Going Nuclear

Kent Leung above 'the swimming pool' of the nuclear research reactor at the Institut Laue-Langevin. Photo / Supplied

As the red doors close on the airlock, I find myself glancing down nervously at the radiation gauge clipped to my pocket. The blue booties stretched over my shoes are ridiculous. With my zipped blue lab coat, they make me look like Disney's Gyro Gearloose. In the moment before the doors swing open on the other side there is a fleeting sense of claustrophobia.

I'm sure I detect the drop in pressure, but it's probably the power of suggestion. "Inside there is a slight underpressure," the guide has reassuringly told us in preparation. "So if there is a leak in the reactor, all the air will be flowing in, so nothing leaves the reactor." There is that word again - reactor. As in nuclear. And that other word - leak. As in that can't be good.

I'm from New Zealand, home of nuclear free. Like many I was outraged by French nuclear testing in the 60s and 70s on Mururoa. I was proud when Big Norm sent frigates there in 1973. Nuclear warships? Hell no. When David Lange banned them in 1984, I cheered. Then Greenpeace's Rainbow Warrior was sunk by French spies in my harbour.

Yet here I am, about to go inside a nuclear reactor - a French one, no less. I should have read the itinerary more closely. I was so focused on the prime event of my trip - avoiding being sucked into a black hole at Cern in Geneva, home of the Large Hadron Collider, where they shot some of Angels and Demons - I hadn't thought about the possibility of being irradiated.

The first sign something odd was afoot was when the security guys at the entrance gate demanded a busload of journalists hand over their passports. It didn't go down well. "This is France," shrugged the Italian journalist. "These are the people who invented bureaucracy." Reluctantly we acquiesce. Some of our party, especially those from less democratic nations, are visibly shaken. "I'm sorry if you're upset," says our minder. "But there is a nuclear reactor
just up the road and they need to be careful about security."

In Grenoble, surrounded by the majesty of the French Alps - the Chartreuse mountains to the north, the Vercors to the west, and the Belledonne range in the east - it's hard not to be in awe. What is hard to figure out is how, in the middle of this natural splendour, at the fork of the Drac and the Isere rivers, there's a whopping great nuclear reactor.

There's another incongruous shock. "I'm a nuclear and particle physicist," says Kent Leung, our guide in the proper white coat. "About myself - I'm a PhD student. What you see is from Hong Kong and the accent is from New Zealand, where I grew up."

Two New Zealanders inside a French nuclear reactor - what are the odds? Leung came to New Zealand when he was 6, lived in Birkenhead on Auckland's North Shore, attended Rosmini College, then spent five years at Auckland University gaining his bachelors and masters degrees. When he was 15 he had a part-time job in the bakery of my local supermarket. Small world.

Leung, 24, in his third and final year of his PhD at the Institut Laue-Langevin, or ILL, an international research centre at the cutting edge of neutron science, is about to take us to the swimming pool. "You cannot swim in it," he advises. "Water is a very good absorber of neutrons and when it absorbs neutrons, it absorbs deuterium, which is poisonous."

Deuterium. It's the so-called "heavy water", separate from the light water in the swimming pool, that slows down the over-excitable and alarmingly energetic neutrons produced by the spontaneous fission that goes on here. Fission. As in nuclear - splitting apart the middle (nucleus) of atoms - in this case atoms of Uranium 235.

New Zealanders do not like it. Except, of course, that it was one of our own, Sir Ernest Rutherford, the father of nuclear physics, who started this whole business of splitting atoms in 1917. A top bloke who is constantly dragged out as proof that we are the best at just about everything.

Deuterium is not so bad. "You need to drink several litres of pure deuterium a day for several weeks before it becomes hazardous," says Leung. Handy to know. He points out the ILL has lots of mechanisms to keep its "cold store" of liquid deuterium completely sealed. "The legal regulation is if one drop leaks out, then the reactor is closed down. We've never had a single drop escape."

Just when I think it's safe, he tells us that the main concern is actually that trace amounts of salts (such as sodium and chlorine) in the swimming pool can become radioactive due to the neutron flux. They monitor that closely too.

