An environmental group won its request to review safety and engineering records of a Department of Energy nuclear reactor 100 miles upwind of Yellowstone National Park, according to federal court records.

The Jackson-based Keep Yellowstone Nuclear Free will be able to review 1,400 pages evaluating the safety of the advanced test reactor (ATR) at the Idaho National Laboratory, according to the Sept. 14 order by Chief U.S. District Judge William Downes. The lab is a 890-square-site with three main complexes west of Idaho Falls.

"KYNF has been anxiously awaiting this decision because they maintain that the redacted documents contain the DOE's assessment of the safety and consequences of an accident at the controversial ATR, the largest nuclear test reactor in the world, said Mary Woollen, the environmental group's director.

However, the environment group did not disagree with a Department of Energy motion granted by Downes to put the order on hold until Nov. 27 because of a possible appeal. The government also needs the time to review the documents and edit certain details.

Three years ago, Keep Yellowstone Nuclear Free and the Environmental Defense Institute -- under the Freedom of Information Act -- sued the Department of Energy to release certain documents about the 40-year-old reactor: safety problems, faulty equipment, vulnerability to earthquakes, and the intent to produce the extremely toxic Plutonium-238

"If a severe accident were to occur at the ATR, two of the most nation's most cherished national parks, Yellowstone National Park and Grand Teton National Park, as well as the health and safety of tens of thousands of people living in southeastern Idaho and western Wyoming, would be at risk," according to the lawsuit filed by Keep Yellowstone Nuclear Free's attorneys Carter Ledyard & Milburn LLP in New York City.

"According to DOE's own documents, in the event of a serious accident, the ATR could release as much as 175,000,000 curies of radiation, which would contaminate a vast area and rank second only to Chernobyl in terms of radiation released.

The Department of Energy responded an accident of this magnitude could not occur, that no severe accident had ever occurred at the INL, and that it supplied the documents requested by the environmental groups.

But some documents were exempt from disclosure because of personnel rules and practices, privileged interagency memorandums, and law enforcement purposes, the government argued.

The disclosure of safety procedures also would give terrorists an important tool to access and attack the reactor site, according to the Department of Energy. "After bypassing the physical security measures in place at the ATR, a terrorist could use the safety analyses to accomplish the main objective -- damaging the reactor or facility, resulting significant radiological releases and public panic."

In September 2007, Downes wrote the Department of Energy could not withhold the requested documents based on the exemptions in the Freedom of Information Act.

But he wanted to err on the side of caution and ordered the department to provide an expert to help him review the documents.

With the review completed, Downes on Sept. 14 ordered the department to produce the documents.

Contact reporter Tom Morton at 307-266-0592 or tom.morton@trib.com. Read his blog at tribtown.trib.com/TomMorton/blog