Systems for Nuclear Auxiliary Power (SNAP)

The Systems for Nuclear Auxiliary Power, or SNAP program, was a major focus for a wide range of organizations in the US for many decades. The program extended everywhere from the bottom of the seas to deep space travel with electric propulsion. SNAP was divided up into an odd/even numbering scheme, with the odd model numbers (starting with the SNAP-3) being radioisotope thermoelectric generators (a basic outline of which will be available soon), and the even numbers (beginning with SNAP-2) being fission reactor electrical power systems.

Due to the sheer scope of the SNAP program, even eliminating systems that aren’t fission-based, this is going to be a two post subject. This post will cover the US Air Force’s portion of the SNAP reactor program, the SNAP-2 and SNAP-10A reactors, their development programs, the SNAPSHOT mission, and a look at the missions that these reactors were designed to support, including satellites, space stations, and other crewed and uncrewed installations. The next post will cover the NASA side of things: SNAP-8 and its successor designs as well as SNAP-50/SPUR. The one after that will cover the SP-100, SABRE, and other designs from the late 1970s through to the early 1990s, and will conclude with looking at a system that we mentioned briefly in the last post: the ENISY/TOPAZ II reactor, the only astronuclear design to be flight qualified by the space agencies and nuclear regulatory bodies of two different nations.

The Beginnings of the US Astronuclear Program: SNAP’s Early Years

Beginning in the earliest days of both the nuclear age and the space age, nuclear power had a lot of appeal for the space program: high power density, high power output, mechanically simple systems were in high demand for space agencies worldwide. The earliest mention of a program to develop nuclear electric power systems for spacecraft was the Pied Piper program, begun in 1954. This led to the development of the Systems for Nuclear Auxiliary Power program, or SNAP, the following year (1955), which was eventually canceled in 1973, as were so many other space-focused programs.

Once space became a realistic place to send not only scientific payloads but personnel, the need to provide them with significant amounts of power became evident. Not only were most systems of the day far from the electricity efficient designs that both NASA and Roscosmos would develop in the coming decades, but at the time the vision for a semi-permanent space station wasn’t 3-6 people orbiting in a (completely epic, scientifically revolutionary, collaboratively brilliant, and invaluable) zero-gee conglomeration of tin cans like the ISS, but many space stations that provided centrifugal gravity, staffed round the clock by dozens of individuals. These weren’t just space stations for NASA, which was an infant organization at the time, but the USAF, and possibly other institutions in the US government as well. In addition, what would provide a livable habitation for a group of astronauts would also be able to power a remote, uncrewed radar station in the Arctic, or in other extreme environments. Even if crew were there, the fact that the power plant wouldn’t have to be maintained was a significant military advantage.

Responsible for both radioisotope thermoelectric generators (which run on the natural radioactive degay of a radioisotope selected based on its’ energy density and half-life) as well as fission power plants, SNAP programs were numbered with an even-odd system: even numbers were fission reactors, odd numbers were RTGs. These designs were never solely meant for in-space application, but the increased mission requirements and complexities of being able to safely launch a nuclear power system into space made this aspect of their use the most stringent, and therefore the logical one to design toward. Additionally, while the benefits of power-dense electrical supply are obvious for any branch of the military, the need for this capability in space far surpassed the needs of those on the ground or the seas.

Originally jointly run by the AEC’s Department of Reactor Development (who funded the reactor itself) and the USAF’s AF Wright Air Development Center (who funded the power conversion system), full control was handed over to the AEC in 1957. Atomics International Research was the prime contractor for the program.

There are a number of similarities in almost all the SNAP designs, probably for a number of reasons. First, all of the reactors that we’ll be looking at (as well as some other designs we’ll look at in the next post) used the same type of fissile fuel, even though the form, and the cladding, varied reasonably widely between the different concepts. Uranium-zirconium hydride was a very popular fuel choice at the time. Assuming hydrogen loss could be controlled (this was a major part of the testing regime in all the reactors that we’ll look at), it provided a self-moderating, moderate-to-high-temperature fuel form, which was a very attractive feature. This type of fuel is still used today, for the TRIGA reactor – which, between it and its’ direct descendants is the most common form of research and test reactor worldwide. The high-powered reactors (SNAP 2 and 8) both used variations on the same power conversion system: a boiling mercury Rankine power conversion cycle, which was determined by the end of the testing regime to be possible to execute, however to my knowledge has never been proposed again (we’ll look at this briefly in the post on heat engines as power conversion systems, and a more in-depth look will be available in the future), although a mercury-based MHD conversion system is being offered as a power conversion system for an accelerator-driven molten salt reactor.

