Sandia and Space Nuclear Systems Launch Safety
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SAND2022-13231 O Sandia Fireball Model is used in the assessment of liquid propellant fireballs in the source term analysis for space nuclear systems launch safety. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
To achieve future goals in space exploration a long life, compact power system will be necessary, and nuclear power sources are a promising option. The goal of this project is to achieve mass optimization with a supercritical Brayton Cycle coupled to a direct-cooled nuclear reactor. It is critical to minimize the total mass of this system because of space launch costs. The total mass involves both the components’ masses as well as the fuel mass which is related to system efficiency. This paper discusses a project in which a detailed reactor model is integrated with a carefully constructed cycle model in order to simultaneously optimize the design of these two aspects of the system. Component models are discussed as well as an initial optimization study. A robust, simple recuperated Brayton cycle model is complete and is in the process of integration with a developing reactor model. Preliminary observations of the cycle model have led to the conclusion that there will be an optimum point between a large recuperator and small reactor with high system efficiency, and a large reactor and small recuperator with low recuperator mass for any given radiater size. Once the reactor model is integrated into the cycle optimization, the tradeoffs between the sizes of the radiator, recuperator, and reactor will be further investigated and an optimum system mass will be apparent.
To achieve future goals in space exploration a long life, compact power system will be necessary, and nuclear power sources are a promising option. The goal of this project is to achieve mass optimization with a supercritical Brayton Cycle coupled to a direct-cooled nuclear reactor. It is critical to minimize the total mass of this system because of space launch costs. The total mass involves both the components’ masses as well as the fuel mass which is related to system efficiency. This paper discusses a project in which a detailed reactor model is integrated with a carefully constructed cycle model in order to simultaneously optimize the design of these two aspects of the system. Component models are discussed as well as an initial optimization study. A robust, simple recuperated Brayton cycle model is complete and is in the process of integration with a developing reactor model. Preliminary observations of the cycle model have led to the conclusion that there will be an optimum point between a large recuperator and small reactor with high system efficiency, and a large reactor and small recuperator with low recuperator mass for any given radiater size. Once the reactor model is integrated into the cycle optimization, the tradeoffs between the sizes of the radiator, recuperator, and reactor will be further investigated and an optimum system mass will be apparent.
A long life, reliable, and compact surface power system will be necessary to achieve future goals in space exploration. This application uniquely requires the system to be optimized with respect to mass because system mass directly drives the space launch cost associated with transporting the system to its desired location. In this study, a supercritical CO 2 Brayton cycle coupled to a direct-cooled nuclear reactor was designed and optimized for mass. Robust models were developed for each Brayton cycle component in order to model the cycle performance. The three most massive components of this cycle are the radiator-based heat rejection system (subsequently referred to as the “radiator”), recuperator, and reactor. Mass correlations for the recuperator and radiator were established through interactions with component experts from industry and national labs. A reactor model was developed to predict the minimum mass reactor that satisfies neutronic and thermal limitations for given cycle conditions. The system optimization explores tradeoffs between the reactor, recuperator, and radiator sizes in order to identify the least massive system that will satisfy the power (40 kWe) and life (10 yr) requirements. To explore the effects of turbine inlet temperature on system mass, three types of microtube and shell recuperator technologies were considered: baseline stainless steel (which is consistent with the industry partner’s current designs), stainless steel with non-heritage tube sizes (which requires further development of manufacturing techniques), and Inconel (which is not a current/legacy design). Both stainless steel designs have a temperature limit of 823 K, which limits the turbine inlet temperature to 900 K. The baseline stainless steel design results in a combined mass of 738 kg. The stainless steel design allowing for non-heritage tube sizes reduces the combined mass to 674 kg (a 9% improvement). The Inconel design leads to an optimal turbine inlet temperature of 1120 K and reduces the combined mass to 391 kg (a 47% improvement). Furthermore, the interesting conclusion from this study include: (1) radiator mass dominates the total mass, and this drives the cycle to relatively high heat rejection temperatures resulting in a compressor inlet state point that is not close to the vapor dome; thus, the typical advantages of an sCO 2 system are not realized, and a working fluid with a higher critical temperature may be more suitable, and (2) neutronic limitations cause the reactor size to be relatively unaffected by the power level.
Since the early 1960’s the Department of Energy (DOE) and its predecessor agencies have provided radioisotope power systems (RPS) to NASA as an enabling technology for deep space and various planetary missions. They provide reliable power in situations where solar and/or battery power sources are either untenable or would place an undue mass burden on the mission. In the modern era of the past twenty years there has been no time that multiple missions have been considered for launching from Kennedy Space Center (KSC) during the same year. The closest proximity of missions that involved radioisotope power systems would be that of Galileo (October 1989) and Ulysses (October 1990). The closest that involved radioisotope heater units would be the small rovers Spirit and Opportunity (May and July 2003) used in the Mars Exploration Rovers (MER) mission. It can be argued that the rovers sent to Mars in 2003 were essentially a special case since they staged in the same facility and used a pair of small launch vehicles (Delta II). This paper examines constraints on the frequency of use of radioisotope power systems with regard to launching them from Kennedy Space Center using currently available launch vehicles. This knowledge may be useful as NASA plans for its future deep space or planetary missions where radioisotope power systems are used as an enabling technology. Previous descriptions have focused on single mission chronologies and not analyzed the timelines with an emphasis on multiple missions.
