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= 0.12 and 0.07, respectively, were prepared from a distillate, remelted in an arc furnace in an atmosphere of pure helium. Prolonged exposure of the ingots at a temperature of 1520~ led to the formation of concretions of singte crystals of sufficient size. Samples in the form of rectangular plates (Fig. 1), the ribs of which coincided with the principal crystallographic axes, were cut out of several large crystallites by an electroerosion method. The accuracy of the orientation was ensured within �9 1 ~ by goniometric adaptation. Since a single crystal of beryllium is readily split along the basal plane, its orientation with respect to the mechanical shear piane successfully supplemented the Roentgenographic orientation. Contacts were soldered onto the sample with indium for measurement at helium temperature. At nitrogen and room temperatures clamped on potential contacts of bronze and current contacts, which were soldered oz~ with a cadmi~nn-zine solder, were used

The reactor tests of fuel elements with heat-exchange intensifiers, operating with full evaporation of the water, with superheated steam, and without the use of an intermediate separator, shows that it is possible in principle to design a single-pass steam generator in reactors with tubular fuel elements.

Austenitic stainless steels are widely used in fast-reactor cores; they represent metastable solid solutions. They work at high fast-neutron fluxes and elevated temperatures, which accelerate the decomposition substantially [I]. The decomposition produces segregations of carbide, nitride, intermetallide, and other phases [2], which largely determine the properties [3]. Electron microscopy is widely applied to irradiated materials but does not always enable one to identify these segregations. When the decomposition products are ferromagnetic, there are certain advantages in magnetic methods. Interest attaches to the magnetic parameters for stainless steels irradiated to high fast-neutron fluences because they may be used in fusion reactors.

In future D--T tokamak power r e a c t o r s the t he rma l f luxes f r o m the p l a sma to the wall will be 0.4-1 M W / m 2. With a p l a s m a t e m p e r a t u r e of 10-20 keV at the axis of the r e a c t o r , a densi ty n ~ 102~ m "s, and a smal l f rac t ion of multiply charged impuri ty ions, radia t ion may play only a s econd-o rde r ro le in the r emova l of energy f r o m the r e a c t o r , The r equ i red t h e r m a l f luxes may occur if turbulence develops in the p l a sma volume due, e.g. , to the t rapped par t ic le instabi l i ty which is cha rac t e r i zed at high t e m p e r a t u r e s by l a rge t r a n s por t coefficients [1]. The r e a c t o r walls would then be in contact with a hot p l a sma (T ~ 3 keV) and be bombarded by pa r t i c l e s with energ ies grea t ly in excess of the sput ter ing threshold of the wall m a t e r i a l . Thus, power r e ac to r des igns include the use of d ive r to r s which at tenuate the flux of pa r t i c l e s and energy to the f i r s t wall by two o r d e r s of magnitude.

Emergency protection drives (EPD's)arewidely usedin nuclear reactors. Electromagnets (EM's) are used in retaining the safety rods outside the reactor core, while springs attempt to insert them into the core. The operation time of such an EPD is made up of the EM pick-up time (i.e., the time from the instant the the voltage is applied to the EM to the instant the EM armature begins to move) and the travel time of the EPD mechanical system, which amounts to the travel time of the safety rods. As the spring force increases, the travel time of the EPD mechanical system tms is reduced, while the EM pick-up time increases, as a consequence of which the latter has to be designed for larger forces. Therefore, there is a basis to assume that an optimum ratio between the components exists, which ensures a minimum operating time top of the EPD. The aim of this article is to determine this ratio. It would be helpful to obtain the results for cases in which the displacement of the safety rod is first a function of the instant at which the limiting permissible reactor power is achieved under emergency conditions and, second, a function of a given quantity (a variant that Ks frequently encountered when developing EPD's). Let us consider the optimum ratio for the first case. Let us assume that as a result of some cause (e. g., operator error), a surge of positive reactivity arises in the reactor, and the reactor power rises sharply. Figure ! shows the reactor-power curve for this case. The operating time of the automatic equipment in the emergency protection control system is small in relation to the EPD operating time, and can be assumed to be zero. The EM is energized at instant h. At t 2 the EM armature moves and the safety rods beghn to enter the reactor core. Because of this the rise rate of the reactor power declines. At |nstant t k a negative reactivity equal to Ok is introduced by the safety rod, which is sufficient to ensure an end to the power rise. A sharp decrease in power occurs at t k as the negative reactivity continues to be introduced, e.g., by a brake on the safety rod.

The possibility of achieving controlled thermonuclear fusion by using relativistic electron beams (REB), first pointed out by Zavoiskii [i], is arousing ever-increasing interest. As shown by Rudakov [2, 3], REB with a current of the order of 107 A and a power density of the order of i0 *s W/cm2 are required to accomplish this. The present paper describes the Kal'mar i accelerator producing REB with a power density of 5.10'*-5-i0 *= W/cm 2. We give the results of investigations on REB focusing in a hlgh-voltage diode as a function of the electrode geometry and the magnitude of the voltage prepulse.

The thermal neutron yield from paraffin spheres 15 and 20 cm in diameter with α-Be neutron sources at the center was measured. The neutron yield varied from 0,11 to 0.13 depending on the type of source. Also measured was the neutron spectrum emitted from a sphere 20 cm in diameter heated to 80°C. It was shown that the slow neutron spectrum was satisfactorily described by a Maxwellian distribution with a temperature around 600~ Recommendations are given for the calibration of neutron dosimeters with such sources.

A method of adjusting a synchrotron with external single-turn injection and a single-turn release of electrons with an electromagnet of special construction is described.

The paper describes the results of the first experiments with the PR-5 apparatus, an adiabatic trap with the magnetic field increasing both longitudinally and radially. It is shown that in such a trap there is no hydromagnetic instability of the plasma; the lifetime of the plasma is limited by charge exchange of fast ions with neutral gas. The maximum decay times of the plasma observed in these experiments are 10-15 msec.