Is DOE/NNSA Already Cutting Corners on Worker Protection at its New Plutonium Processing Plant?

by Don Moniak

September 6, 2023 (Updated Sept 7, 2023)

As of this past Labor Day, there are strong indications that future workers at the planned, new Savannah River Plutonium Processing Plant (SRPPF) may face unnecessary, increased risks of exposure to radiological hazards inherent in plutonium toxicity and chemical complexity.

According to an August 3, 2023  letter from the Defense National Facilities Safety Board (DNFSB) to the Department of Energy’s (DOE) National Nuclear Security Agency (NNSA), the SRPPF project leadership team does not consider vital plutonium processing safety equipment as “safety significant controls.”

According to the letter, NNSA’s project leadership team believes a reliance on worker sense of sight, hearing, taste, smell, and touch is sufficient to detect and/or prevent accidents such as plutonium fires and dispersal of plutonium oxide powder. 

In the hierarchy of nuclear safety,  the Department of Energy standards place “Safety Significant Controls” above administrative controls that are reliant upon the absence of human error.

The motive for SRPPF project team’s preference for administrative controls is unknown.

The New Plutonium Processing Plant. 

The plutonium/MOX (Pu/MOX) fuel facility was a massive, multi-billion dollar endeavor designed to help dispose of dozens of tons of surplus nuclear weapons plutonium (Pu). This Savannah River Site (SRS) project was abandoned in the late 2010’s, following a chronic array of technical issues, mismanagement, major cost overruns, cutting of corners, and the lack of commercial Pu/MOX fuel customers.  

After the project was abandoned, the Department of Energy’s (DOE) National Nuclear Security Agency (NNSA) decided to repurpose the unfinished facility into a new “plutonium pit”production plant. The Mixed Oxide Fuel Fabrication Facility (MFFF) was then renamed the Savannah River Plutonium Processing Plant (SRPPF).  This $11 billion plus repurposed facility is already burdened by cost overruns—-the original estimate was $3.7 billion.

Plutonium pits are referred to as the primary nuclear explosives, or triggers,” (1) that dominate the known U.S. nuclear weapons arsenal. Pits acquired their quaint nickname by virtue of the resemblance of the configuration of high explosives surrounding the primary nuclear explosive to stone fruit like peaches and plums—an example of early nuclear weaponeers’ inside humor. 

The Pu pits are pressure vessels with nested shells of material, comprised of other non-nuclear parts, including the metal cladding, welds, a pit tube, neutron tamper(s) and initiator, as well as the usually hollow-cored plutonium hemispheres. In most pit designs, a sealed pit tube carries deuterium-tritium gas into the hollow-core to boost the nuclear explosive power of weapons.

But unlike the sweet, fruity, and and delectable flesh surrounding plum and peach pits, a Pu pit is surrounded by a high explosives package powerful enough to implode the plutonium metal sphere contained in the pit. This is not like compressing a tin can, as plutonium is the most durable of the transuranic heavy metals. 

The current plan is to annually produce at least eighty new plutonium pits in the SRPPF. Pit fabrication was once the exclusive task at the long-closed Rocky Flats plant in Colorado, and the work processes constitute the most dirty—in terms of waste production—and dangerous workplace in the national nuclear weapons complex. In this century, Los Alamos National Laboratory (LANL) has failed miserably to reconstitute a tiny fraction of the Rocky Flats pit production rate.

Pit production is unlikely to be the only task at the SRPPF.  An estimated ten to twelve-thousand surplus plutonium pits, containing a sum of 30 to 34-metric tonnes of plutonium, could also be processed at a plutonium pit disassembly and conversion line at the SRPPF. The resulting plutonium oxide powder would then be sent to the SRS K-Area’s Pu waste production facility, where the powder is diluted to a three to five percent level within a larger mixture of inert materials.

While this is not the NNSA’s “preferred” plutonium disposition option, it is a more cost-effective choice since it would require substantially less transportation and leverage the new SRPPF for some semblance of cost-effectiveness. A second motive is that SRS is production-oriented, while LANL struggles with large-scale nuclear materials production and processing tasks. And a final reason is that Los Alamos is surrounded by communities increasingly at odds with the lab, and DOE prefers to minimize controversy in its efforts to win community hearts and minds.

Some Plutonium Processing Hazards

There is a negligible level of debate that plutonium is toxic at the scale of micrograms, deadly at the scale of milligrams, and useable in nuclear weapons of mass destruction at the scale of kilograms. This is why plutonium work requires rigid, intensive safety systems, referred to as “defense in depth,” to protect workers and the surrounding people and landscape; as well as extreme levels of security and material accounting. 

