"We found that DOE's [Department of Energy] quality assurance efforts did not always ensure detection of problems such as engineering errors and construction deficiencies, and some problems are recurring," the report said.
Reactors at the Hanford site produced plutonium used in US nuclear weapons until the late 1980s, when one of the world’s largest operations to clean up radioactive byproducts began, according to the DOE.
By today’s standards, the Plutonium-making process was extremely "inefficient" in that a massive amount of liquid and solid waste was generated, the website explained.
The GAO report noted that the cleanup effort of nearly 30 years has faced persistent challenges, and that the cost of the project has more than tripled to nearly $17 billion.