The exception to this rule was the SNAP-50, a reactor developed by Pratt and Whitney. This reactor started life in the Aircraft Nuclear Propulsion program for the US Air Force, and ended its life with NASA, as a power plant for the future modular space station that NASA was planning before the budget cuts of the mid to late 1970s took hold.

Because it came from a different program originally, it also uses different technology than the reactors we’ve looked at on the blog so far: uranium nitride fuel, and higher-temperature, lithium coolant made this reactor a very different beast than the other reactors in SNAP. However, these changes also allowed for a more powerful reactor, and a less massive power plant overall, thanks to the advantages of the higher-temperature design. It was also the first major project to move the space reactor development process away from SNAP-2/10A legacy designs.

SNAP-2

SNAP-2 Artist’s Cutaway, image DOE

The first of the reactors developed, SNAP-2 was the first uranium-zirconium hydride fueled, sodium-potassium liquid metal cooled reactor in the SNAP series. Proposed and developed by Atomics International in the 1950s and 1960s, this reactor took advantage of the self-moderating nuclear characteristics of the U-ZrH fuel which had been developed recently for a variety of reactors (a competing nuclear engineering firm, General Atomics, used the same fuel in their wildly successful Training, Research, and Isotope, General Atomics – or TRIGA – reactor in the same time period). Low temperature liquid metal coolant, mostly transparent to neutrons, was another popular concept at the time, and a eutectic mixture of sodium and potassium, NaK-78, was selected for good thermal transport qualities in the temperature range desired.

Original SNAP-2 configuration with Hg Rankine conversion system, image DOE

Originally meant to use a mercury vapor Rankine turbine for power, this reactor core design ended up being integrated with the SNAP-10’s reactor core, to form the SNAP-2/10A. The eventual plan was to use the different power conversion systems for different power levels, trading mechanical complexity for increased power output as the mission called for. the mercury vapor Rankine system, called the CRU, went through five iterations before being declared flight-ready as the CRU-V, and had many innovative concepts, including using the condensed Hg metal as a bearing fluid for the turbine itself.

Extensive testing, including may criticality tests (both nominal and accidental criticality), power transient testing, flow dynamics testing, erosion testing, mechanical tests, and others were conducted, both in support of the SNAP-2 directly in the beginning and as part of the SNAP-2/10A program. Three test reactors, the SNAP Critical Assembly reactors, SNAP Experimental Reactor, and the SNAP 2 Development Reactor, each logged extensive testing runs both at partial and full design power and temperature. As part of the SNAPSHOT program, the 2/10-A variant of the core was tested in both breadboard and flight configurations (more on that on the SNAP-10A page). Sadly, this work was complete well before the CRU-V power conversion system was ready, so the nuclear portion of the design was placed on hold (as the SNAP-2) until that was completed.

CRV-series power conversion system

The SNAP-2 itself was never flown. The CRU mercury Rankine system completed its full development process and reached the required 10,000 hour operation life, power level cycling, and materials reliability requirements set out by the US Air Force and the AEC (the customers for the reactor), but by the time the system was ready for deployment, the need for it had passed, and no missions were ever funded that were a good and cost effective match for the power supply.

Read more about the SNAP-2 reactor system here.

SNAP-4/COMPACT

Also known as the Compact Multi-Purpose Automatic Controlled Transportable (COMPACT) system, SNAP-4 was an effort to leverage the knowledge gained during the rest of the SNAP reactor programs into a more flexible power supply for maritime and terrestrial use. With a prototype design target of 2000 kWe, the final design was meant to provide 12 MWt (2 MWe) for one year.

Naval (and naval support) use, remote base and facility use, and other remote operations were the niche for the reactor, eliminating the need to supply diesel or other power for electricity.

Based on the fuel of the other SNAP systems, SNAP-4 used the initial criticality immersion testing as a benchmark to do a water-cooled and -moderated system, with a closed coolant loop transferring to a steam generator cycle.

SNAP-4 was designed from the outset to be modular, and transportable by air (although not as a single unit). The fuel would be divided up into seven (bundles), for instance, both for burnup management and for security.

Further Reading

SNAP 4 SUMMARY REPORT VOLUME I. APPLICATIONS AND SUMMARY 1973 https://www.osti.gov/servlets/purl/4448449

SNAP 4 SUMMARY REPORT VOLUME II. SYSTEMS DESCRIPTION 1973
https://www.osti.gov/servlets/purl/4447429

SNAP-6

The SNAP-6 reactor was designed for underwater facilities. This is not a system that I have researched at all, but I offer the documentation I’ve run across for those interested.