So what is the swimming pool for? "This lighter water is more for biological protection, so if you have lots of it and you stand up here, you don't get too much radiation." Right. Water is shielding me from the "Danger d'Irradiation" - as the signs everywhere warn. I check my gauge. It still says "00.16" For all I know, that's good.

"If I did fear working in a reactor, I would have a very stressful life, since I spend around 100 days a year in there," says Leung. A flight to New Zealand and back gives about the same dose as what he gets working half a year in the reactor, he reckons. Both doses are around 10 times less than the natural dose he gets from the environment.

Not a problem then. But he does wear an electronic dosimeter every day, which beeps at him if his current dose rate is too high. Yes, he does know what to do if there is a worst-case scenario, catastrophic meltdown at the ILL. Get the hell out of there. "If I evacuate the site within a few hours the dose is about the same as an x-ray scan," he says casually.

Inside Level D, the top floor, an overhead crane bisects the roof dome. The space has a central structure, festooned with gantries, mysterious machinery, and pipes and tubes running every which way. As we step up to the scaffolding platform poolside, we're advised to make sure nothing falls in. It's the sort of warning that immediately has me clutching my glasses.

The view through crystal-clear water into the core, about 15 metres below, is eerie - the deep is bathed in a violet blue glow that's strangely beautiful and unnerving. Cherenkov light - named after the Russian physicist Pavel Cherenkov who discovered it - is one of the few ways to actually see nuclear radiation. It's caused by energetic particles travelling extremely fast in the water - so fast in fact they make a sort of sonic boom of blue light.

Why are they going so fast? Well, there's stuff going on in the deep blue involving nuclear fuel, splitting of atoms and the emitting of things like beta particles which buzz about the place. It's these little buggers that have me worried. I know from my meagre understanding of physics that they can penetrate living matter and change the structure of molecules they smack into - mostly doing very bad things.

Yet when they're harnessed properly, they can also be used to treat things like eye and bone cancer. I'm just a bit worried these ones may not be harnessed that well. I'm told the glow of Cherenkov radiation, in itself, is relatively harmless. I check my gauge. It still says "00.16".

"These are the beam pipes, neutron optical fibres that allow us to guide neutrons to be cooled down and sent out to various instruments," says Leung. Then he points out the reactor core, a two-metre cylinder housing thin blades of highly enriched Uranium 235. Uranium. Unlike David Lange at the Oxford Union debate, I can't smell it on anyone's breath here. Later, in a lower level of the reactor, where there are experiments with the neutron beams - everything
from pure curiosity science, to finding stress fractures in machinery, railway tracks and hip joints, plus looking into the structure of the H1N1 virus - the issue Lange was talking about in 1985 is still relevant.

"Uranium 235 is the one they use for making nuclear weapons because it burns very, very quickly - so it's bomb-grade material," says Andrew Wildes, an Australian who gives us all heart attacks by yelling, "Shit!" when the daily 4pm meeting bell sounds. It does sound like an alarm.

He also advises us to wash our hands when we've finished, because we're likely to have picked up a bit of cobalt from the surfaces. In large amounts, cobalt is highly toxic. At the exit, we thrust our hands into two slots and wait apprehensively while the machine makes strange noises as it scans for contamination. We all get the green light, but everyone heads straight for the bathroom.

"On the other hand, it's very clean - the decay products from Uranium 235 all disappear between, I don't know, 50 to 100 years," continues Wildes. "Whereas the stuff they use in power reactors is much lower grade. You get all sorts of stuff like plutonium out of that - the half-life of plutonium is 30,000 years."

Uranium 235, says Wildes, is much cleaner but, on the other hand, it's politically sensitive. "You could say to the Iranians or North Koreans, 'yes, have some Uranium 235 to make a nuclear reactor'. But then you have to make sure they don't go sticking it into bombs."

There is no military research at the ILL - just lots of scientists from all over the world obsessed with neutrons. The main focus is neutron radiography and "tomography" - essentially the same as a medical Cat scan, but using neutrons to show up internal structures. "Neutrons will go through just about everything. It's hard to absorb them," says Wildes. "But they scatter like crazy off hydrogen. So they're very good for detecting hydrogen."

