[en] This report summarizes work done after 2 years of a 3-year project. Using analytic electron microscopic and selective laser spectroscopic techniques, the authors first examined lanthanide orthophosphate crystals of YPO₄ and LuPO₄ that accumulated self-radiation damage from dopant (1 wt.%) ²⁴⁴Cm ions for 17 years. Although the accumulated dose of radiation (> 10¹⁸ alpha-decay events/mg) is significantly high, the samples that they examined physically remain crystalline on a macroscopic scale. Amorphization is not evident, even though isolated defects of various sizes were observed. Microscopic radiation effects in the crystals were manifested by (1) individual defect clusters of 2 to 5 nm size, which resemble disordered fission tracks, and (2) bubbles of 5 to 20 nm that are attributed to accumulation of He atoms generated during alpha decay events. These bubbles are relatively mobile and easily coalesce in electron microscopy studies due to enhanced diffusion arising from electron irradiation. They have observed that, when exposed to an electron beam, the bubbles aggregated as a function of exposure time. This observation thus provides additional evidence that the bubbles developed from the aggregation of helium atoms that were created from alpha-decay of Cm-244, and the local lattice recovered from radiation damage. In addition to bubbles and fission tracks of nanometer sizes, there exist smaller scale structural defects and lattice strains that were revealed from selective laser excitation and fluorescence spectra. These defects are attributed to alpha-decay induced structural damage that occurred randomly throughout the lattice. Annealing of the samples at 773 K for 12 hours removed more of the residual defects

[en] This report discusses the power generation problems faced in China due to inability to increase the capacity to transport increased amounts of coal for fuels. The use of nuclear power is described. A pressurized pool reactor is currently under consideration for power generation

[en] In order to observe and analyze the behavior of semiconductor devices under radiation exposure, a real time measurement system has been built so that investigations can be carried out before, during, and after radiation exposure. The system consists of an IBM personal computer with IEEE488 I/O interface board and various Hewlett-Packard instruments. Real time measurement and device parameter characterization programs have been written to accommodate the study. Such a system provides the ability to do not only direct and dynamic measurements, but also comprehensive parameter analyses for semiconductor devices. It is well known that MOS devices are vulnerable to radiation produced ionization. Many MOS device parameters are radiation sensitive. Based on real time measurement results and the mathematical model of a CMOS inverter, a radiation hardening design method has been developed. With the example of noise margin optimization, the concept of desensitizing device parameters is expected to minimize radiation damage to MOS integrated circuits

[en] Many particles proposed by theories, such as GUT monopoles, nuclearites and 1/5 charge superstring particles, can be categorized as Slow-moving, Ionizing, Massive Particles (SIMPs). Detailed calculations of the signal-to-noise ratios in various acoustic and mechanical methods for detecting such SIMPs are presented. It is shown that the previous belief that such methods are intrinsically prohibited by the thermal noise is incorrect, and that ways to solve the thermal noise problem are already within the reach of today's technology. In fact, many running and finished gravitational wave detection (GWD) experiments are already sensitive to certain SIMPs. As an example, a published GWD results is used to obtain a flux limit for nuclearites. The result of a search using a scintillator array on Earth's surface is reported. A flux limit of 4.7 x 10^-12 cm^-2sr^-1s^-1 (90% c.l.) is set for any SIMP with 2.7 x 10^-4 < β < 5 x 10^-3 and ionization greater than 1/3 of minimum ionizing muons. Although this limit is above the limits from underground experiments for typical supermassive particles (10¹⁶GeV), it is a new limit in certain β and ionization regions for less massive ones (∼10⁹GeV) not able to penetrate deep underground, and implies a stringent limit on the fraction of the dark matter that can be composed of massive electrically and/or magnetically charged particles. The prospect of the future SIMP search in the MACRO detector is discussed. The special problem of SIMP trigger is examined and a circuit proposed, which may solve most of the problems of the previous ones proposed or used by others and may even enable MACRO to detect certain SIMP species with β as low as the orbital velocity around the earth

[en] 'This project seeks to understand the microscopic effects of radiation damage in nuclear waste forms. The authors approach to this challenge encompasses studies in electron microscopy, laser spectroscopy, and computational modeling and simulation. During this first year of the project, efforts have focused on a-decay induced microscopic damage in crystalline orthophosphates (YPO₄ and LuPO₄) that contain the short-lived a-emitting isotope ²⁴⁴Cm (t_1/2 = 18.1 y). The samples that they studied were synthesized in 1980 and the initial ²⁴⁴Cm concentration was ∼1%. Studying these materials is of importance to nuclear waste management because of the opportunity to gain insight into accumulated radiation damage and the influence of aging on such damage. These factors are critical to the long-term performance of actual waste forms [1]. Lanthanide orthophosphates, including LuPO₄ and YPO₄, have been suggested as waste forms for high level nuclear waste [2] and potential hosts for excess weapons plutonium [3,4]. The work is providing insight into the characteristics of these previously known radiation-resistant materials. They have observed loss of crystallinity (partial amorphization) as a direct consequence of prolonged exposure to intense alpha radiolysis in these materials. More importantly, the observation of microscopic cavities in these aged materials provides evidence of significant chemical decomposition that may be difficult to detect in the earlier stages of radiation damage. The preliminary results show that, in characterizing crystalline compounds as high level nuclear waste forms, chemical decomposition effects may be more important than lattice amorphization which has been the focus of many previous studies. More extensive studies, including in-situ analysis of the dynamics of thermal annealing of self-radiation induced amorphization and cavity formation, will be conducted on these aged ²⁴⁴Cm:LuPO₄ and ²⁴⁴Cm:YPO₄ samples, along with other related compounds and glasses, in next two years of this project.'