Thermal Analysis of the SNAP 6 Reactor 1963 https://www.osti.gov/servlets/purl/982043

SNAP-8

SNAP-8 Development Reactor in vacuum test stand, image DOE

Originally designed for NASA, in cooperation with the AEC, as a space station and lunar base power supply, the SNAP-8 was a far higher powered reactor than the SNAP-2. This reactor, another Atomics International program, used very similar fuel element materials, primary coolant, and power conversion system configuration choices to the SNAP-2’s original proposal, but over time the only thing that stayed mostly the same was the basic core geometry. Never flown, the SNAP-8 reactor helped inform NASA’s future design requirements for a fission power supply, and was the first reactor to be considered for interplanetary nuclear electric probes, as well as space station use.

By the end of the reactor family’s design iterations, the overall electric output of the reactor stayed at a similar level, but the initial mercury Rankine system – an uprated, modified pair of turbines that were derived from the SNAP-2 CRU-V system – was replaced by a thermionic solid state power conversion system, trading greater thermal power output requirements for the reactor with a reduction in the complexity and challenges involved in ensuring reliability of the power conversion system. This design change would occur consistently for virtually all of NASA’s space reactor designs until the development of the Advanced Stirling Radioisotope Generator and Kilopower reactor in the last couple of decades.

Reference ZrH Reactor, image DOE

SNAP-8 evolved into the Reference Zirconium Hydride Reactor,a more powerful, mechanically simpler design intended for space station and lunar base power supply. With an extended reactor design life, a simpler power conversion system, and more stable fluid dynamics behavior than its predecessor, the RZrHR was a great improvement over the SNAP-8 as it was originally proposed. Mission planning for space station resupply, lunar base power stations, and a nuclear electric uncrewed probe were all proposed, and variants in power level were also designed to better tailor the reactor to potential mission requirements.

By this time, however, the more powerful SNAP-50 reactor was also available at a similar level of technological development, and the design remained on the shelf, never to be flown but still influencing every NASA reactor design, mission and safety planning, and reliability standards for decades.

More on the SNAP-8, Reference ZrH Reactor, and other iterations is available at the SNAP-8 page, here.

SNAP-10

SNAP-10A Cutaway Drawing, Image DOE

The only astronuclear system to fly, the SNAP-10 used U-ZrH self moderating fuel like the SNAP-2 and -8, but unlike those systems was always designed with a solid-state thermoelectric power conversion system in mind. This was meant to deal with the challenges that the mercury Rankine cycle would pose, and allow for earlier deployment of the system.

While the core was originally of a different configuration (the SNAP-10), relatively quickly the core was made to be identical to the SNAP-2 core. This resulted in a change of designation from SNAP-10 to SNAP-10A. However, the power conversion system requirements were barely changed, leading to the program overall for these two reactors to be combined.

The SNAP-10A was not meant to power crewed facilities, since the power output was so low that multiple installations would be needed. This meant that, while all SNAP reactors were meant to be largely or wholly unmaintained by crew personnel, this reactor had no possibility of being maintained. The reliability requirements for the system were higher because of this, and the lack of moving parts in the power conversion system aided in this design requirement. The design was also designed to only have a brief (72 hour) time period where active reactivity control would be used, to mitigate any startup transients, and to establish steady-state operations, before the active control systems would be left in their final configuration, leaving the reactor entirely self-regulating. This placed additional burden on the reactor designers to have a very strong understanding of the behavior of the reactor, its long-term stability, and any effects that would occur during the year-long lifetime of the system.

At the end of the reactor’s life, it was designed to stay in orbit until the short-lived and radiotoxic portions of the reactor had gone through at least five product half-lives, reducing the radioactivity of the system to a very low level. At the end of this process, the reactor would re-enter the atmosphere, the reflectors and end reflector would be ejected, and the entire thing would burn up in the upper atmosphere. From there, winds would dilute any residual radioactivity to less than what was released by a single small nuclear test (which were still being conducted in Nevada at the time). While there’s nothing wrong with this approach from a health physics point of view, there are major international political problems with this concept. The SNAPSHOT reactor continues to orbit the Earth (currently at an altitude of roughly 1300 km), and will do so for more than 2000 years, according to recent orbital models, so the only system of concern is not in danger of re-entry any time soon; but, at some point, the reactor will need to be moved into a graveyard orbit or collected and returned to Earth – a problem which currently has no solution.

