Final Report
On November 10, 1992, Argonne National Laboratory East (ANLE) personnel conducted a radiological control assessment of eight plutonium-handling facilities at the New Brunswick Laboratory. The assessment was performed in response to an event at Lawrence Livermore National Laboratory (LLNL) regarding the integrity of welds on exhaust duct work in plutonium laboratories (ORPS Reports SAN--LLNL-LLNL-1992-0098, CH--NBL-NBL-1992-0002). LLNL personnel had discovered cracking and evidence of corrosion around chemical operations ventilation exhaust ducts and welds. Investigation was continuing at LLNL. ANLE personnel conducted comprehensive radiation surveys of the exhaust duct work at New Brunswick Laboratory and completed them on December 2, 1993. Personnel planned to perform non-destructive evaluation (NDE) of the duct welds found to be contaminated, and a DOE Chicago Field Office ad hoc group was formed to define the evaluation specifications.
Laboratories 143, 151, and 159 had detectable fixed and smearable plutonium levels on duct welds in excess of limits specified in Table 2-4 of the Radiological Control Manual in areas not appropriately posted in accordance with Articles 235 and 236 of the Manual. Investigators evaluated the cause (pending the final results) to be poor quality of original welds and poor quality control/quality assurance of the facility acceptance process.
On June 26, 1993, personnel at the Savannah River HB-Line plutonium processing and handling facility discovered a crack in a vertical weld of an exhaust duct above a glovebox exhaust fan. Investigators determined that the weld was a partial penetration weld that had failed as a result of fatigue arising from duct work vibration. Examiners discovered that facility drawings and specifications required butt welds (full penetration welds) and later concluded that incorrect visual inspection standards were used to inspect welds during the initial fabrication and installation of ducts. (ORPS Report SR--WSRC-HBLINE-1993-0016)
ONS described preliminary findings of these events as well as several others involving corrosion and cracking in ventilation systems at other DOE facilities in OE Weekly Summaries 92-26, 93-26 and 93-44. These events emphasize the need for personnel at DOE facilities to be aware of the potential for cracking or corrosion in aging ventilation systems. Undetected cracking or corrosion in such systems could result in the loss of system integrity and breakdown of physical barriers designed to protect the public, plant personnel, and the environment from hazardous radioactive materials.
In addition, personnel at DOE facilities should be aware that certain critical areas of ventilation systems (welds, transition joints, or seams) are more prone to cracking or corrosion and could potentially deteriorate well before the expected lifetime of the ventilation system. In some cases, weld inspection practices and standards used during the initial installation of ventilation ducting were less than adequate when measured against current requirements, resulting in accelerated deterioration of the physical barrier of the ventilation system. Personnel at DOE facilities should establish periodic inspection requirements to ensure that a loss of the system physical barrier does not remain undetected for long periods of time, raising the potential for release of radioactive materials. Facility personnel should also consider the following recommended corrective actions:
Assessment of quality assurance programs to determine program adequacy and full implementation, including vendor (if the ducts were fabricated) and installation quality assurance programs.
Assessment of the need to reconcile as-built ducts with design specifications, including resolution of deviations or findings during installation.
ONS is developing a Safety Notice to provide additional information on this topic.