Space Nuclear Technology (U.S. nuclear rocket engine program: Project Rover/NERVA) and the Department Of Energy (DOE) had its beginnings in Los Alamos 1955, with those that advocated nuclear rocket studies the group known as the "Rover Boys". Initial applications considered were for aircraft applications, but when NASA was established, the shift in interest to rocket propulsion was established as its future course (Project Rover/NERVA lasted till 1973).
Back then the nuclear side of the DOE was called the AEC, The Atomic Energy Commission. The present DOE was formed 28 years ago by merger of federal energy agencies and departments into a single agency.

HEAT CONVERTED INTO ENERGY

  Radioisotope Thermoelectric Generators (RTG) for space applications has been available since 1961.

Older Radioisotope Thermoelectric Generator (RTG) Used on Voyager 1 & 2

  The simple concept based on the principle of thermoelectrics. Thermoelectrics can convert thermal energy into electrical energy or use electrical energy to move heat. The temperature difference, produces and electric potential (voltage) which can drive an electric current in a closed circuit. Today, this is known as the Seebeck effect.
  Two thermal emitting isotopes are Strontium 90 (Sr90) a beta emitter and the more efficient isotope Pu238 discovered by American, Glenn T. Seaborg with McMillan, Kennedy and Wahl by deuteron bombardment of uranium in the 60-inch cyclotron at Berkeley, California in 1941. Plutonium also exists in trace quantities in naturally occurring uranium ores. Plutonium has 15 known isotopes. RTG's generate electrical power by converting the heat from a Pu238 heat source into electricity using thermoelectric couples. Plutonium 238 is a non-fissile, alpha emitting particle (helium nuclei) isotope which can be stopped easily by shielding as thin as a sheet of paper with a half life of 87 years. A sample of pure material would produce approximately 0.54 kilowatts/kilogram of thermal power. A small heap of Pu238-O2 is warm to the touch and in more abundant quantities can boil water. In some configurations, the surface temperature of a Pu-238 fuel element can reach 1050 degrees C.
   Another consideration in Pu-238 production is cost. Unfortunately, Pu-238 is difficult to manufacture, making it extremely expensive. An accurate price is difficult to determine because of the lack of an open market, but the recent estimates by experts in the field indicate that the material costs several thousand dollars per gram in kilogram sized lots - if available at all. Since RTG conversion efficiency is on the order of six to eight percent, this puts the price of a 50 W power supply at close to a million dollars.

  Like all hazardous material safety and care must be followed. Plutonium poses a health hazard only if it is taken into the body because all isotopes but plutonium-241 decay by emitting an alpha particle, and the beta particle emitted by plutonium-241 is of low energy. Minimal gamma radiation is associated with any of these radioactive decays.
Inhaling airborne plutonium is the primary concern for all isotopes, and cancer resulting from the ionizing radiation is the health effect of concern.
The ingestion hazard associated with common forms of plutonium is much lower than the inhalation hazard because absorption into the body after ingestion is quite low. Laboratory studies with experimental animals have shown that exposure to high levels of plutonium can cause decreased life spans, diseases of the respiratory tract, and cancer. The target tissues in those animals were the lungs and associated lymph nodes, liver, and bones. However, these observations in experimental animals have not been corroborated by epidemiological investigations in humans exposed to lower levels of plutonium. (see, pdf file Pu-238 fact sheet)

U.S. DOMESTIC PRODUCTION OF PU-238

...Currently, DOE’s ongoing RPS-related production operations are located at three DOE sites in Idaho, New Mexico and Tennessee, requiring the transport of radioactive material that could be avoided by consolidation of these activities at a single site. The proposed consolidation of these operations, which includes production, purification, and encapsulation of plutonium-238 (Pu- 238), would be consistent with DOE’s approach on consolidating nuclear materials, increasing the security of nuclear materials, and reducing risks associated with transportation of nuclear materials. The EIS will analyze all reasonable alternatives for the consolidation of the RPS operations as well as the No Action alternative.