The most hazardous plutonium operations involve plutonium pit fabrication. After pit disassembly, the plutonium within pits is converted to a finely dispersed powder form (2), made up of sticky grains containing energetic alpha particles that easily damage soft lung tissues. Sticky plutonium oxide particles clinging to ductwork can also hinder ventilation systems over time.

Recycling plutonium for pit production then requires difficult and dangerous processes to remove impurities and undesirable decay products such as intensely radioactive Americium-241. (3) The resulting plutonium form is transferred to the next step, the plutonium foundry. 

The foundry work involves a complex ten-step process, summarized as melting, casting, and heat treating of plutonium metal. Gallium is added at a one-percent ratio to produce an alloy that is considered almost as easy to machine as aluminum or silver. The risk from explosion, criticality, and spill hazards must be rigidly controlled; while contaminated parts such as crucibles pose unique waste management measures.

The final plutonium processing step is machining the foundry product into a precise sub-critical configuration. Like any machining, Plutonium metal work casts tiny shavings and creates fine dust. 

These shavings can ignite upon exposure to air and lead to larger fires that can destroy glove boxes and ventilation systems, and cause large releases of plutonium into the atmosphere. The Rocky Flats experience suggests that fires of any size are not a remote possibility, they are a probability.

The task is to keep Pu metal fires small and nondestructive, while preventing injury and harmful exposures to workers. A small fire can render costly equipment useless. A large fire can lead to a countryside contaminated with particles that become more intensely radioactive for decades. 

Extreme care must also be taken to keep plutonium metal in a non-critical configuration at all times. The wrong geometry or placement of metal pieces in the wrong configuration can produce the deadly blue light that signifies criticality accidents. In 2009, a number of Los Alamos criticality engineers walked off the job at the lab’s pit production line, citing a casual approach to criticality safety.

The final step is assembly, where the parts that make pits tick are introduced. The making of these parts pose their own toxic hazards, such as the fine dust from machining beryllium metal.

Those are just several aspects of the safety issues involved with the plutonium pit fabrication.

The True, and False, Necessity for New Pit Fabrication and Production. 

Why is pit production, with its inherently high-hazard and high-consequence operations, scheduled at SRS—especially when more than 10,000 existing surplus pits may be scheduled to simultaneously pass through the disassembly and conversion process as part of long-term Pu waste production?

The necessity of new production, which has been debated since the end of Rocky Flats production in the late 1980’s, involves two primary rationales.

The first reason, and the least discussed by nuclear weaponeers and Pentagon nuclear warfare planners, is to facilitate new weapon designs.  Even though there are well over 10,000 surplus pits separated from their high explosive fruit and in long-term storage, pits are considered difficult to reuse. 

There are over forty-four types of pits, but each one is designed for specific warheads, and are difficult to repurpose into new warhead designs. Simply put, new nuclear warhead designs require new plutonium pit designs, and the U.S. is developing new weapons designs.

The second, and most commonly cited, rationale is that the uncertainties of plutonium aging require a “just in case” strategy. The concern is that aging impacts ranging from alpha particle damage to metal cladding to the accumulation of decay products could negatively affect the thousands of pits set aside for the existing nuclear arsenal.

Aging concerns lead in turn to “reliability” concerns. In this case, reliability is much more complicated than a “to explode or not to explode” question.

College recruits to those National Laboratories whose primary mission is nuclear weapons safety, surety, and reliability are taught that a hydrogen bomb fizzle is merely “a degraded yield relative to the design yield.” Such a “fizzle” might still constitute a yield that is still up to 10x the explosive power of the Hiroshima or Nagasaki atomic bombs. 

In other words, a warhead designed for a 100-kiloton explosion that only yields a 60 to 70-kiloton explosion is considered militarily unreliable for nuclear warfare strategic planners. A one-megaton bomb that yields a 200-kiloton explosion is even more militarily unreliable, even though the latter explosion was ten times more powerful than the ~20-kiloton yields of the Hiroshima and Nagasaki bombs. 

In practical terms, this could very well be the case. A militarily unreliable high-yield nuclear explosive targeted at the Washington D.C. metro area should reliably leave a vast, sizzling, apocalyptic radioactive landscape. The same unreliability for a warhead designed to penetrate and destroy a deep underground military installation might be of greater concern to nuclear warfare planners. 

But pits are just one of many reliability factor variables. Bombs can fail to meet explosive expectations due to any number of non-nuclear parts failing to function as designed. Pre-initiation that is unrelated to pit aging might result in a mere “fizzle” with catastrophic, though less than desirable, effects.

The Pit Plant’s Initial Design: One Less Layer of Safety Depth?

Because of all these factors, new pit production is considered essential, and a new, smaller scale—by Cold War Standards—plutonium pit fabrication capacity is presently in the preliminary design phase at the SRPPF complex.

