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**Source: **STP38177S

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Considerable efforts have been expended to measure radiation damage effects on materials. These radiation damage studies can generally be justified by their impact upon nuclear reactor design and operation. However, radiation damage experiments can be difficult to interpret. A large number of parameters, including temperature, material variables, neutron spectrum, and fluence, are entailed in the evaluation of radiation damage data. The general case is further complicated as each of these variables may change with time.

The concept of a damage function was introduced some time ago to relate radiation damage to the neutron spectrum. This concept now forms the basis of conventional damage function analysis. The damage function in this conventional description is related to the “cross section” for damage at each neutron energy. However, this conventional formulation is unduly restrictive.

In order to construct a rigorous description of damage function analysis, a generalized damage function is postulated which includes not only neutron energy dependence, but also time dependence. Other important material variables as well as fluence are also considered to be explicit variables of the generalized damage function.

A number of important implications of this generalized integral representation are discussed. In order to provide guidance and insight in this investigation, radiation dosimetry analysis is used as a fundamental analog. It is shown that the generalized damage function is unique. Additional characteristics of generalized damage functions are determined by considering constraints imposed by physical requirements and conditions, such as nonnegativity, continuity, and boundedness.

For actual application it is necessary to reduce generalized radiation damage function analysis to simple models. Various assumptions that can be invoked to provide these simplified models are discussed, including separation-of-variables and restriction to steady-state irradiation conditions. In particular, it is shown that conventional damage function analysis follows directly from generalized damage function analysis upon the introduction of these simplified models.

Although some success may be possible for these simplified models, the complexity of this integral representation of generalized radiation damage function analysis cannot be overemphasized. Alternative formulations of radiation damage function analysis should be investigated with the hope that such efforts will supply not only further insight, but descriptions of considerably less complexity.

**Keywords:**

radiation effects, radiation damage, neutron irradiation, dosimetry, neutron flux, particle fluence, spectral determination reactors (nuclear), fission, fusion, monitors, evaluation

**Author Information:**

Gold, R *Fellow scientist, senior scientist, manager, and advanced scientist, Westing-house Hanford Co., Hanford Engineering Development Laboratory, Richland, Wash.*

Lippincott, EP *Fellow scientist, senior scientist, manager, and advanced scientist, Westing-house Hanford Co., Hanford Engineering Development Laboratory, Richland, Wash.*

McElroy, WN *Fellow scientist, senior scientist, manager, and advanced scientist, Westing-house Hanford Co., Hanford Engineering Development Laboratory, Richland, Wash.*

Simons, RL

**Committee/Subcommittee:** E10.07

**DOI:** 10.1520/STP38177S