Chapter 1 - INTRODUCTION

Abstract

A nuclear reactor is a prolific source of potentially dangerous nuclear radiation because most of the radiation released originates with the fission process itself. In addition to the energetic neutrons and gamma rays that are emitted simultaneously with the fission event, the fission fragments formed are highly radioactive nuclides that emit alpha, beta, and gamma radiation. Although many types of nuclear particle are released directly and indirectly in and around the reactor core, the essential shielding problem is the attenuation of the penetrative fast neutrons and high energy gamma rays that are released in the reactor core and reactor shield. The charged particles released, such as the alpha and beta particles, and the heavily ionizing fission fragments are readily stopped within a few centimeters of a dense material under normal operating conditions. During its passage through the shield, most of the neutron and gamma radiation is absorbed and the energy carried by the absorbed radiation reappears as heat in the materials of the shield in a phenomenon referred to as nuclear heating.