Plutonium Pit Basics

Plutonium pits are the triggers in most nuclear explosives. Pits are sealed weapon components containing plutonium and other materials and came into being in 1956, replacing the plutonium "capsule" trigger design.^xli Pits are surrounded by carefully machined high explosive spheres. When the high explosives are detonated the plutonium is compressed and imploded, thus triggering the nuclear detonation (see Figure 1-1).

Pits were fabricated at the Rocky Flats plant in Colorado from about 1954 to 1989, when safety and environmental problems forced a production shutdown. Rocky Flats is infamous for thirty five years of unsafe operations and costly accidents resulting in massive radiological contamination, but in the nuclear weapons complex it is equally known for producing high quality, "diamond-stamped" plutonium pits considered the most durable and resilient parts of nuclear weapons.

There are about 48 different types of pits (see Table 3-1), each designed for use in specific nuclear weapon systems and to be stored for 20 years or more inside a weapon environment. Long-term storage (more than five years) of pits outside of weapons is a program filled with uncertainties. Designers and weaponeers within DOE refer to the variety of designs in terms of "pit families,"with some more important variations including:

· shape and mass of the plutonium within the pit;
· the presence or absence of highly enriched uranium;
· the presence or absence of tritium;
· the type of metal cladding;
· bonded vs. nonbonded.

Pit numbers and DOE management terminology

Normal operations coupled with START I treaty between the U.S. and Russia turned the Pantex nuclear weapons plant into a disassembly facility in the 1990's (Figure 3-2). 11, 875 weapons were dismantled, with most of the plutonium pits being sent to "Zone 4" for "interim" storage.^xlii More than 11,000 plutonium pits accumulated at Pantex during this time, (Figure 3-2).

About 1200 pits were shipped to Pantex between 1997 and 1999 from Rocky Flats, and another 60 pits were shipped from SRS to Pantex in 1998. Pantex in turn shipped about 20 pits/year to Los Alamos for its surveillance/inspection program, and an undisclosed amount (but less than 100) to Los Alamos for plutonium pit disassembly and conversion demonstration program, leaving more than 12,000 pits at Pantex today.^xliii

Figure 3-2. Weapons Dismantlement at Pantex, 1990's.
(427 dismantlements were scheduled for Year 2000).

DOE now categorizes pits as surplus to military needs or as "national security assets" (NSA), the latter a category concocted in 1998 and composed of:

· strategic reserve pits, including surplus pits considered defense program "assets;"
· "enduring stockpile" pits that belong to existing weapon systems;
· "enhanced surveillance" pits that may include surplus pits.^xliv

National Asset pits are scheduled to be stored indefinitely at Pantex in retrofitted Building 2-116, possibly the most robust facility at Pantex but not one without problems. At least one "national security asset" pit, the problematic W-48, is not allowed in 12-116 because of heat concerns; and there is no funding to move the national asset pits into 12-116 this fiscal year.^xlv

The list of NSA pits is not constant, and the "design agencies"-Lawrence Livermore and Los Alamos National Laboratories--have failed to update their list of national security assets since February 1999, leaving Pantex in the dark:

"an updated list has been requested by letter, in briefings, and verbally to the person in charge of the list. To date, an update has not been received. This is an open issue." ^xlvi

The total amount of plutonium in surplus pits was declared to be 21.3 MT in 1996. DOE maintains this number is current, but the reclassification of some surplus pits as "national assets" leaves this questionable. If START II arms reductions are implemented, another 7.0 MT of surplus plutonium in about 2,000 to 2,500 pits is likely to be declared.

Surplus pits are scheduled to remain in Zone 4 at Pantex (see Pit Storage at Pantex, page 3. )
until they are sent to a Plutonium Pit Disassembly and Conversion Facility (PDCF) scheduled to open later this decade at Savannah River Site. (SRS). Plutonium pit disassembly and conversion refers to "the removal of the plutonium from the nuclear weapon pit and conversion [of the plutonium and other parts] to an unclassified form that is verifiable in the sense that, containing no classified information, the form can be examined by inspectors from other nations." ^xlvii Size, shape, mass and isotopic composition of the plutonium and other parts are considered traits in need of declassification at the PDCF.

