* Test was scheduled after break-in by nun, peace activists
* WSI, unit of G4S, distributed material as 'training aide'
* Firm has since been fired from its contract
WASHINGTON, Oct 31 (Reuters) - Guards at the U.S. government's maximum-security facility for weapons-grade uranium were given a copy of a test and its answers before they were to take it, an official report by the Energy Department's Inspector General said on Wednesday.
The test was prompted by a major security breach at the government's Y-12 nuclear facility in Oak Ridge, Tennessee in July, when an 82-year-old nun and two aging peace activists broke into the complex and vandalized it.
The building, designed after the Sept. 11, 2001, al Qaeda attacks on New York and Washington, was supposed to be one of the most secure complexes in the United States.
The recent break-in led to a series of detailed reviews of the Energy Department's oversight of its nuclear weapons facilities.
A federal inspector from the Energy Department's Office of Health, Safety and Security was at the site on Aug. 29, the day before the test was to be given. He found a copy of the test and answer key, in the car of the security guard who was his escort, the report said.
The compromised test was pulled, and a revised version was given.
An investigation found the test's questions and answers had been widely distributed as a "training aide" for guards by WSI Oak Ridge, owned by international security firm G4S.
G4S was the focus of a political and media storm this summer after it failed to provide enough guards for the London Olympics, forcing the British government to mobilize thousands of troops at the last minute to help with security.
WSI officials said there was "no intent to cheat" on the test, Inspector General Gregory Friedman wrote in his report, terming the credibility of their testimony "questionable."
The firm was fired from Y-12 on Oct 1, and the security work was taken over by contractor B&W Y-12, a unit of Babcock & Wilcox Co, which operates the site for the Energy Department.
The test had been shared with B&W to get comments on its accuracy, but Friedman said federal officials did not give detailed instructions on keeping the information secure.
A spokeswoman for B&W Y-12 was not immediately available for comment.
"Based on disclosures by contractor officials, there is also a possibility that compromises of test materials may have occurred at other sites without discovery," Friedman wrote.
'TROUBLING DISPLAYS OF INEPTITUDE'
In an earlier report, Friedman had excoriated the department for "troubling displays of ineptitude" at the plant, where among other missteps a broken security camera was left unfixed for about six months.
His review of the incident in July found guards ignored motion sensors tripped by the peace activists because they were routinely triggered by wildlife.
"Security of the nation's most sensitive nuclear material storage and processing facilities must not be left to chance," he said.
The Energy Department's Office of Health, Safety and Security said it has tightened its test procedures as a result.
But the head of the Nuclear National Nuclear Security Administration (NNSA), the agency in the department responsible for the sites, disagreed that problems with its oversight of contractors played a role in the compromised test.
In an official response, Thomas D'Agostino said the issue was due to "the unilateral decision on the part of the contractor to make further internal dissemination to a broader number of individuals."
The NNSA has said it fixed the immediate security issues. A task force is currently assessing its oversight of the nuclear weapons complex.