ANS is committed to advancing, fostering, and promoting the development and application of nuclear sciences and technologies to benefit society.
Explore the many uses for nuclear science and its impact on energy, the environment, healthcare, food, and more.
Division Spotlight
Human Factors, Instrumentation & Controls
Improving task performance, system reliability, system and personnel safety, efficiency, and effectiveness are the division's main objectives. Its major areas of interest include task design, procedures, training, instrument and control layout and placement, stress control, anthropometrics, psychological input, and motivation.
Meeting Spotlight
Utility Working Conference and Vendor Technology Expo (UWC 2024)
August 4–7, 2024
Marco Island, FL|JW Marriott Marco Island
Standards Program
The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
Latest Magazine Issues
Jul 2024
Jan 2024
Latest Journal Issues
Nuclear Science and Engineering
August 2024
Nuclear Technology
Fusion Science and Technology
Latest News
BWXT will scout potential TRISO fuel production sites in Wyoming
BWX Technologies Inc. announced today that its Advanced Technologies subsidiary has signed a cooperation agreement with the state of Wyoming to evaluate locations and requirements for siting a potential new TRISO nuclear fuel fabrication facility in the state.
Paul W. Levy
Nuclear Technology | Volume 60 | Number 2 | February 1983 | Pages 231-243
Technical Paper | Radiation Effects and Their Relationship to Geological Repository / Radioactive Waste Management | doi.org/10.13182/NT83-A33078
Articles are hosted by Taylor and Francis Online.
As part of a program to investigate radiation damage in geological materials of interest to the radioactive waste disposal program, radiation damage—particularly radiation-induced sodium metal colloid formation—has been studied in 14 natural rock salt samples. All measurements were made with equipment for making optical absorption and other measurements on samples, in a temperature-control irradiation chamber, during and after 1.5-MeV electron irradiation. Samples were chosen for practical and scientific purposes from localities that are potential repository sites and from different horizons at certain localities. At room temperature and at low doses, only F-centers (Cl− ion vacancies) and a variety of “V-region”absorption bands (mostly holes trapped on a variety of defects) are present. Above 100°C and at high doses, intense sodium metal colloid particle absorption bands are formed. Formation of F-centers begins immediately after the irradiation is initiated and increases monotoni-cally to a well-defined plateau, reached at doses of 106 to 107 rad. In natural rock salt samples, not purposely strained in the laboratory, the colloid formation is well described by classical nucleation and growth curves with the initial induction, or low growth rate nucleation region, extending to 106 to 107 rad. In all samples measured to date, the rapid colloid growth region is well described by C(irradiation time)n or C(dose)n relations. Aside from the temperature dependence, at least three other factors modify the colloid growth rate: 1. The induction period is shortened by straining samples prior to irradiation. For strains up to ∼10%, it is progressively shortened. Around 10% strain, the induction period is negligible or zero. Strains above this value do not produce large additional effects. 2. The colloid formation rate increases as the dose rate decreases, i.e., on a unit dose basis, lower dose rates produce more colloids than higher dose rates. 3. Colloid formation appears to be related to the salt impurity level It is suppressed in regions of crystals containing ∼1% calcium and sulfur. Both the F-center and colloid particle formation is strongly temperature dependent. At fixed irradiation conditions, the F-center plateau level is high at 100°C and decreases monotonically to a low or negligible level at 300°C. The colloid formation rate is low or negligible at irradiation temperatures of 100 to 115°C and, as the radiation temperature is increased, increases to a broad maximum at 150 to 175°C and then decreases to a negligible level at 250 to 300°C. The colloid growth curve induction period is >104 s at 100°C, decreases to <3000 s at 150 to 175°C, and is >104 s at 275 to 300°C. Colloid formation has been carefully studied in the 14 “naturally impure” rock salt samples at a temperature where the colloid formation rate is a maximum—namely 150°C at a dose rate of 1.2 × 108 rad/h and to total doses of 2 to 4 × 108 rad. Colloid formation rates vary by a factor of 10 or more between samples from different localities. Using the C(dose)n relation to estimate the colloid formed in actual repositories indicates that in 50 to 400 yr, a dose of 1010 rad will convert between 0.1 and 10%, and 2 × 1010 rad will convert between 1 and 50% of the salt to colloidal sodium metal. The chemical and physical properties of rock salt containing colloid sodium metal at these levels differs markedly from that of normal rock salt, and irradiated salt is likely to interact vigorously with canisters, backfill materials, water, etc.