[ RadSafe ] Po-210: What is a unit?

[Ivor Surveyor]

The following report is from the 
AUSTRALIAN.    Can somebody please explain what 
is meant by a "unit of radioactivity," as quoted in the article.

Russian spy's fatal dose of poison cost $13m
Correspondents in London
19dec06

BRITISH police believe the radioactive substance 
used to kill former Russian spy Alexander 
Litvinenko cost more than $US10 million ($13 million).

According to The Times, preliminary results from 
the post-mortem examination on Litvinenko's body 
have shown he was given more than 10 times the 
lethal dose of polonium-210, large quantities of 
which were found in his urine.

"Only a state-sponsored organisation could obtain 
such a large amount of polonium-210 without 
raising suspicion on the international market," 
said Alexander Goldfarb, a friend of Litvinenko.

United Nuclear Scientific Supplies, based in New 
Mexico - one of the few companies allowed to sell 
polonium-210 over the internet - said it would 
take at least 15,000 units of the isotope to kill someone.

With each unit costing $US69, it would have cost 
more than $US10 million to deliver Litvinenko's fatal dose.

"You can't buy this much off the internet or 
steal it from a laboratory without raising an 
alarm, so the only two plausible explanations for 
the source are that it was obtained from a 
nuclear reactor or very well-connected 
black-market smugglers," an unidentified British security source said.

British detectives working on the case in Moscow 
were due to return to Britain this week.

Security sources said Russian officials refused 
to ask questions of Andrei Lugovoi and Dmitri 
Kovtun - both of whom met Litvinenko on the day 
he fell ill - that British detectives wanted 
answered. They had not complained publicly 
because of the importance of the case to 
diplomatic relations between Britain and Russia.

High-ranking Kremlin officials have mocked 
Litvinenko's boasts, after he defected to 
Britain, about his role in their security services.

Minister of Defence Sergei Ivanov claimed that 
Litvinenko, far from being a top KGB spy as he 
liked to claim, was merely a prison guard.

Mr Ivanov said Litvinenko had never had access to 
secret or important information and was "of such 
poor character" he was dismissed from the Russian 
security agency when it was being run by Vladimir Putin.

"He was never a spy and never knew anything of 
any real value to give to any (foreign 
intelligence) service," Mr Ivanov said. "He was 
just a Russian who meant nothing to us."

Referring to the letter in which Litvinenko 
accused the Kremlin of poisoning him, Mr Ivanov 
said:"We didn't care what he said and what he wrote on his deathbed."

Kremlin officials again described the accusations 
of Russian involvement made by Litvinenko and his friends as ludicrous.

Valentin Velichko, a colonel who is president of 
Honour and Dignity, a powerful group of KGB 
veterans, dismissed Litvinenko as "a nonentity".

He said in an interview with the Rossiiskaya 
Gazeta newspaper that Litvinenko was never a 
target for Russian intelligence because he was 
not important enough to bother with.

The Times, AFP

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Ivor Surveyor, MD (Brist), FRACP, FRCP
Emeritus Consultant Physician, Nuclear Medicine,
Royal Perth Hospital.

[isurveyor at vianet.net.au]