Contamination Incident At The Iaea Safeguards Analytical Laboratory Involving A Small Quantity Of Np-237

Since December 2015, the International Atomic Energy Agency (IAEA) completed the modernization and replacement of its vintage Safeguards Analytical Laboratory (SAL) by commissioning the new Nuclear Material Laboratory (NML) to maintain and enhance verification activities of the Office of Safeguards Analytical Services (SGAS). The commissioning of the new NML involved the transfer of thousands of nuclear material items including a broad range of Certified Reference Materials routinely used to ensure the quality of analyses performed. Some of these reference materials were already stored for more than 20 years as being extremely rare, seldom produced and therefore extremely valuable for the laboratory operation. On December 11th, 2017, an incident later described as INES below scale level 0 occurred in the Pu storage area of the NML during physical status checking of a set of glass ampules containing standards solutions of neptunium-237. At 14:48, one of the ampules spontaneously burst whilst in the hands of a staff member. This resulted in the spread of Np-237 and broken glass in the room. The most likely cause of the burst ampule was an overpressure induced by alpha radiolysis inside the ampule, which caused disassociation of water and hydrogen, oxygen build up in the headspace of the ampule. This paper describes the root cause leading to the incident as well as its consequences and the actions to prevent other similar incidents to occur.