This was the only system to go into orbit for the US space program (in this case the US Air Force), as part of SNAPSHOT, which is covered in the next section.

SNAPSHOT: America’s Only Fission System to Launch

SNAPSHOT consisted of a SNAP-10A fission power system mounted to a modified Agena-D spacecraft, which by this time was an off-the-shelf, highly adaptable spacecraft used by the US Air Force for a variety of missions. An experimental cesium contact ion thruster (read more about these thrusters on the Gridded Ion Engine page) was installed on the spacecraft for in-flight testing. The mission was to validate the SNAP-10A architecture with on-orbit experience, proving the capability to operate for 9 days without active control, while providing 500 W (28.5 V DC) of electrical power. Additional requirements included the use of a SNAP-2 reactor core with minimal modification (to allow for the higher-output SNAP-2 system with its mercury vapor Rankine power conversion system to be validated as well, when the need for it arose), eliminating the need (while offering the option) for active control of the reactor once startup was achieved for one year (to prove autonomous operation capability); facilitating safe ground handling during spacecraft integration and launch; and, accommodating future growth potential in both available power and power-to-weight ratio.

While the threshold for mission success was set at 90 days, for Atomics International wanted to prove 1 year of capability for the system; so, in those 90 days, the goal was that the entire reactor system would be demonstrated to be capable of one year of operation (the SNAP-2 requirements). Atomics International imposed additional, more stringent, guidelines for the mission as well, specifying a number of design requirements, including self-containment of the power system outside the structure of the Agena, as much as possible; more stringent mass and center-of-gravity requirements for the system than specified by the US Air Force; meeting the military specifications for EM radiation exposure to the Agena; and others.

atlas-slv3_agena-d__snapshot__1
SNAPSHOT launch, image USAF via Gunter’s Space Page

The flight was formally approved in March, and the launch occurred on April 3, 1965 on an Atlas-Agena D rocket from Vandenberg Air Force Base. The launch went perfectly, and placed the SNAPSHOT spacecraft in a polar orbit, as planned. Sadly, the mission was not one that could be considered either routine or simple. One of the impedance probes failed before launch, and a part of the micrometeorite detector system failed before returning data. A number of other minor faults were detected as well, but perhaps the most troubling was that there were shorts and voltage irregularities coming from the ion thruster, due to high voltage failure modes, as well as excessive electromagnetic interference from the system, which reduced the telemetry data to an unintelligible mess. This was shut off until later in the flight, in order to focus on testing the reactor itself.

The reactor was given the startup order 3.5 hours into the flight, when the two gross adjustment control drums were fully inserted, and the two fine control drums began a stepwise reactivity insertion into the reactor. Within 6 hours, the reactor achieved on-orbit criticality, and the active control portion of the reactor test program began. For the next 154 hours, the control drums were operated with ground commands, to test reactor behavior. Due to the problems with the ion engine, the failure sensing and malfunction sensing systems were also switched off, because these could have been corrupted by the errant thruster. Following the first 200 hours of reactor operations, the reactor was set to autonomous operation at full power. Between 600 and 700 hours later, the voltage output of the reactor, as well as its temperature, began to drop; an effect that the S10-F3 test reactor had also demonstrated, due to hydrogen migration in the core.

On May 16, just over one month after being launched into orbit, contact was lost with the spacecraft for about 40 hours. Some time during this blackout, the reactor’s reflectors ejected from the core (although they remained attached to their actuator cables), shutting down the core. This spelled the end of reactor operations for the spacecraft, and when the emergency batteries died five days later all communication with the spacecraft was lost forever. Only 45 days had passed since the spacecraft’s launch, and information was received from the spacecraft for only 616 orbits.

SNAPSHOT Artist’s Impression, image DOE

What caused the failure? There are many possibilities, but when the telemetry from the spacecraft was read, it was obvious that something badly wrong had occurred. The only thing that can be said with complete confidence is that the error came from the Agena spacecraft rather than from the reactor. No indications had been received before the blackout that the reactor was about to scram itself (the reflector ejection was the emergency scram mechanism), and the problem wasn’t one that should have been able to occur without ground commands. However, with the telemetry data gained from the dwindling battery after the shutdown, some suppositions could be made. The most likely immediate cause of the reactor’s shutdown was traced to a possible spurious command from the high voltage command decoder, part of the Agena’s power conditioning and distribution system. This in turn was likely caused by one of two possible scenarios: either a piece of the voltage regulator failed, or it became overstressed because of either the unusual low-power vehicle loads or commanding the reactor to increase power output. Sadly, the cause of this system failure cascade was never directly determined, but all of the data received pointed to a high-voltage failure of some sort, rather than a low-voltage error (which could have also resulted in a reactor scram). Other possible causes of instrumentation or reactor failure, such as thermal or radiation environment, collision with another object, onboard explosion of the chemical propellants used on the Agena’s main engines, and previously noted flight anomalies – including the arcing and EM interference from the ion engine – were all eliminated as the cause of the error as well.

