Module 1: Nuclear gauge design, theory and operation

Authors: Evett, Steven - Steve

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 1/20/2000
Publication Date: 1/25/2000
Citation: Evett, S.R. 2000. Module 1: Nuclear gauge design, theory and operation. In: USDA-Radiation Safety Staff, editors. Nuclear Gauge Train-the-Trainer Course. Beltsville, MD: USDA-Radiation Safety Staff. Module 1. p.1-23.

Interpretive Summary: Several USDA agencies use nuclear gauges to determine soil water content, density of compacted earth and concrete for dams, and for safety monitoring of dams and levees. Nuclear gauges are essential tools for water management and dam and levee safety, and they are used by USDA stakeholders for the same purposes, including the use of nuclear gauges for irrigation scheduling of high value crops, ensuring high crop quality and efficient use of water. Because nuclear gauges contain a small radioactive source, Nuclear Regulatory Agency rules require that users be trained in radiation safety, which includes understanding of how gauges function, what their important components are, the type and strength of radioactive materials that they contain, and the safe use of the gauges. A USDA ARS scientist at Bushland, Texas, compiled this chapter, “Nuclear Gauge Design, Theory and Operation”, for the USDA Radiation Safety Staff Train-the-Trainer course, which was used to train personnel of USDA and other federal agencies so that they could effectively deliver radiation safety training to their respective employees who use nuclear gauges.

Technical Abstract: The neutron scattering and gamma methods are widely used for sensing of soil water content and soil density in agricultural research, monitoring, and management. It is the most accurate method of determining soil profile water content when correctly calibrated and used. This chapter on nuclear gauge design, theory and operation is intended to prepare the user to understand the principles of sensing soil water and bulk density using nuclear gauges, how gauges operate and their major components, understand the two geometries used for measurements, and understand basic operation of the gauges. The reader will also learn the radionuclides used in these nuclear gauges, learn safe procedures for gauge operation, and understand how effective and proper gauge use supports the radiation safety principle of keeping radiation exposure As Low As Reasonably Achievable (ALARA).