From the Introduction Low-level radioactivity is related to those radioactive sources of ionizing radiation that are characterized by low activities. Sometimes activity here does not represent total amount of radionuclides but rather their concentration. In other cases, the total activity may be quite high, but we can measure only a relatively small portion of the material. "Low" may have, for different situations and circumstances, not only considerably different meanings but also different absolute values as far as the activity or activity concentration is concerned. For example, one can refer to low activity in the case of radiocarbon dating, where the concentration of 14C is actually lower than its natural concentration, and also in the case of radon monitoring where, especially in mines or in some enclosed spaces, its concentration may be several thousand times higher than the outdoor "atural" concentrations. Emphasis is now being placed on the analysis of naturally occurring radionuclides in the environment or on the release of radionuclides from their different man-made sources because liquid and aerial discharge level controls have become more rigorous. In addition, the applicability of low-level methodology increases the extent of different radionuclide applications considerably. Since individual radionuclides differ in their decay scheme and particles emitted as well in their energies, there is no universal method for the accurate measurement of all radioactive sources. Moreover, there is usually a mixture of radionuclides in a sample, causing some difficulties in a selective evaluation of a given radionuclide. Due to the random nature of radioactive disintegrations, the appropriate interpretation of the experimental results would be, in most cases, impossible without elaborate statistical treatment and evaluation of the data obtained. Thanks to the availability of computer-based instrumentation, the measuring data can be, in most cases, processed and evaluated on-line, which makes it possible to control and optimize the experiment in order to extract the maximum amount of information carried by the detector response. The purpose of this book is to provide an introduction to low-level radioactivity assessment and to clarify the nature of its sources, as well as the principal methods used in its measurement. Our evaluation is concentrated on the present-day aspects of low-level methodology. The book may be useful for all who need highly sensitive analysis of natural or artificial radioactivity both within and outside the nuclear field. The attempt of this book is to summarize the sources of environmental radioactivity and their possible radiological impact in terms of resulting doses to the population, and to present a sound review of the measuring methods and techniques for the evaluation of low-level radioactivities encountered in both the environment and in a number of applications where radioactive sources are used as a means of obtaining important information.

The Department of Energy's Office of Environmental Management (DOE) is responsible for the safe cleanup of sites used for nuclear weapons development and government-sponsored nuclear energy research. Low-level radioactive waste (LLW) is the most volumetrically significant waste stream generated by the DOE cleanup program. LLW is also generated through commercial activities such as nuclear power plant operations and medical treatments. The laws and regulations related to the disposal of LLW in the United States have evolved over time and across agencies and states, resulting in a complex regulatory structure. DOE asked the National Academies of Sciences, Engineering, and Medicine to organize a workshop to discuss approaches for the management and disposition of LLW. Participants explored the key physical, chemical, and radiological characteristics of low-level waste that govern its safe and secure management and disposal in aggregate and in individual waste streams, and how key characteristics of low level waste are incorporated into standards, orders, and regulations that govern the management and disposal of LLW in the United States and in other major waste-producing countries. This publication summarizes the presentations and discussions from the workshop.

The primary aim of the handbook series will be to include as much useful data as possible for the specialist needing ready access for the solution of problems most likely to arise in the radiation protection professions. However, some selected review of fundamental concepts is also included to enable persons with a basic science or engineering background to acquire the necessary knowledge to solve a majority of problems in especially important aspects of radiation protection. Also since the profession is broad in discipline, an attempt has been made to fulfil the frequent need of professionals for a refresher course in some of the more important fundamentals needed to utilize data included in the handbook. Principles of management, organization, and procedures related to radiation safety will also be summarized in later volumes, with attention to presentation of methods for establishing new radiation safety programs based on the accumulated experience of others.

Naturally occurring radionuclides are found throughout the earth's crust, and they form part of the natural background of radiation to which all humans are exposed. Many human activities-such as mining and milling of ores, extraction of petroleum products, use of groundwater for domestic purposes, and living in houses-alter the natural background of radiation either by moving naturally occurring radionuclides from inaccessible locations to locations where humans are present or by concentrating the radionuclides in the exposure environment. Such alterations of the natural environment can increase, sometimes substantially, radiation exposures of the public. Exposures of the public to naturally occurring radioactive materials (NORM) that result from human activities that alter the natural environment can be subjected to regulatory control, at least to some degree. The regulation of public exposures to such technologically enhanced naturally occurring radioactive materials (TENORM) by the US Environmental Protection Agency (EPA) and other regulatory and advisory organizations is the subject of this study by the National Research Council's Committee on the Evaluation of EPA Guidelines for Exposures to Naturally Occurring Radioactive Materials.