05 Nuclear fuels (scientific, technical)

96JO4999 Nonlinear analysis of low-quality density wave instabilities in a natural circulation system at heating reactor conditions Zhou, Z. and Heusser, P. Kerntechnik, May 1996, 61, (2), 86-92. An nonlinear analysis of low-quality two-phase flow density-wave oscilla- tions in a natural circulation system at heating reactor conditions is reported in this paper. A onedimensional homogeneous equilibrium two- phase flow model was applied. Comparisons between the numerical analy- sis results and data obtained from an experiment for investigating the sta- bility behaviour of an integrated natural circulation heating reactor show fairly good agreement.

96105000 Nuclear condensed matter physics - Nuclear meth- ods and appllcatlons Von Schatz, G. and Weidinger, A. John Wiley & Sons, Baffins Lane, Chichester, UK, f50.00, 280 pp.

96105001 On a Bayeslan estlmatlon procedure for determln- Ing the average ore grade of a uranium deposlt Heising, C. D. and Zamora-Reyes, J. A. Ann. Nucl. Energy, May 1996, 23, (7), 543-552. A Bayesian procedure is applied to estimate the average ore grade of a specific uranium deposit (the Morrison formation in New Mexico). Experi- mental data taken from drilling tests for this formation constitute deposit specific information, E,. This information is combined, through a single stage application of Bayes’ theorem, with the more extensive and well established information on all similar formations in the region, E,. It is assumed that the best estimate for the deposit specific case should mclude the relevant experimental evidence collected from other like formations giving incomplete information on the specific deposit.

96105002 On the Interpretation of a posltlve scram reactlvlty Khotylev, V. A. Ann. Nucl. Energy, Jun. 1996, 23, (9), 779-784. Hashimoto et al. (1994) published an article (Ref. 1) that contains some important results relevant to the role of the positive scram reactivity in the Chernobyl unit 4 accident. The primary goal of the current paper is to investigate whether the 2D R-Z reactor model and the approximation used in Ref. 1 are applicable to the Chernobyl accident analysis as well as to the analysis of any RBMK-1000 reactor behaviour.

96lO5003 Potentlal exposure In nuclear safety INSAG-9, IAEA, Wein, 1995, 29 pp.

A report by the International Nuclear Safety Advisory Group.

96105004 The potential of accelerator drlven cores In a self- consistent nuclear energy system Artisyuk, V. er al., Kerntechnik, May 1996, 61, (2), 106-110. The self-consistent nuclear energy system proposed as an ultimate goal for further nuclear development simultaneously satisfies four objectives: energy generation, fuel breeding, transmutation of radionuclides, and sys- tem safety. Assuming advanced fast reactors as main contributors in a nuclear energy system, the authors consider the potential role of accelerator driven cores to facilitate the solution of the transmutation problem from the standpoint of self-consistency requirements. They discuss the scientific feasibility of neutron excess generation in accelerator driven cores, which is required to incinerate fission products without isotope separation. A target made of uranium-bismuth compounds is proposed to provide the fuel and neutron generation which are required for self-consistency.

96/05005 The pro]ect management unit Nuclear Engineering In!., Aug. 1996, 41, (505) 37-38.

Discusses the establishment of a Project Management Unit at Ignalina which was a milestone development in Western-sponsored nuclear safety assistance. The programme of technical safety improvements was the first internationally-funded nuclear safety backfitting project in the former Soviet Union.

96/05006 Quality control of nuclear charcoals: particle size effect and trapplng mechanism Nacapricha, D. and Taylor, C. G. Carbon, 1996, 34, (2), 155-163. The efficiency of activated, impregnated charcoal for trapping radioiodine release from nuclear plants is expressed as a K value, measured by dosing a bed of charcoal with methyl iodine (I-131). K value measurements on commercial charcoals are often imprecise. A major source of this impreci- sion lies in the range of particle sizes that can exist in charcoals used for trapping. Charcoals impregnated with potassium iodide by spraying or by rotary evaporation has been graded by sieving, and the K value and other parameters of the main fractions have been measured. K values have been found to increase with decreasing particle size over the size range 6-12 BSS.

96/05007 R&enacting the Chernobyl accident Nuclear Engineering Int., Aug. 1996, 41, (SOS), 33-34.

Reports that in the ten years since the Chernobyl accident many modelling exercises have been carried out to shed light on the course of the accident. But it is only in recent months that it has been possible to reproduce the event in real time on a full-scope RBK-1000 simulator.