Production of Pu-238: The Pu-238 production process consists of the fabrication of neptunium-237 (Np- targets, irradiation of the targets in suitable irradiation facility, and the recovery of Pu-238 from the irradiated targets through chemical processing. the past, Pu-238 was produced at Savannah River Site (SRS), using reactors that are no longer operating. After SRS stopped producing Pu- DOE satisfied its Pu-238 requirement using DOE’s available inventory in storage at LANL. This inventory was augmented by Pu-238 purchased Russia for use in space missions.

B. Consolidation of Nuclear Operations Related to Production of RPS at the Idaho Site, the Preferred Alternative: Under this alternative, DOE would consolidate all activities related to RPS production within the secure area at the Idaho Site. New construction for the Pu-238 production, purification, and encapsulation part of the infrastructure would be required due to the very limited capability of existing facilities in the secure area. No new construction would be required for the assembly and test operations that are already being located in the secure area at the Idaho Site. As previously stated, the consolidation of the RPS production infrastructure would include the following activities: (1) Np-237 would be stored at the Idaho Site as already decided; (2) Pu-238 production capability (including Np–237 target fabrication and processing) would be established at the Idaho Site with ATR serving as the primary irradiation facility, and HFIR would be used only as a back-up facility if necessary; (3) Pu- 238 operations carried out at the TA–55 complex at LANL would be transferred to the Idaho Site; and (4) the existing facility, the Space and Security Power Systems Facility, at the Idaho Site would continue to be established and maintained for RPS assembly and test operations as already planned. This area of the Idaho Site where RPS nuclear operations are proposed to be consolidated is a highly secure location within the DOE complex.

(see more at DOE EIS website: consolidationeis.doe.gov)

INTERVIEW

...Virtually any combination of plutonium isotopes -- the different forms of an element having different numbers of neutrons in their nuclei -- can be used to make a nuclear weapon. Not all combinations, however, are equally convenient or efficient.

The most common isotope, plutonium 239 (Pu-239), is produced when the most common isotope of uranium, uranium-238, absorbs a neutron and then quickly decays to plutonium. It is this plutonium isotope that is most useful in making nuclear weapons, and it is produced in varying quantities in virtually all operating nuclear reactors. As fuel in a reactor is exposed to longer and longer periods of neutron irradiation, higher isotopes of plutonium build up as some of the plutonium absorbs additional neutrons, creating plutonium-240, plutonium-241, and so on. Plutonium-238 also builds up from a chain of neutron absorptions and radioactive decays starting from uranium-235.

These other isotopes create some difficulties for design and fabrication of nuclear weapons.

First and most important, plutonium-240 has a high rate of spontaneous fission, meaning that the plutonium in the device will continually produce many background neutrons, which have the potential to reduce weapon yield by starting the chain reaction prematurely.

Second, the isotope plutonium-238 decays relatively rapidly, thereby significantly increasing the rate of heat generation in the material.

Third, the isotope americium-241 (which results from the 14-year half-life decay of plutonium-241 and hence builds up in reactor-grade plutonium over time) emits highly penetrating gamma rays, increasing the radioactive exposure of any personnel handling the material.

Because of the preference for relatively pure plutonium-239 for weapons purposes, when a reactor is used specifically for creating weapons plutonium, the fuel rods are removed and the plutonium is separated from them after relatively brief irradiation (at low "burnup"). The resulting "weapons-grade" plutonium is typically about 93 percent plutonium-239.

Such brief irradiation is quite inefficient for power production, so in power reactors the fuel is left in the reactor much longer, resulting in a mix that includes more of the higher isotopes of plutonium. In the United States, plutonium containing between 80 and 93 percent plutonium-239 is referred to as "fuel-grade" plutonium, while plutonium with less than 80 percent plutonium-239 -- typical of plutonium in the spent fuel of light-water and CANDU reactors at normal irradiation -- is referred to as "reactor-grade" plutonium.

