, R.; Das, S.K. & Kaminsky, M.
Partner: UNT Libraries Government Documents Department

DT fusion neutron radiation strengthening of copper and niobium

Description: The initial results of a comparative study of the radiation strengthening and damage structures produced in Cu and Nb by D-T fusion and fission reactor neutrons are described. The radiation strengthening produced by a given fluence of fusion neutrons above about 10$sup 17$ n/cm$sup 2$ is equal to that produced by a fluence of fission reactor neutrons (E greater than 0.1 MeV) ten times as great. This difference is about twice as large as would be expected if the strengthening scaled with damage energy or dpa. Initial transmission electron microscopy observations of the damage structures in fusion and fission reactor neutron irradiated copper indicate that the same type of primary structural defects, vacancy and interstitial point defect clusters and small dislocation loops with a/3 (111) and a/2 (110) Burgers vectors, are produced in both cases. The difference in the radiation strengthening produced by fusion and fission reactor neutrons in Cu appears to result from a substantially greater rate of accumulation of damage, in the form of point defect clusters, during irradiation with fusion neutrons than during irradiation with fission reactor neutrons plus a significant difference in the size and spatial distributions of the damage clusters. (auth)
Date: September 29, 1975
Creator: Mitchell, J.B.; Van Konynenburg, R.A.; Echer, C.J. & Parkin, D.M.
Partner: UNT Libraries Government Documents Department

Radiation blistering of Nb implanted sequentially with helium ions of different energies (3-500 keV)

Description: Cold rolled, polycrystalline niobium samples were irradiated at room temperature with $sup 4$He$sup +$ ions sequentially at 14 different energies over an energy range from 3 keV--500 keV in steps of 50 keV. The dose for each energy was chosen to give an approximately uniform concentration of helium between the implant depths corresponding to 3 keV and 500 keV. In one set of experiments the irradiations were started at the Kurchatov Institute with 3 keV $sup 4$He$sup +$ ions and extended up to 80 keV in several steps. Subsequently, the same target area was irradiated with $sup 4$He$sup +$ ions at Argonne National Laboratory (ANL) starting at 100 keV and increased to 500 keV in steps of 50 keV. Another set of irradiations were started at ANL with 500 keV $sup 4$He$sup +$ ions and continued with decreasing ion energies to 100 keV. Subsequently, the same area was irradiated at the Kurchatov Institute starting at 80 keV and continued with decreasing ion energies to 3 keV. Both sets of irradiations were completed for two different total doses, 0.5 C cm$sup -2$ and 1.0 C cm$sup -2$.
Date: January 1, 1976
Creator: Guseva, M.I.; Gusev, V.; Krasulin, U.L.; Martinenko, U.V.; Das, S.K. & Kaminsky, M.S.
Partner: UNT Libraries Government Documents Department

Characteristics of 15 MeV and fission neutron damage in niobium

Description: Displacement damage by 15 MeV (d-Be source) and fission neutrons at 30$sup 0$C in high purity niobium single crystals has been studied by transmission electron microscopy. The fluence of the 15 MeV neutrons was 1.5-- 2.0 x 10$sup 17$ n/cm$sup 2$ and the fluence of the fission neutrons (5 x 10$sup 17$ n/cm$sup 2$) was chosen so that samples from both types of irradiations had approximately the same damage energy. In both 15 MeV and fission neutron irradiated specimens, the loops were observed to be about $sup 2$/$sub 3$ interstitial and $sup 1$/$sub 3$ vacancy type. The analysis of Burgers vectors of the dislocation loops showed that more than $sup 2$/$sub 3$ of the loops were perfect a/2(111) and that the rest were a/2(110) faulted. It is concluded that at equal damage energies, the detailed nature of the damage is the same for 15 MeV and fission neutron irradiated niobium. (auth)
Date: February 1, 1976
Creator: Narayan, J. & Ohr, S.M.
Partner: UNT Libraries Government Documents Department

Neutron damage calculations in Cu, Nb, and Au to 32 MeV: application to sputtering and deuteron-breakup neutron sources

Description: Primary recoil distributions and specific damage energies have been computed for high energy deuteron-breakup neutrons in Cu, Nb, and Au. The calculations are based on theoretical neutron cross sections, and consider in particular a d-Be spectrum broadly peaked at 15 MeV with some neutrons above 30 MeV. The theoretical results are similar to corresponding calculations for monoenergetic 15-MeV neutrons and are in good agreement with range measurements of (n,2n) recoils generated by high energy d-Be neutrons in Nb and Au. The calculations are also consistent with recent d-Be neutron sputtering experiments in Nb and Au and demonstrate the usefulness of deuteron-breakup neutron sources for simulating fusion neutron effects. (auth)
Date: February 1, 1976
Creator: Roberto, J.B.; Robinson, M.T. & Fu, C.Y.
Partner: UNT Libraries Government Documents Department

Pacific Northwest Laboratory report on controlled thermonuclear reactor technology, January 1975 - September 1975

Description: The PNL staff has been studying fusion technology in areas such as economics, fusion-fission hybrid concepts, materials, neutronics, environment and safety. These studies have been scoped to make efficient use of ERDA resources, and to complement and support efforts at other laboratories. The effect the plasma and associated radiation and emission will have upon the surfaces of the first wall are being studied. Neutron sputtering experiments were made on niobium and gold and the results were evaluated for absolute neutron yields. Molybdenum and vanadium were studied for effects of ion bombardment under various conditions of helium injection. Graphite cloth is being irradiated for examination of radiation effects because it is suggested for use in several CTR concepts as a shield between the plasma and the first wall. Helium effects are being studied to characterize degradation of structural metal properties. Work is progressing on absolute measurement of the electrical resistivity of insulators and the demonstration of the feasibility of producing insulating coatings by sputter deposition. (auth)
Date: October 1, 1975
Partner: UNT Libraries Government Documents Department