Plutonium Mass, Beryllium, and HEU

Figure 3-3. Plutonium mass in pits is reduced through the use of neutron tampers. Source: An Introduction to Nuclear Weapons. 1972.

The amount, or mass, of plutonium that is inside of a pit varies and even the average amount remains classified. But enough evidence exists to declare a range of 1 to 6 kilograms (2.2 to 13.2 pounds) of plutonium mass in pits. Only one kilogram of plutonium is necessary for a 1 kiloton explosion,^liv and Los Alamos defined a maximum material weight of 6 kilograms in pit shipping containers.^lv Considering there is 66.1 MT of plutonium in approximately 20,000 plutonium pits, the average plutonium content is just over 3.0 kilograms per pit, or 6.6. pounds.

Two design variations can be used to decrease the plutonium mass:

1. Neutron tampers (Figure 3-3) are used to scatter escaping neutrons back into the plutonium or HEU core after the nuclear chain reaction starts.^lvi One of the more common neutron tampers is beryllium, a highly toxic light metal. Because classified nonnuclear pit parts will be "declassified" at a PDCF by using furnaces to melt down the classified shapes,^lvii this operation poses extreme workplace hazards when the tamper is high-purity beryllium (Figure 3-4).

2. The use of Highly Enriched Uranium (HEU), also known as "Oralloy, in pits creates what are referred to as "composite cores" and were a "major advance" in weapons design that reduced the probability of pre-initiation of the nuclear explosive, and allowed for a reduction in the amount of plutonium in the pit.^lviii As a result, "the pits in the US stockpile can be generally grouped into two types: (1) those containing weapons-grade plutonium and (2) those containing weapons-grade plutonium and highly enriched uranium."^lix

The presence of HEU in pits poses accounting, handling, and classification problems at a PDCF.

In 1998 the ability to perform adequate materials control and accounting measurements on incoming pits was found to pose a technically high risk at the planned PDCF.^lx This risk is higher with HEU pits since there are no "proven techniques for measurement" of this type. ^lxi

Having HEU parts in plutonium pits also necessitates decontamination of the HEU to levels that meet strict acceptance criteria at the Y-12 plant at Oak Ridge, Tennessee. The Y-12 plant is responsible for all storing all military HEU, it is not a plutonium processing site, and designation as such would meet stiff and justifiable resistance from the state and local communities.

Los Alamos encountered difficulties meeting the previous criteria of 20 disintegrations per minute of plutonium 239 in HEU metal, "with 30% of the shipped parts presently being returned." However, the new limit for plutonium contamination in HEU-oxide form has changed to 2.7 parts-per-million, allowing plutonium levels "several orders of magnitude" higher than the metal standard.^lxii

Because of this issue, the final form of the HEU at a pit disassembly and conversion plant was undecided as of a year ago. The decontamination methods under consideration include:

· electrolytic etching, the current method at LANL that has achieved marginal success at meeting metal acceptance criteria at Y-12 but generates less waste;
· Acid spray-leach; the historical process that involves spraying parts with acid and then soaking in a diluted acid solution for up to three hours, producing large volumes of liquid waste; or
· brushing of parts with a wire brush or blasting parts with "some medium," both of which "are not expected to achieve the Y-12 acceptance criteria." ^lxiii

Plutonium Shape

Because the critical mass for a spherical shape is "less than for any other geometrical form of the given material,"^lxiv most pits are reported said to be spherical in shape. It is unlikely that plutonium in pits are only spherical:

· Passive NMIS measurement systems are in development to estimate the shape of plutonium assemblies inside of containers.^lxv
· DOE continues to censor the discussion of shape of critical masses in the sanitized version of Introduction to Nuclear Weapons (Section 1.22).^lxvi
· Criticality experiments at Rocky Flats in the 1960's included cylindrical shapes of plutonium.^lxvii

Isotopic Composition

The amount of Plutonium-240 is the key isotopic variable in weapon-grade plutonium because its high rate of spontaneous fission poses a higher risk of "pre-initiation," or an early chain reaction, of the fissile material. Higher quantities of plutonium-240 mean increases in critical mass requirements, and therefore costs more to design, develop, and produce the warhead.^lxviii

Early weapons had plutonium-240 content as low to 1.5% but more commonly 4-7%; and in 1972 the Pu-240 content in most stockpile weapons was said to be about 6%.^lxix The isotopic composition varied slightly according to the source of the plutonium (Figure 3-5) and the design of the pit.

