Neutron irradiation experiments

The Omega West Reactor (OWR) is a water-cooled pool reactor operated by for the DOE by Los Alamos National Laboratory (LANL) for neutron irradiation experiments at a power of 8 MWt... 

Kumashiro, Y, K. Kudo, K. Matsumoto, Y. Okada, and T. Koshira. 1987. Thermal neutron irradiation experiments on BP single crystal wafers. In Proceedings of the Ninth International Symposium on Boron Borides Related Compounds, ed. H. Werheit, pp. 371-372. Duisburg Duisburg University Press. 

Measurements of the effect of radiation on the dielectric properties of CVD diamond have been reported using neutron irradiation experiments with fast neutron fluences up to at least lO nm (energy >0.1 MeV) [65]. Differences before and after irradiation were found to be more pronounced at lower frequencies. At 145 GHz specimens that started with values of tan 5 of 2 x 10 maintained these levels (or even showed a decrease in loss). Further experiments to extend radiation fluencies to 10 nm are in progress [68]. 

Soft errors can be detected and corrected by the system s logic, meaning that it does not require a hard reset to recover from an error. Sections 7.1.2 and 7.2.2 present neutron irradiation experiments simulating the effect of SEE in Flash-base and SRAM-based FPGAs, while Chaps. 5 and 6 present fault injection simulation experiments simulating SEEs at RTL level and in the configuration memoiy bitstream, respectively. In this work, SEUs and SETs will be used to describe transient faults that the proposed techniques can cope with. 

Finally, for the traveling wave reactor (TWR) concept, HT9 steel was chosen as cladding and wrapper material [29]. In this particular case, the requirements on in-core materials are particularly demanding, since the peak dose on the TWR cladding is evaluated to be in the range 500—600 dpa, i.e., much more than the maximum irradiation dose ever achieved in a neutron irradiation experiment of FM steels. 

NAA cannot be used for some important elements, such as aluminum (in a Si or Si02 matrix) and boron. The radioactivity produced from silicon directly interferes with that ftom aluminum, while boron does not produce any radioisotope following neutron irradiation. (However, an in-beam neutron method known as neutron depth profiling C3J be used to obtain boron depth profiles in thin films. ) Another limitation of NAA is the long turn-around time necessary to complete the experiment. A typical survey measurement of all impurities in a sample may take 2-4 weeks. 

In the framework of CUORICINO [41] and CUORE [42] experiments (see Section 16.5), Ge crystal wafers of natural isotopic composition have been doped by neutron irradiation, and the heavy doping led to materials close to the metal insulator transition. Several series of NTD wafers with different doping have been produced [43], After an implantation and metallization process on both sides of the wafers, thermistors of different sizes can be obtained by cutting the wafers and providing electrical contacts. 

In addition to SiC/SiC, irradiation effects on insulators such as AI2O3 were also examined [70]. As a result, synergistic effects such as the diffusion of H and the growth of cavities were observed in samples irradiated with triple beams. As for carbon fiber composites, the microhardness increased by triple-beam irradiation [71], which was a different result from that obtained from 14-MeV neutron irradiation (8 x lO n/cm ) experiment. 

Neutron Irradiation on Military Grade Ammonium Perchlorate , BRL-MR-2448, Ballistic Res Labs, Aberdeen Prov Grnd, Md (1975) (AD-B003210L) 235) C-W. Nelson A.W. Barrows, Short Lived Bum Rate Changes in Neutron Radiation Experiments , BRL-MR-2475, Ibid (1975) (AD-B003940L) 236) P.L. Morgan et al, Biblio-... 

In actual experiments, of course, things are not quite so simple. In the first place, one does not observe the instantaneous release but only its integration in discrete temperature steps. Problems also arise because of the recoil effect mentioned earlier and various interferences and other uncertainties arising in the neutron irradiation. 

For both nuclear and solar systems, appropriate material selection will be essential. A qualification programme for high temperature metallic materials must demonstrate their good long-term performance. In the nuclear case, candidate materials will be exposed to helium of 1 000°C with impurities such as CO, C02, H2, H20, CH4 and to neutron irradiation. The experience gained so far has disclosed that the technical solution of material problems requires further efforts in the future. 

Analysing the solution for new species derived from the solid such as metal ions, complex ions, or co-ions. Their concentrations may be too small for detection by conventional means and it may be helpful to employ newer techniques like atomic absorption, ion chromatography, or radioactivity measurements after prior neutron irradiation of the solid. If new species are found, an experiment could be carried out to see if their deliberate addition to the homogeneous reaction mixture reproduces the "catalytic rate. 