Despite the spacecraft’s mysterious early demise, SNAPSHOT provided many valuable lessons in space reactor design, qualification, ground handling, launch challenges, and many other aspects of handling an astronuclear power source for potential future missions: Suggestions for improved instrumentation design and performance characteristics; provision for a sunshade for the main radiator to eliminate the sun/shade efficiency difference that was observed during the mission; the use of a SNAP-2 type radiation shield to allow for off-the-shelf, non-radiation-hardened electronic components in order to save both money and weight on the spacecraft itself; and other minor changes were all suggested after the conclusion of the mission. Finally, the safety program developed for SNAPSHOT, including the SCA4 submersion criticality tests, the RFT-1 test, and the good agreement in reactor behavior between the on-orbit and ground test versions of the SNAP-10A showed that both the AEC and the customer of the SNAP-10A (be it the US Air Force or NASA) could have confidence that the program was ready to be used for whatever mission it was needed for.

More detailed information can be found on the SNAPSHOT page, here.

SNAP-50

SNAP-50 Mockup, image DOE

The SNAP-50 was the last, and most powerful, of the SNAP series of reactors, and had a very different start when compared to the other three reactors that we’ve looked at. A fifth reactor, SNAP-4, also underwent some testing, but was meant for undersea applications for the Navy. The SNAP-50 reactor started life in the Aircraft Nuclear Propulsion program for the US Air Force, and ended its life with NASA, as a power plant for the future modular space station that NASA was planning before the budget cuts of the mid to late 1970s took hold.

Because it came from a different program originally, it also uses different technology than the reactors we’ve looked at on the blog so far: uranium nitride fuel, and higher-temperature, lithium coolant made this reactor a very different beast than the other reactors in SNAP. However, these changes also allowed for a more powerful reactor, and a less massive power plant overall, thanks to the advantages of the higher-temperature design. It was also the first major project to move the space reactor development process away from SNAP-2/10A legacy designs.

This reactor ended up using a form of fuel element that we have yet to look at in this blog: uranium nitride, UN. While both UC (you can read more about carbide fuels here) and UN were considered at the beginning of the program, the reactor designers ended up settling on UN because of a unique capacity that this fuel form offers: it has the highest fissile fuel density of any type of fuel element. This is offset by the fact that UN isn’t the most heat tolerant of fuel elements, requiring a lower core operating temperature. Other options were considered as well, including CERMET fuels using oxides, carbides, and nitrides suspended in a tungsten metal matrix to increase thermal conductivity and reduce the temperature of the fissile fuel itself. The decision between UN, with its higher mass efficiency (due to its higher fissile density), and uranium carbide (UC), with the highest operating temperature of any solid fuel element, was a difficult decision, and a lot of fuel element testing occurred at CANEL before a decision was reached. After a lot of study, it was determined that UN in a tungsten CERMET fuel was the best balance of high fissile fuel density, high thermal conductivity, and the ability to manage low fuel burnup over the course of the reactor’s life.

From SNAP-50/SPUR Design Summary

Perhaps the most important design consideration for the fuel elements after the type of fuel was how dense the fuel would be, and how to increase the density if this was desired in the final design. While higher density fuel is generally speaking a better idea when it comes to specific power, it was discovered that the higher density the fuel was, the lower the amount of burnup would be possible before the fuel would fail due to fission product gas buildup within the fuel itself. Initial calculations showed that there was an effectively unlimited fuel burnup potential of UN at 80% of its theoretical density since a lot of the gasses could diffuse out of the fuel element. However, once the fuel reached 95% density, this was limited to 1% fuel burnup. Additional work was done to determine that this low burnup was in fact not a project killer for a 10,000 hour reactor lifetime, as was specified by NASA, and the program moved ahead.

