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For immediate release May 18, 2015
Los Alamos-Supported Congressional Study Suggests Efficiency Improvements for Plutonium Warhead “Pit” Manufacturing
Billion-Dollar Underground “Modules” Apparently Not Needed Even for Aggressive Manufacturing Requirements Set by Congressional Hawks
Contact: Greg Mello, 505-265-1200 or 505-577-8563
Albuquerque – This past Friday the Congressional Research Service (CRS) published an in-depth study of possible plutonium warhead core (“pit”) manufacturing efficiencies, the latest in a series of reports and briefings on this topic (a total of seven prior CRS products are provided here.)
A pit is the plutonium core of a thermonuclear weapon. Imploding it with conventional explosives provides the energy to detonate the rest of the weapon. The Rocky Flats Plant made up to 2,000 pits per year (ppy) through 1989; since then, the United States has made 29 pits for the stockpile. Yet the FY2015 National Defense Authorization Act requires the National Nuclear Security Administration (NNSA), which manages the nuclear weapons program, to produce at a rate of 80 ppy for 90 days in 2027. How can that requirement be met?
Pits are to be made at Los Alamos National Laboratory’s main plutonium facility, PF-4. To manufacture pits, a facility must have enough laboratory floor space and a high enough limit for Material At Risk (MAR), the amount of radioactive material a worst-case accident could release.
Producing 80 ppy requires enough “margin,” the space or MAR available to produce pits minus space or MAR required for that production rate. While space and MAR available have been calculated, amounts required to produce 80 ppy have never been calculated rigorously, leaving space and MAR needs undefined. Further, the report cannot address whether certain options could meet the 2027 date because time to implement them cannot be determined. Accordingly, this report presents 16 options that seek to increase the feasibility of producing 80 ppy by 2027, including:
• The radiation dose an individual would receive from a worst-case accident determines MAR permitted in PF-4. A ten-factor equation calculates dose as a function of MAR. NNSA uses worst-case values in this equation, yet median values may provide sufficient conservatism. Median values reduce calculated dose by orders of magnitude, permitting a large increase in PF-4 MAR. Yet merely doubling permitted MAR might suffice for producing 80 ppy. Providing this increase through construction at PF-4 could be costly and take years.
• In determining MAR for PF-4, the closest offsite individual is at a nearby trailer park. Relocating it would place the next closest individual farther away. The added distance would reduce dose, permitting increased MAR in PF-4.
• Using a different meteorological model and different assumptions would greatly reduce the currently calculated dose, perhaps permitting doubling PF-4 MAR.
• Plutonium decays radioactively, creating elements that various processes remove to purify plutonium. One process generates byproducts; plutonium is recovered from them with processes that take space and MAR. Since the United States has tons of plutonium surplus to defense needs, byproducts could be dispositioned as waste.
• Pits use weapons-grade plutonium (WGPu). U.S. WGPu is about 50 years old. About nine-tenths of plutonium-241, a WGPu isotope, decays to americium-241 in that time. Since plutonium-241 is the source of americium-241 in WGPu, removing the current americium-241 would prevent WGPu from ever reaching its americium-241 limit, permitting reduction in equipment for that process and reducing worker radiation exposure.
• A plutonium isotope used in space probes, plutonium-238, is extremely radioactive. It accounts for a small quantity of PF-4 plutonium but a quarter of PF-4’s MAR. Building a “module” near PF-4 for plutonium-238 work would free MAR and space in PF-4, so one module might suffice instead of two or three.
• To reduce risk of collapse, loss of life, and radiation release from an earthquake, NNSA increased the seismic resilience of PF-4. More steps are planned; more could be taken.
Achieving the congressionally mandated capacity will probably require choosing among options to create a package. MAR margin could be increased by relocating a trailer park, using a new meteorological model, installing rugged containers in the PF-4 production line, increasing PF-4’s seismic resilience, and using less conservative assumptions in the MAR-to-dose equation. Similar choices exist for other options. At issue for Congress: What are the risks, costs, and benefits of the options? What is the optimum combination of options?
 We said, “Pit production for the stockpile is not needed…” LANL agreed with us “with specific limitations:” LANL: Agreed with specific limitations. Pit production to replace pits in the deployed stockpile due to plutonium aging is not required, nor is it planned to occur. If this situation were otherwise, the NNSA decision in the SSMPEIS would have established a Modern Pit Facility pathway and be constructing a “large” production facility capable of producing several hundred pits per year and spending billions of dollars a year to do it. (emphasis added).”
NNSA has posted 2010 Study Group recommendations on pit production here. These are also available on our web site (U.S. Plutonium "Pit" Production: Additional Facilities, Production, Restart are Unnecessary, Costly, and Provocative, Nov 20, 2010). Further analyses of this topic can be found on our CMRR pagebut may be obscure. Feel free to call.