The properties of materials change under the action of ionizing radiation. The degree of change per unit absorbed energy usually characterizes the radiation resistance of a material, i.e., the capability of the material to maintain the normalized technical indicators within established limits. It is obvious that the most reliable information about the radiation resistance and service life of a polymer material is obtained by performing tests under natural conditions. However, such tests are rare because they are expensive, and often they are difficult to perform. For this reason, there arises the problem of simulating the test conditions. An important question is the possibility of performing accelerated tests, since the operating time scale of the materials can differ by several factors from the time scales of the tests. The obvious method for accelerating tests by increasing the dose rate and reducing the exposure is valid in those cases when the radiation-induced changes in the characteristic properties of materials do not depend on the absorbed dose rate. In the opposite case, it is necessary to know the dependence of the radiation-induced changes on the absorbed dose rate.Besides the radiation environment, the operating conditions also include the composition of the surrounding medium, the temperature, the mechanical loads, and the electromagnetic fields. Many of these factors affect the materials together with the radiation, and the result of this action is not simply additive.One of the main problems of radiation materials science is to construct models required for predicting the changes in the properties of and determining the real service life of materials. The construction of such models is based on the knowledge of the mechanism and kinetics of processes occurring in materials. In the absence of such information (which, as a rule, is not available) only empirical models can be constructed, but their range of application is usually limited. The objective of the present paper is to consider some problems arising in the assessment of the radiation resistance of materials taking into account multifactor operating conditions.
CHARACTERISTIC INDICATORS OF THE RADIATION RESISTANCE OF MATERIALSEvery material has a complex of physical-chemical properties. In connection with the functions which a material must perform, only certain of its properties, namely, the operating properties, are of interest. The change in the indicators of the operational properties of materials (physical-mechanical, electrophysical, thermophysical, optical, and others) under the action of ionizing radiation characterizes their radiation resistance. The characteristic indicators of the radiation resistance of a polymer material were introduced in accordance with GOST 25645.321-87 [1]. In most cases, the common characteristic indicators of the radiation resistance of materials used for different purposes are the physical-mechanical properties, as stated in GOST 25645.331-91 [2], since other indicators become meaningless in the case of r...
