The Rock that Changed the World
Uran – Twisting the Dragon’s Tail (2015) je třídílný televizní dokumentární seriál o uranu, jeho historii a jeho použití. Produkce byla vyrobena Gene Pool Productions pro PBS a SBS a premiéru v obou sítích koncem července a srpna 2015. Série byla koncipována, vytvořena, napsána a režírována Wain Fimeri, byla natočena v devíti zemích a je představena Derekem Mullerem, inženýrským fyzikem a PhD v oboru fyziky a přednášejícím na vědeckém programu ABC Catalyst. Muller je také znám svým YouTube kanálem Veritasium.
Druhý díl: Uran je přítomen v mytologii domorodých národů severní Austrálie. Říká se, že velké duchovní stvoření spí pod zemí a vyrušení tohoto démona způsobí katastrofu. Použití uranu na konci druhé světové války zahájilo atomový věk. Uran byl od té doby využíván jako zdroj energie i při léčbě rakoviny.
The Rock that Changed the World
Legends say there’s a world beneath this one where a dragon lies sleeping they say be careful how you wake the dragon around the turn of the 20th century uranium is almost unknown it is basically worthless but then in 40 years just a single generation it becomes the most desirable and terrifying Rock on earth this is uranium and as a physicist I’m fascinated by its unique scientific properties but even more so by how this one Rock has shaped the entire modern world uranium changes everything in our last episode we discovered how uranium is forged in the explosion of a star uranium is a shapeshifter it transforms itself a lump of uranium will do this all by itself we learn how to release the incredible energy inside uranium a little bit of mass can be converted into a lot of energy we took a rock and we made a bomb on July 16th 1945 at exactly 5:29 and 45 seconds in the morning the dragon roars now come with me on a journey into the Atomic Age this is a nuclear reactor an age of promise and fear where uranium offers a dream of clean limitless power or a nightmare of a silent and poisoned earth this is the story of how a rock changed the world uranium twisting the Dragons tail is made possible.
in 1945 America is at war with Japan the Americans dropped a uranium bomb on the city of Hiroshima it explodes like the fiery breath of a dragon and then three days after her Ashima neither bomb is dropped on the city of Nagasaki to look at these pictures is to see the paradox of uranium the two atomic bombs have killed at least 100,000 people but a war that killed tens of millions has ended these people don’t know it but they’re dancing the old world away tomorrow will be different uranium has brought us a new age the Atomic Age was born there is no denying that since that moment the shadow of the atom bomb has been across all our lives wisdom demands that we take time to understand this force because here in fact is the answer to a dream as old as man himself a giant of limitless power at man’s command despite the rubble of Hashima uranium promised a new age its potential was clear the atomic fire that destroyed a city could be controlled we could harness the nuclear dragon no longer would we get our energy from burning coal or oil instead we would get it from manipulating the fundamental particles of the universe from within the atom the future of the world brand new age would be atomic today we are reaching into the core of nature itself for a source of energy so great that one ounce of matter can yield enough energy to light this 100 watt bulb for 1 million years uranium promised a new world where everything would be perfect turning down work is done for miles my winning hit pound shake because it feels just like uranium would take us into a dreamy future of limitless energy but that future would come at a cost
after the war the United States is the only country to possess the secret of the atom bomb it’s an exclusive club of just one member but that’s about to change in 1949 Soviet Russia tests an atomic bomb two superpowers Russian communism and Western democracy face off against each other President Truman’s dramatic announcement that Russia had the atom secret cause State Department’s all over the world to stir uneasily uranium fuels a new type of conflict not a hot shooting war but a cold war and everyone began to test bigger bonds here at the Atomic Energy Commission Nevada Test Site a program to test the effects of an atomic blast upon the things we use in our everyday lives naturally I was very interested in preparations for the testing of textiles and synthetic fabrics
uranium forces people to confront an elemental power of the universe but it also forces them to confront something elemental within themselves fear uranium transforms into its own unique genre of movie the Atomic Age monster but the real horror is that with uranium we now have the power to destroy all life on Earth we all burn together there’ll be no need to stand and wait your turn when it’s time for the fallout and Saint Peter calls us all out we’ll just drop our agendas and adjourn when the air becomes Uranus oh we will all go simultaneous yes we are deep underground beneath my feet is the closest you might come to a certain type of Hell a place where the end of the world begins hey how you doing good welcome to 1:7 oh there’s a nice ride you got here have you hop on board and we’ll take a look around thank you this facility was operational from 1963 until 1982 and it was built to house a terror weapon from the Cold War deep in an underground silo Derek this is level 2 of the silo were down some 10 meters below the surface now and this is the launch duct and that is Titan to the largest and most powerful missile weapon system ever deployed by the United States it’s a 9 Megaton weapon compared to Hiroshima Oh call it 650 times an enormously powerful weapon the idea behind titan 2 was to instill in a fear in the mind of the enemy to cause them to think twice about launching an attack against us knowing that 10 metres below the desert than our fortified concrete bunker we can ride out their first strike and live to retaliate if we’re forced to do that the consequences or the enemy would be so unspeakably horrible that maybe they would prefer not to get into it with us in the first place that’s the essence of deterrence