All of these grades of plutonium can be used to make nuclear weapons. The only isotopic mix of plutonium which cannot realistically be used for nuclear weapons is nearly pure plutonium-238, which generates so much heat that the weapon would not be stable. (International rules require equal levels of safeguards for all grades of plutonium except plutonium containing more than 80 percent plutonium-238, which need not be safeguarded.)

In other words the isotope Pu-238 decays relatively rapidly thereby significantly increasing the rate of heat generation in the material. I can imagine it could be used as fissile material for bomb makers, but American designers since the '70's opt for the latest technologies and most innovative methods for lightweight, very powerful yields, 100 kiloton plus, like the W-76 style that can pack 12 warheads or more reliably into a missile faring while reducing costs without the fuss of constant monitoring, maintenance, replacement and safety considerations of crews responsible in manufacturing, safeguarding and delivery of weapon systems.

So domestic top quality production of Pu-238. This production is more related to manufacturing things other than bomb making material-is that correct ?

TF: Absolutely...We are not making [bomb grade] plutonium the variety of plutonium 238 in the fashion of which you spoke. We are producing ours by fabrication of neptunium-237 (Np-237) targets and irradiation with neutrons in a secure reactor facility and recovery of Pu-238 over all other types of plutonium produced. The US/DOE has used significant quantities of plutonium-239 there is absolutely no need for the department or the U.S. to go back into plutonium-239 production. We are specifically trying to produce plutonium-238 to support these radioisotope power systems for national security and for NASA. We have no intention, it's not in the plan, there is no requirement to produce plutonium-238 for any of the nuclear weapons. While in fact. It is true you can theoretically make a weapon out of Pu-238 the engineering that would have to go into its manufacture makes it impractical. It gives off .56, .57 watts thermal energy per gram. So if you had for example, metal your challenge would be to keep materials inside the weapon from deteriorating due to high temperatures.

BB: By definition all isotopes release energy some more than other much this energy can be harnessed as heat and can power special Stirling motors, Stirling Radioisotope Generators (SRG) to electrical interfaces with controllers and AC/DC converters to power mission platforms. Essentially heat source generators also come in forms like Radioisotope Heater Units (RHU), General Purpose Heat Sources (GPHS), Multi Mission Radioisotope Thermal Generators (MMRTG).
For our readers the main advantage of RTG technology is its record of 25 space missions flown involving 44 RTG's including servicing the Apollo astronauts and the latest example as the Cassini/Huygens mission orbiting the Saturnian system. I would say this is one of NASA's prized solar independent power servicing mission technology in the wattage classification.
In that vain could you explain what has transpired historically with RTG fuel? Why this DOE change in facilities management since now all of these different facilities are to be condensed down to the Advanced Test Reactor (ATR) in Idaho?

TF: Right now Pu-238 production would be done in Oak Ridge, TN. Oak Ridge would then ship material to Idaho where it would go into the Idaho (ATR), they would irradiate the Neptunium targets, ship them back to Oak Ridge. Oak Ridge would extract Plutonium and then ship the newly produced domestic Plutonium to Los Alamos then Los Alamos would purify and encapsulate it making the little heat sources and then send it back to Idaho. Once back in Idaho out at the site they would assemble, test and make ready for delivery the radioisotope power systems. That's a grand total of 8,000 miles of public road transportation that essentially goes to zero. The only deliveries [time] that our Pu-238 would be on the road would be when we deliver it to a user, be it for national security or be it for the Kennedy Space Center for a launch.

BB: I have an online publication dated 12/01/04, Jackson Hole News & Guide. I'm reading an article by Rebecca Huntington entitled: INEEL Eyes Nuclear Upgrade.

It says;

"The eye of the nuclear future is right there in Idaho at the Idaho National Engineering and Environmental Laboratory (INEEL), and that is worth talking about," said Mary Woollen Mitchell, executive director of Keep Yellowstone Nuclear Free. Mitchell said she is not advocating support or opposition for specific programs but wants the community to consider what INEEL's new role might mean to the region.