Figure 3-5. Variation in average isotopic composition by source.
From: An Introduction to Nuclear Weapons. 1972.

During five years of Environmental Impact Statements, DOE never informed the public that declassification of pits included declassifying the isotopic composition. One month after the January 2000 Record of Decision to build a PDCF at SRS was signed, the "blending" of plutonium oxides from two or more pit types was required to declassify the isotopic composition of the powder.^lxx It is unclear whether this requirement is an artifact of the Atomic Energy Act or a requirement for the plutonium fuel factory.

Cladding and Beryllium Problems

Plutonium pits have an outer cladding of beryllium, aluminum, or stainless steel. Vanadium is another cladding element, but it is unknown whether it is just experimental or in use. Vanadium was used in 1993 during the W89 pit re-use program at Pantex as a fire resistant cladding on W68 pits being converted for use as W89 pits,^lxxi and the classified plutonium part inventory at RFETS presently includes six Pu/Vanadium hemishells.^lxxii

At least seven pit types are known or suspected to be clad with beryllium. (Table 3.1.B),^lxxiii posing the most significant problems with storage and dismantlement of pits:

· pit disassembly can expose workers to highly toxic beryllium dust and fumes;
· beryllium clad pits appear to be more likely to require cleaning (see Table 3.1.B to remove any potentially corrosive organic materials, and pit cleaning can expose workers to airborne beryllium;
· higher sensitivity to temperature fluctuations;
· increased risk of corrosion from chlorides and moisture which are found in storage containers;
· pits clad with beryllium "are more vulnerable to fracture under impact loading."^lxxiv

Pits as a Heat Source

Many pits are sensitive to temperatures, particularly those clad with beryllium. Los Alamos and Lawrence Livermore have expressed major concerns over heating of pits since early this decade.^lxxv In 1995 Lawrence Livermore and Los Alamos National Laboratories recommended temperatures between 65 and 75 degrees Fahrenheit for storage buildings with strategic reserve pits, and less stringent recommendations for "surplus" plutonium pits.^lxxvi

In August 1998 an estimated thirty plutonium "W76" pits were moved from one Pantex Zone 4 "bunker" to another "due to potential temperature concerns during the recent heat wave."^lxxvii The W76 pits are part of the large "strategic reserve"of pits scheduled to be stored indefinitely at Pantex.

Tritium in Pits

In 1998 Los Alamos released a fact sheet that stated:

"A significant number of pits processed by the ARIES facility will contain tritium."^lxxviii

The "fact that tritium is associated with some unspecified pits" was declassified in 1992.^lxxix During the Environmental Impact Statements for plutonium disposition, DOE vaguely admitted that some plutonium pits were "contaminated" with tritium and that these pits would have to be decontaminated; but finally acknowledged that some pits contain tritium by writing:

"DOE knows how many pits contain tritium."^lxxx

The reason for having tritium in pits by design is unknown but the impacts of this design on the disassembly of plutonium pits are now more open.

Pits that contain tritium must be processed up-front in a highly secretive "Special Recovery Line" where plutonium "is separated from highly enriched uranium (HEU) and other parts and then processed in a vacuum furnace that drives off tritium and produces a metal ingot. The tritium is captured and packaged as a low level waste. The resulting plutonium ingot is assayed and then reprocessed if it still contains tritium."^lxxxi This process was sufficiently difficult enough to dissuade Los Alamos from processing pits containing tritium in its original ARIES demonstration project when only 40 pits were planned for disassembly and conversion.^lxxxii

The major environmental impact of this process is tritium air pollutants. In the June 1998 Environmental Assessment for the plutonium pit demonstration project at Los Alamos involving 250 plutonium pits over a four year period, DOE reported air emissions of "up to 69 curies of tritium each year." In the 1998 Draft SPDEIS, DOE buried the impacts in a source document by choosing to omit a small table occupying less than a half-page reporting that 1100 curies of tritium will be emitted annually at a PDCF.^lxxxiii

Tritium Contamination vs. Pits that contain tritium

Pits could become contaminated if they contain tritium by design, or if they become contaminated with tritium by accident. In any case, any kind of hydrogen-plutonium reaction is undesirable because it could induce hydride corrosion of the plutonium metal, causing pitting and a growth of hydride film along the surface,"^lxxxiv as well as producing a pyrophoric plutonium hydride compound.

