[en] This letter summarized the recent simultaneous evaluation of 12 important neutron cross sections at an energy of 14.7 MeV. A full report of the evaluation is also available. The cross sections included in the evaluation, which are listed, were either measured as ratios or ''absolutely'' using a neutron fluence rate determined by the associated particle technique, which served to normalize the results. (author)

[en] The best we can do in the short term to deal with the greenhouse effect is to keep from making the problem worse. Even with our best conservation efforts, however, we will need new energy supplies. For the long term, we must develop new techniques for burning fossil fuels more cleanly and, everywhere possible, substitute non-combustible forms of energy. Unless we devise a practical substitute like electric cars or acceptable mass transportation, automobiles will continue to be a major problem. Much of our electricity will still have to be made with coal. New techniques growing out of coal gasification research may make it possible to trap the carbon dioxide and divert it from release into the atmosphere, but questions about cost and technical feasibility make the prospects uncertain. Nuclear power is the only large-scale energy source, except falling water, that produces no greenhouse gases. The greenhouse problem far overshadows the concerns that are keeping us from using nuclear power more widely. We should also redouble our efforts to develop renewable energy sources. We can no longer afford to let economics - or our obsession with minor safety risks or even aesthetics - dictate our energy choices. (author)

[en] The greenhouse effect, electricity shortages, more imported oil -1988 has taught us that there is not just one energy crisis, but three. And it has shown that many of the solutions proposed in the past have turned into problems themselves. The U.S. produces one-fourth of the world's greenhouse gases, and burns one-fourth of the world's oil production. It is time for it and the rest of the industrialized world to take the three energy crises seriously and place a new emphasis on the three non-combustion solutions available now: conservation, solar and nuclear power. (author)

[en] A new method for performing the depletion calculations, based on the static generalized perturbation theory (GPT), is developed. This new method is compared with another perturbation method which makes use of both the static and the time-dependent GPT. Results obtained for a very simple but significant example of a zero-dimensional PWR reactor are presented. Comparison of both methods to direct calculation shows that the method proposed here is more efficient than the other perturbation method, is very accurate and has less computing time than direct computation, indicating it can become a useful tool for performing depletion calculations. (author)

[en] A method for deriving the nodal representation of multivariate linear systems in the steady state is presented. The basic idea is to breakdown the system into subsystems in each of which a representative variable is defined by the weighted sum of system variables. This is performed using the theory of orthogonal projection on a real vector subspace. A set of nodal equations for representative variables is derived rigorously and the critical condition is proved identical with that for the original system. The method is demonstrated by application to such problems as the determination of equations for spatial nodes and for two coupled cores, and the derivation of a zero-power point reactor model for neutrons and a representative precursor from that for neutrons and six-group precursors. (author)

[en] A concept for a passive reactor shutdown cooling system for the Trench Reactor, using a gravity-assisted, heat pipe heat exchanger is presented. The Trench Reactor is a conceptual study for an advanced liquid metal fast reactor of the pool type. Passive cooling of the pool is achieved by natural circulation of the containment building atmosphere (N gas) around the reactor vessel, and rejection of the heat from the gas to the outside environment through a system of heat-pipe exchangers. These latter are located at the top of the containment structure. An analysis based on a quasi-steady numerical model indicates that the heat removal rate from the Na pool should be sufficient to prevent excessive Na temperature in the pool after reactor shutdown. The heat transferred from the reactor is at the rate of 13.8 MW at 482⁰C, the design value of the Trench Reactor pool Na temperature during normal operation: at 538⁰C, heat is removed at 16.1 MW. The reactor wall temperature peaked at 487⁰C, 0.4 h after reactor shutdown. (author)

[en] Generalized hypergeometric functions include, as particular cases, many special functions occurring in nuclear sciences (for example Bessel functions and incomplete γ-functions). Owing to their various properties, hypergeometric functions have found a large number of applications in fields such as atmospheric radionuclide releases, heat transfer, statistical distributions and hydrodynamics. Their representations entail parameters that are written in the form (a)_n, which is known as Pochhammer's symbol. When transforming higher order hypergeometric functions to ones of lower orders and in other operations, one often encounters particular difficulties due to the fact that there may be no trivial relations between compound parameters of the Pochhammer kind. For example, one may be faced with breaking up the product (a+b)_n. The result presented here helps to overcome this particular problem. (author)

[en] Cross section measurements for the reactions ⁵²Cr(n,2n)⁵¹Cr, ⁶⁶Zn(n,2n)⁶⁵Zn, ⁸⁹Y(n,2n)⁸⁸Y and ⁹⁶Zr(n,2n)⁹⁵Zr were carried out in the neutron energy range 13.47-14.79 MeV applying the activation technique. Neutrons were produced via the T(d,n)⁴He reaction, making use of the variation of neutron energy with the emission angle. The neutron fluences incident on the samples were determined relative to the well-evaluated cross section for the reaction ⁹³Nb(n,2n)^92mNb. The induced γ-ray activities of the irradiated Zn, Zr and Y₂O₃ samples and their monitor foils were measured by means of a calibrated Ge(Li) γ-ray detector. Relative γ-ray measurements using a high-purity Ge detector were combined with integral γ-ray counting by means of a NaI(Tl) well-type detector on the Cr, Zn and Zr foils of highest activity and on some Nb monitor foils; integral γ-ray counting only was applied in the case of the Y₂O₃ samples. All necessary corrections were taken into account. The results are compared to the corresponding results of cross section measurements published in the literature. The uncertainties obtained in this work are considerably smaller in most cases than the uncertainties given by other authors. (author)

[en] The problem of constructing sequential tests for fault detection methods that are based on the concept of Mahalanobis distance is addressed. First the distribution of the Mahalanobis distance that belongs to the degraded (alternative) state of a multivariate system is determined. Then three sequential tests are constructed and their performance investigated for fault detection. For each test, the average sample number and an upper limit for the number of samples necessary so that the test will terminate with a given probability are calculated. (author)

[en] An analogue research-level, particle transport, Monte Carlo code for studying the attenuation and leakage of gamma ray photons in simple, multilayer, shielding configurations, originally written for conventional (i.e. serial) computers, is modified and re-written to run efficiently on the AMT DAP-610 highly parallel computer. The philosophy and algorithms adopted in transferring the code to the parallel machine are described. Two illustrative problems are solved using realistic cross-section data, involving a 9 MeV source of gamma photons in a lead-void-water sphere and slab. Integral quantities, such as fraction of particles absorbed and escaped, and differential quantities, such as flux distributions and leakage spectra, computed by the DAP parallel code, are presented in tables and graphs. These results are compared with those from the corresponding serial Monte Carlo code and also with an independent, deterministic, finite element method transport code. For equivalent calculations, the CPU times on the DEP and a number of serial computers (i.e. ICL-3900, CRAY XMP/28 in scalar mode, and VAX 11/750) are compared, and the resulting speedup factors quoted. (author)