By George Lobsenz
A federal safety oversight board has questioned “non-conservative” Energy Department estimates of potential offsite radiation doses from accidents at the Y-12 plant, saying they may lead to “less than adequate protection of the public and workers” at the Tennessee uranium and warhead components facility.
The Defense Nuclear Facilities Safety Board (DNFSB), an independent federal agency that monitors safety at DoE nuclear weapons sites, said site officials used analytical methods that inappropriately understated potential radiation doses from fires involving uranium metal stored in Y-12’s 9212 complex.
The board expressed concern that such understated dose estimates might be used to justify less robust safety systems at the 9212 complex, a 60-year-old structure considered susceptible to fires and earthquake damage and holding significant amounts of combustible and radioactive materials.
Further, the DNFSB said that while Y-12 officials had previously committed to resolving the board’s concerns about the offsite dose estimates, that had not occurred in the most recent safety analyses done for the 9212 complex, which the board said remained deficient.
“These inadequacies included nonconservative approaches for estimating off-site dose consequences resulting from design-basis accidents that led to a less than adequate set of safety-class controls,” the DNFSB said in a Jan. 17 letter to Thomas D’Agostino, head of the National Nuclear Security Administration (NNSA), the semi-autonomous DoE agency that runs the department’s nuclear weapons complex.
“The board expected these non-conservative methodology issues to be fully resolved during subsequent updates to the documented safety analysis (DSA) at Y-12. However, recent activities related to the preparation of preliminary DSAs for new facilities at the site, as well as the annual update of the DSA for the 9212 complex, indicate that the methodology issues identified by the board in 2006 have not been resolved and may lead to improper classification of safety systems and less than adequate protection of the public and workers.”
The board’s letter follows repeated DNFSB warnings to NNSA and Babcock & Wilcox Technical Services Y-12 LLC, which operates Y-12 for NNSA, that the aging 9212 complex lacks adequate fire protection systems and structural support.
And that is of major concern, the safety board told NNSA in a March 2007 letter, because Y-12 may need to continue operating the 9212 complex for another 15 years to carry out its weapons missions while NNSA builds a new Uranium Processing Facility (UPF) at Y-12, which is located at Oak Ridge.
The safety issues–in conjunction with the need to continue operating the 9212 complex–are problematic for NNSA because the agency does not want to spend big dollars installing new safety systems at the 9212 complex.
The understated offsite dose estimates cited by the DNFSB in its letter last month are important because they could enable NNSA to avoid installation of expensive new safety equipment. Specifically, NNSA could point to the understated dose projections to claim that the offsite consequence of an accident at the 9212 complex would be adequately mitigated by existing emissions controls at the facility.
The DNFSB has been pushing for better safety at the 9212 complex for several years. In a March 13, 2007, letter to NNSA, the board warned that continued operations at the facility “involve significant risks to workers and the public.” The board pointed to “numerous structural deficiencies” and other deteriorating equipment, as evidenced by a February 2007 leak of acid containing high-enriched uranium through degraded seals on storage vessels.
In the March 2007 letter, the board noted that previous warnings about the 9212 complex prompted NNSA to remove uranium solutions, powder and metal from the building in an effort to reduce accident risks.
In the same letter, the DNFSB also agreed with NNSA that expensive safety equipment upgrades at the 9212 complex would be “impractical” given the limited remaining operating life of the building.
However, the board said that “increased vigilance” on safety issues might not be enough to assure adequate protection of workers and the public assuming the 9212 complex must continue operating for another 15 years until the new Uranium Processing Facility is complete.
“The board remains concerned that the 9212 complex may reach a point in the near future where adequate safety cannot be assured without significant investments to upgrade safety systems,” the DNFSB concluded in its March 2007 letter.
In its follow-up letter last month, the safety board suggested NNSA was improperly limiting safety analyses to exclude data that would raise offsite dose estimates from potential accidents at the 9212 complex.
Specifically, the DNFSB said NNSA excluded data from outdoor burn tests that show greater emissions from uranium fires with temperatures exceeding 600 degrees Centigrade. By excluding that data, the board said, Y-12 officials improperly reduced projected “airborne release fractions,” or so-called ARF values, in potential accident scenarios at the 9212 complex.
The safety analysis done by Y-12 “uses only results from the constant temperature laboratory testing…and thereby arrives at reduced values for ARF,” the board said.
“It is not appropriate to exclude data from these [outdoor burn] tests in determining the ARF value to be used in evaluating the unmitigated consequences of a…facility fire scenario” for determination of whether safety systems needed to upgraded at the 9212 complex, the board said.
The DNFSB has raised similar concerns about safety analyses done by Y-12 officials for the new Uranium Processing Facility to be built at the site.
The board said Y-12 officials recently agreed to review the DNFSB’s complaints about the safety analyses and report back to the board within 90 days of receiving the Jan. 17 letter.
Y-12 officials had no comment on the board’s letter.