RELIABILITY OF THE FUEL IDENTIFICATION PROCEDURE USED BY COGEMA DURING CASK LOADING FOR SHIPMENT TO LA HAGUE

As consignors, COGEMA and Nuclear Transport Umited (NTL) are in charge of spent fuel transports from the European power plants to the COGEMA reprocessing plant at LA HAGUE. Transports are shared between COGEMA and NTL in the following way: - COGEMA- STS (Service des Transports Speciaux) directly operates the transports from the Electricite de France (Ed F) French power plants representing 50 reactors; - NTL acts as a COGEMA sub-contractor and operates the transports tom all the other European power plants representing about 29 reactors. For this purpose COGEMA- STS and NTL use a wide range of transport casks from several designers, with a capacity varying from 3 PWR fuel assemblies to 12 PWR or 32 BWR fuel assemblies. A transport cask for Ught Water Reactor irradiated fuel mainly consists of a gamma and a neutron shielding made of steel or lead, which also provide containment, combined with resin. A basket containing the fuel assemblies fits into the cask cavity. A common characteristic of all the transport casks is the control of the criticality by the basket. This is achieved by the neutron poison, consisting of boron distributed in the walls of the compartments of the basket. The use of transport casks is subjected to package approvals issued by the competent authorities. These package approvals are supported by a safety report, partly based on a criticality assesssment, which defines the performance of the cask and its basket in terms of maximum fuel enrichment in fissile material. Nowadays, European power plants are burning a very wide range of fuel assemblies and in order to optimise their plant management and operating cycles length, the actual trend is to use more and more reactive fuel with higher initial enrichment in fissile material. In the mid 80's the traditional assumption of \"fresh fuel\" used in evaluating criticality of the spent fuel casks proved to be insufficient for the existing basket designs to accommodate the new types of fuel assemblies that we had to transport. In order to extend the capability of their basket designs, COGEMA and TRANSNUCLEAIRE started to consider the new assumption of \"bumup credit\" for their criticality calculations thus reducing the amount of fissile material. For instance, it has been possible to increase the initial enrichment of the 16X16 KWU fuel type loaded in the 904 basket design from 3.3 % to 3.55 % of U235 with a limited bumup credit of 3200 MWd!feU (TN 13/2 package approval). This has been accepted by the French competent authority according to the philosophy of the consignor's responsibilities defined in the IAEA regulations (1985) and provided that: - The fuel assemblies are burnt with a high safety margin with regard to the assumption of the safety case; - The consignor verifies, according to quality assurance procedures, the irradiation status of each fuel assembly by a go-no go measurement ( e.g. by gamma scanning) prior to loading in the transport cask; - The consignor has a full control of the identification procedure of the fuel assemblies. The purpose of this study was to quantify the reliability of the fuel identification procedure used to implement the third condition.