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First positron annihilation lifetime measurement of Pu

Description: We have made the first measurement of defects in an aged sample of {delta} phase, Ga stabilized Pu, using positron annihilation lifetime spectroscopy. This measurement validates the procedure necessary to perform measurements on this highly toxic material and obtain data representative of sample conditions. Comparison of the positron annihilation lifetime analysis of the data with calculated values suggests that He filled vacancies or vacancy clusters dominate the defect population. Such defects are the necessary precursor to void growth and swelling. The evolution of defects resulting from the radioactive decay of Pu during its life in the stockpile is one of the unknown quantities affecting our confidence in predictions of the limit on stockpile components. Radiation damage leads to changes in the size and strength of metals studied for reactor and accelerator use and similar effects may be expected in Pu. The evolution of radiation produced vacancies into larger void structures and accompanying macroscopic swelling may occur in Pu at some age. A detailed understanding of the defects in self irradiated Pu is required to predict the time scale of void swelling and related radiation effects. 1 fig.
Date: November 21, 1996
Creator: Colmenares, C.; Howell, R.H.; Ancheta, D.; Cowan, T.; Hanafee, J. & Sterne, P.
Partner: UNT Libraries Government Documents Department

Self-Irradiation Effects on 99Mo Reagents and Products

Description: produced in 1996 and shipped to pharmaceutical houses for evaluation of compatibility with oxime solution used to precipitate `?vfo as the oxime complex is both air and light-sensitive, and containing a black precipitate that forms during shipment, presumably as a result of self- irradiation. Addition of sodium hypochlorite to the product solution prior to shipment prevents precipitate formation, indicating the precipitate is a reduced form of `%lo. to remove any precipitate. Duplicate aliquots of the filtered samples were titrated to a phenolphthalein irradiation and afler standing at room temperature for 86.4 hours. Precipitates were washed to a FTIR analysis of the white precipitate showed it to be alpha benzoin oxime. Since the basic After 86.4 hours, no precipitate had formed in bottles containing sodium hypochlorite. Black precipitate had formed in all bottles that did not contain sodium hypochlorite after 14.4 hours. The precipitate appeared to initially form on the surface of the HDPE sample bottles and Black precipitate was first noticed in sample set 1 after 28.8 hrs' irradiation. No visible sample containing precipitate was kept at room temperature in the original bottle. Precipitate in sample sets 2 and 3. Since no precipitate formed in these bottles, this was equivalent to duplicate samples. Once the precipitate in the 20-mL aliquots that had been set aside had returned to sample sets 1 through 3 and the samples with redissolved precipitate all experienced an average decrease in base strength of 0.013 meq mL-l. Sample 1-C had a decrease of 0.004 meq mL-l and sample 1-D had returned to the initial value of 0.198 meq mL-l. Raman spectra for the black precipitate from samples l-C, 1-D and supplemental sample set 1 Fig. 2. Raman spectra of the black precipitate formed in 9%40 product solutions after 28.8,43.2, 72 and 86.4 hours of `oCo irradiation ...
Date: October 7, 1998
Creator: Carson, S.D.; Garcia, M.J.; McDonald, M.J.; Simpson, R.L. & Tallant, D.R.
Partner: UNT Libraries Government Documents Department

SPHINX Measurements of Radiation Induced Conductivity of Foam

Description: Experiments on the SPHINX accelerator studying radiation-induced conductivity (RIC) in foam indicate that a field-exclusion boundary layer model better describes foam than a Maxwell-Garnett model that treats the conducting gas bubbles in the foam as modifying the dielectric constant. In both cases, wall attachment effects could be important but were neglected.
Date: December 14, 1998
Creator: Ballard, W.P.; Beutler, D.E.; Burt, M.; Dudley, K.J. & Stringer, T.A.
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

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

1.06 μm 150 psec laser damage study of diamond turned, diamond turned/ polished and polished metal mirrors

Description: Using a well characterized 1.06 μm 150 ps glass laser pulse the damage characteristics for diamond turned, diamond turned/ polished, and polished copper and silver mirrors less than 5 cm diameter were studied. Although most samples were tested with a normal angle of incidence, some were tested at 45$sup 0$ with different linear polarization showing an increase in damage threshold for S polarization. Different damage mechanisms observed will be discussed. Laser damage is related to residual surface influences of the fabrication process. First attempts to polish diamond turned surfaces resulted in a significant decrease in laser damage threshold. The importance of including the heat of fusion in the one dimensional heat analysis of the theoretical damage threshold and how close the samples came to the theoretical damage threshold is discussed. (auth)
Date: July 24, 1975
Creator: Saito, T. T.; Milam, D.; Baker, P. & Murphy, G.
Partner: UNT Libraries Government Documents Department

Radiation blistering of structural materials for fusion devices and reactors

Description: From surface effects in controlled thermonuclear fusion devices and reactors meeting; Argonne. Illinois, USA (10 Jan Radiation blistering can be an important erosion process when the structural components of controlled thermonuclear fusion devices or reactors are exposed to the impact of energetic particles leaving the plasma region. A brief review of some of the important parameters governing the radiation blistering process is given. Erosion rates associated with helium blistering in V, Nb, and Type 304 stainless steel are reported for different irradiation temperatures and different projectile energies. (auth)
Date: January 1, 1974
Creator: Das, S.K. & Kaminsky, M.
Partner: UNT Libraries Government Documents Department

Theory of radiation induced defect production

Description: The theory of defect production in solids by neutron irradiation is reviewed, including discussions of the nuclear reactions which produce the primary recoils and the loss of energy from the displacement cascade by electron excitations. The theoretical predictions are compared with the limited available experiments on thermal and fast neutron irradiation. The results are in rough agreement in most instances, but further improvements in the theory are clearly needed. (auth)
Date: October 1, 1975
Creator: Robinson, M.T.
Partner: UNT Libraries Government Documents Department

Replacement collision sequences in metals

Description: The concept of radiation-induced defects traveling large distances by focussed collision sequences (focusons) without thermal activation has important consequences in radiation effect studies. The focussed collision sequences are of two types: (1) ''Silsbee focussing'' or momentum focussing which can cause defect pairs to form large distances from the primary knock-on and (2) focussed replacement collisions also called ''dynamic crowdions'' where mass transport causes a large separation between the vacancy and its interstitial. Direct experimental evidence for focussed collision sequences is in short supply and conflicting. The sputtering patterns associated with close packed crystalline directions from the backscattering of charged particles seemed to substantiate long-range focussed collisions until it was pointed out that collision chains need not be long to yield such patterns. More recently, transmission sputtering has been used with conflicting results. Ecker et al. found no evidence for focusons greater than 17 atom distances whereas preliminary results of Siedman et al. suggest several hundred atom distances. Keil and co-workers found evidence for replacement collision sequences of 100 atom distances by stereo electron microscopy of interstitial agglomerates interjected by low energy heavy ion bombardment. Experiments by Kirk et al. and Becker and co-workers on ordered alloys, are only sensitive to dynamic crowdions. Kirk and co-workers result on the changes in magnetic properties of Ni$sub 3$Mn induced by thermal neutron bombardment strongly support long range focusons (greater than 30 atom distances) whereas Wollenberger found no evidence for focusons with 1 and 3 MeV electron irradiation. Theoretical treatments of Liebfried suggest a maximum length of 30 atom distances whereas Holmes' modified treatment suggests less than 10 atom distances. (10 fig, 23 references) (auth)
Date: October 1, 1975
Creator: Blewitt, T.H.; Kirk, M.A. & Scott, T.L.
Partner: UNT Libraries Government Documents Department