with the breakup of the Soviet Union and the end of the Cold War we think that the threat of nuclear annihilation has gone away but there are still more than 16,000 nuclear weapons in the world today enough to destroy all of us many times over it’s easy to fear these terrifying missiles of the atomic age but it’s also easy to forget that – they’re bombs they carried us into the new world of space Neil Armstrong first lifted off atop one of these missiles and in 1977 there was a Titan that launched the Voyager spacecraft almost 40 years later and Voyager has left our solar system it’s still traveling still sending data it’s battery is nuclear the slow release of its radiation creates heat which is converted into electricity solar wouldn’t work out here and normal batteries don’t last these images come to us courtesy of uranium uranium has taken us on an incredible journey my journey has brought me to an ancient land that has some of the richest deposits of uranium on earth where ancient stories warned that a powerful creation spirit sleeps underground here I met Jeffrey Lee the traditional owner of this country do not touch anything Jeffrey’s people believe that disturbing the powerful spirit beneath this land will unleash disaster Jeffrey refused to share of five billion dollars to mine here the tons and tons of uranium yeah and I don’t want anything coming up from the ground don’t to any other country because if you do start in other country he’s gonna come for you and you’re gonna happen this aster
and the age of uranium we learned to live uneasily with the dragon then on April 26th 1986 far away from here at the Chernobyl nuclear reactor there’s a catastrophic accident there has been a nuclear accident in the Soviet Union and the Soviets have admitted that it happened one of the atomic reactors at the Chernobyl atomic power plant in the city of Kiev was damaged in 1986 the uranium-fueled nuclear reactor at Chernobyl suffers a catastrophic failure radiation is released across Europe a radioactive cloud headed north across Poland today and into Denmark where radiation levels were five times normal to Finland six times normal soldiers are ordered to smother the reactor and to limit their exposure to the intense radiation they’re allowed to work for short periods only before they must be replaced by others the first responders to the accident in the early hours of that morning with a Chernobyl firemen they charged with incredible courage into a massive level of radiation they put out the fires and then they were taken to hospital where they began to die in the nearby city of pripyat people are asked to pack a few small personal belongings they are to be temporarily evacuated but they have never returned high levels of radiation mean the city and the countryside around the reactor remain an abandoned exclusion zone the Chernobyl exclusion zone I’m traveling with a physicist who works in nuclear medicine she prefers to be called bionerd she’s been here several times before studying radiation getting a rise in levels here okay we’re up over five microsieverts analogy whoa up over eight nine microsieverts an hour the alarms going off on my Geiger counter the thing is screaming yeah yeah eleven like receive its analogy it’s like a hundred times natural background natural background is the level of radiation naturally occurring on earth on average it’s around point two microsieverts per hour but this place isn’t going to be natural bionerd and I are going into the site of the world’s worst nuclear accident we are going into the city of Pripyat where the warm forest slowly claims the city visitors are allowed in here but only for brief periods and never overnight
this was a model city about 50,000 people lived here mostly workers at the nuclear power plant and their families
this is what the world looks like without people nuclear reactors like the Chernobyl reactor split uranium atoms they smash them into fragments and that releases heat which is how they generate electricity when uranium atoms smash they break into smaller fragments and when the Chernobyl reactor blew it spread those fragments across the city like dust the light dusting of invisible smashed uranium atoms still radioactive is what our Geiger counters are picking up the radiation level is about 20 times average background that’s not too dangerous for this place because the radiation released from the reactor coated this city unevenly so there’s hot spots that are really dangerous even lethal a lot of people are afraid of radiation but you’re not why not I’m not scared of radiation because you know I just can attach a different kind of sense to myself by using a Geiger counter and if you know what you’re doing and if you know how to interpret these readings then