Saturday, July 14, 2012
DNFSB Disagrees with NNSA Analysis
In December 2008, the National Nuclear Security Administration (NNSA) undertook the first major update to Los Alamos National Laboratory's plutonium facility (PF-4) safety basis since 1996. During this update, analysis revealed that a seismically induced fire at PF-4 could credibly lead to an offsite radiation dose to the general public of > 2000 rem. [This is a near-fatal radiation dose. See my blogposts of Nov. 24, 2011 "Accidental Fall-out from LANL", and Nov. 18, 2011 "DNFSB Criticizes LANL's Risky Practices."]
Because of this predicted, albeit improbable, very large offsite radiation release, the Defense Nuclear Facilities Safety Board issued Recommendation 2009-2, "Los Alamos National Laboratory Plutonium Facility Seismic Safety." In this Recommendation, DNFSB urged NNSA to execute immediate and long-term actions to reduce the risk posed by a seismic event at PF-4. This Recommendation is still open. See (http://www.dnfsb.gov/sites/default/files/Board Activities/Recommendations/rec_2009-2_32.pdf.) Related to this is Recommendation 2010-1 "Safety Analysis Requirements for Defining Adequate Protection for the Public and the Workers", which is also still open.
NNSA responded to DNFSB Recommendation 2009-2 with a variety of corrective measures [see below], and now claims that the concerns of DNFSB have all been satisfied. But, DNFSB disagrees.
In a letter from DNFSB Chairman Peter Winokur to NNSA Chief Administrator Tom D'Agostino, dated June 18, 2012, the Board expressed its disagreement with the recent claims made by NNSA regarding the maximum credible radiation release from LANL's PF-4 plutonium facility, following a seismically induced fire burning over and through the facility. See http://www.dnfsb.gov/board-activities/reports/staff-issue-reports/documented-safety-analysis-and-post-seismic-accident-co.
NNSA claims that 23 rem is now the maximum credible dose to the general public, in such an event; i.e., at the site boundary. DNFSB disagrees, claiming instead that the maximum credible dose at the site boundary is > 100 rem. Currently, DOE sets 25 rem as the maximum allowable dose to the general public, in the event of a major accident at a nuclear weapons facility.
According to DNFSB Chairman Winokur:
"The Defense Nuclear Facilities Safety Board (Board) has reviewed the approved safety basis for the Plutonium Facility (PF-4) at Los Alamos National Laboratory (LANL) and concludes that for one accident the mitigated dose consequences to the public exceeds 100 rem total effective dose equivalent (TEDE), which would require additional safety controls for the facility. The Board's analysis differs from Revision 1 of the 2011 Documented Safety Analysis(DSA) by LANL that presents a mitigated offsite dose of 23 rem TEDE. A detailed review by the Board's staff identified a number of deficiencies in the technical basis that supports the 2011DSA, including concerns with the quality review process for documents and analyses."
"The Board issued Recommendation 2009-2, Los Alamos National Laboratory Plutonium Facility Seismic Safety, on October 26, 2009, to address the potential consequences associated with seismically-induced events at PF-4 and requested that the Department of Energy develop and implement an acceptable seismic safety strategy. The mitigated consequences associated with the seismically-induced fire scenario were two orders of magnitude higher than the Department of Energy evaluation guideline of 25 rem TEDE; i.e., >2000 rem. Subsequently, the National Nuclear Security Administration (NNSA) and LANL personnel implemented near-term compensatory measures to reduce seismic risk, identified and implemented new safety controls, completed a series of physical upgrades to the PF-4 building structure, and developed a long term plan to seismically upgrade the ventilation and fire suppression systems."
"Laboratory personnel also refined the analysis of the seismically-induced fire scenario to support the 2011 DSA that was approved by the NNSA's Los Alamos Site Office (LASO) in October 2011 and is in the process of being implemented. The Board's staff identified multiple, substantial deficiencies of a non-conservative nature in this refined analysis, specifically with the technical basis for selection of key input parameters, analytical assumptions, and methodologies. The Board's estimate of this accident's mitigated dose consequence in excess of 100 rem TEDE accounts for conservatism in the leak path factor and respirable fraction for one material. Additional use of appropriately conservative parameters would further increase the dose consequence for this postulated accident. The staff also identified issues with the quality assurance process that was applied to documents and analyses that support the DSA. In particular, key DSA input documents were not independently reviewed as required by laboratory procedures. The Board has discussed many of these issues with NNSA in its review of previous DSA revisions."
"Contractor development and submission of high quality DSA documents in accordance with Title 10 Code of Federal Regulations Part 830, Nuclear Safety Management; and thorough and critical review by NNSA, are fundamental elements for ensuring safe operations at defense nuclear facilities. The issues identified above and in the enclosed report require prompt action by NNSA. Therefore, pursuant to 42 U.S.C. § 2286b(d), the Board requests a briefing and report, within 30 days of the receipt of this letter, which contain the following:"
"1. NNSA plans for providing a sound and technically justifiable Safety Basis that includes correction of the non-conservative deficiencies identified in the enclosed report."
"2. Necessary actions to ensure that quality assurance requirements are adequately implemented at LANL for Safety Basis development."
"3. NNSA actions to ensure Safety Basis review and approval processes are performed with sufficient rigor to prevent technically deficient Safety Bases from being approved."
"In response to the Board's Recommendation 2009-2, NNSA and LANL personnel: (1) executed a series of near-term compensatory measures designed to reduce the risk of a seismically induced fire at PF-4; (2) identified a number of new safety-class engineered controls, including seismic cutoff switches for electrical power, seismically qualified material storage safes, and fire-rated material storage containers; and (3) developed a Project Execution Plan for longer-term upgrades to enable the confinement ventilation and fire suppression systems to perform safety class functions following a Performance Category (PC)-3 seismic event."
"In addition to physically upgrading the building structure and implementing new safety class engineered controls, laboratory personnel completely reanalyzed the seismically-induced fire scenario in the 2011 DSA. The new analysis in the 2011 DSA concludes that the mitigated offsite dose consequence for the seismically-induced fire scenario is 23 rem TEDE, which is less than the Department of Energy (DOE) Evaluation Guideline of 25 rem TEDE. This analyzed offsite dose consequence is two orders of magnitude lower than the mitigated offsite dose consequence calculated by the 2008 DSA. The roughly 100-fold decrease results from changes to four accident analysis parameters: the quantity of material at risk, airborne release fractions, respirable fractions, and leak path factor (LPF). Revision 1.0 of the 2011 DSA was approved by LASO on October 13, 2011, and the DSA and its associated technical safety requirements (TSR) are currently scheduled to be implemented by June 25, 2012."