[en] The Gentilly 1 station, a 250-MW(e) light-water-cooled and heavy-water-moderated nuclear reactor, is being decommissioned to a static state (variant of stage 1) condition by Atomic Energy of Canada Limited (AECL). The scope of the decontamination program at the Gentilly 1 site includes the fuel pool and associated systems, the decontamination center, the laundry, the feedwater pumps and piping systems, the service building ventilation and drainage systems, and miscellaneous floor and wall areas. After an extensive literature review for acceptable decontamination methods, it was decided that the decontamination equipment used at Gentilly 1 during the program would include a hydrolaser, a scarifier, chipping hammers, a steam cleaner, an ultrasonic bath, and cutting tools. In addition, various foams, acids, detergents, surfactants, and abrasives are used alone and in tandem with the above equipment. This paper highlights the result of these decontaminations, their effectiveness, and the recommendation for future application. The methodology in performing these operations are also presented

[en] A mathematical model of an operating LMFBR reactor consists of a large, complicated system of equations. Computer simulation requires selection of appropriate numerical methods to solve this system approximately, reduction of these numerical methods to efficient algorithms, and extensive testing of the resulting computer program. Several different programs of this sort, such as MELT-III, and SAS, have been developed and used to study various kinds of reactor accidents. For the past two years, the Department of Energy has sponsored a Mathematics Clinic study designed to examine the behavior of such codes and possibly to make suggestions for their improvement. Each year a Clinic team has concentrated on a particular aspect of what is called an overpower accident

[en] The probable formation mechanism of He bubble superlattices relies on long range anisotropic diffusion of self-interstitial atoms (SIAs). Here we study He ion irradiation of pure Ni and two equiatomic concentrated solid-solution alloys (CSAs) of FeNi and FeCrNiCo. It is expected from the significantly reduced diffusion of SIAs in CSAs, including high entropy alloys (HEAs), that long range anisotropic SIA migration cannot be active. We report the formation of a He bubble lattice in pure Ni, and for the first time in FeNi and FeCrNiCo systems under 30 keV He ion irradiation at room temperature. The ion dose and flux required to form a bubble superlattice increase with chemical complexity. Comparing to Ni, SIA clusters change directions more frequently due to anisotropic elementally-biased diffusion from the higher degree of chemical non-homogeneity in CSAs. Nevertheless, anisotropic 1-D diffusion of interstitial defects is possible in these complex alloys over incrementally longer time scales and irradiation doses. The sluggish diffusion, characteristic in CSAs, leads to smaller superlattice parameters and smaller bubble diameters. The chemical biased SIA diffusion and its effects on He evolution revealed here have important implications on understanding and improving radiation tolerance over a wide range of extreme conditions.

[en] Anticrossings induced by the motional Stark effect created by atoms moving perpendicular to a strong magnetic field have been observed in ₄He. These anticrossings couple the n ₁P state with the nominal n ₁D, n ₁F, n ₃F, and n ^1,3H states via first-order (for the ₁D) and second-order Stark effects. The theory is derived to explain the line shape in the second-order case. This theory, along with the previously existing first-order-effect line-shape theory, is used to obtain the zero-velocity crossing points. These values are used in a least-squares fit to determine the zero-field intervals. The ₁P-- ₁D² interval is determined precisely for n = 6, 7, and 8 and the n ₁G--nH_av interval is determined for n = 6 and 7. A power-series expansion establishes the n ₁P energy levels with respect to the higher nL states with high precision

[en] A novel inductive control system for a tokamak transformer is described. The system uses the flux change provided by the transformer primary coil to control the electric current and the internal inductance of the secondary plasma circuit load. The internal inductance control is used to regulate the slow flux penetration in the highly conductive plasma due to the skin effect, providing first-order control over the shape of the plasma current density profile. Inferred loop voltages at specific locations inside the plasma are included in a state feedback structure to improve controller performance. Experimental tests have shown that the plasma internal inductance can be controlled inductively for a whole pulse starting just 30ms after plasma breakdown. The details of the control system design are presented, including the transformer model, observer algorithms and controller design. (Author) 67 refs.

[en] A precision determination of the 4 ³S-³P interval in ⁴He is accomplished by observing resonances between Zeeman-tuned He ³S and ³P sublevels with four different CO₂ laser frequencies. This value is compared with the previous best experimental and theoretical values

[en] Interesting architectures built with electrically conductive substrates of interest for microelectrochemical power sources were obtained by directly growing carbon nanotubes on each microfibre constituting a carbon paper. The carbon nanotubes were fabricated by the chemical vapour deposition technique. Results of electrochemical tests showed high-resolution responses in different chemical media, which indicate good electrical contact between the carbon nanotubes and the carbon paper substrate. These architectures hold great promise for incorporation into microelectrochemical power sources

[en] The objective is to analyze an overpower accident in an LMFBR. A simplified model of the primary coolant loop was developed in order to understand the instabilities encountered with the MELT III and SAS codes. The computer programs were translated for switching to the IBM 4331. Numerical methods were investigated for solving the neutron kinetics equations; the Adams and Gear methods were compared

[en] Low temperature plasmas have excellent potential as on board transportation reformers for fuel cells. Because of their low temperature operation, they start up and shut down rapidly, and little energy is lost in waste heat that cannot easily be recovered from high temperature processes. Their use of electricity to drive reactions certainly requires good efficiency, but may simplify on-board systems. Partial oxidation has been shown to operate effectively as has steam reforming under these conditions. Hydrogen, CO_x, and C₂s are the primary products of plasma reforming of methane. In this paper, the major reaction pathways and the results of the partial oxidation and steam reforming of methane will be discussed. (author)

[en] Short communication