you’re pretty much as safe as if you were to cross a road and just look left and right for the cars I’m only walk when there’s no car what are the biological effects of getting exposed to radiation these high doses of radiation if it’s very very high doses like this it does not only damage your immune system but it also yeah demet just your entire body you could you could say it’s pretty much to being hit by a truck so your DNA gets wrecked the cells don’t function anymore and if your cells don’t function you know you’re done but the effects radiation has on a person always depends on the dose and the time it’s received you know for example if I give you one bottle of vodka and I say chuck it down and you’ll be going to the hospital because it will be intoxicated the poison plant if I give you one bottle of vodka and say drink that evenly over a year you won’t feel anything so it’s the amount of substance or radiation exposure in their terms that actually makes a poisonous or non poisonous the most insidious thing about radiation is how invisible it is you can’t feel it you can’t smell it or see it this could be pristine wilderness but it’s not and even the effects of radiation are almost invisible it may make you sick but perhaps not today or this year maybe you’ll find out in 10 years time that you have certain form of leukemia was that caused by your exposure to radiation or were you gonna get it anyway and that’s the problem with radiation that’s why people fear it I think so much I’m about to go into the hospital at Pripyat this is where the firemen were taken after they fought the fires at the Chernobyl reactor that is the door to the emergency room at the per Fiat hospital this is where the firemen were brought after fighting the blaze over at the Chernobyl reactor their clothing is actually still in the basement but I want to go down there to see how contaminated that clothing is and I want to understand what those firemen went through bionerd says the radiation down there might be ten thousand times higher than natural background and that’s dangerous so we need protection you don’t want to ingest or breathe in this stuff I think this is the time when I get a real sense of the danger of radiation it’s right here the main radiation down here is from one particular fragment of split uranium atoms it’s called cesium 137 and the radiation it’s releasing is what you can hear the basement is not too high one micro sievert per hour that’s five times natural background
on the floor up ahead what we had come to see a boot from one of the Chernobyl firemen that’s 10,000 times natural background radiation and then we found a room with a pile of the fireman’s gear tunics boots and helmets heaped on the floor that’s 2,500 times higher than natural background radiation and I was happy to stay outside but then bionerd went in
we had been down there just four minutes but that was enough we had seen the clothing of the firemen of Chernobyl it was intense that put that in perspective if you’re down there for an hour that would be what you’d normally receive in a year and they’ll also you know if you receive your dose all at once that’s much worse than having it spread out throughout the year because over that time your body is time to repair any damage but you know you get higher doses all at once that’s when it becomes dangerous to understand why this place is still so toxic we need to understand half-life the rate at which radioactive atoms decay imagine this soccer ball is an atom of cesium 137 it is unstable and at some point in the future it will spit out particles decaying into something that is no longer dangerous but I cannot tell you when it will do that it could be today or next week or even a hundred years from now but what I can tell you is that if you have a whole bunch of these atoms but then in 30 years exactly half of them will have decayed emitted their radiation and become no longer dangerous that is the half-life of cesium 137 it’s 30 years now it’s been about 30 years since the Chernobyl accident and in that time half of the caesium-137 that was released has decayed and the other half of it is still here still releasing radiation that is why the firemen’s clothing is still dangerous it’s also why people won’t live here again for hundreds of years
uranium has ensured the people of Pripyat will never return
some fragments of split uranium atoms have half-lives of just seconds but others like cesium 137 last for decades high above the city out on the horizon the Chernobyl reactor itself and the most astounding half-life of them all uranium that is the damage true noble nuclear reactor in 1986 after the accident it was encased in the sarcophagus that you can see now but it’s weathering and cracking and needs to be replaced so they’re building a new confinement structure over here they can’t build it above the old sarcophagus because the levels of radiation are still too high so they’ll have to slide the whole structure across it’ll cost billions of dollars and this structure will last a hundred years and that is only a temporary solution because the half-life of uranium 238 is four and a half billion years it’s the same as the lifetime of the earth so in five billion years when all life has ceased on this planet and the Sun is engulfing the earth only half of the uranium which is still in that sarcophagus will have decayed away but there are other dangerous radioactive fission fragments in there with much shorter half-lives and the astounding thing is some of these can be used to save lives in this unremarkable building they take what makes Chernobyl so dangerous and they make a life-saving medicine all right I am all set suited up and ready to go into Australia’s one and only nuclear reactor this is not a power reactor it is a research reactor and here they create medicine and technology