For the first time, experiments on the DIII-D tokamak have demonstrated electron cyclotron current drive with more than double the conventional efficiency by tailoring the wave–particle interactions in velocity space using a novel ‘top launch’ geometry. Steering the EC waves to propagate nearly parallel to the resonance drives current more efficiently by (1) selective damping on electrons with higher parallel velocity v ||, and (2) longer absorption path to compensate for inherently weaker absorption at higher v ||. Experiments using a fixed-injection top launch system find an optimal velocity space interaction for maximum current drive efficiency at ρ ~ 0.5 where the ease of drawing out a high v || electron tail is balanced by sufficient absorption.
SAND2024-09978O The Launch Accident Sequence Evaluation Program is used to calculate the source term for the consequence analysis involving a launch vehicle accident with a space nuclear system. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
For more than five decades, Radioisotope Power Systems (RPS) have played a critical role in the exploration of space, enabling missions of scientific discovery to destinations across the solar system by providing electrical power to explore remote, challenging and extreme environments. In particular, RPS enable deep space missions where increased heliocentric distances reduce the ability of solar power to adequately meet spacecraft and instruments power requirements. Some previous notable missions that were enabled by RPS include Nimbus III, the Apollo Surface Experiments, the Pioneers 10 and 11, the Viking Mars Landers, Galileo, Ulysses, Cassini, New Horizons and Curiosity. The current operating set of missions that are enabled by RPS are Voyagers 1 and 2, Cassini, New Horizons, and Curiosity. The Multi-Mission Radioisotope Thermal Generator (MMRTG) is the current RPS used for missions. An enhanced version of this generator outfitted with higher efficiency thermoelectrics is under development for potential use in the future. Other previously deployed power systems include the Multi-hundred Watt Radisotope Thermo-electric Generator (MHW RTG) and the General Purpose Heat Source Radisotope Thermo-electric Generator (GPHS RTG). The common thread for all of these power systems is that they are fueled with Pu-238. The use of this unique isotope involves additional planning activities and requires specific actions when the devices are delivered to Kennedy Space Center (KSC), launch site, and incorporated into the assembly, test and launch operations (ATLO) process to ensure mission success, met safety and security challenges. It has been forecasted that the use of a nuclear reactor system is on the horizon. This system could be used for either specifically powering S/C propulsion system or for surface power use once the mission arrived at its destina-tion. Since a nuclear-fission-based system has never been handled or integrated into a spacecraft at KSC, this nuclear reactor system would potentially require further challenges that must be accounted for in the ATLO process. This paper will explain ATLO considerations for the recent RTG-enabled launches that have occurred and planned in the near future (Mars 2020 NASA mission). It will also describe where further challenges that need to be met for the placement of a nuclear reactor (either for propulsion or transportation for surface power use) onto a space mission. Specifically, the following topics will be addressed: • Approach for nuclear safety planning for nuclear material use and its transportation to launch site • Planning for security posture for nuclear materials at launch site • Preparation for transportation of the nuclear power system from the fueling/testing location to the launch site • Preparation of documentation and procedures for nuclear material use at launch site • Planning for coordination between power system and space mission groups • Planning for appropriate staffing and scheduling of operations
As compact and light weight power sources with reliable, long lives, Radioisotope Power Systems (RPSs) have made space missions to explore the solar system possible. Due to the hazardous material that can be released during a launch accident, the potential health risk of an accident must be quantified, so that appropriate launch approval decisions can be made. One part of the risk estimation involves modeling the response of the RPS to potential accident environments. Due to the complexity of modeling the full RPS response deterministically on dynamic variables, the evaluation is performed in a stochastic manner with a Monte Carlo simulation. The potential consequences can be determined by modeling the transport of the hazardous material in the environment and in human biological pathways. The consequence analysis results are summed and weighted by appropriate likelihood values to give a collection of probabilistic results for the estimation of the potential health risk. This information is used to guide RPS designs, spacecraft designs, mission architecture, or launch procedures to potentially reduce the risk, as well as to inform decision makers of the potential health risks resulting from the use of RPSs for space missions.
To increase manufacturing flexibility and system understanding in pharmaceutical development, the FDA launched the quality by design (QbD) initiative. Within QbD, the design space is the multidimensional region (of the input variables and process parameters) where product quality is assured. Given the high cost of extensive experimentation, there is a need for computational methods to estimate the probabilistic design space that considers interactions between critical process parameters and critical quality attributes, as well as model uncertainty. In this paper we propose two algorithms that extend the flexibility test and flexibility index formulations to replace simulation-based analysis and identify the probabilistic design space more efficiently. The effectiveness and computational efficiency of these approaches is shown on a small example and an industrial case study.
