All nuclear thermal propulsion (NTP) ground testing conducted in the 1950s and 1960s during the ROVER/(Nuclear Engine Rocket Vehicle Application (NERVA) program discharged engine exhaust directly into the open air. However, due to current US Environmental Protection Agency (EPA) radiation protection guidelines and health regulations from the Nuclear Regulatory Commission (NRC), this practice is no longer acceptable. With NTP engine exhaust, hot gaseous hydrogen is nominally expected to be free of radioactive byproducts from the nuclear reactor; however, it does have the potential to be contaminated due to off-nominal engine reactor performance. One NTP ground testing option that has been documented by the ARES Corporation on Nuclear Thermal Propulsion Ground Test Facility (2006), which has been recommended as one of three acceptable ground test facility options, is to fully contain the engine exhaust. The concept in this particular ground test design is accomplished by injecting hydrogen exhaust with a high mixture ratio of oxygen that reacts with the hydrogen to produce steam. Oxygen and any trace amounts of radioactive noble gases released by off-nominal NTP engine reactor performance would then be captured, contained, and either held until the radiation has decayed to an environmentally safe/acceptable level (below background exposure) for release and/or treatment. The design concept goals in this project are to explore methods to minimize the overall volume of the containment system, more completely define the system requirements and designs, and then perform a systems trade study to validate feasibility, safety and cost. The concept for this project is to take the hydrogen exhaust and inject it with a high mixture ratio of oxygen so the reaction produces steam. In theory, in a radioactive state, any trace amounts of radioactive noble gases released by off-nominal NTP engine reactor performance would be contained in the steam. Water is injected to condense the potentially contaminated steam into water. This water and the Gaseous Oxygen (GO2) would then be captured in a containment area where the water and GO2 would be divided into separate containment tanks. Additionally, the project will also look at mechanisms that may minimize the storage requirements, thereby, reducing hazard risk of these respective systems by using two methods for GO2 retention: (1) compressed gas storage system and (2) liquid storage. The compressed gas option would pump residual GO2 from the containment area at near ambient pressure to a 1000 psi Maximum Allowable Working Pressure (MAWP) storage vessel. The liquid storage option flows GO2 from the containment area through a liquid nitrogen (LN2) heat exchanger to liquefy the GO2 and store the liquefied oxygen (LO2) in a vacuum/LN2 jacketed tank for storage, decay, and subsequent disposal.