the medicine they make here is called technetium-99m but what’s really exciting is where they make it okay please proceed this is a nuclear reactor it’s actually an open pool reactor which means that the core is visible 12 meters underneath that water
you can see a blue glow down there which is actually called Cherenkov radiation and what that is is electrons moving through the water faster than light can move through the water and that creates what’s kind of like an optical sonic boom that’s the blue glow of light which forms a cone behind every electron down there they are splitting uranium atoms into fragments it’s the first step in making the medicine technetium-99m technetium-99m has a half-life of just six hours it’s a crucial medicine used to detect cancer here I met up with Jason it was actually 2001 and I was playing Australian rules football and it was a pain in my leg and it just got worse and worse and I assumed I had a hip injury and saw a orthopedic surgeon expecting a hip operation and he said you’ve got a tumor about that long you’re like there’s a there’s a few key tests but this one is the key test so what do you reckon should you be radioactive you’re gonna tell me you don’t seem very radioactive that reading is about the same as everywhere around this hospital and now the highly radioactive technetium-99m is injected into Jason this is the kind of radiation we saw in Chernobyl and what they’re injecting you with is actually fragments of uranium there you go doesn’t freak you out well eyes are open and I’m breathing as you can hear from my Geiger counter I’m getting close to a radioactive source in this case it’s Jason he is actually emitting lots of gamma rays right now and in the same way that my Geiger counter picks up these gamma rays this machine is actually detecting those gamma rays and making a picture out of them because technetium gathers at the site of fast-growing cancers and that allows us to determine if there are any tumors in Jason’s body because they’ll be glowing quite brightly so this allows us to spot cancer earlier and treat it better but what about Jason who’s now full of radioactive technetium-99m well that’s where the six-hour half-life kicks in to 6d I yeah 200-300 look at that that bit of you is going on well I saw something similar when I was a few hundred meters from the Chernobyl reactor that blew up it’s amazing have you heard about half-life have you heard that term before that half-life means how long it takes for half of the stuff they’ve put in you to decay so when it’s reading right now around 200 micro sieverts an hour the half-life of this substance that they put in here is about 6 hours so in 6 hours this should be reading 100 yeah in another 6 hours it’ll read 50 and then 25 and so on so it cuts in half every 6 hours 6 hours yep the uranium fragments that foul over Chernobyl had a longer half-life than just six hours and I wanted to know what happened to the people who lived here I’ve come to London to meet someone who knows a lot about Chernobyl chair of molecular pathology of cancer at Imperial College London professor Geraldine Thomas Geraldine has been studying the health effects of Chernobyl through a collection of tissue samples gathered for almost 20 years in the early 1990s it became apparent fairly quickly that there was an increase in thyroid cancer in those who were very young at the time of the accident Farah cancer in children particularly those under about 1416 is very very rare and it was obvious that more and more children were starting presents with thyroid cancer in the case of Chernobyl there was an aweful of iodine that was released and that iodine was shot up into the atmosphere and then came back to earth very quickly when it rained and was deposited on the ground the cows eat the grass and the idea becomes concentrated in the cow’s milk which the children then drink so quite a lot of the the iodine that’s taken in that’s radioactive we release its radiation while it’s inside the thyroid hence you get an increase in thyroid cancer iodine is very short-lived in the environment it has a short half-life of eight days so within three months of the being a release of radioactive iodine it has disappeared from the environment what I wanted to know from Geraldine was what happened to the people of Chernobyl there were 28 people who were exposed to very high amounts of radiation the firefighters they were trying to put out the fire who died of acute radiation syndrome and to date there have been about 15 deaths from thyroid cancer that’s all more people died from falling out of bed in the UK every year than have died from the effects of Chernobyl the toll of Chernobyl is controversial a United Nations report acknowledges those 15 fatal cases of thyroid cancer and to date no persuasive evidence of any other health effect that can be attributed to radiation the important part though is those two words to date because some cancers take decades to develop how long do you think Chernobyl won’t be inhabitable for Chernobyl is not uninhabitable and there are quite a lot of people who live in that area they’re mainly