Corrosion hard alpha particle detectors have been fabricated from thin diam
ond layers grown on silicon using the microwave enhanced chemical vapour de
position technique (CVD). The devices can be directly immersed in radioacti
ve liquid solutions and enable the real time and in situ measurement of the
ir alpha activity. We report here measurements on devices immersed in a plu
tonium-239 radioactive source diluted in concentrated nitric acid. The test
s have shown excellent reliability of the CVD diamond detectors which would
be of great benefit in monitoring nuclear fuel assembly reprocessing. We b
elieve that this is the first detection application of CVD diamond which re
lies on its corrosion hardness. (C) 2000 Elsevier Science S.A. All rights r
eserved.