Challenges remain for completing a system to deliver and feed radioactive waste to the Hanford vitrification plant, according to an audit released Tuesday by the Department of Energy Office of Inspector General.
But overall, DOE has made progress in completing the system that will allow the vitrification plant now under construction to eventually begin operating, the audit concluded.
"We found the department completed a number of waste feed delivery sub-projects earlier than planned and was on track to complete other critical path activities," the audit concluded.
The $12.2 billion vitrification plant is planned to turn up to 56 million gallons of radioactive and hazardous chemical waste now held in underground tanks into a stable glass form for disposal. The waste is left from the past production of plutonium for the nation's weapons program.
The waste will be staged at double shell tanks nearest the vitrification plant that will serve as feeder tanks. There, the waste will be mixed to make sure that it can be delivered in consistent batches and then piped to the vitrification plant's Pretreatment Facility. The waste will be sampled in the transfer lines.
However, the criteria the waste must meet to be treated in the plant have yet to be set, and uncertainties with tank waste mixing and sampling also could affect the delivery of the waste to the vitrification plant, the audit said.
"The department was aware of these problems and told us that it had plans and strategies in place to mitigate the associated risks," the audit said.
DOE has committed to having waste acceptance criteria set in 2015 as part of its plan to address Defense Nuclear Facilities Safety Board concerns about keeping waste adequately mixed in the plant. The mixing issue is related to the waste that is accepted for treatment.
Certain waste could present a small risk of a criticality if it is not kept well mixed within the plant and plutonium settles out and builds up at the bottom on the plant's tanks. In addition, the defense board has been concerned that potentially flammable gases could build up.
While continued testing of the vitrification plant mixing systems is being done, separate tests also are being conducted to make sure waste can be well mixed in the feeder tanks to keep all particles in suspension. Current feeder tank testing is focused on how large particles can be without affecting work to keep them mixed, transfer them and sample them.
Washington River Protection Solutions, the DOE tank farm contractor, told DOE it will have enough time to formulate the waste to meet waste acceptance criteria for the vitrification plant if the criteria are finalized by 2015.
To DOE's credit, it has formed a Waste Feed Technical Resolution Team with members from DOE, the tank farm contractor and the vitrification plant contractor to resolve process issues and challenges that could affect the vit plant, the audit said.
In addition, Energy Secretary Steven Chu is expected to spend much of the next week in the Tri-Cities with a team of high-level experts resolving potential issues with the plant's "black cells," enclosed rooms holding tanks and piping that will be too radioactive for workers to enter for maintenance and repair.
Work on preparing the waste feed delivery system made significant progress with Recovery Act federal economic development money available through last fall, the audit said. Many of the upgrades completed were done sooner than planned because of the additional money.
But despite that progress, DOE is behind schedule on purchasing mixer pumps that can be submerged in the feeder tanks to mix the waste, the audit said.
Purchases were held up by erosion and corrosion testing that has since been finished. However, now a lack of money is delaying the purchase of mixer pumps until the fiscal year that starts in October, the audit said.
Delivery mixing and sampling also are behind schedule and over budget, the audit said. A new requirement to increase ventilation system safety at the tank farms has delayed the work for about a year, according to the audit.
However, DOE senior management believes all work will be completed in time to deliver the waste to the vitrification plant when it is legally required to start operating at the end of 2019, according to the audit.
The audit recommended that Hanford officials closely monitor the waste acceptance criteria, the purchase of in-tank mixer pumps and the cost and schedule of work.
DOE appreciates the recommendations and is continuing to work with the defense board and DOE contractors to develop testing programs to further refine waste acceptance criteria, DOE said in a statement.
"Tests are being conducted to further develop this criteria and ensure safe operations," it said.
-- Annette Cary: 582-1533; email@example.com