On December 6, 1995, a Los Alamos occurrence investigator and an assistant DOE facility representative noticed that several magnehelic gages on gloveboxes in Plutonium Processing Facility TA-55 were pegged at -1.0 inch negative pressure, which is greater than the -0.6 inch specified in the Operational Safety Requirements (OSRs). They informed the facility manager who confirmed that the pressures had been changed without proper review and approval and were in violation of the OSRs. (ORPS Report ALO-LA-LANL-TA55-1995-0060)

Actinide Ceramics and Fabrication operators had requested the increase to the negative pressure for several gloveboxes containing fine Pu-238 oxide particles. The intent of the change was to improve Pu-238 confinement by minimizing migration of the particles during window and glove changes. The operators are aware of the OSR requirements, but they do not know all the specific parameters under OSR jurisdiction. A facilities management engineer who had responsibility for ensuring compliance with the OSRs granted approval for the increase. However, he gave the approval without verifying that the change would not violate OSRs and without submitting the change to the Configuration Change Team for a safety evaluation. Either review would have identified the violation and triggered an unreviewed safety question determination that would have properly evaluated the change.

Operators immediately returned the glovebox pressure to the required -0.6 inches. Safety engineers are performing an unreviewed safety question determination to evaluate the safety significance of the glovebox pressure change. Of particular concern is that the gages were pegged at -1.0 inches and they do not know how negative the pressure in the gloveboxes became.

An occurrence investigator reported that similar pressure changes had been made in past years before the recent emphasis on compliance with the OSRs and other safety authorization basis documents. These past practices may have contributed to the belief that the change was acceptable. In addition, the OSR did not provide a range of acceptable pressures, only the - 0.6-inch number, making it difficult to comply with and open to interpretation. This lack of clarity in the OSRs could have contributed to a belief that, because negative pressure provides glovebox confinement, a greater negative pressure is acceptable.

NFS has described numerous events involving non-compliance with OSRs in Weekly Summaries. This event is a reminder of two key lessons learned related to OSR compliance. First, OSR compliance should be an integral part of the conduct-of- operations program. OSR-related parameters should be clearly identified and administrative controls, including formal procedures, should exist to prevent these parameters from being changed without specified review, approval, and control. Failure to do so can result in operation outside the authorized safety basis.

In addition, OSRs and Technical Safety Requirements (TSRs) should be written such that they provide clear guidance that does not allow too much room for interpretation. There have been many events at DOE facilities that occurred because lack of clarity resulted in an incorrect interpretation leading to violations of the facility safety basis. DOE Order 5480.22, Technical Safety Requirements, states that "TSRs should be written in a clear and concise manner, in language that is directed at and clearly understandable by those in the facility operating organization." Operations and facility managers should consider reviewing past events at their facilities to determine if failure to provide clear guidance in OSRs has contributed to violations and, if so, improve their OSRs accordingly. Reviewing corrective actions documented in related occurrence reports from other DOE facilities may also help identify improvements in OSR compliance.