DOE officials, meanwhile, see INEEL as pivotal to national security.

Consolidating plutonium-238 production and processing in one, secure location would enhance national security, said Timothy Frazier, document manager for DOE's Office of Space and Defense Power Systems.
"The material is now transported quite a distance across the roads in the United States," Frazier said Tuesday. "The miles the material will be shipped will essentially go to zero if the proposal [to consolidate] goes through." Moving the radioactive stockpiles and production, purification and encapsulation capabilities to Idaho would cost more than $200 million and take five years to complete, he said."

I understand from this quote what you're trying to do. As far as meetings in pubic involvement opportunities seeking public comment and scope. Naturally it's a good gesture by the DOE. This is one group commenting and I'm sure you've had more than a few groups comment. I happen to listen to President Bush in his, 'State of the Union Address' he mentioned "Hydrogen" and hydrogen powered vehicles and the lessening dependence on foreign energy sources, especially foreign petroleum dependence. As we all know a lot of these policies are driven by money, which technologies get it, which contractors are in line to receive it. This leads me to the nuclear production of hydrogen as it holds considerable promise both from a technological and an economic point of view. "Cracking" water, breaking H2O down to its components hydrogen and oxygen in large quantities for hybrid fueled automobiles, fuels used in space missions and maybe provide a little electrical power on the side all without the nasty side effect of contributing to greenhouse gases. Applause for this proposal was muted. What do you feel is the problem? Could you tell us what people respond to? Are they in favor or against the DOE measure?

TF: I feel it's perception. I feel the largest issue I'm fighting is education. People that I talk to, people that I deal with in a lot of these public meetings- is the specter of nuclear anything.

We've tried hard to inform and educate. Lots of people have the perception of how bad nuclear is. What we have tried to communicate to the public at these scoping meetings and what we'll do whenever the draft of the EIS is published is we can perform and we have been operating these facilities to produce radioisotope power systems for years and years and done it safely. We protected the workers, protected the environment and protected the public. There's a lot of speculation out there that this is somehow an attempt to reinitiate a nuclear weapons production capability in Idaho. That's absolutely incorrect... we have no intentions what so ever in getting involved in the nuclear weapons production business. They don't need our systems, they don't desire our systems. We talked earlier about the fact that if you had to make a nuclear weapon you would not use Plutonium-238 you would use Plutonium-239. And there is a lot of concern about waste generation.

Quite frankly we would expect to generate some wastes. There is no way you can do these type operations without generating some radioactive waste. The question is how much? And where does it go?

We have identified low level waste in what is called transuranic waste. Transuranic wastes are at higher radioactive levels, they are made out of elements above Uranium on the periodic table of elements that's where the trans-uranium comes from (prefix trans meaning that an element is 'beyond' uranium in the periodic table). We have identified some transuranic wastes, however we have also identified a disposal path for all the wastes we are going to generate. The low level waste we will ship out of Idaho and shipped it to places that want to bury it like Utah, or perhaps Nevada test site. The transuranic wastes will go to the isolation pilot plant (WEP) which is in Carlsbad, NM.
We are simply using essentially excess neutrons from the ATR reactor in Idaho. Most of our transuranic wastes and our low level wastes are going to come out of the process of extracting plutonium out of the target material and then going on to the process of purification of the material, encapsulating the material to make the heat sources.

BB: Of course, there is a bit of a business in MOX (mixed oxides). Responsible governments acquire MOX from the U.S.

Some groups opposed to DOE Pu-238 production facilities consolidation claim, a single speck of dust Pu-238 is 247 times more toxic (by weight) than Pu-239. Both Pu-238 and Pu-239 are routinely handled with rubber gloves because the radiation is so non-penetrating. But a single dust speck of either one will cause certain lung cancer if inhaled. If Pu-239 dust gets loose in a room, then that room becomes uninhabitable, but if Pu-238 dust gets loose in a room, then the whole building becomes uninhabitable. That is the magnitude of the handling risk of this process.