In some of the scatter experiments at ILL, scientists put a sample in front of a detector, "shine" a neutron beam on it and take a kind of photograph, like an x-ray, except it shows the lighter bits, the hydrogen, rather than the solid things like bone.

Back at the ILL guesthouse where we stayed, I overhear a student talking about her day. "I've just finished a 48-hour experiment and now I'm going to do my laundry." Is that how it is for Leung? "It's pretty flat-out, especially when you get beam time because that's valuable - it costs 10,000 ($21,600) a day to work on the experiment beams. During those stages you work pretty much overtime."

What made him become a nuclear physicist? "Physics wasn't really my thing. As cheesy as it sounds, I read Stephen Hawking's A Brief History of Time when I was 16. It got me completely baffled at the things you can learn about the universe. That you can have complete knowledge of things you can't see. For me it's a big intellectual challenge." At university he found that he was "quite good" at doing experiments. "I'm quite a DIY kind of guy. I like to do
things with my hands and build stuff."

The big intellectual challenge for his PhD is measuring the lifetime of the neutron. It's one of the really big questions of nuclear physics. Liberate a neutron from the nucleus of an atom and it will decay with an average lifetime of about 15 minutes. The question is why 15 minutes? For some unknown reason, 15 minutes seems to be the perfect amount of decay time to allow the universe to form the way it did.

In the beginning, so the story goes, a few minutes after the Big Bang, there were no atoms, just little bits of stuff, floating about. Scientists believe that in the next few moments, the fundamental particles coalesced into neutrons and protons - the two basic building blocks of the nucleus of atoms. Some of these particles then combined to form atoms of helium and other light elements, while the remaining free neutrons began to steadily decay. It's known as
the Big Bang Nucleosynthesis period. That led, a few hundred million years later, to the formation of stars and then, many billions of years after, to solar systems, rocky planets and life itself.

Which is why the 15-minute decay period is so important. "If the value of the neutron lifetime was much different than what it is, then I wouldn't be standing here talking to you today." To get a better understanding of why this is so, Leung and others are aiming to get a very precise lifetime measurement. But neutrons aren't the easiest subjects to study. First you have to capture them. Easier said than done, because they move darn fast and then disappear.

Leung and his colleagues catch the fickle neutrons with weird cylinders - magnetic traps or "boxes" with no material walls and ultra cold "cryostats" filled with "superfluid" helium. It's with the cryogenic trap, holding very slow-moving neutrons, that they hope to get even better measurements.

Meanwhile, Leung is adding to our lamentable brain drain by pursuing his curiosity. Yes, he does tend to emphasise the particle, rather than the nuclear when he tells New Zealanders what he does. He doesn't think New Zealand needs nuclear power, but he does wish people were not so closed-minded about the whole issue. "Since nuclei make up all matter, I think a true 'nuclear free' country like New Zealand would be nothing more than a gas of electrons."

On nuclear weapons he's pro-non-proliferation and pro-disarmament. "Pretty much all technology can be used for good or for harm. No technology or science can be intrinsically evil. I don't believe we can hope to stop the drive to discover new technology since it is exactly this same curiosity which gave us the world we live in today."

He misses New Zealand sometimes, but gets home for Christmas. "You do miss the sea and ocean a little bit." But he also loves living in Grenoble, cycling 15 minutes to work, skiing, and travelling around Europe. "I'm pretty happy doing the work I'm doing and having some fun. The quality of work here is so much higher, meeting new people and all the different cultures. I've learnt a lot. It's such an eye-opener for me."

Me too. My visit to ILL hasn't completely changed my view on matters nuclear. But it has made me realise that reducing science to slogans isn't particularly intelligent. That sooner or later New Zealand needs to realise the world is on its way into the quantum age where the very small is beautiful, not to mention useful.

* Chris Barton visited the ILL in Grenoble on a travel scholarship from the World Conference of Science Journalists.