[en] 'This project seeks to understand the microscopic effects of radiation damage in nuclear waste forms. The authors approach to this challenge encompasses studies of crystals and glass containing short-lived alpha- and beta-emitting actinides with electron microscopy, laser spectroscopy, and computational modeling and simulation. Much of the initial effort has focused on alpha-decay induced microscopic damage in 17-year old samples of crystalline yttrium and lutetium orthophosphates and thorium dioxide that initially contained ∼1% of the alpha-emitting isotope Cm-244 (18.1 y half life) or the beta-emitting isotope Bk-249 (0.88 y half life). Studies will also be conducted on borosilicate glasses that contain Cm-244 or Am-241, respectively. The goal is to gain clear insight into accumulated radiation damage and the influence of aging on such damage, which are critical factors in the long-term performance of high-level nuclear waste forms. Amorphization previously has been thought to be the most important effect of radiation damage in crystalline and ceramic materials. The studies show that for alpha-emitting actinide ions in certain crystalline phosphates, amorphization is not a significant effect of radiation damage. Instead, formation of microscopic cavities (bubbles) is an important consequence of alpha-decay events. This amorphization-resistant property makes orthophosphates a very attractive high level nuclear waste form. However, aggregation and mobilization of cavities (bubbles) might increase the leach rate of radionuclides and influence the long-term stability of the waste forms. Further research is needed before the authors can draw a final conclusion on the long-term effects of radiation damage in high level waste forms.'

[en] The micromechanisms involved in the processes of deformation and fracture in a Ti-24Al-11Nb (at. pct) alloy were investigated using TEM in situ deformation technique. The material contained three different crystal structures (the alpha-2, B2, and orthorhombic (O) phases). It was found that slip in this alloy is first initiated in the B2 and O phases. Alpha-2 phase was observed in the deformed material, but only in high-stress regions and only in some laths. Cracks were seen to originate most frequently in the regions that were fully transformed to alpha-2 laths, and sometimes in the regions that contained alpha-2 phase at prior beta grain boundaries. Crack branching in the alpha-2 phase was common, particularly in the vicinity of phase boundaries. 19 refs

[en] The results of crystal field calculations in the framework of exchange charge model (ECM) are reported for trivalent lanthanide and actinide ions doped into LaCl₃. Whereas the scalar strength of the model crystal field parameters are consistent with that previously determined by fitting the experimental data, the sign of the second-order parameter is found to be negative, in contrast to previous reports. The contribution from long-range electrostatic interactions exceeds that from the nearest neighboring ligands and leads to the negative sign of the second-order crystal field parameter. Other interaction mechanisms including overlap, covalence, and charge exchange are less important to the second order parameter, but dominate the fourth- and sixth-order parameters. This work provides a consistent interpretation of the previously controversial experimental results for both lanthanide and actinide ions in this classical host

[en] This is an analysis of thermoacoustic detectability of magnetic monopoles. Thermodynamical arguments make the thermal noise calculation much simpler. The result shows that the prototype detector is far from being able to detect magnetic monopoles. The possibility of improvements made by focusing techniques is discussed

[en] Laser spectroscopic and extended X-ray absorption fine structure (EXAFS) spectra have shown that uranium in B₂O₃ glass matrix forms uranyl in the electronic configuration of (UO₂)²⁺,but its surrounding structure is not well known. Understanding of uranyl local structure, ion-ligand interaction, and chemical stability on the nanometer scale in glasses is essential in management of long-term performance of high-level nuclear wastes after disposal in a geologic repository. In the present work, the structure, phonon density of states, and vibrational spectrum of vitreous B₂O₃ and the surrounding environment that contains a uranyl ion have been studied using a molecular dynamics (MD) simulation method that utilizes the Born-Mayer-Huggins and Coulomb pair potentials and the Stillinger-Weber three-body potential. A system of 406 ions was considered in our calculation. Simulation of a thermal quenching from 3000 K to 300 K was performed to generate a uniform and equilibrium model glass matrix before structure configuration and vibrational frequencies were obtained from the system. The structure of the simulated glass is in agreement with that reported by Krogh-Moe and Mozzi et al. The characteristic network of planar boroxol (B₃O₆) rings is evident in the simulated system. A configuration of a U⁶⁺ cation in the vitreous B₂O₃ matrix is shown in Fig. 1. It is shown that a nearly linear (UO₂)²⁺ uranyl ion is coordinated by four equatorial oxygen anions in an approximately planar arrangement. The U-O bond length is approximately 0.178 nm for the axial oxygen and 0.254 nm for the equatorial oxygen, which is in good agreement with the U-O distances obtained from fitting EXAFS spectra. Based on the simulated model structure, the uranyl vibrational spectrum is simulated and compared with experimental results obtained using site-selective fluorescence line narrowing (FLN) techniques