Further examples of positron study of defects in HTSC are studies carried out to understand the nature of flux-pinning defects that lead to an increase in critical-current density on neutron-irradiated Y 1 2 3. Experiments [59] on positron lifetime and critical-current density measurements on various neutron-irradiated samples of Y 1 2 3 indicate that the critical current density is correlated with the micro-void density, as obtained from the analysis of positron lifetime measurements. Investigation of defects in other HTSC superconductors, such as La-Sr-Ca-Cu-0 [60], Bi-Sr-Ca-Cu-0 [49], and Nd-Ce-Cu-O [52], have also been carried out. 

Because °Po is the daughter of °Bi, and because it has been produced by the neutron irradiation of °Bi, an established procedure for its separation has involved its precipitation from acid solution with H2S. Measurements of the radioactivity indicated that the precipitation was essentially quantitative. Suggestions that the precipitate was P02S3 did not survive the scratiny of experiment. 

The most important method of production of the first transuranium elements is neutron irradiation of uranium. After the discovery of the neutron by Chadwick in 1932, this method was applied since 1934 by Fermi in Italy and by Hahn in Berlin. The method is based on the concept that absorption of neutrons by nuclides with atomic number Z leads to formation of neutron-rich nuclides that change by fi decay into nuclides with atomic numbers Z - -1. Unexpectedly, the experiments carried out by Hahn and Strassmann led to the discovery of nuclear fission in 1938. 

Research reactors are widely used for scientific investigations and various applications. Neutrons produced by research reactors provide a powerful tool for studying matter on nuclear, atomic, and molecular levels. Neutrons, often are used as probes by nuclear and solid state physicists, chemists, and biologists. Neutron experiments can also be performed outside the biological shield by means of installed beam tubes. Additionally, specimens can be positioned in or near research reactor cores for neutron irradiation, e.g. to produce radioactive isotopes for medical or research use. 

Micro-Raman spectroscopy was used to characterise 4H-SiC layers grown from a variety of precursor systems.381 FTIR data were able to characterise hydrogenated amorphous silicon nitride films with embedded nanoparticles. Oxidation leads to the appearance of an Si O feature at 1070 cm 1,382 Raman spectra were used to determine the degree of micro-crystallinity of pc Si I I layers, using the intensity ratio of bands at 520 cm-1 and 480 cm-1.383 IR and Raman spectra were used to determine the effects of neutron irradiation on a-SiC H films.384 A range of a-SiCx I I and a-SiCxNy H films were studied using IR spectroscopy 385 similar experiments were carried out on a-Si i xGcx Il,F films.386... 

Abstract The Lifshitz - Slezov theory is applied to study the metastable states of the matrix damage clusters, MA, and the copper enriched clusters, CEC, in neutron irradiated steels. It was found that under irradiation conditions the CE Cs are at the Ostwald stage for a neutron fluence of about 0.0002 dpa. The time dependence of number density, MDn, is determined by summarizing all differential equations of the master equation for MA with neglecting of dimmers concentration in comparison with concentration of the single vacancies and subtraction of the number CEC that replace the MA, namely vacancy clusters, due to the diffusivity of copper and other impurity atoms to them. For binary Fe-0.3wt%Cu under neutron irradiation with dose 0.026, 0.051, 0.10 and 0.19 dpa the volume content of the precipitates from the SANS experiment is found to be about 0.229, 0.280, 0.237 and 0.300 vol% respectively. The volume fraction of CEC, in these samples is 0.195 vol% and the calculated volume fraction ofMA is 0.034, 0.085, 0.042 and 0.105 vol% for doses 0.026, 0.051, 0.10 and 0.19 dpa respectively. 

For reactor steels the determination of the change in mechanical properties due neutron irradiation as well as recovering annealing procedure can be done on the basis of SANS experiment and some analytical results of theory of metastable states related to the volume content of new phase. The following procedure is suggested to find the volume content of the CEC ... 

Hon and Bray discussed the effects of neutron irradiation damage in cubic lattices using Br SSNMR experiments on a KBr single crystal and SSNMR (as well as Li and Na) experiments on Lil, Nal, and They provided... 

Elegant experiments have shown that endohedral transmutation of an element can take place within the fullerene cage while it is practically unaffected by high-energy neutron capture and )5-emission events. This was carried out on non-radioactive Gd Cg2, which transmutes into Tb Cg2 under neutron irradiation with emission of a -particle [21]. Monoisotopic Ho in macroscopic quantities (mg) of pure samples of Ho Cg2, Ho2 Cg2, or Ho3 Cg2 was also activated with a high neutron flux to produce stable Er [22]. These initial results strongly suggest that endohedral metallofullerenes may find a useful place in nuclear medicine in a way similar to boron neutron capture therapy (BNCT) [23]. 

Tamaki et al. also examined the in situ method in thermal annealing of neutron-irradiated potassium chromate and of Cr-doped potassium chromate. Variation of the X-ray intensity ratio in neutron-irradiated potassium chromate is not so prominent as in the Cr-doped crystals from Collins experiments, making the chemkal effect somewhat obscured. 

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