Bonded vs. NonBonded Pits

DOE had declassified information about bonded weapon components prior to 1996.^lxxxv A 1998 Technical Risk Assessment of the Plutonium Pit Disassembly and Conversion Facility identified the implications of this distinct design variable when it identified an option with the least technical risk for disassembly and conversion of most plutonium pit types. The Metal-Only Option was suggested to process only "nonproblem pits" to produce only a metal plutonium product and no plutonium oxide. This was because "many of the pits, perhaps as many as 80%, can bypass the hydride/dehydride (conversion to metal) module as the plutonium metal can be mechanically separated from the pits."^lxxxvi

The pit types where plutonium metal can be mechanically separated using a lathe are called "non-bonded" pits; whereas the pits that require chemical processing-either pyrochemical or liquid-to separate the plutonium in the pit from other pit parts are called "Bonded" pits. In bonded pits, the the plutonium is bonded to other metals in the pit, such as stainless steel, beryllium, and/or uranium.^lxxxvii At least one Los Alamos source reports that all Russian plutonium pits are nonbonded.^lxxxviii

Figure 3-6. Plutonium Pit Bisector.
"The prototype bisector was designed and tested at Livermore. Using a chipless cutting wheel, it can separate weapon pits into two half-shells in less than 30 minutes so that the plutonium in them can be recovered for disposition." Science and Technology Review. April 1997. Lawrence Livermore National Laboratory.

Bonding and Pit Disassembly and Conversion Issues

To avoid liquid acid "aqueous" processing of pits, Lawrence Livermore National Laboratory developed the ARIES system that included a pit "bisector" for cutting plutonium pits in half (Figure 3-6) --which suggests that most or all bonded pits are of Livermore design.^lxxxix The bisector is the front end the Advanced Resource Integrated Extraction System (ARIES) that DOE chose as a major part of the pit disassembly and conversion process while it was still in the design and experimental phase.


Following the pit bisection, the plutonium must the be chemically separated from the pit cladding and other pit parts. The two experimental technologies proposed are hydride-dehydride, which recasts the plutonium as a metal, and HYDOX, which utilizes the reaction of plutonium with hydrogen to produce a plutonium oxide powder.

Pit Tubes and Pit Re-Use at Pantex

While DOE pursues plutonium pit fabrication at Los Alamos and possibly SRS, it has abandoned, at least for now, the plutonium pit re-use project planned for Pantex. A pit-re-use project occurred at Pantex in the early 1990's when Rocky Flats was shut down. This project allowed DOE to proceed to complete the W-89 weapon program by re-using W68 pits and converting them to fire-resistant pits by cladding them with vanadium. Heralded then as an innovative approach that avoided messy pit fabrication, the latest plan for pit-re-use went unfunded in fiscal year 2000,^xc and there is no indication that DOE plans to pursue this work, indicating a preference for new pit production at SRS.

One of the sticking points regarding pit-re-use involves pit tubes. Plutonium pit tubes are designed to carry the booster tritium gas from the tritium reservoir to the hollow core of the pit at the time of detonation. According to pit-tube fabrication experts, pit tubes:

· are constructed of annealed type 304 stainless steel that is "very ductile" and able to take severe deformation without cracking or leaking;
· are placed at assembly within tightly fitting slots in the high explosive and must be straight and within true position within 0.02 in 1 inch.
· are usually of 0.12 inch diameter, for pressure testing, evacuation and filling.
· are attached to stainless steel shell by TIG welding or electron beam welding and to beryllium and aluminum shells by high temperature braze ^xci
.
Pit re-use was always described as "non-intrusive" during the Environmental Impact Statement process. After Pantex was selected for the pit re-use mission, the mission was renamed "pit requalification" and changed from non-intrusive to intrusive because it included pit tube replacement and refurbishment:

"SNM Requalification at PANTEX for FY 98 has been as continuation of the original
effort and has included an increase in scope to address pre-screening, tube replacement and reacceptance...tube replacement is a capability that was utilized at Rocky Flats. A similar capability is being supported as a part of the Pit Rebuild program at LANL" ^xcii

Figure 3-7. Sun-Woo, Characterization of Stainless Steel 304 Tubing.

