[en] The standard nongravitation force model has been modified by allowing the water-vaproization curve to peak a certain number of days (DT) either before or after perihelion, and the modification is shown to often improve the data fit. The best fit to the astrometric data is generally achieved for a value of DT corresponding to the offset in the comet's visual light curve. The asymmetric model, which more accurately mimics the comet's outgassing history, suggests only weakly that the rotation direction of Comet Halley is direct, and it does not provide evidence that the rotation axis of Comet Kopff passed through its orbit plane in the early twentieth century. Approximate lag angles of 4 deg for Comet Halley and 10 deg for Comet d'Arrest are found using the asymmetric model, and it is noted that these values are lower than those obtained with the standard model. 34 refs

[en] Experimental studies of boiling in particle beds representing reactor core debris have been restricted to very small beds compared with those that may be found in a reactor. The use of air and water to simulate some of the many features of boiling in a particle bed has given results that were inconclusive. The work reported here is that carried out at Winfrith to extend the dryout data to larger particle diameters, and to provide new experimental data which removes earlier doubts, and makes the air-water analogue position much clearer. (U.K.)

[en] Spectra obtained for the coma, nuclear fragments A and D, and tail of Comet West 1976 VI on April 1, 2 and 7, 1976 are noted to encompass coma spectra which differed from those of the nuclear fragments, which exhibited a strong continuum with superimposed emissions that included a stronger CO(+)-band system than that of the coma. A detailed comparison between fragment spectra has revealed great differences in both quasi-simultaneously obtained and five-day-separated cases. The relative intensities of different CO(+) bands are compared to the theoretical ones, and the abundances of CO(+) ions corresponding to different vibrational transitions are determined relative to that of CN. 24 references

[en] In a previous paper, a model was presented for the dissolution of a silicate glass under static conditions in a finite volume of water. In the present paper, this model is extended to describe dissolution in a finite volume of water which is replenished or through which there is a small flow. Dissolution equations appropriate to the model are derived and compared with experimental data for the dissolution of Vycor. The behaviour of the model is found to be consistent with the experimental results, and the dissolution parameters derived to be comparable with those found in previous static experiments. (author)

[en] In this paper, the effect of vertical walled obstacles on circular fronts propagating on the surface of shallow water is discussed. The amplitude of the transmitted acceleration waves is determined together with a recurrence relation for the reflection and transmission coefficients at successive obstacle walls. (author)

No abstract available

[en] When steam is condensed in pool water, the oscillation of pressure and fluid occurs depending on the flow rate of steam and pool water temperature in a vent pipe system. This phenomena arouse interest as the problem of dynamic load evaluation for the pressure-suppressing containment vessels for BWRs in the case of loss of coolant accident and excess steam discharge. The oscillation phenomena are divided into chugging when the flow rate of steam is small and pool water temperature is low, condensing oscillation when the flow rate of steam is large, and bubbling when pool water temperature is high. On these classification and the range of occurrence of each mode, researchers almost agreed. For the purpose of clarifying the mechanism of these oscillation phenomena, the authors carried out a small scale experiment. The thinking that the high frequency oscillation component is the oscillation having steam bubbles at the exit of a vent pipe as the control volume, and the low frequency component is the oscillation having a large space including a steam header as the control volume was shown. The threshold of oscillation occurrence, its analysis and the comparison with experiment are reported. (Kako, I.)

[en] The effects of thermal stress on the evolution of comets are explored analytically in an elastic approximation. The total stresses undergone by the comet are modeled in terms of a linear expansion of the comet. Ice creep is accounted for with a viscoelastic treatment. The icy cometesimals and surrounding inclusions of other materials which are the principal components of a comet undergo thermal stresses which surpass the strength of water ice near the surface when the nucleus is over 10 m in diam. Cracking at the surface exposes new material, causing surface evaporation and ejection of up to one trillion grams of material from one outburst from a 60 m diam comet. 26 references

[en] Hypothetical transient criticality of irradiated fuel elements in a transport flask has been considered in a collaborative study by the CEA and AEA. The accidents are assumed initiated when water enters a dry flask with criticality being reached when the water reaches a height of 1.2 m, and the water continues to rise. Subsequent events have been calculated using the computer codes CHATEAU and SARTEMP. These codes calculate the variation of power with time, and associated temperature changes in fuel, clad and water (including boiling), taking into account the reactivity changes due to the Doppler effect, water expansion and boiling. It is shown that the temperature changes are limited to a few hundred degrees rise. (author)

[en] High-resolution images of IRAS 09371 + 1212 in the J, H, and K bands show that this source is a small bipolar nebula viewed in the equatorial plane. A spectrum of this object in the 2.0-3.4 micron region shows a very narrow ice feature, interpreted as absorption by primarily pure crystalline water ice. 24 references