TF: Not necessarily true...

BB: That's what I figured.

TF: If you read the (see, pdf file Pu-238 fact sheet) Plutonium Fact Sheet. That talks about potential health effects and differences between Pu-238, Pu-239, Pu-241.

(excerpt from DOE fact sheet)

  ...Lifetime cancer mortality risk coefficients have been calculated for nearly all radionuclides, including plutonium (see box at right). While ingestion is generally the most common route of exposure, the risk coefficients for this route are much lower than those for inhalation. As for other radionuclides, the risk coefficients for tap water are about 80% of those for dietary ingestion. (As a note, the common myth that plutonium is the “deadliest substance known to man” is not supported by the scientific literature. It poses a hazard but is not as immediately harmful to health as many chemicals. For example, for inhalation - the exposure of highest risk - breathing in 5,000 respirable plutonium particles, about 3 microns each, is estimated to increase an individual’s risk of incurring a fatal cancer about 1% above the U.S. average “background” rate for all causes combined.)

  What people are talking about is if you get Pu-238 in a specific size of the particle in the 5-10 microns range (small) you could inhale it and it could go in what is called, 'deep deposition' into your lung-that would be trouble. Depending on how much you were to inhale, depends on how much, what kind of committed dose equivalent that you would bear and it could increase. Just because of a particulate inhalation incident that does not guarantee you'll catch lung cancer or cause a cancer. People that tend to exaggerate the etiology of Plutonium ingestion don't realize it has a statistical factor. This doesn't make it any better for example, if you happen to be the person out of 1000 people that has contracted cancer due to Pu-238 inhalation. The particulate sizes that are larger than say 10 microns don't make it into your lungs it can be stopped in the nostrils or the back of your throat and the ones that are substantially smaller you can actually inhale and exhale it's a question of particulate size range.

BB: The way I see it. These newer labs are efficient at mitigating those circumstances. You would have to be really foolish to expose yourself to Pu-238 by not following stringent safety protocol.

TF: Absolutely... Bruce. In all fairness there has been some releases in operations at Los Alamos.

BB: In past years.

TF: Yes...Releases into the building not outside the building. If fact when you look at the stack monitoring data all of the air that goes into a nuclear facility from the outside and then exhausted through a stack. Before it goes through a stack it goes through a series of HEPA filters (High Efficiency Particulate Air [HEPA] Filters). So even though you may have a release into the room the environment and the public outside never sees it.

BB: Some agencies that work with hazardous material are trusted in their labs to stop deadly incurable Ebola viral filaments measuring up to 14,000 nanometers in length, and have a uniform diameter of 80 nanometers or influenza A virus causing disease worldwide. Past influenza pandemics have led to high levels of illness, deaths in the millions, social disruption and economic loss. It occurs in spherical or filamentous forms measuring 50-120 nm in diameter or 20 nm in diameter.
(1 nanometer = 0.001 micrometer or 0.00000003937 of an inch or 0.000000001 of a meter. 1 micron = 0.001 millimeter or 0.00003937 of an inch.)

Like in the Center For Disease Control, CDC labs. DOE facilities can surely stop a much larger particle-right?

TF: You can and we have done it very safely and effectively at Los Alamos, before that we have done it at Savannah River site (South Carolina), before that we did it at Miamisberg, Ohio plant called Mound when I was growing up around the Mound plant as a kid. They were doing this kind of work there. The pellets that are encapsulated in RTG's like those that power the Cassini spacecraft those are the ceramic kind they're center pressed pellets.