The highest standards of safety are expected to prevent accidents or mitigate the impacts of spills, fires, leaks, and dispersion of fine radioactive dust. A less rigid approach to safety is quite unexpected for a high hazard, hardened nuclear facility that would only be the second its kind in the weapons complex—-the last being the Rocky Flats plant built in the 1950’s.

But according to the August 3, 2023  letter from the Defense Nuclear Facilities Safety Board (DNFSB), the DOE/NNSA’s project leadership team does not consider vital plutonium processing safety equipment as “safety significant controls.”

The Defense Board is charged with oversight of DOE weapons work and related radioactive waste stabilization work, which in bureaucratic terms is called “environmental management,” and in layperson’s terms is simply called “cleanup.” 

On January 24, 2022, the Defense Board issued a conceptual design review, detailing eight safety concerns. National Nuclear Security Agency Administrator Jill Hubry finally replied six months later. Ms. Hubry wrote in her two-paragraph response that the issues “merit attention as the design is matured.”

The focus of the Boards’ August 3rd letter was worker safety. The Board’s succinct and clear narrative is worth reviewing paragraph-by-paragraph. After an introductory paragraph, the Board defined a few of the primary hazards plutonium pit fabrication workers will face:

“Gloveboxes in SRPPF will stage and process kilogram quantities of highly hazardous weapons-grade plutonium. Inhalation of small quantities results in large radiological doses. Some forms of this material will be pyrophoric, meaning it can readily ignite upon exposure to air and immediately begin releasing aerosolized plutonium. In the past, pyrophoric behavior of plutonium was implicated in major fires at DOE’s Rocky Flats Plant. Other forms of weapons- grade plutonium that will be staged and processed in gloveboxes in SRPPF include plutonium oxide, which is dispersible and readily aerosolizes when spilled. Multiple scenarios can result in significant radiological exposure to the facility worker. DOE safety standards require that safety significant controls shall be selected for cases where significant radiological exposure to a facility worker may occur.” 

Plutonium pit fabrication is unlike the more routine plutonium production work performed at the Savannah River Plant (SRP) for four decades. SRP, renamed SRS around 1990, was always on the front end of weapons plutonium production, not on the finishing end of weapon parts production; which was the primary reason cited in a 1998 report describing SRS as a weak candidate for plutonium foundry and machining work.

The third paragraph described a less rigid approach to worker safety by project managers:

“On May 11, 2023, project personnel briefed the Board on their position that additional safety controls are not required. Project personnel assert facility workers can use their senses to detect accidents such as a glovebox spill or fire and exit the area before receiving significant radiological exposure. Using this assumption of worker self-protection, project personnel avoided designating safety significant controls, such as gloveboxes, glovebox ventilation, continuous air monitors, and glovebox fire controls, that other DOE plutonium processing facilities have traditionally designated. The controls mentioned above are part of the existing design of SRPPF, but they are not currently classified as safety significant. As a result, they lack the increased reliability of designated safety controls needed to protect the worker.””

This paragraph is astonishing. The idea that workers have to see, smell, hear, taste, or touch  a fire, leak, spill, or large puff of fine grained plutonium powder, sounds like something out of the early Cold War when military demands dictated production over safety. Workers will be asked to conduct more self-monitoring of their workplace while performing precision metallurgy tasks that Los Alamos experts describe as “kind of artisanal…It’s very exacting work.”

DOE Standard 1186-2016, Special Administrative Controls, defines “safety significant” as “a hazard control that indicates the control provides a preventive or mitigative function that is a major contributor to defense-in-depth and/or worker safety.” 

According to DOE’s own standard, safety class controls are at the top of the hazard control hierarchy for systems, structures and components. followed by safety significant controls. Administrative controls are generally least preferred and often at the the bottom of the hierarchy, but exceptions do exist. (Correction and Update: Safety significant controls are higher in the safety hierarchy than administrative controls.) (4)

“Based on this hierarchy, administrative controls, including SACs, represent the least preferred means of implementing safety controls. While SACs can provide acceptable and effective controls, they should only be used if adequate engineered controls are not readily available. In general, SSCs are preferable to SACs due to the uncertainty of human performance inherent in implementation of SACs.”

At this point, the SRS plutonium processing facility planners have chosen the absence of human error in the hierarchy of safety control—for a facility that will house the most dangerous of plutonium tasks, especially in terms of worker safety.

The motive for this approach is unknown. Are project managers being rewarded for cutting short-term project costs, without optimal regard for long-term worker safety? If so, have project planners forgotten one lesson learned from the failed Pu/MOX project—that the accumulation of small cost-cutting measures contributed to that managerial boondoggle ?

