Agreed, this case is bananas.
If his "plutonium sample" is actually (probably) trinitite which you can just buy online [1], and if we assume an exposure of 1 uR/hr at one inch[2], then convert that to BED (Banana Equivalent Dose[3] - that taken from the naturally occurring potassium-40 in bananas) that's (handwaving actual dose calculations) about, what, 1/10 of a banana?
[1] https://engineeredlabs.com/products/plutonium-element-cube-t...
[2] https://www.orau.org/health-physics-museum/collection/nuclea...