Authors:G. Cook, E. Scott, A. MacKenzie, F. Naysmith, K. Isogai, P. Kershaw, R. Anderson, and P. Naysmith
Prior to 1984, the reported marine 14C discharges from Sellafield were estimates: 0.2 TBq per annum from 1952 to 1969 and 1 TBq per annum until 1984 when measurements
commenced. The relationship between the net excess 14C activity in annually collected Nori (Porphyra umbilicalis) seaweed samples and the annual discharges (estimated and measured) implies that the discharges were not as constant as the
estimates. Based on the relationship between post-1984 measured discharges and the excess 14C in the seaweed, two simple empirical models were used to re-calculate the discharges between 1967 and 1984. Gamma-spectrometry
measurements on the seaweed also indicate that Porphyra is a sensitive indicator of changes in discharge of other radionuclides, brought about by the introduction of new waste clean-up
technologies within Sellafield.