Or is the NNSA seeking to push the envelope of its own modern standards, which were developed long after the closure of Rocky Flats? Is the brushing aside of Defense Board concerns a sign that the agency is nostalgically looking backwards towards the era of minimal to zero oversight and lower standards, in order to reconstitute its most difficult nuclear warhead production task?

In either case, the existing reliance upon human senses to prevent accidents suggests that DOE/NNSA might be well advised to subject pit manufacturing recruits to testing for the presence of a sixth sense.

Footnotes and References:

(1) The nuclear explosive “trigger” is initiated by a power high-explosive blast that implodes a plutonium pit and the sub-critical plutonium hemisphere within. The primary blast generally involves an infusion of tritium gas, generally about four grams, that greatly boosts the power of the plutonium explosion—thus the name “hydrogen bomb.” 

Together the explosion triggers a larger “secondary” explosion of highly enriched uranium found in parts called “canned subassemblies. The catastrophic impacts of a nuclear explosive using only plutonium, and prior to the introduction of tritium gas, can be found in the Nagasaki, Japan historical record following the explosion of a nuclear explosive with a 20 kiloton yield (TNT equivalent). 

(2) In the surplus plutonium process, the processing ends at this point of conversion to oxice. Theplutonium oxide powder is transferred to a “dilution” line where it is mixed with inert materials to create a more stable waste form.  Information regarding this process can be found in Offsite Insights 2022:1.

(3) Plutonium pit recycling at Rocky Flats involved the following steps and processes:

ü Pit disassembly with lathes or other machine shop technology

ü Aqueous processing in which nitric acid, other solvents, and water are used to dissolve the metal, followed by either solvent extraction or ion exchange to separate the plutonium. This was probably necessary only for bonded pit types (as well as metal and oxide scrap material), which might account for references to although references to dissolution of pits;#

ü Molten Salt Extraction (MSE) to remove the Americium-241 ingrowth, described by the GAO in 1992 as “mixing the metal with a combination of salts, such as sodium chloride, potassium chloride, magnesium chloride, or calcium chloride.

This mixture is put into a crucible and heated in a furnace until the mixture of salts and metals becomes molten. While the molten mixture is being stirred, the americium reacts to the salts to form americium chloride. Then the plutonium metal, with the americium removed, settles to the bottom of the crucible. After cooling and removal from the surface, the crucible is broken to remove the contents.

The plutonium metal is then separated from the hardened salts, which now contain the americium chloride and some residual plutonium. The leftover salts and the used crucible are saved and stored so that the plutonium can be recovered” from the plutonium chloride mix.

ü Electro refining was also used to purify plutonium metal, although generally applied to scrap material and not relatively clean pit material. Electro refining uses a controlled electrical current in a salt mixture similar to Molten Salt Extraction, and involves similar equipment, and future plutonium chloride recovery .

ü Direct oxide reduction can be used to convert pure plutonium oxide powder to a metal.

(4) DOE Standard 1186-2016 states:

1.6 SELECTION AND HIERARCHY OF CONTROLS

Preventive or mitigative controls are selected using a judgment-based process that applies hierarchy of control preferences. DOE has established a control selection strategy based on a hierarchy of controls. DOE O 420.1C, Attachment 2, Chapter I, Section 3(b)(4)(d) requires that new nuclear facilities and major modifications to existing nuclear facilities be designed to “provide controls consistent with the hierarchy described in DOE-STD-1189-2008.” The second principle of DOE-STD-1189-2008 “Safety Design Guiding Principles” presents this hierarchy, which was subsequently clarified in DOE-STD-3009-2014.
Following efforts to minimize hazardous materials, this control selection strategy translates into the following hierarchy of controls, listed from most preferred to least preferred.

(1) SSCs that are preventive and passive

(2) SSCs that are preventive and active1

(3) SSCs that are mitigative and passive

(4) SSCs that are mitigative and active

(5) Administrative controls that are preventive

(6) Administrative controls that are mitigative

(SSC = Safety Significant Controls)

References:

Burning and Extinguishing Characteristics of Plutonium Metal Fires. R.E. Felt. 1967. An interesting look at the slow burn of plutonium metal.

Plutonium in Pits. Blue Ridge Environmental Defense League. 2001. A review of pit storage, classification, and process hazards.

Plutonium. An Introduction. R.H. Condit. 1994. A full review of properties, chemistry, complexity, metallurgy, applications, and toxicity.

Excess Plutonium Disposition: The Failure of MOX and the Promise of Its Alternatives,. Edwin S. Lyman December 2014, Union of Concerned Scientists. The definitive work of the rise and fall of the Pu/MOX project.

Does America Need a New Nuclear Bomb Plant. BREDL. 2003.