Pit tube replacement was being advocated by Los Alamos prior to the funding cutoff for this program. Because pit tubes are bent to very specific configurations and there is no record of the number of times they have been bent, Los Alamos wanted to replace all pit tubes. However, a LLNL report discussing the stainless steel used in W87 pits reported that the tube would need to be bent at least ten times to pose a great risk of failing (Figure 3-7). ^xciii

PLUTONIUM STORAGE AT PANTEX: Stockpile Negligence?

Plutonium pits are multimillion dollar weapon components being stored in substandard conditions.

Most pits are stored in the AL-R8 container (Figure 3-11) which is unsuitable for long-term storage. Designed by Dow Chemical in the 1960's. AL-R8's are unsealed and pits stored in them:
· require extra humidity and temperature controls
· are prone to corrosion because the internal celotex packing-sugar cane, paper, starch, and wax--is a source of chlorides and moisture that can lead to corrosion of the pit cladding.
· do not meet all safety criteria-specifically the 1100 pound dynamic crush test.
· provide poor radiation shielding.

There are about 2,000 corroded AL-R8's at Pantex because they were procured without the corrosion resistant liner.

Figure 3-8. AL-R8.

THE AT-400A Fiasco

DOE spent $50,000,000 designing and developing the
AT-400-A (Figure 3-9) dual-use shipping and storage container for plutonium pits. Its advantages included:
· a sealed, inert gas environment that would prevent corrosion and other degradation of pits
· better radioactive shielding;
· a 50-year design life.

It's disadvantages included cost ($8,000/unit) and problems associated with the weld-possible burn through of the containment vessel.

DOE estimated that 2,000 plutonium pits per year could be repackaged in the AT-400A, leaving pits in the safest container within a five year period. After the repackaging startup was delayed by more than a year, 20 pits were repackaged in a pilot run before DOE pulled the plug on the entire program. Twenty W-48 pits remain in AT-400A's.

Figure 3-9. AT-400A

The Sealed Insert

Figure 3-10. AL-R8 with Sealed Insert, 2030 model. There is still a need for 2040 models for several pit types, including national asset pits

DOE replaced the AT-400A with the AL-R8 Sealed Insert (Figure 3-10). It is a significant improvement over the AL-R8 because of the sealed, bolted, stainless steel inner container, but is still not considered worthy of shipping certification. Problems now plaguing this program include ^xciv :

· a lack of funding to buy new containers at a cost of $2800/unit.
· the need to certify larger "2040-type"AL-R8 sealed inserts for about several pit types ome pits, including most stockpile pits;

?
Figure 3-11. DOE still has no pit shipping container

· the lack of a pit cleaning station for 1500 pits too dirty for long term storage, so Pantex is having to double-handle some pits;
· a lack of funding for labor, so Pantex is not able to run two shifts;
· a lack of funding for monitoring;
· limited funds for dealing with another cracked pit.
· DOE has only 300 shipping containers called FL's, the certification for the FL's expires in 2002, and more than 200 of these were recently found to not match design drawings;

Figure 3-12. Zone 4 Bunkers at Pantex. Plutonium pits are literally stacked to the ceilings in these WWII and 1960's vintage bunkers. All but a few of these facilities lack required humidity or temperature controls, and are unlikely to withstand an aircraft crash - a serious issue due to the proximity of Amarillo International Airport. Pantex has little space for additional pits.

· DOE has made no reported progress developing a new shipping container (Figure 3-11) to replace the FL and AT-400A.;
· a planned upgrade to Building 12-66 at Pantex was abandoned after the design work was complete, leaving decades-old bunkers as the main storage buildings. (Figure 3-12) These facilities were not supposed to be used after the Year 2000, but will be used indefinitely.