Early NEP spacecraft using SNAP-50 reactor, image DOE

Unlike in the SNAP-2 and SNAP-8 programs, the SNAP-50 kept its Rankine turbine design, which had potassium vapor as its working fluid. This meant that the power plant was able to meet its electrical power output requirements far more easily than the lower efficiency demanded by thermoelectric conversion systems. The CRU system meant for the SNAP-2 ended up reaching its design requirements for reliability and life by this time, but sadly the overall program had been canceled, so there was no reactor to pair to this ingenious design (sadly, it’s so highly toxic that testing would be nearly impossible on Earth). The boiler, pumps, and radiators for the secondary loop were tested past the 10,000 hour design lifetime of the power plant, and all major complications discovered during the testing process were addressed, proving that the power conversion system was ready for the next stage of testing in a flight configuration.

This design went through many iterations before it withered through lack of funding in the 1970s.

More on this design can be found on the SNAP-50 page, including different design iterations of the reactor system.

References and Further Reading

Detailed references for each reactor in the program can be found in the pages for said reactor. These references are for the program as a whole, as well as the various broad progress and summary reports.

Overall Program

SNAP TECHNOLOGY HANDBOOK 1964/65

VOLUME I LIQUID METALS https://www.osti.gov/servlets/purl/4038102

VOLUME II HYDRIDE FUELS AND CLADDINGS https://www.osti.gov/servlets/purl/4485359

VOLUME III REFRACTORY FUELS AND CLADDINGS https://www.osti.gov/servlets/purl/4632885

SNAP SYSTEMS CAPABILITIES

VOLUME 1 OSTI Identifier: 4299012 Report Number(s): NAA-SR-Memo-10579 NSA Number:NSA-30-002020 Other Information: Declassified 28 Nov 1973

VOLUME 2 STUDY INTRODUCTION, REACTORS, SHIELDING 1965 https://www.osti.gov/servlets/purl/4480419

SNAP Programs Summary Report, Staub et al, Atomics International (AI) 1973 https://www.osti.gov/servlets/purl/4433247

SNAP PROGRAM MILESTONES 1962 https://www.osti.gov/servlets/purl/966277

TECHNOLOGICAL IMPLICATIONS OF SNAP REACTOR POWER SYSTEM DEVELOPMENT ON FUTURE SPACE NUCLEAR POWER SYSTEMS, Anderson Rockwell International 1982 https://www.osti.gov/servlets/purl/5445023

NUCLEAR REACTORS BEING BUILT, or PLANNED in the UNITED STATES as of Dec. 31, 1970 (SNAP pg 17) https://www.osti.gov/servlets/purl/4023739

Mission Proposals

THE PRACTICAL APPLICATION OF SPACE NUCLEAR POWER IN THE 1960’S, Wetch et al 1960 https://www.osti.gov/servlets/purl/4110787

APPLICATION OF NUCLEAR POWER SUPPLIES TO SPACE SYSTEMS, Sigma Corp for AI 1960 https://www.osti.gov/servlets/purl/4759160

Electric Propulsion Applications for SNAP Systems, Morse AI 1962
https://www.osti.gov/servlets/purl/4784763

SNAP POWER FOR HARDENED BASES 1962 https://www.osti.gov/servlets/purl/4665490

Bibliographies and Literature Reviews

Systems for Nuclear Auxiliary Power (SNAP), A Literature Search, Raleigh 1964 https://www.osti.gov/servlets/purl/4034092

Bibliography, SNAP Program Reports, Memos, and Motion Picture, AI 1966
https://www.osti.gov/servlets/purl/4069882

SNAP Programs Bibliography, Eggleston 1973
https://www.osti.gov/servlets/purl/4450505

Fuel Element Development and Analysis

COMPATIBILITY OF SNAP FUEL AND CLAD MATERIALS 1960
https://www.osti.gov/servlets/purl/4477291

SNAP FUEL AND CORE MATERIALS COMPATIBILITY SCREENING TESTS 1964 https://www.osti.gov/servlets/purl/4471732

PARAMETRIC STUDIES ON THE SHORT-TERM TENSILE MECHANICAL PROPERTIES OF Zr – 10 U ALLOY HYDRIDE 1964
https://www.osti.gov/servlets/purl/4475841

MICROSTRUCTURE STUDIES OF SNAP FUELS 1965 https://www.osti.gov/servlets/purl/4476911

EFFECTS OF IRRADIATION ON HYDRIDED ZIRCONIUM-URANIUM ALLOY NAA 120-4 EXPERIMENT 1970 https://www.osti.gov/servlets/purl/4211648

