A study has been made of the radioactive nuclides present in the cooling water of the Low Intensity Test Reactor. Prominent nuclides which have been identified include Np239 and certain fission products. The experimental evidence points to the probability that there could be adequate U235 contamination on the fuel plates to quantitatively account for the fission products identified in the LITR cooling water. inasmuch as new aluminum does not contain uranium, it must be assumed that the contamination occurs during the fabrication of the fuel elements.