The final stage of reprocessing of spent nuclear fuel involves the separation of plutonium in a solvent phase (tributyl/phosphate/odourless kerosene) from the uranium/plutonium/fission product mixture. The solvent containing plutonium as nitrate at about 10E+6 Bq/ml is sampled in a number of lightly shielded cabinets before the solvent is stripped to leave plutonium nitrate in the aqueous phase. On 12 January flow of solvent to an instrument in a cabinet became restricted and caused an overflow of plutonium laden solvent to the floor of the cabinet and then to the operating area floor of the reprocessing plant via a leak path from the cabinet. No abnormal doses were received. No air contamination resulted. The area has been decontaminated. Total spillage was 6 x 10E+9 Pu (alpha) plus a.8 x 10E+10 Bq Pu 241, equivalent radiologically to 1 x 10E+10 Bq Pu (alpha). "On site" spillage criteria require comparison with the radiological equivalence of "a few hundred GBq of Ru 106". Pu (alpha) is about 10E+4 times more radiologically restrictive per Bq than Ru 106. Hence the spillage is radiologically equivalent to about 1 x 10E+14 Bq Ru 106. Level 2 is therefore appropriate.