Measurement of 237Np in environmental mater samples by accelerator mass spectrometry

Accelerator mass spectrometry (AMS) was used to measure Np-237 in environmental water samples extracted from Irish Sea sediments. The samples were of limited volume ( similar to 700 ml) and of low activity (0.0-0.79 mBq 1(-1); 2.30-30.3 pg 1(-1)). AMS proved to have the required sensitivity for measuring these samples, and was in principle capable of measuring much smaller amounts, as low as 0.4 mu Bq (3.9 x 10(7) atoms). However, the background level in the procedural blanks showed that there was a systematic low level Np-237 contamination of each sample, arising from the Np-239 yield monitor used in the separations procedure, which effectively increased the detection limit of these analyses.