Speaker
Description
The ISIS Neutron Source uses ion exchange resins contained in shielded ion exchange columns (IECs) to control the coolant chemistry of the most radioactive parts of the ISIS machine- the target, reflector and moderator (TRaM) systems. The columns are replaced periodically, generating intermediate level waste (ILW).
Legacy IECs from Target Station 1 (TS1) were transported away from RAL during 2020/21 for sampling and analysis. Data from this campaign showed that Tritium (H-3) dominates resin originating from TS1. Furthermore, some of these IECs contained elevated alpha activity, not consistent with expected nuclide composition generated from ISIS. During a secondary sampling campaign, significant gaseous H-3 at ~350 MBq/m3 was released from one of the IECs and did not dissipate after 24 hours venting. Due to this complication, the IECs were returned to RAL awaiting further work.
These legacy IECs, plus more recent ion exchange resins, including from Target Station 2 (TS2) must be characterised to determine if a treatment or disposal route is available. This cannot be accurately done in-situ due to the shielding effects of the columns and the non-gamma emitting nuclides likely to be present, so the columns need to be sampled for radiochemical analysis of the resin.
Planning is underway to undertake the sampling at RAL. This will require assessing the radiological risk of removing the IEC lids to access and sample the resin. Whilst gaseous H-3 is the predominant risk for TS1 IECs, high gamma dose rate is the main risk for TS2 IECs so requires management. Furthermore, planning for the physical sample collection is underway.