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Progress made to resolve Hanford vit plant technical issues

The inside of the test vessel contains six pulse jet mixers used to keep the solids suspended in the simulated radioactive waste. The pulse jet mixers draw in waste and expel it, similar in operation to a turkey baster. This set of tests is to verify the control mechanism for mixer operations.
The inside of the test vessel contains six pulse jet mixers used to keep the solids suspended in the simulated radioactive waste. The pulse jet mixers draw in waste and expel it, similar in operation to a turkey baster. This set of tests is to verify the control mechanism for mixer operations. Courtesy Bechtel National

Progress is being made to resolve the technical issues that have stopped some construction at the Hanford vitrification plant since 2012.

The Department of Energy and its contractor, Bechtel National, announced on Tuesday that full-scale testing has begun to make sure certain tanks within the vit plant can keep high-level radioactive waste well-mixed.

It is a key issue among eight technical problems that must be resolved before construction on parts of the vitrification plant that will handle high-level radioactive waste can be completed.

Three of the other technical issues were expected to be essentially resolved by the end of 2016, said Kevin Smith, manager of the DOE Hanford Office of River Protection, at a Hanford Advisory Board meeting earlier this month,

He expected to send letters by this week on each of the three issues to DOE headquarters for official review and then to the Defense Nuclear Facilities Safety Board.

The three letters will cover developing safety strategies for the possible combustion of hydrogen if it builds up in the head space of vit plant tanks, the same issue in piping, and the buildup of plutonium particles that could create a small risk of an unplanned nuclear reaction in the plant.

A division of EnergySolutions, which has since been acquired by Atkins, built a laboratory at Washington State University Tri-Cities to resolve the fourth issue — keeping high-level radioactive waste well-mixed within tanks after it is transferred to the vit plant. The company donated the lab to the university in 2012, with a plan to lease it back until testing is completed.

This represents substantial progress and will lead to restarting engineering, procurement and construction on the Pretreatment Facility.

Bill Hamel, DOE assistant manager for the vit plant

Full-scale testing of certain tanks within the vitrification plant was ordered by former Energy Secretary Steven Chu, after he spent several days at Hanford with a team of experts in 2012 to evaluate potential risks.

The plant is being built to turn radioactive waste from the past production of weapons plutonium into a stable glass form for disposal. Although construction is stopped on parts of the plant that will handle high-level radioactive waste, building continues on parts of the plant that will handle low-activity radioactive waste.

The third and final phase of testing of the control equipment and systems designed to safely mix waste in tanks at the vit plant’s Pretreatment Facility began using a full scale tank late last week at the Atkins Engineering Laboratory at WSU Tri-Cities, according to Bechtel.

The Pretreatment Facility tanks will store and process radioactive waste before it is glassified at other vit plant facilities.

“This represents substantial progress and will lead to restarting engineering, procurement and construction on the Pretreatment Facility,” said Bill Hamel, DOE assistant manager for the vitrification plant project.

Proper mixing of waste in the vessels is critical to safely processing and treating the waste stored in Hanford’s underground tanks.

Peggy McCullough, Bechtel vit plant project director

Previous tests used smaller tanks to confirm that control equipment can reliably operate mixers before a full-size, 65-ton prototype tank was finished and barged up the Columbia River to the Hanford area in July. It is a 22,000-gallon tank.

The Atkins lab test tank is outfitted with six pulse jet mixers, which have no moving parts that might require repairs after they become contaminated with high-level radioactive waste.

They work like a turkey baster, sucking up mostly liquid waste and then expelling it, mixing waste in the process and preventing solid particles from settling on the bottom of the tank, or vessel.

“Proper mixing of waste in the vessels is critical to safely processing and treating the waste stored in Hanford’s underground tanks,” said Peggy McCullough, Bechtel project director for the vitrification plant.

Hanford has 56 million gallons of radioactive waste held in underground tanks waiting for treatment at the vit plant to allow permanent disposal. The tanks contain a range of chemical and physical characteristics, which will present unique challenges in mixing tank waste at the vit plant.

Full-scale testing of the pulse jet mixing system is expected to be finished in late 2017.

Work also continues on the other four technical issues at the vit plant — preventing corrosion and erosion of equipment that could shorten the plant’s planned 40-year life, some additional work to analyze the possibility of unplanned nuclear reactions, some additional structural analysis of the planned tanks within the Pretreatment Facility, and issues with the ventilation system.

Annette Cary: 509-582-1533, @HanfordNews

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