AQUEOUS HOMOGENEOUS REACTORTECHNICAL PANEL REPORT

Considerable interest has been expressed for developing a stable U.S. production capacity for medical isotopes and particularly for molybdenum- 99 (99Mo). This is motivated by recent re-ductions in production and supply worldwide. Consistent with U.S. nonproliferation objectives, any new production capability should not use highly enriched uranium fuel or targets. Conse-quently, Aqueous Homogeneous Reactors (AHRs) are under consideration for potential 99Mo production using low-enriched uranium. Although the Nuclear Regulatory Commission (NRC) has guidance to facilitate the licensing process for non-power reactors, that guidance is focused on reactors with fixed, solid fuel and hence, not applicable to an AHR. A panel was convened to study the technical issues associated with normal operation and potential transients and accidents of an AHR that might be designed for isotope production. The panel has produced the requisite AHR licensing guidance for three chapters that exist now for non-power reactor licensing: Reac-tor Description, Reactor Coolant Systems, and Accident Analysis. The guidance is in two parts for each chapter: 1) standard format and content a licensee would use and 2) the standard review plan the NRC staff would use. This guidance takes into account the unique features of an AHR such as the fuel being in solution; the fission product barriers being the vessel and attached systems; the production and release of radiolytic and fission product gases and their impact on operations and their control by a gas management system; and the movement of fuel into and out of the reactor vessel

Distribution of zeros of the partition function for the finite two-dimensional Heisenberg model

The exact excitation spectrum of the 3 × 3 square and the 3 × 4 rectangular lattices interacting via the nearest-neighbor anisotropic Heisenberg interaction H=JΣ(ij)[SizSjz+y(SixSjx+SiySjy)] has been obtained for various values of the anisotropy constant γ. For 0≤γ≤1, the zeros of the partition function in the complex µ=exp(-mHe/kBT) plane obey the generalized Lee-Yang theorem for ferromagnetic coupling. The usual ferromagnetic transition seems to persist up to γ≃0.6. For 0.6≲γ≤1, nothing definite about a ferromagnetic transition can be inferred from the behavior of the zeros. When γ>1, the ferromagnetic zeros do not obey the generalized Lee-Yang theorem at sufficiently low temperatures. For antiferromagnetic coupling, the zeros lie on the negative real axis for all values of γ and of the temperature of the studied lattices

Exact numerical results on finite one- and two-dimensional Heisenberg systems

Results of exact numerical work on the spectra and thermodynamic properties are presented for finite clusters in one and two dimensions, for the isotropic Heisenberg Hamiltonian and the Heisenberg Hamiltonian with longitudinal anisotropy. Eigenvalues of the isotropic Heisenberg loops (that is, those with periodic boundary conditions) of N≤12, 8, 6, 5, 5 particles, each of spin ½, 1, 3/2, 2 and 5/2, respectively, are found. It is shown that the spin-S linear chain (N→∞) will have ground-state energy per spin ε∞s/2J=-1.404±0.002, -2.85±0.03, -4.7±0.4 and -7.1±0.5, for S=1, 3/2, 2, and 5/2, respectively. For antiferromagnetic interaction, the lowest excited states of the loops with even number of particles have spin 1 and the familiar double sine spectrum; while for the spin-½ case the eigenvalues are very different from the result of the spin-wave theory, they approach this limit as the spin increases, and for spin 5/2, the infinite-spin results of the spin-wave theory should be quite accurate. For ferromagnetic loops, there exist spin-wave bound states for higher spins just like those familiar in the spin-½ linear chain. Effective magnetic moments for these loops are tabulated. We also present the moments for the N=8 spin-½ chain (with open ends), and find the difference to be small. Results on the 3×4 two-dimensional Heisenberg antiferromagnet are presented and compared with experimental data. Finally, we show some examples of the violation of the nondegeneracy rule, similar to those found by Heilmann and Lieb; levels belonging to different representations of a symmetry group remain permanently degenerate when a parameter is varied

Modelling energy-economic interactions in developing countries : a linear-programming approach /

An energy economic assessment model for application to energy assessments in developing countries is described. A simple comprehensive treatment of the energy sector is emphasized. The input output model is directly incorporated in the Energy system LP. The major supply sectors, as well as the major energy using industries, are modelled as capacity expansion problems, in which explicit distinction is made between capital stock and energy flows. For most developing countries the notion of energy supply curves is far fetched, since energy prices are set by planning authority, not established by market clearing equilibrium."Prepared for presentation at the 9th International Conference on Operational Research, International Federation of Operations Research Societies, Hamburg, Germany, July 23, 1981, Workshop on O.R. Applications to Energy Planning in Developing Countries."An energy economic assessment model for application to energy assessments in developing countries is described. A simple comprehensive treatment of the energy sector is emphasized. The input output model is directly incorporated in the Energy system LP. The major supply sectors, as well as the major energy using industries, are modelled as capacity expansion problems, in which explicit distinction is made between capital stock and energy flows. For most developing countries the notion of energy supply curves is far fetched, since energy prices are set by planning authority, not established by market clearing equilibrium.Photocopy. -Mode of access: Internet

Aqueous Homogeneous Reactor Technical Panel Report

Considerable interest has been expressed for developing a stable U.S. production capacity for medical isotopes and particularly for molybdenum- 99 (99Mo). This is motivated by recent re-ductions in production and supply worldwide. Consistent with U.S. nonproliferation objectives, any new production capability should not use highly enriched uranium fuel or targets. Conse-quently, Aqueous Homogeneous Reactors (AHRs) are under consideration for potential 99Mo production using low-enriched uranium. Although the Nuclear Regulatory Commission (NRC) has guidance to facilitate the licensing process for non-power reactors, that guidance is focused on reactors with fixed, solid fuel and hence, not applicable to an AHR. A panel was convened to study the technical issues associated with normal operation and potential transients and accidents of an AHR that might be designed for isotope production. The panel has produced the requisite AHR licensing guidance for three chapters that exist now for non-power reactor licensing: Reac-tor Description, Reactor Coolant Systems, and Accident Analysis. The guidance is in two parts for each chapter: 1) standard format and content a licensee would use and 2) the standard review plan the NRC staff would use. This guidance takes into account the unique features of an AHR such as the fuel being in solution; the fission product barriers being the vessel and attached systems; the production and release of radiolytic and fission product gases and their impact on operations and their control by a gas management system; and the movement of fuel into and out of the reactor vessel