old people people whose land that has been for generations often move back and stay there I met Ivan and Maria who despite the radiation had moved back to their village do you enjoy undermine Cooper with us you can somehow achieve ordinary Barbara boys did this for eg doc this couple lives completely off the grid their self-reliance they get their own water from a well you use a scythe cut down their weeds they grow their own crops I will keep going I will keep going all it took for this to happen was the biggest nuclear accident in the history of life on Earth this area is to the south of the reactor and because the wind was blowing the other way when the accident happened most this land is not contaminated at all we’re reading about 0.15 microsieverts an hour just probably very similar to the level of radiation where you are right now no one doubts high levels of radiation are dangerous what is less clear is how much low-level radiation is dangerous radiation is a bit like sun exposure we know there’s a relationship between exposure to the Sun and development of skin cancer melanoma in particular now we all accept that and we we aren’t asking somebody to say this is a safe dose for sun exposure yet for radiation it’s exactly the same the principles are the same a small amount of exposure is perfectly okay a large amount of high dose exposure as with alcohol is extremely dangerous we’re a very long-lived species so our bodies must have found ways over our evolution to be able to cope with low-dose radiation it may even be that low-dose radiation is responsible for evolution because we know it causes mutations and evolution is related to mutation events in our DNA so you can argue that we are extremely well adapted to a low-dose radiation environment life evolved on a radioactive earth inside the earth uranium decay helps keep the earth hot and fluid our continents slide slowly about the surface like a moving crust the movement causes earthquakes but the one on March 11th 2011 Friday afternoon off the coast of Japan
just ten minutes warning after the quake came the tsunami a 7 meter wave relentless in its power the huge white cloud bursting across the horizon is the number one reactor shed at the Fukushima Daiichi nuclear atomic emergency and there are fears of radioactive leaks from a nuclear reactor in the disaster zone this is the town of Okuma which has been abandoned for over three years now and the level of radiation here is around five or six microsieverts an hour it’s a lot higher than natural background like 50 times higher so people aren’t allowed to come in here the mask is probably overkill it’s just to stop radioactive dust from getting into my lungs this is definitely one of the most radioactive places where I’ve been on this trip even though the release of radioactive material was less than Chernobyl only about 10% because it’s much fresher there’s still much more of it here much less of it has decayed there was another deeply surprising impact of Fukushima about 150 thousand people were evacuated from around the Fukushima reactor families compelled to leave their homes many have no choice but to live in portable housing like this I’ve come here to meet the Tagawa family they were evacuated in 2011 and have been here ever since Yuka you know the two cows are not allowed to return to their family home but they can visit so leaving the kids behind mr. Tagawa his wife Yuka and I set off to visit their home
it’s my first alarm which is set around 5:00 that was just a little hot spot there’s an exclusion zone around the Fukushima reactor just like at Chernobyl access is generally limited to people who used to live in the zone provided their town is declared safe to visit
mr. GAO is getting suited up but it’s not because of the levels of radiation it’s actually just because of all the weeds the yard is so overgrown and there’s a lot of little prickly things with burrs the level of radiation here at the house is about two microsieverts an hour may get a little higher as we walk into the yard but you know I think it should be fairly safe for us to go in there we ran inside the towers old house and when they left three years ago they thought they wouldn’t be away for long so most of their stuff is still here the kids old school uniforms just met these kids this morning definitely outgrown these uniforms who knows what the machi not so we’re taking Hawkeye Saturday mihari no quest key Dakota 9s Catalina Soren are in Qatar study session thinking oh gosh we’re not just a little Kauai off the dome I mustn’t the hidden cost of the disaster was psychological depression illness and suicide I hope we have a lot better understanding of what moving people in response to a radiation accident like that does to them psychologically and I think the most important studies will be those on the mental effects of disaggregating a community and I hope we learn our lessons we didn’t learn it from Chernobyl I really hope we learned it from Fukushima over 16,000 people died in the earthquake and tsunami the number who died from radiation in the nuclear accident is so far none not one after Fukushima Japan shuts down all nuclear reactors Germany starts doing the same and it seems that uranium may be finished as a source of energy but our hunger for energy hasn’t diminished there are now seven billion of us on this planet and from now until 2050 we will use more energy than in all of human history combined and uranium the rock forged in the explosion of