I finally managed to track down a designation on this satellite. It is NRO L-21, launched from Vandenberg AFB on December 14, 2006. It was an experimental satellite with classified equipment on board for testing purposes. From what I have read the chances of Hydrazine being left on board are high. While it is unlikely to have contained a reactor, I don't think anyone can rule out an RTG being on board. Well, those who could rule it out are not likely to say much.
Edit: Heavens Above has elements here:
http://www.heavens-above.com/orbitdi...ET&satid=29651