Scientists and engineers at Los Alamos National Laboratory are using a unique centrifuge facility to evaluate a flight-ready telemetry system for evaluating a nuclear weapons test missile launch. "The telemetry unit was designed and manufactured by Los Alamos' Intelligence and Space Research Division," said Telemetry Program Manager Myles Fitzgerald. "Telemetry is a data stream of information on temperature, acceleration, vibration, strain, all the conditions a system encounters during a test flight." Because a test missile flight ultimately ends with the test system completely destroyed, telemetry data from the flight must be collected by receiving stations along the flight path. "The purpose of the centrifuge test is to subject the electronics to a high gravitational load (G-load) that's representative of what the system will experience when re-entering the Earth's atmosphere," said weapons test engineer Alex Cusick.
Scientists and engineers at Los Alamos National Laboratory are using a unique centrifuge facility to evaluate a flight-ready telemetry system for evaluating a nuclear weapons test missile launch. "The telemetry unit was designed and manufactured by Los Alamos' Intelligence and Space Research Division," said Telemetry Program Manager Myles Fitzgerald. "Telemetry is a data stream of information on temperature, acceleration, vibration, strain, all the conditions a system encounters during a test flight." Because a test missile flight ultimately ends with the test system completely destroyed, telemetry data from the flight must be collected by receiving stations along the flight path. "The purpose of the centrifuge test is to subject the electronics to a high gravitational load (G-load) that's representative of what the system will experience when re-entering the Earth's atmosphere," said weapons test engineer Alex Cusick.
The use of radioisotope power systems (RPSs) for nuclear-enabled National Aeronautics and Space Administration (NASA) missions is made possible through a long-standing arrangement between the Department of Energy (DOE) and NASA. The requirements for the power system come from NASA, but DOE performs the procurement, fueling, testing, and delivery. A challenge has been interplay between the schedule for RPS availability from DOE versus the schedule for competitively selected missions. By mutual agreement, the actual operations to procure an RPS and prepare it for fueling have always been delayed until the final selection of a mission. The timeline for a New Frontiers–class mission leaves approximately 5 to 6 years from the time of final mission selection to the actual launch date. The number of RPSs used for a New Frontiers–class mission can be one to three units. If one or two units are needed, the timeline from the decision point to the launch date is a challenge, but it is achievable. The activities taking place include manufacturing the power system, producing the fuel, and performing the assembly/testing and delivery operations. If the mission selected requires three RPSs, the logistics of accomplishing all activities during the 5–6 years is problematic. The challenge involves obtaining the necessary resources for plutonium production, heat source production, and assembly/testing operations. Typically, the time between RPS-enabled missions requires staffing reduction down to 65%–75% of peak staffing levels to reduce costs. Coupling the ~2 year duration needed for hiring, training, and obtaining the appropriate security clearances for the required staff with the requirement for the RPS to arrive at Kennedy Space Center 6 months before the launch erodes much of the 5–6 years available to comfortably support the use of three RPSs. To provide better support for NASA RPS missions, a different approach for the production of heat sources was devised—constant rate production. This involves a higher level of base capability at DOE national laboratories to provide a stabilized workforce. This will enable 10–15 heat sources to be produced annually and placed into a stable intermediate form to enable storage for up to several years leading to quick production of general purpose heat source modules when a mission is selected. The upfront production of 238 Pu is maintained so material is constantly in the pipeline. Production of key specialized components is also maintained using this model.
The Space Nuclear Power and Isotope Technologies (SNPIT) division at Idaho National Laboratory (INL) fuels, performs acceptance testing, and provides spacecraft integration support of Radioisotope Power Systems (RPS) in support of National Aeronautics and Space Administration (NASA) missions. Recently the SNPIT team completed assembly, testing and launch support of the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) for the Mars 2020 Perseverance Rover mission.
The Space Nuclear Power and Isotope Technologies (SNPIT) division at Idaho National Laboratory (INL) fuels, performs acceptance testing, and provides spacecraft integration support of Radioisotope Power Systems (RPS) in support of National Aeronautics and Space Administration (NASA) missions. Recently the SNPIT team completed assembly, testing and launch support of the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) for the Mars 2020 Perseverance Rover mission.
The sounding rocket mission MAIUS-1 has the objective to create the first Bose–Einstein condensate in space; therefore, its scientific payload is a complete cold atom experiment built to be launched on a VSB-30 sounding rocket. An essential part of the setup is an ultrahigh vacuum system needed in order to sufficiently suppress interactions of the cooled atoms with the residual background gas. Contrary to vacuum systems on missions aboard satellites or the international space station, the required vacuum environment has to be reached within 47 s after motor burn-out. This paper contains a detailed description of the MAIUS-1 vacuum system, as well as a description of its qualification process for the operation under vibrational loads of up to 8.1 g{sub RMS} (where RMS is root mean square). Even though a pressure rise dependent on the level of vibration was observed, the design presented herein is capable of regaining a pressure of below 5 × 10{sup −10} mbar in less than 40 s when tested at 5.4 g{sub RMS}. To the authors' best knowledge, it is the first UHV system qualified for operation on a sounding rocket.