Examples of flanged tritium waste containers. Courtesy photo
BY MAIRE O’NEILL
Los Alamos National Laboratory has notified the Environmental Protection Agency that plans for venting four flanged tritium waste containers (FTWCs) at Technical Area 54 have been finalized with an amended scope of work. However, according to NNSA Los Alamos Field Office spokesperson Toni Chiri, the operations, originally slated for this month, have been postponed due to COVID -19 and won’t be executed until the Laboratory is able to support the activity with a full complement of operational personnel.
“FTWCs are stored in a safe and compliant manner at TA-54 and do not represent a risk to the public or the environment,” Chiri said.
A letter to EPA from LANL, which is dated March 3 but was only released on the electronic reading room Friday morning, says the project has now determined that each FTWC may be vented multiple times, if necessary and these venting activities may take place at more than one location.
“The original application only discussed a single venting operation for each FTWC at a single location, TA-54. However, the radionuclide inventory and expected air releases remain bounded by the values described in the Application,” the letter signed by Group Leader Taunia Van Valkenburg states.
In the original process approved by the EPA in May 2019, the described process flow involved venting one FTWC at a time, moving each FTWC out of TA-54 Building 1028 immediately after it was vented and transporting them to the Weapons Engineering Tritium Facility for final disposition, however it is now possible that secondary venting may be required on one or more of the FTWCs.
“All four FTWCs will be vented at Building 1028 prior to any of the FTWCs being moved to WETF. This venting process is currently estimated to take at least one workday for each FTWC. At the end of each FTWC venting, the drum will be evacuated to a slight negative pressure (about one-third of an atmosphere). After all four FTWCs are vented, they will be moved, one at a time, to WETF,” the letter states. “Prior to any FTWC being moved, the pressure in each FTWC in Building 1028 must meet certain criteria, indicating that no releases have occurred from FTWC internal components since the last venting. If the FTWC does not meet the established criteria, it will be vented again to ensure all drums have minimal tritium inventory in the headspace gas.”
The plan indicates that if the pressure of a drum is observed at any of various checkpoints to have risen above established levels, it will be vented again before subsequent moves are made.
The letter states that the majority of the tritium in the FTWCs is adsorbed (forms a thin film) onto high-surface area material, molecular sieve or “getter beds.”
“Most of this adsorbing material is held inside containers called AL-Mls, which were welded shut at the time of placement within the FTWC. As the tritium inside the AL-Ml decays, the pressure inside these sealed vessels will increase. If the welds on the AL-Ml fail, the vessel may leak tritium into the FTWC headspace. Additional adsorbing media and tritium contaminated material was placed into bags or into smaller sealed cans called ‘paint cans’ inside the FTWCs. These additional containers may also have leaked tritium into the FTWC headspace,” the letter notes.
The original plan was to release the tritium currently in the FTWCs headspace up to this point which is still the plan. This will “relieve pressure within the drums and mitigate the potentially hazardous hydrogen mixture within”.
“However LANL safety analyses have raised concerns that movement of the FTWC after initial venting – during handling, loading onto the transport vehicle, or transportation – may jostle the inner containers and cause additional leaks from the inner containers. Such leaks may cause another buildup of tritium into the FTWC headspace, replicating the potentially hazardous situation that the venting is intended to alleviate,” the letter states.
New leaks from the FTWCs will be measured and if operators notice that pressure is again building up inside the FTWCs above established thresholds, the container will go through the venting process again. This secondary venting will take place at whatever point it is discovered which could be at any of the following locations
- within Building 1028;
- the parking lot outside of Building 1028;
- on the transport truck at TA-54, prior to departure;
- on the transport truck at TA-16, after arrival;
- at the receiving facility at TA-16, outside WETF
These secondary venting operations will have a nearly identical setup to the initial venting and will occur only if the pressure inside the FTWC increases sufficiently to indicate that an inner container has leaked.
Once the FTWCs are inside LANL’s Weapons Engineering Tritium Facility (WETF) at TA-16, they will be managed as other tritium containers in that facility and part of routine operations at WETF. Any emissions from further handling or repackaging will be measured by the WETF monitored stack.
“Since the emissions and off-site dose calculations in our May 2019 Application addressed the entire inventory of tritium in these FTWCs, those estimates remain conservative upper bounds. Tritium that is emitted during secondary venting represents material that was not emitted during the initial venting operations,” the letter states.
It adds that emissions estimates in the original application remain bounding, however, the offsite dose received by a member of the public can change depending on the location of the venting operation and the meteorological conditions during the venting.
The procedure presented to EPA indicates that when tritium emissions reach 3 mrems or 11,300 curies, the venting would be a pause for evaluation. At 6 mrems or 22,500 curies, there would be a pause for evaluation. A “hard stop” would be implemented a 8 mrems or 22,000 curies and venting would cease for the year.
Several New Mexico groups have demanded a halt to the venting plans including Nuclear Watch New Mexico, Concerned Citizens for Nuclear Safety, the All Pueblo Council of Governors and Tewa Women United.