The long-term retention of systemic protactinium-231 and actinium-227

The behaviour of 231Pa and 227Ac in a man who acquired systemic burdens of these nuclides via a puncture wound has been studied over a period of 9 yr. From body radioactivity measurements and excretion analysis it is concluded that 70–80% of the 231Pa and approximately 90% of the 227Ac which were translocated from the wound are being retained almost indefinitely, with biological half lives of 70–125 and ∼ 125 yr respectively. Distribution studies suggested that 3 yr after the intake the activity was principally deposited in bone, with some involvement of fiver, but after 9 yr the contamination appeared to be almost exclusively skeletal.