Nuclear Design and Analysis

SNAP REACTOR HANDBOOK – TRANSIENT ANALYSIS 1964
https://www.osti.gov/servlets/purl/4034094

WATER IMMERSION SAFETY FOR SNAP REACTORS Hawley 1967 https://www.osti.gov/servlets/purl/4480219

SELECTED COMPUTER CODES AND LIBRARIES VOLUME IV. A 28-GROUP CROSS SECTION LIBRARY FOR SNAP REACTOR ANALYSIS 1973
https://www.osti.gov/servlets/purl/4472867

Experimental Criticality Benchmarks for SNAP 10A/2 Reactor Cores April 2005 https://info.ornl.gov/sites/publications/Files/Pub57468.pdf

Primary Coolant Loop Design and Development

THERMAL DESIGN OF SNAP REACTORS 1962
https://www.osti.gov/servlets/purl/4471210

TEMFR 8 ; STEADY STATE THERMAL SIMULATION OF A SNAP REACTOR, Magee 1964 https://www.osti.gov/servlets/purl/4387512

Thermal Model for Use in SNAP system Simulation 1965
https://www.osti.gov/servlets/purl/4615605

DESIGN AND FABRICATION OF PROTOTYPE PRIMARY NaK LOOP VALVE SETS; FOLDER 2: BUSINESS MANAGEMENT AND COSTS, Aerojet 1969
https://www.osti.gov/servlets/purl/4227667

Liquid Metals Corrosion Meeting December 14-15,1961 https://www.osti.gov/servlets/purl/4790688

DESIGN OF TWO ELECTROMAGNETIC PUMPS FOR NaK 1960
https://www.osti.gov/servlets/purl/4159743

SURVEY OF SODIUM PUMP TECHNOLOGY 1963
https://www.osti.gov/servlets/purl/4620065

CORROSION OF TYPE 316 STAINLESS STEEL IN NaK SERVICE – – A LITERATURE SURVEY https://www.osti.gov/servlets/purl/4650758

ZIRCONIUM HYDRIDE REACTOR CORE HEAT TRANSFER STUDIES SUMMARY REPORT 1973 https://www.osti.gov/servlets/purl/4472834

Power Conversion System Development and Testing

Direct Energy Conversion and Systems for for Nuclear Auxiliary Power, a Literature Search, Lanier and Raleigh 1963 https://www.osti.gov/servlets/purl/4728266

VAPOR CYCLE COOLANT REQUIREMENTS FOR NUCLEAR SPACE POWER PLANTS 1964 https://www.osti.gov/servlets/purl/4690151

AIAA Specialists Conference on RANKINE SPACE POWER SYSTEMS Volume 1 1965 https://www.osti.gov/servlets/purl/4524921

REVIEW OF UZr-HYDRIDE DRIVER FUEL ELEMENTS FOR THERMIONIC REACTORS 1972 https://www.osti.gov/servlets/purl/4633883

SPACE NUCLEAR SYSTEM VOLUME ACCUMULATOR DEVELOPMENT SUMMARY REPORT 1973 https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730018855.pdf

SNAP SYSTEMS IMPROVEMENT PROGRAM MERCURY-RANKINE PROGRAM

JULY-SEPTEMBER 1966 VOLUME I https://www.osti.gov/servlets/purl/4453835

OCTOBER-DECEMBER 1965 VOLUME II
https://www.osti.gov/servlets/purl/4474878

Shielding Design and Development

Generalized Shielding Study for Nuclear Electric Space Powerplants, Barry, Aerospace Corp 1963 https://www.osti.gov/servlets/purl/4005255

THE OSNL-SNAP SHIELDING PROGRAM 1971 https://www.osti.gov/servlets/purl/4045094

Facilities (design, building, costs, etc.)

SNAP Building Requirements for SNAP 2, 4, 8, and 10A Programs, AI Staff 1961 https://www.osti.gov/servlets/purl/966774

ENVIRONMENTAL LABORATORY AND EQUIPMENT (Fuel Element Testing) 1964 https://www.osti.gov/servlets/purl/4686759

SNAP PRELAUNCH TEST FACILITY SAFEGUARDS REPORT 1963
https://www.osti.gov/servlets/purl/4000357

Component Design, Development, and Analysis

The Development Philosophy for SNAP Mechanisms O. P. Steele, III 1969 https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19690002476.pdf

BEARING MATERIALS COMPATIBILITY FOR SPACE NUCLEAR AUXILIARY POWER SYSTEMS 1961 https://www.osti.gov/servlets/purl/4787093

