Reactors. In the course of the atomic energy investigation, the common word "pile" which already had so many different uses in the English language took on a new and specialized meaning. A pile is a kind of nuclear installation maintaining a continuous, controllable chain reaction with the view of getting atomic energy. No less signal is its turning out radioactive isotopes, to say nothing of the tremendous amounts of heat accompanying the chain reaction.

Instead of the term "pile", scientists nowadays often use a more accurately descriptive one of "nuclear reac­tor". If a reactor is to operate at a steady preselected fis­sion rate, each fission must produce only one other fission. However, each fission is expected to produce 2 or 3 fresh neutrons that may cause other fissions. The first question to be asked about any reactor is just how these surplus neutrons are disposed of, the object of every reac­tor designer being to make them die usefully.

Most of nuclear reactors, roughly speaking, are instal­lations usually consisting of the following elementary parts: a moderator used to slow down fission neutrons, fuel elements containing fissionable material, heat remov­ing means, and a geometric structure in which a chain reaction can be maintained.

The installation is referred to as a thermal reactor pro­vided most of the fissions result from the capture of neut­rons which have been slowed down to thermal energies by collisions with the moderator, the so-called thermal neutrons.

When most of the fission processes are caused by the absorption of neutrons of higher energy, the system is said to be an intermediate reactor. We find the usual ran­ge of neutron energies in such a kind of reactor to be from thermal energy up to about 1,000 ev.

In case the main source of fissions is the capture of fast neutrons directly by the fuel without the neutrons having suffered any energy losses the unit under consideration is known as a fast reactor.

Variations of all main characteristics suggest, however, the possibility of variations in these fundamental types of reactors.

One can't but add in this connection that reactors of different types have been put into operation at the Beloyarskaya and the Novovoronezhskaya atomic electric stations.

Accelerators. A truly scientific investigation of the forces acting inside the atomic nucleus, of its structure and properties has been made possible owing to accelerators. These are special installations destined to accelerate "elementary" particles of matter and impart them enor­mous energy. In other words, accelerators are destined to create conditions under which the above particles can best be studied. Strange as it may seem but to investigate the tiniest particles of matter, invisible even through the most powerful microscope, scientists need weighty, complex installations occupying much space and requiring great amounts of electric power.

It is of interest to note here that a 10 Bev (billion electron volts) synchrotron is located near Moscow. In April, 1957, the proton synchrotron was put into operation in the laboratory of high energy physics of the international nuclear centre in Dubna. This enormous machine is capab­le of accelerating electrons up to 10 Bev.

Wonderful as the synchrotron in question is, it is by no means the limit. Such unique installations have been built in this country as the Erevan electronic accelerator and the world's most powerful seventy-milliard electron-volt proton accelerator located near Serpukhov.