DOE's Dirty Plutonium Secret
Plutonium Pit Production at Savannah River Site

In the newly downsized U.S. Nuclear Weapons Production Complex, Savannah River Site is the only remaining major plutonium processing site in the country and is in line for three new facilities promoted as "nonproliferation" missions:

a Plutonium Pit Disassembly and Conversion Facility that will process surplus plutonium pits and convert the plutonium in those pits to an unclassified plutonium oxide powder.
b Mixed Oxide (MOX) Fuel Fabrication Facility where "pure" or nearly pure surplus plutonium will be purified using liquid acid processing and then mixed with uranium to make MOX plutonium fuel for nuclear reactors;
c. A Plutonium Immobilization Plant (PIP) where impure and very difficult to purify surplus plutonium will be mixed with uranium and a "titanate" ceramic to make ceramic "pucks." (See below for explanation of can in canister)

Tritium production and recycling is said to be the only nuclear weapons production mission at SRS. However, because Rocky Flats no longer produces nuclear weapons triggers called plutonium pits, new pit production is slated for SRS, and this would inevitably involve the PDCF, making it a dual-use facility:

Plutonium Aging and ARIES as a Weapon Program

In 1998 the Government Accounting Office reported that:

"DOD was concerned that the aging of pits was not clearly identified in our report as
a driving force of pit-production requirements. DOD said that it could not give detailed pit-manufacturing requirements until the lifetime of pits is specified more clearly by DOE."

DOE plans to spend over $1.1 billion through fiscal year 2007 to establish a 20-pits-per-year capacity. But this budget does not include disassembly work ^xcv which is clearly being funded by OFMD under the ARIES development. In addition, plutonium pit enhanced surveillance program, a SSM program, ARIES was identified as a "pertinent task" for the "Pit Focus Program."
material property data from pits dismantled in the ARIES process in order to expand the age-
correlated database of applied plutonium properties.^xcvi

Chairman Spence and the Foster Panel

In 1996 Chairman of the House National Security Committee Floyd Spence (R-South Carolina) issued a report titled "The Clinton Administration and Stockpile Stewardship: Erosion by Design," in which he wrote that,"Unprecedented reductions and disruptive reorganizations in the nuclear weapons scientific and industrial base have compromised the ability to maintain a safe and reliable nuclear stockpile...unlike Russia or China, the United States no longer retains the capacity for large-scale plutonium "pit" production and DOE's plans to reconstitute such a capacity may be inadequate."

In December 1999 a congressional panel called the Foster Panel published "FY 1999 Report of the Panel to Assess the Reliability, Safety, and Security of the United States Nuclear Stockpile,"
recommending that DOE:

"immediately begin the conceptual design phase of a pit production facility adequate to meet national security needs." ^xcvii

The Chiles Commission

Another vote for pit production was cast by the Chiles Commission, which was established to review the nuclear weapons workforce and determine needs and priorities. The Commission concluded in 1998 report that, "large numbers of workers are reaching retirement and a new generation of workers must be hired and trained in order to preserve essential skills." One of these essential skills is the machining of "materials unique to nuclear weapons," such as plutonium, highly enriched uranium, and beryllium. Their recommendations called for a renewed emphasis on plutonium pit production:

"DOE needs to give a much higher priority to detailed planning for the production of replacement weapons components. In the absence of such planning, the sizing of the nuclear weapons workforce at the production facilities is left unnecessarily uncertain" ^xcviii

The SRS Strategic Plan

The Savannah River Site is very explicit about its potential pit production mission within some documents but does not publicize its intentions in an up-front manner. The Savannah River Site Strategic Plan: A Strategic Plan for 2000 and Beyond ^xcix lists three focus areas for SRS:

· Nuclear Weapons Stockpile Stewardship
· Nuclear Materials Stewardship
· Environmental Stewardship

The plan states that Nuclear Weapons Stockpile Stewardship "emphasizes science-based maintenance of the nuclear weapons stockpile. SRS supports the stockpile by ensuring the safe and reliable recycle, delivery, and management of tritium resources; by contributing to the stockpile surveillance program; and by our ability to assist in the development of alternatives for large-scale pit production capability, if required. associated with products and services essential to achieving the Department of Energy's (DOE) goals."^c Under Goals, Objectives, and Strategies, the strategic plan states as a goal:

"Consolidate existing facilities and plan, design, and construct new facilities to support current and future stockpile requirements."