96105006 Risk assessment of the beneficial impact of a filtered venting containment system in a PWR wlth large, dry containment Schechtman, R. and Heising, C. D. Ann. Nucl. Energy, May 1996, 23, (S), 641-661. Many of the potential high consequence Class-9 accidents in pressurized water reactors (PWRs) involved containment failure by overpressurization. Filtered Venting Containment Systems (FVCS) has been suggested to pre- vent this mode of containment failure and to reduce the radioactive releases. This study quantified the beneficial effect of an FVCS on the risk to the public from accidents in a PWR with a large, dry containment (Surry-plant). The accidents considered were those found to be the most likely to cause containment failure by overpressurization. The results for those dominant accidents were then used to infer the risk reduction poten- tial of the FVCS. This study developed a phenomenological event tree to characterize the ex-vessel accident scenarios which might be encountered by the FVCs.

96105009 Screw compressor capacity regulated by stepless speed control Rolfsman, L. and Wihlborg, S. ABB Review, 1996, (4), 18-23. ABB Refrigeration has developed a new screw compressor drive for refrig- eration and freezing plant. Called STAL Rotatune, it is based on a special high-speed motor that is fed with power from an advanced frequency con- verter. Stepless control allows the compressor to maintain high total effi- ciency even at considerably reduced loads. With a normal load profile, energy consumption can be reduced by up to 15% compared with conven- tional capacity control, and by as much as 20% when an economizer is used with the compressor.

96105010 SG replacement project update Kocourek, J. Nuclear Engineering fnt., Aug. 1996, 41, (SO5), 18-19. Reports that SG replacement is becoming routine work and the time needed to do the job has decreased significantly. Tough competition for the business in the USA and Europe has become a real challenge for the leading SG manufacturing and replacement companies.

96105011 Spatlally dependent resonance cross sectlons In a fuel rod Stoker, C. C. and Weiss, Z. J. Ann. Nucl. Energy, Jun. 1996, 23, (9), 765.778. The classical resonance absorption theory which treats a fuel pin as a single region, surrounded by moderator, is generalized to an arbitrary sub- region of the fuel lump. Based on that generalization, a method is presented by which shielded resonance cross sections can be calculated by any number of annular regions in the fuel pin, using pretabulated resonance integrals, such as those appearing in the WIMS code. Numerical results obtained using that method are compared with those of ROLAIDS, a micro-group slowing down code in annular geometry, used here as reference.

96105012 The Swedlsh connectlon Nuclear Engineering fnf., Aug. 1996, 41, (505). 39-40.

As well as the EBRD funded effort to upgrade Ignalina there are also bilateral programmes with several countries, e.g. Canada and the USA. The largest and longest-running bilateral programme is that with Sweden, which is managed by SIP (Swedish International Project on Nuclear Safety) an organisation set up by the Swedish regulator, SKI. The focus of the Swedish programme was to identify areas where short term safety improvements could, without deeper safety analysis, be judged necessary. One such area was fire protection.

96105013 Technlcal note. Measurements of fast neutrons and secondary gamma rays In graphlte Makarious, A. S. er al., Ann. Nucl. Energy, May 1996, 23, (7). 617-623. The spatial fluxes and energy distributions of fast neutrons, total gamma rays and secondary gamma rays transmitted through different thicknesses of graphite have been measured. The graphite samples were arranged in front of one of the horizontal channels of the ET-RR-l reactor. Gamma ray measurements were carried out for bare, cadmium filtered and boron car- bide filtered reactor beams. A fast neutron and gamma ray spectrometer with a stilbene crystal was used to measure the spectrum of fast neutrons and gamma rays. Pulse shape discrimination using the zero cross over technique was used to distinguish the proton pulses from the electron pulses. The total fast neutrons macroscopic cross section and the linear attenuation coefficient for gamma rays were derived both for the whole energy range and at differnt energies.

96105014 Technlcal note. Verlflcatlon of the three-dlmen- slonal modular nodal method for spherlcal harmonic equatlons Inane. F. Ann. Nucl. Energy, May 1996, 23, (7), 613-616. The three-dimensional nodal neutron transport code based upon a modular least squares approximation is used for solving various problems for veri- fying the method. While the code provides successful comparable results for some benchmark problems, it fails for another problem. In addition, the concept of modularity is tested for some problems and shown to be a viable approach to be implemented in transport computations.

352 Fuel and Energy Abstracts September 1996