RICHLAND, Wash. (AP) — Officials say the possible collapse of a second Hanford tunnel storing radioactive waste is both more likely than thought a year ago and the effects potentially more severe.

The Tri-City Herald reported Tuesday that the risk of failure, based on Department of Energy nuclear safety standards, has increased from "unlikely" to "anticipated." The potential severity has been increased from "low" to "moderate."

Chief operating officer of Hanford contractor CH2M Hill Plateau Remediation Co. Dan Wood said the severity of the possible collapse is still not ranked as "high," but it would be a significant event with the potential for the airborne release of radioactive particles.

After the partial collapse in May 2017 of the older of two tunnels storing radioactive waste at Hanford's PUREX processing plant, an initial structural analysis of the other tunnel was conducted.

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Information from: Tri-City Herald, http://www.tri-cityherald.com