Within this goal is the objective to:

"Support the development of contingency plans for a new pit production facility to meet future stockpile requirements as national needs emerge."
Within this objective is the strategy to:

"Develop partnerships with the national weapons laboratories and Oak Ridge Y-12 Plant to outline roles for each organization in a large- scale pit manufacturing project."

Preparing for Pit Production at SRS?

Several operations at SRS suggest that the site is quietly and surreptitiously implementing its strategic plan as it relates to large-scale plutonium pit production:

1. Developing Plutonium Casting Capability. An essential part of plutonium pit fabrication is "casting plutonium metal feed ingots after adding gallium to the plutonium metal and shape-casting the feed ingots into hemishells."

The Los Alamos Perspective

Stephen Younger, the Associate Laboratory Director for Nuclear Weapons at Los Alamos National Laboratory, which is operated by the University of California under contract to DOE. recently wrote, in Nuclear Weapons in the Twenty-First Century that "Plutonium pit production can be maintained at a small rate at Los Alamos, but any stockpile above about one thousand weapons will require the construction of a new large production plant to replace the Rocky Flats facility, which ceased production in 1989." "In the case of DOE, an extensive infrastructure of laboratories and plants is required for the Stockpile Stewardship program, including a new manufacturing capability for plutonium pits" Yet, even under START III conditions, "the U.S. has offered to begin negotiations on ceilings of 2,000 to 2,500 weapons immediately upon Russian ratification of the START II treaty" Obviously, as long as the U.S. intends to maintain more than 1,000 nuclear warheads, then demands for large-scale pit production will be made.

In 1998 SRS developed the capability to recast plutonium metal in the FB-Line "using an M-18 reduction furnace with a new casting chamber." Plutonium metal is recast by charging a standard FB-Line magnesia crucible and placing the charge in the casting chamber. In October 1998, "a [plutonium] button was produced by combining plutonium and gallium metals to produce an alloy in which the plutonium is stabilized in the d phase. Delta (d ) phase metal is not susceptible to low temperature induced phase changes like a phase metal." ^ci

This effort was portrayed by SRS only as a contingency for plutonium metal storage and not as a dual-purpose program that integrated storage goals with pit production goals:

The capability to produce d stabilized metal in FB-Line would provide a contingency for plutonium metal storage at the SRS in the event that experimental programs show that the a to b phase transition (and resulting decrease in density) has the potential to create harmful mechanical stresses in storage containers. The continued use of the casting process for the declassification and consolidation of plutonium from weapons components also provides a disposition path for classified metal parts and alloys currently stored at the RFETS." ^cii

2. Measuring Plutonium Density in Pits. Another capability SRS has developed is a new measurement system for determining plutonium density in finished plutonium pits. The Savannah River Technology Center (SRTC) and Los Alamos undertook a collaborative research project in which SRTC designed, fabricated, and tested a gas pycnometer "to be used to measure densities of surrogate [plutonium pit] parts." The project's objective was to find a more environmentally friendly method for measuring the density of plutonium hemishells in pits. ^ciii

The plutonium density project is not a dual-use program, and is only necessary for plutonium pit fabrication. Although the project occurred prior to the issuance of the SRS strategic plan, it clearly is an example of collaborating with the national laboratories to define roles for pit production.

3. The Plutonium Pit Disassembly and Conversion Facility. Every analysis of plutonium pit production lists pit disassembly as the first step in the process. For example, a joint paper issued by Lawrence Livermore and Los Alamos National Laboratories specified the first two steps of pit fabrication as:

· dismantlement of the pit;
· conversion of the metal through hydride and oxidize to plutonium oxide (HYDOX) or hydride and reduce to metallic plutonium (HYDEC); ^civ

4. The Plutonium MOX Fuel Factory. The capability to purify plutonium for pit fabrication is the missing ingredient in the current version of the PDCF is plutonium purification processing. However, the planned plutonium fuel factory will have the capability to purify plutonium oxide powder.

Blue Ridge Environmental Defense League, Inc. 2001

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