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"Forget the Rest" blog

Embargoed until 6 pm Tuesday, October 9, 2007

Los Alamos Plutonium Work Halted to Resolve
Uncertainties over Nuclear Criticality Safety

Federal inspectors repeatedly cite nuclear safety program failings,
Failure to meet nuclear industry or Energy Dept. standards

Halting operations “right thing to do” for safety, group says

Needless warhead core (“pit”) production among roots of problem

Albuquerque – In late September, most plutonium operations at the main plutonium facility at Los Alamos National Laboratory (LANL) were halted due to uncertainties concerning the safety margin of the plutonium storage vault with respect to self-sustaining nuclear chain reactions or “criticality events.” 

The facility in question is Building PF-4, the main building at LANL’s Technical Area (TA)-55.  The building is often just called “TA-55.” 

Criticality events at LANL in 1945, 1946, and 1958 each killed one person.  For background and convenience we have posted a classic reference on historic criticality events worldwide at

The potential consequences of nuclear chain reaction(s) in LANL’s main plutonium storage vault are not clear but would, at a minimum, be very serious. 

The degree to which PF-4 can passively plutonium in the event of accident, and the need to maintain active confinement during accidents, have been strongly contested issues for the last few years between federal officials and the laboratory, as records of the independent Defense Nuclear Facility Safety Board (DNFSB) show.

Repeated calls to the LANL contractor (LANS) public affairs office to provide more information regarding the current shutdown and the criticality concerns underlying it have not resulted in return phone calls, let alone additional information. 

Based on conversations with federal officials, the basic facts of the situation appear to be as follows.  Sometime within the last two and half weeks, the contractor LANS (which operates LANL) and/or the National Nuclear Security Administration (NNSA) (which owns and oversees LANL), suspended all fissile materials operations at TA-55 except for relatively minor operations conducted for the purpose of bringing selected operations into a safer shutdown condition.  Examples of work still being done include moving plutonium from furnaces and stabilizing plutonium solutions. 

This suspension was ordered for two reasons: 1) a recalculation of criticality margins – the margin of safety against runaway nuclear reactions – in 4 vault rooms revealed that these margins were less than previously thought, and 2) the criticality safety margins that would remain during certain “credible upset” conditions were unknown. 

These particular criticality safety issues appear to have been previously unknown and unpredicted.  Both LANL and NNSA have claimed to adequately understand criticality issues at LANL, a stance which is also implied by their decision to continue operations despite approximately 300 deficiencies in the LANL criticality safety program. 

For both reasons mentioned, vault operations were shut down, which led to the decision to halt TA-55 plutonium operations as a whole.  Work involving plutonium-238 is not suspended. 

According to the DNFSB, 

The roughly 20 existing criticality safety evaluations (CSEs) for the TA-55 vault are convoluted, occasionally contradictory, and heavily reliant on expert judgment; these are among about 300 CSEs that LANL has identified as missing, technically deficient, or having some other problem that LANL has committed to address during the next few years. (Weekly Site Report, August 31, 2007)

These known program deficiencies date from an October 2005 NNSA review, which revealed the LANL criticality safety program did not meet nuclear industry or DOE standards in 14 key respects.[1]  LANL then (slowly) initiated a corrective action process – which DNFSB say may have declined in institutional priority in the same time-frame that LANS assumed full responsibility for site operations:

Criticality safety is one of the LANL safety programs for which NNSA and LANL's intentions are unclear and the priority may be falling…LANL is falling behind on its criticality safety improvement plan, intended to bring the LANL program into compliance with the standards; the schedule is undefined…on-site criticality staff is about half that estimated just to sustain the status quo and a quarter of that estimated to drive the improvement plan to completion in FY-07. The NNSA Site Office still lacks full-time federal expertise to provide oversight of the program. While these issues persist, NNSA and LANL are accepting higher risk than would be accepted in nuclear industry practice.[2] 

Criticality safety concerns are tightly connected with other pressing nuclear safety concerns at LANL.  These include serious deficiencies in training, management, oversight, a chronic lack of follow-through after safety problems become known, chronic informality of operations, lack of approved, up-to-date safety plans for major facilities, production pressures, and many other problems.  A full accounting of all these safety problems is far beyond the scope of this press advisory.  A chronological history of DNFSB’s criticality safety concerns at LANL, together with a partial outline of these related pertinent safety issues, can be found at  The Study previously attempted to summarize the sweep of nuclear safety issues at LANL in February of this year. [3]  Concerns about declining federal oversight have been provided to the DNFSB twice in formal Study Group testimony.[4]  

A previously-planned TA-55 shutdown was to begin on November 5 and last until the end of the annual lab-wide winter shutdown, which usually ends on the Monday following January 1.  It is possible the current shutdown could grade into the previously planned shutdown.

According to Study Group director Greg Mello, “Even before these latest problems, the increasing number and gravity of safety issues documented by the DNFSB and NNSA over the past few years, and over the past 14 months especially, were of great concern.  These new concerns regarding criticality “unknowns” began to surface two months ago.  I believe, coming as they do on top of all the rest, they have made the need for a shutdown very clear.  Halting plutonium work is now the right thing to do from any perspective, regardless of anyone’s views about the purpose of or need for that work in the first place. 

“Unfortunately, the timing of the halt is suspicious.  It almost looks like LANL pushed past well-documented safety concerns all year to get pit production started and only halted production at the very end of the fiscal year, after its pit production milestones were met, having worked around the clock for months, with hundreds of safety issues unresolved in the meantime.

“Why the pressure to produce more pits?  And why it is acceptable to carry safety deficiencies for years, unresolved?  Are the Executive Branch and Congress failing in governance here, having outsourced a full 96% of the U.S. nuclear weapons program to a handful of politically-connected contractors?[5] 

“No one has ever offered a coherent explanation as to why it is necessary to restart U.S. nuclear warhead production after 19 years, which is what this day-and-night campaign is all about.  Adding to the U.S. arsenal of 24,000 pits has national security costs, not benefits, and many other kinds of costs – including, as we see in this instance, safety concerns.” 


1. Cited in report, “Nuclear Criticality Safety at Los Alamos National Laboratory,” 9/6/06, attached to letter from DNFSB to NNSA, 9/22/06, quoted in full at

2. DNFSB weekly site report, 8/4/06.

3. “Informal pit production talking points, Feb 24, 2007,” at

4. See for example “Declining Federal Oversight at Los Alamos, Increasing Production Incentives: A Dangerous Divergence,” Mar 22, 2006, at

5. Los Alamos Study Group, “Competition - or Collusion? Privatization and Crony Capitalism in the Nuclear Weapons Complex: Some Questions from New Mexico,”

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