Sodium Coolant Technology

Sodium Technology 1948- 1961, 1962 https://www.osti.gov/servlets/purl/4629566

Sodium Technology, AEC 1972/1973 (overview of then-current state of the art and testing) https://www.osti.gov/servlets/purl/4330934

Sodium Technology, AEC July 1973-December 1974 https://www.osti.gov/servlets/purl/4147644

Progress Reports

SNAP Reactor Programs Progress Reports

May-July 1968 https://www.osti.gov/servlets/purl/4214266

August-October 1968 https://www.osti.gov/servlets/purl/4258955

November 1968- January 1969 https://www.osti.gov/servlets/purl/4228622

May-July 1969 https://www.osti.gov/servlets/purl/4212329

August-October 1969 https://www.osti.gov/servlets/purl/4221105

February-April 1970 https://www.osti.gov/servlets/purl/4212328

MAY-JULY 1970 https://www.osti.gov/servlets/purl/4246642

August-October 1970 https://www.osti.gov/servlets/purl/4228647

November 1970- January 1971 https://www.osti.gov/servlets/purl/4330707

February-April 1971 https://www.osti.gov/servlets/purl/4195598

May-July 1971 https://www.osti.gov/servlets/purl/4195597

August-October 1971 https://www.osti.gov/servlets/purl/4702221

November 1971- January 1972 https://www.osti.gov/servlets/purl/4632562

February- April 1972 https://www.osti.gov/servlets/purl/4619955

May-July 1972 https://www.osti.gov/servlets/purl/4583280

August-October 1972 https://www.osti.gov/servlets/purl/4531598

SNAP Supporting R&D

DECEMBER 1960-MARCH 1961 https://www.osti.gov/servlets/purl/4487057

JANUARY-MARCH 1962 https://www.osti.gov/servlets/purl/4571425

MAY – JULY 1964 https://www.osti.gov/servlets/purl/4480424

MAY-JULY 1965 https://www.osti.gov/servlets/purl/4468285

FEBRUARY-APRIL 1966 https://www.osti.gov/servlets/purl/4474602

NOVEMBER 1966 – JANUARY 1967 https://www.osti.gov/servlets/purl/4368389

MAJOR ACTIVITIES IN THE ATOMIC ENERGY PROGRAMS

January-December 1961 (SNAP starts on pdf page 78) https://www.osti.gov/servlets/purl/1364338

January-December 1962 (SNAP starts on pdf page 197) https://www.osti.gov/servlets/purl/1364343

Operational Development

Safety and Decommissioning

Minutes of SNAP Hazards Subcommittee Meeting 1958
https://www.osti.gov/servlets/purl/1411944

QUARTERLY TECHNICAL PROGRESS REPORT SNAP AEROSPACE SAFETY PROGRAM OCTOBER-DECEMBER 1962 https://www.osti.gov/servlets/purl/4704076

SNAP (SYSTEMS FOR NUCLEAR AUXILIARY POWER) TECHNICAL BRIEFS PART 8, AEROSPACE SAFETY AI 1963 https://www.osti.gov/servlets/purl/4042000

BIBLIOGRAPHY SNAP AEROSPACE NUCLEAR SAFETY PROGRAM REPORTS, AI 1973 https://www.osti.gov/servlets/purl/4564693

Proceedings of the Conference on Decontamination and Decommissioning of ERDA Facilities [including the SNAP development reactors and associated facilities], Idaho Falls, ID, Aug 19-21, 1975
https://www.osti.gov/servlets/purl/4113135

Rockwell International Hot Laboratory decontamination and dismantlement interim progress report 1987-1996, Rocketdyne (Boeing) staff 1997 https://www.osti.gov/servlets/purl/762749

Environmental Assessment For Cleanup and Closure of the Energy Technology Engineering Center (including AI Santa Susanna Laboratory). Final Report, DOE 2003 https://www.osti.gov/servlets/purl/823425

Materials Compatibility of SNAP Fuel Components during Shipment in 9975 Packaging, Vormelker 2006 https://sti.srs.gov/fulltext/WSRC-STI-2006-00140.pdf

INDEPENDENT VERIFICATION SURVEY REPORT OF THE BUILDING 4059 SITE (PHASE B); POST HISTORICAL SITE ASSESSMENT SITES, BLOCK 1; and RADIOACTIVE MATERIALS HANDLING FACILITY HOLDUP POND (SITE 4614), SANTA SUSANA FIELD LABORATORY, Vitkus 2008
https://www.osti.gov/servlets/purl/946693