Paddy Regan Department of Physics, University of Surrey, Guildford, gu2 7XH

• Paddy Regan

• Department of Physics, University of Surrey, Guildford, GU2 7XH

• &

• Radioactivity Group, National Physical Laboratory, Teddington, TW11 0LW

• [e-mail] ; [e-mail]

The s-process ‘terminator’...end point of element production the stars.

• The s-process ‘terminator’...end point of element production the stars.

• Mme. Curie & colleagues c.1898 -1930

• There’s a lot of it about; NORMs and 238U chains.

• Polonium-210 properties (,  signatures, lifetime)

• How does it harm you…how much do you need ?

Radioactive decays occur as a result of conservation of mass/energy E=mc2

• Radioactive decays occur as a result of conservation of mass/energy E=mc2

Estimated annual internal ‘whole body’ dose equivalent from natural 210Po radioactivity in the USA = 30 Sv (same as 222Rn).

• Estimated annual internal ‘whole body’ dose equivalent from natural 210Po radioactivity in the USA = 30 Sv (same as 222Rn).

• 40K =170Sv for comparison

• Annual dose equivalent to epithelial tissue lining the lungs from Radon and its daughters (210Po) ~20Sv (double this for cigarette smokers).

Radiation damage measured in ‘Grays’

• Radiation damage measured in ‘Grays’

• 1 Gy = 1 Joule imparted per kilogram

• Estimates are ‘assessed’ depending on

• type of radiation (i.e., gammas, betas, alphas…)
• body tissues/organs affected…different cells
• have different tolerances to radiation damage.

• Biological effect measured in

• Sieverts (Sv) = WR x Grays

A = N = (ln2 / T1/2 ) x N

• A = N = (ln2 / T1/2 ) x N

• The Activity depends on number of atoms present and the

• decay half-life.

• A = decays per second for 1 mCi =3.7x107/s

• T1/2 = 138 days = 1.2x107s

• N = number of Po-210 atoms for 1 mCi = 6.4x1014

• Mass of 1 210Po atom is 210 x1.66x10-27 kg = 3.5x10-22g

• Mass of 1mCi of 210Po = 6.4X1014 x 3.5X10-22 = 2x10-7g

• = 0.2 micrograms

210Po has an interesting history…named after Poland (which didn’t exist at the time).

• 210Po has an interesting history…named after Poland (which didn’t exist at the time).

• It occurs naturally (from the decay of 238U).

• It is responsible for ‘terminating the s-process (limiting number of chemical elements).

• You can make it in neutron-capture reactions on 209Bi.

• Can be detected by  - or gamma-ray spectroscopy.

• Don’t eat or drink it (few gm are deadly): No problem really outside the body.

• Physicist are useful to the public. Numbers matter in calming peoples fears….