Hanford Nuclear Waste ‘Vit Plant’ Has Safety Board Worried
RICHLAND, Washington, February 7, 2012 (ENS) – Bechtel National, Inc. is designing and building the world’s largest radioactive waste treatment plant for the U.S. Department of Energy at the Hanford Site near the Columbia River in southeastern Washington state.
The $12.2 billion Waste Treatment and Immobilization Plant, also known as the “Vit Plant,” will immobilize the highly radioactive liquid waste now stored in 177 underground tanks by turning it into large glass logs using a process called vitrification.
Construction of the Vit Plant began in 2001 and is more than 60 percent complete.
But now the Defense Nuclear Facilities Safety Board, DNFSB, has rung an alarm bell about the ability of the plant’s stainless steel piping, process vessels, and pulse jet mixers to withstand the erosion and corrosion of the radioactive waste during the 40-year life of the facility.
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Process cell vessels are installed in the Hanford vitrification plant, October 2011. (Photo by Bechtel National, Inc. on behalf of the U.S. Department of Energy) |
Vitrification involves blending the waste with molten glass and heating it to to 2,100 degrees Fahrenheit. The mixture is then poured into stainless steel canisters. In glass form, the waste is stable and impervious to the environment, and its radioactivity is expected to decay over hundreds to thousands of years.
In a January 20 letter to David Huizenga, acting assistant secretary for environmental management at the Department of Energy, DNFSB Chairman Peter Winokur wrote, “…the Board is concerned that the project team has not shown that the design wear allowances for vessels, piping, and PJM nozzles are adequate to ensure that components located in the black cells will reliably function for the 40-year design life of the facility.”
The radioactive waste is corrosive and contains heavy metals and abrasive particles that could eat holes in the stainless steel in the part of the plant that is too radioactive for people to access. The black cells will be sealed and not accessible either.
Winokur attached a report from DNFSB staff to his letter showing that after a nine-month evaluation of wear allowances specified by Bechtel, the staff found them based on “assumptions” that “have not been adequately validated.”
Expermimental testing was conducted by Bechtel, but the DNFSB staff found that “the scope of that testing was limited and the results were flawed.”
In one assumption, the Bechtel team ignored the effect of high temperatures on stainless steel components. But the DNFSB staff warned in its memo that “some stainless steel vessels, PJM nozzles, and piping will be operating near the critical temperatures for onset of pitting and cracking corrosion. The combination of effects could result in higher than expected wear rates.”
“Much of the piping and many of the vessels are contained in black cells,” wrote Winokur to the Energy Department. “The design of the black cells prevents observation and tracking of wear (erosion and corrosion) on components and does not provide ready (or easy) access for the repair or replacement of failed components.”
“Inadequate wear allowances for piping, vessels, and PJM nozzles could result in component failures,” warned Winokur. “Component failure due to wear jeopardizes the above safety functions and could stop waste processing for indefinite periods resulting in significant extensions in the time required to accomplish the facility mission.”
“The existing design margins offer little or no flexibility for future operations or the opportunity to extend the life of the plant, if required,” Winokur wrote.
The Department of Energy said in a statement that it is aware of concerns about pipe strength and continues to test the durability of the plant’s materials.
Don Alexander, a scientist with the Department of Energy, told radio station KUOW today that he raised these issues years ago, but nothing has been done. “On a scale of 1 to 10, with the hardest metal being a 10, the one that can resist erosion the best being a 10, the metals that were selected for the plant are about a 2,” he said.
The DNFSB staff finds that “the current pace of the contractor’s efforts to close the issues does not support timely resolution.”
Some of these vessels are scheduled for installation in the Pretreatment Facility in August 2012 and the staff notes that modifications become more difficult and costly after the vessels are closed and installed.
Gary Olsen, federal area project manager for the facility, said, “The High-Level Waste Facility is making good progress towards construction complete in 2016 and preparing to treat Hanford’s tank waste in the future.”
The Vit Plant will cover 65 acres with four nuclear facilities – Pretreatment, Low-Activity Waste Vitrification, High-Level Waste Vitrification and Analytical Laboratory – as well as operations and maintenance buildings, utilities and office space.
The project is scheduled to complete construction in 2016, reach commissioning in 2019 and achieve full operations in 2022.
Copyright Environment News Service (ENS) 2012. All rights reserved.