1. Translate the following sentences:

1. Nuclear fission reactors have developed into a fairly mature technology and have become one of our major sources of energy.

2. Their principal product of a fission reactor is heat, which is often used to gener­ate electricity.

3. Fission reactors are much simpler to build and operate than fission bombs be­cause they don’t require such purified fissionable materials.

4. Several neutron-absorbing rods, called control rods, which are inserted into the reactor’s core, determine whether it’s above or below critical mass.

5. Both cars and reactors respond relatively slowly to movements of their con­trols.

6. It would be impossible to operate a reactor that immediately shut down when you dropped the control rods in and instantly exploded when you pulled the control rods out.

7. A nuclear reactor uses feedback to maintain the fission rate at the desired level.

8. Pulling the control rods out of the core increases the chance that each neutron will induce fission and moves the core toward super criticality.

2. Translate the following information into Russian:

Heavy atomic nuclei are not so stable as light ones, because in the former the repulsive forces exerted by the protons loosen the structure of the nucleus. For this reason it is pos­sible to cause fission of heavy nuclei - such as those of 235 U - by bombarding them with free neutrons. The “fission products” travel at considerable velocity, collide with matter

somewhere in the reactor, and give off their kinetic energy as heat. This is the conversion of nuclear energy into heat. In addition to the fission products and heat formed in the fission of uranium, however, two fresh neutrons are also formed, which in turn can cause the fission of more uranium atoms. In this way the chain reaction is initiated. A neutron strikes the 235 U nucleus and briefly forms the intermediate product 236 U, which disintegrates spontane­ously into strontium and xenon. In order to be able to utilize these neutrons, which are emit­ted from the parent nucleus at high velocity, for the further fissile processes, they have to be slowed down (“moderated”). Low velocity neutrons are much better suited to split atoms than high velocity neutrons are. The slower neutrons can interact with the uranium nucleus for a greater length of time, whereas faster neutrons are in the vicinity of the nucleus for too short a time to initiate the fission process. The velocity of the neutrons is moderated by causing them to collide with light atoms, large number of which must be incorporated in the reactor for this purpose. Materials consisting of such light atoms are, for example, graphite and water. The neutrons which have been slowed down in this way will then cause fission of further 235 U nuclei. Each fission process gives birth to fresh electrons, so that the chain reaction is self-sustaining and the reactor is consequently kept in operation.

1. Translate into Russian:

Pressurized-water reactor is the simplest form of thermal reactor, in which water serves as the coolant and also as the moderator (i.e., the substance that is used to re­duce the velocity of the fast neutrons produced by nuclear fission).The pressure in the primary circuit is so high, and the boiling point of the water consequently so raised, that no stream can form in the reactor core. The pressure, and therefore the attainable temperature, is limited by the technically practicable dimensions of the reactor ves­sel. Ordinary water as well as “heavy” water (deuterium oxide) may be used as the coolant. The water in the primary circuit is kept in circulation by pumping. The heat absorbed in the core is transferred by means of a heat exchanger to the secondary cir­cuit, where it is utilized to raise steam which drives turbines, which in turn drive the generators for producing electricity.

The reactor fuel consists of slightly enriched uranium dioxide (average 3% 235 U), which is enclosed sealed zircaloy (a zirconium alloy) tubes. One hundred eighty such fuel rods are combined into one fuel assembly. There are 121 fuel assemblies in the reactor core. 27 control rods are uniformly distributed over the core, which are inserted into it from above.