BB: RTG pellets encapsulation is very roughed. In fact if you were to take the latest Mars Exploration Rover (MER) missions you would find 8 Light Weight Radioisotope Heater Units (LWRHU) per mission, LWRHU modules are not expected to fail by ablation burn-through for orbital decay reentry, based on tests previously conducted by JHU/APL at the NASA Ames 20 megawatt (MW) arc-jet tunnel that simulates reentry ablation. The LWRHU aeroshells were subjected to the equivalent thermal loading of three orbital decay reentries without ablation failure.

What I really want to discuss is the positive side of Pu-238 production. From powering cardiac patient pacemakers to powering deep ocean seismographic equipment in an effort to provide a possible Tsunami early warning system. There are plenty of reasons and purpose for all this activity in our field of nuclear space technology. Especially the scientific data that people like to see, Titan and the other moons in the Saturn system and in the near future robust lab equipped Mars Rovers with the capacity to mission much long than present rovers. All this work is necessary if we are to increase the chances of survivability in a future human mars mission.

TF: Sure, Think about this. We're not going to have a space program unless we can maintain the national security, that's the other key complement of this. The national security users of this technology use them for the same reasons that NASA does. They provide power for long periods of time in harsh environments where they don't need human intervention.

BB: Since the DOE has administratively decided to shuffle facilities. And Idaho being "Pu-238 Production Central" where does this leave other areas where some of these facilities will be dropped?

TF: Good Question. In our preliminary look the main place affected would be Los Alamos. It's our perception the Los Alamos workers we have are the most skilled, the most qualified workers at Los Alamos in the nuclear facilities. We are expecting there will be little if any impact from relocating those operations out of Los Alamos to the Idaho site. We think that the other programs at are in existence at Los Alamos and could be coming on line at Los Alamos are likely to take any worker that we might make available. So we think that any impact on the workers is going to be negligible.

BB: Do you have enough trained personnel to properly implement these changes?

TF: At Idaho?

BB: Yeah.

TF: One of the great things about Idaho is it's a large nuclear site with many different disciplines and existing nuclear infrastructure were the ATR, (Advanced Test Reactor) is up and operating. The particular location at the Idaho National Lab we would propose to locate these operations is now called, "Materials and Fuels Complex" formally called, "Argon West". A complication factor in some of this is that effective Tuesday the Argon west site out at INEEL was moved under the big Idaho National Lab and called, The Materials and Fuels Complex that's were we plan to locate these operations. Yes, we're planning to build a fairly large facility. We are very confident the Idaho National Labs' ability to meet mission objectives.

BB: I also wanted to find more information about MMRTG technology (new RTG's) since it's thermal couple this involves materials and temperature management. Essentially the desire to squeeze more efficient power out of the system before it's dumped out to the space environment.

TF: You know, I'm in charge of all that development.

BB: Oh...Good. So what do you think about Stirling Hybrid RTG's, and the Multi Mission RTG's?

TF: The MMRTG's is being specifically designed to operate in both space and on the Mars surface. You know that's a big change.

BB: Is Teledyne doing this or Boeing?

TF: Boeing has the major contract and Teledyne has the subcontract.

BB: Teledyne has the experience they've been at it longer.

TF: If you go back to the early years of radioisotope power systems many, many were built by Teledyne or Teledyne's precursors.

BB: Thanks...Tim for your time with NS.

TF: Thanks Bruce...Bye.

 

 

sources:

Mars Exploration Launch Contingency Efforts; B.E. McGrath, D.A. Frostbutter, K.N. Parthasarathy, G.A. Heyler, Y.Chang, STAIF 2004, M.S. El-Genk .AIP

Office of Nuclear Energy, Science & Technology

Excerpt from the US Department of Energy Publication: Nonproliferation and Arms Control Assessment
of Weapons-Usable Fissile Material Storage and Excess Plutonium Disposition Alternatives (pages 37-39) January 1997.

PLUTONIUM

Plutonium-238: Use Origin and Properties

Jackson Hole News & Guide

Further reads:

Updated Critical Mass Estimates for Plutonium-238

Article research assistance provided by: Tyson Moore