Steven R. Sherman

TRITIUM MOVEMENT AND ACCUMULATION IN THE NGNP SYSTEM INTERFACE AND HYDROGEN PLANT

Tritium movement and accumulation in a Next Generation Nuclear Plant with a hydrogen plant using a high temperature electrolysis process and a thermochemical water splitting sulfur iodine process are estimated by the numerical code THYTAN as a function of design, operational, and material parameters. Estimated tritium concentrations in the hydrogen product and in process chemicals in the hydrogen plant of the Next Generation Nuclear Plant using the high temperature electrolysis process are slightly higher than the drinking water limit defined by the U.S. Environmental Protection Agency and the limit in the effluent at the boundary of an unrestricted area of a nuclear plant as defined by the U.S. Nuclear Regulatory Commission. However, these concentrations can be reduced to within the limits through use of some designs and modified operations. Tritium concentrations in the Next Generation Nuclear Plant using the Sulfur-Iodine Process are significantly higher as calculated and are affected by parameters with large uncertainties (i.e., tritium permeability of the process heat exchanger, the hydrogen concentration in the heat transfer and process fluids, the equilibrium constant of the isotope exchange reaction between HT and H2SO4). These parameters, including tritium generation and the release rate in the reactor core, should be more accurately estimated in the near future to improve the calculations for the NGNP using the Sulfur-Iodine Process. Decreasing the tritium permeation through the heat exchanger between the primary and secondary circuits may be an an effective measure for decreasing tritium concentrations in the hydrogen product, the hydrogen plant, and the tertiary coolant.

Stress Analyses of Intermediate Heat Transfer Loop

The Department of Energy and the Idaho National Laboratory are developing a Next Generation Nuclear Plant (NGNP) to serve as a demonstration of state-of-the-art nuclear technology. The purpose of the demonstration is two fold 1) efficient low cost energy generation and 2) hydrogen production. Although a next generation plant could be developed as a single-purpose facility dedicated to hydrogen production, early designs are expected to be dual purpose. While hydrogen production and advanced energy cycles are still in its early stages of development, research towards coupling a high temperature reactor with electrical generation and hydrogen production is under way. Many aspects of the NGNP must be researched and developed in order to make recommendations on the final design of the plant. Parameters such as working conditions, cycle components, working fluids, and power conversion unit configurations must be understood. A number of configurations of the power conversion unit were demonstrated in this study. An intermediate heat transport loop for transporting process heat to a High Temperature Steam Electrolysis (HTSE) hydrogen production plant was used. Helium, CO2 , and a 80% nitrogen, 20% helium mixture (by weight) were studied to determine the best working fluid in terms cycle efficiency and development cost. In each of these configurations the relative component sizes were estimated for the different working fluids. Parametric studies were carried out on reactor outlet temperature, mass flow, pressure, and turbine cooling. Recommendations on the optimal working fluid for each configuration were made. Engineering analyses were performed for several configurations of the intermediate heat transport loop that transfers heat from the nuclear reactor to the hydrogen production plant. The analyses evaluated parallel and concentric piping arrangements and two different working fluids, including helium and a liquid salt. The thermal-hydraulic analyses determined the size and insulation requirements for the hot and cold leg pipes in the different configurations. Mechanical analyses were performed to determine hoop stresses and thermal expansion characteristics for the different configurations.Copyright

Treatment Method for Fermi Barrel Sodium Metal Residues

Fermi barrels are 55-gallon drums that once contained bulk sodium metal from the shutdown Fermi 1 breeder reactor facility, and now contain residual sodium metal and other sodium/air reaction products. This report provides a residual sodium treatment method and proposed quality assurance steps that will ensure that all residual sodium is deactivated and removed from the Fermi barrels before disposal. The treatment method is the application of humidified carbon dioxide to the residual sodium followed by a water wash. The experimental application of the treatment method to six Fermi barrels is discussed, and recommendations are provided for further testing and evaluation of the method. Though more testing would allow for a greater refinement of the treatment technique, enough data has been gathered from the tests already performed to prove that 100% compliance with stated waste criteria can be achieved.