a star crackles with an energy too tempting to ignore there are over 400 nuclear power plants in 30 countries and another 70 under construction nuclear power isn’t going away billowing out of that chimney is not smoke but water vapor and it’s not radioactive at all in fact the reading on my Geiger counter is well the lowest I’ve seen it anywhere in the world now this nuclear power plant emits no carbon emissions at all so would you consider it green well only if you overlook a very important problem the way most nuclear power plants operate today they use only about 5% of their uranium fuel the other 95% is highly radioactive waste currently the United States has 72,000 tons of nuclear waste mostly stored in containers like these some of this waste must be stored for at least a hundred thousand years the safety and security of this waste remains the responsibility of a company a board of directors and shareholders who will take responsibility for 100,000 years but what if there was a way to use this waste dr. Leslie Duan is one of a new generation of nuclear engineers designing the next generation of nuclear reactor most nuclear waste lasts for hundreds of thousands of years and my reactor is able to take that long-lived waste and break it down and extract almost all of its remaining energy and if you take all of that waste and put it into these reactors you could power the entire world for about 72 years you’ve been taking into account increasing demand how is your reactor design different it uses a liquid fluoride salt as fuel so if you have an accident it’s able to shut itself down safely our reactor can run entirely on nuclear waste it can’t meltdown and it’s cheaper than coal I think that Fukushima gave us this renewed sense of focus almost that we really need to work to improve these nuclear reactors we know that there are so many benefits to the technology for making cheap carbon-free electricity but it made us more aware of all the work that needs to be done to bring all of the plants into the future Leslie thinks her reactor is less than a decade away but I wanted to know what it felt like living with one of the current reactors in your front yard for me there’s measured risk with being next to a power plant there’s measured risk with you know being next to any factory a chemical factory right obviously if there’s something catastrophic that happens at a place like this you know this place would be a zone for 50 years Robin Shannon moved here in 2011 just after the Fukushima accident so tell me about the siren what’s the idea with that it goes off every first Wednesday of every month and it just goes for a while and then it shuts off they tell us it’s just make sure it’s still working yeah they’re just testing them have you ever heard it go off not on its schedule yeah the kids and I have heard it we all just kind of stopped and they looked at me and it’s just that fear of if it blows what’s gonna happen is or if there’s a leak what’s gonna happen to us so just kind of panicked a little from what I understand it’s but it’s one of the cleanest forms of power that we have and there’s no pollutants that’s the upside I guess the downside is if it doesn’t we the two examples would be Chernobyl and Fukushima but like I said it’s a it’s a it’s a measured risk
Rob and Shannon might be right the entire story of uranium is perhaps one of measured risk
when I began this journey to understand uranium I have to wear this badge everywhere I went it measures my cumulative exposure to radiation I’ve worn it here among some of the largest uranium deposits on earth where uranium is actually woven in to the creation stories of a people who have lived here at thousands of years and have worn this badge into places where people may never live for hundreds of years I discovered how he took uranium and one morning 70 years ago in the New Mexico desert we unleashed the power of the Dragon we launched ourselves into the nuclear then being what they are wouldn’t it really have been better if this thing hadn’t been invented of course you’re right mr. Benson the energy and the atom is the most destructive force the world has ever seen it can also be one of the greatest blessings God has irregular which is it to be because on that depends the future of mankind so what should we do with uranium as a physicist I’m tempted to say it’s such a great source of power it has such incredible energy density and has so many benefits that way how can you ignore it but after studying it after searching the world and following the story of uranium the feeling that I’m left with is that it’s not ready to take over and seeing how far renewable energy has come that suggests to me that there are alternatives these days and that we don’t need to go with uranium we don’t need to risk another place like this and yet every year uranium treats disease and every year saves more lives than it has ever destroyed even including the atomic bombs and just imagine a world where next-generation reactors could produce massive amounts of clean safe energy we live in an age where the nuclear dragon has been unleashed where that leads us remains to be seen but there is no such thing as a future without uranium
uranium had one last surprise for me after all of the radioactive places I had been what was the reading on my radiation monitor well from natural background radiation we all get an average of 2,000 micro sieverts a year my reading was just 280 more for me the journey was worth the risk