By Rob Broomby
BBC Radio 4
Carolyn MacKenzie goes at her job like a terrier.
The search is on for radioactive material missing since the collapse of the USSR
High in the Caucasus Mountains of Georgia she is wielding the latest radiation detector fitted into a backpack which is flashing and beeping as we walk through the thick damp undergrowth.
Part educator, part campaigner she is what is called an Orphan Source specialist with the UN's Nuclear watchdog the International Atomic Energy Agency.
She is supporting a Georgian team hunting down missing radioactive materials - sources as they call them - once used in a range of devices from communications to health care and now lost without trace with the collapse of the Soviet Union.
There are health and security risks here; each one could be used as part of a dirty-bomb if the radiation were dispersed using conventional explosives.
They may not kill many people but the impact on a city, on the economy and on fear could be huge if one was detonated.
Experts now call them weapon of mass disruption.
She was the first IAEA team member to take the risk, of allowing me, a reporter on the inside of a sensitive search in a fragile region with an open microphone.
It was to pave the way for me to spend a successful year monitoring one of the UN's most sensitive agencies.
The threat of rogue radioactive sources is a reality in Georgia
On the basis of this trip I was given a free rein to wander the corridors of the IAEA headquarters in Vienna almost unhindered, quizzing the agency's experts and stalking the diplomats as they wrestled with the crisis surrounding Iran's nuclear programme.
I was given unprecedented access to its leader Dr Mohamed ElBaradei, his nuclear inspectors and his circle of closest advisors.
In Georgia the threat posed by rogue radioactive sources has already become a reality, four people have died horrible deaths from radiation burns in recent years.
They came into contact with some of the bigger radiation nasties on the loose, the so called RTG's which once powered hill-top radio transmitters and which are crammed with radioactive Strontium 90.
And it is not simply the health risks of unwittingly finding a source, there are those who would use this nuclear material for their own ends.
For Dr ElBaradei the threat of nuclear terrorism in all its forms is now the most serious threat the agency faces.
The warning couldn't be more stark, he believes it is even more worrying than another an additional state like Iran getting the bomb.
The Georgian authorities also took huge risks in allowing me to join the search, though I think they were at times mystified by the eccentric Englishman recording everything from the sound of rivers and cowbells to the crackle of Geiger Counters.
This is a fragile nation which barely controls its own territory, there are secessionists within its borders and it is also situated near some of the regions most intractable trouble spots, such as Chechnya.
It is not the kind of place you want radioactive materials on the loose.
The first item we found was no bigger than a finger nail.
It was buried in a pile of rubble in a derelict factory in the middle of a village clinging to the side of a steep valley.
For years the people living here had been subject to levels of radiation twelve times background. This realisation has shocked them.
A second find - more bizarre still- was in farm cottage shed.
The alarms were set off as we approached the simple peasant home and within seconds the Georgian team were squeezing into the blackened outhouse, over piles of logs and past what looked like a side of smoke-cured pork with the frantically bleeping radiation sensors leading us eventually to a box of nuts and bolts on a workbench.
A door opened in the darkness and a woman emerged into the shed from a bedroom.
She had been sleeping next to the tiny device probably for years.
Again it was small physically small, Caesium 137 source which had probably been used at a nearby factory which had been long-since closed and had probably been acquired along with scrap metal.
The Georgians have so far picked-up 300 dangerous items in their search, I had witnessed just two but as we searched we learned that another attempt at trafficking radioactive material had been stymied at the border.
Earlier this year it was announced that a small quantity of highly enriched uranium, had been picked up here in Georgia in the hands of criminals, and that is material usable in a real nuclear warhead.
We never found the missing RTG's, they are still out there somewhere.
All these devices were once useful when they powered X ray machines, airport scanners, and depth gauges.
But now missing and at large, they are a spine chilling health and security menace.