NUCLEAR ENERGY PROFESSIONAL(SPECIAL) ENGLISH COURSE
Chapter 10 Neutron Chain Reactions
(中子链式反应)
Chapter 14 Neutron Chain Reactions (中子链式反应) The possibility of a chain reaction involving neutrons in a mass of nuclear fuel such as uranium depends on:
(a) nuclear properties (特性) such as cross sections (截面) and neutrons produced per absorption;
(b) the size, shape, and arrangement of the materials.
14.1 CRITICALITY AND MULTIPLI- CATION (临界性和增殖性) To achieve a self-sustaining chain reaction (自持链式反应), one needing no external neutron supply, a \临界质量) of uranium must be collected. To appreciate this requirement we visualize the simplest nuclear reactor, consisting of a metal sphere of uranium-235.
接上页(P199 第二段第四行中) Suppose that it consists of only one atom of U-235. If it absorbs a neutron and fissions, the resultant neutrons do nothing further, there being no more fuel. If instead we have a small chunk (大块) of uranium, say a few grams, the introduction of a neutron might set off (导致) a chain of several reactions, producing more neutrons, but most of them would escape through the surface of the body, a process called leakage (泄漏).
接上页（P200 第二行中） Such an amount of fuel is said to be “subcritical ”(次临界的). Now if we bring together about 50 kg of U-235 metal, the neutron production balances the leakage losses, and the system is self-sustaining or “critical (临界的).” The size is the critical volume and the amount of fuel is the critical mass. Neutrons had to be introduced to start the chain reaction, but the number is maintained without further additions. The term (术语) \ has become popular to describe any collection of entities large enough to operate independently.
核技术英语-核技术英语-Chapter10- Neutron Chain Reactions
