Writing for AolNews, Lauren Frayer provides a clearer view than has appeared in other, similar articles, regarding iRobot's donation of four robots, a mix of PackBots and Warriors, for use in helping to bring the emergency at Japan's Fukushima nuclear plant to an end. Frayer quotes Tim Trainer of iRobot as saying

We've got some technology that isn't pointedly designed for the specific [nuclear] mission, but we're going to send that forward and try to understand, 'Could we provide some value to the Japanese, to try to mitigate this horrible situation?' ... Certainly, radiation will have some impact on the circuits. ... Some of this will be understanding what it might be like to operate in such conditions. To be quite honest with you, some of this will be experimentation. ... We are in the robotics business, and I think we'll learn a lot from applying our technology a bit differently here. The hope is that we will become smarter as a result of this.

Trainer also said that (at the time of the interview) he didn't know whether the donated robots had already been sent into the Fukushima Dai-ichi nuclear plant, or when they might be. Such decisions are entirely under the control of Japanese authorities.
Update: This article on the U.K. website Daily Mail includes two photos of PackBots at work and two closeups of a Warrior.