Beginners guide to nuclear power stations ?

As a rule, anything which uses electricity to heat (immersion heaters, electric ovens, washing machines, tumble driers) are going to be very energy intensive. IT kit (PCs etc) can also be energy heavy.
Pop some sub meters on your electrical circuits (might costs a few bob) and see what’s using what. It’s very difficult to reduce what you can’t measure.

Like I say not using leccy for any heating apart from the kettle. Also mostly using laptops not desktops. I only ask because I don’t think we can go much lower.

Cooking? Telly and stuff on standby? |can use surprising amounts of power.

If yu want to check get one of the usage monitor things – I have one. Turn stuff on and off and check he amount of leccy used

I am using 310W at the moment – I desktop one laptop 2 amps, two alarm clocks, power supply to boiler, cooker

Gas hobs, oven rarely used, most things switched off at the wall and are modern so should be reasonable anyway.

Only things on all day are router, cordless phone, microwave, fridge of course, washing machine doesn’t tend to get switched off at the wall or cooker.

You may well be doing all that you can in that case. Domestic properties are not easy places to reduce energy consumption. I’d say just minimise washing machine use, check your refrigerator/freezer door (check seals, turn the thermostat as high as you dare, gas charge and wipe condenser coil), ensure good light switch discipline.

I quite like edukators idea of limiting electrical supplies.
I also think that only “A” rated (or better) appliances should be allowed on the market.

We’re using 450W at present: fridge, two computers, TV, amplifier, satbox, Fibreoptic box and a battery charger. Over 1500W production though.

Leccy bill is about 20 per month, I feel it could be lower.

Interesting report in the Herald today…

http://breakingnews.heraldscotland.com/breaking-news/?mode=article&site=hs&id=N0439221302098236431A

So, without wishing to be argumentative, but really trying to get some facts out of this painful thread:

1) The UK can produce all its electricity from renewables, IF we include some massive tidal barrages, and cut our usage by 75%

2) However, cutting our usage (from the anecdotal evidence from green-minded people on this thread) by that much appears to be an almost impossibility, even for those who care. In a real world democratic situation, despite what the idealists may think, such cuts cannot be made

3) Even if they were, with gas and petrol running out, it would be reasonable to assume that electricity powers more transport and heating than it has traditionally. So in actual fact, to cut current electricity usage to give some room to these sectors would require even greater reductions in ‘traditional’ usage

4) So what will fill that looming and large energy gap? Simply believing it not to be there is effectively tacit approval to build more cheap fossil-fuelled stations when it looms ever closer.

5) Admittedly when they go wrong, uranium cycle nuclear power stations aren’t great places to be. However, from an ecological perspective, a disaster such as Fukushima is minor compared to the destruction that would be caused by a large barrage or hydro scheme. Anyone who thinks that on a global scale, the very rare releases of harmful radiation from the nuclear sector are more damaging than the CO2 and other pollutants released in the day-to-day operation of coal-fired plants needs their head seeing to.

No tidal barrages are needed. Did you not bother to read all the links on this

so zokes – you are going a lot further than anyone in power with saying all fossil fuel must be replaced with something that produces minimal CO2?

Nice moving of the goalposts. so from a position of looking to replace the existing nukes and the old worn out power generation capacity with new and reducing CO2 output you have now gone to a totally ridiculous position of a zero emmisions power generation. That would require 50+ new nuclear stations and is completely unfasable anyway as nukes cannot be turned on and off quickly as demand alters. One of the issues they are finding in France with their 75~% nukes generation. 100 % is completly impossible to do

Now what I was arguing for was a reduction in CO2 output in line with Kyoto and similar agreements. Electricity generation is only a part of what produces CO2 in the UK.

Energy conservation in all energy using sectors has the potential to reduce CO2 output significantly as does renewables energy production.

So we can reduce the total amount of electricity used easily, we can reduce the amount of energy used to heat homes and businesses and that used in transport, we can significantly increase the use of renewables – these measures combined will mean we meet the targets for CO2 reduction.

Reneawables include tidal, wind, wave, solar as heating and photovoltaics. other measures that increase efficiency are such things as combined heat and power at a local level, increased insulation.

Cuts in energy consumption can be made easily across the UK

Anyone who thinks that on a global scale, the very rare releases of harmful radiation from the nuclear sector are more damaging than the CO2 and other pollutants released in the day-to-day operation of coal-fired plants needs their head seeing to.

What utter rubbish

Anyone who thinks the all too frequent releases of radioactivity has no significant effect is burying their head in the sand. Look at the state the Irish sea. People are still dying from the release at Chernobyl. Teh releases from Fukushima are still unknown but clearly getting worse still and will kill people for decades – how many we don’t know.

, a disaster such as Fukushima is minor compared to the destruction that would be caused by a large barrage or hydro scheme.

🙄

What utter rubbish

But then you follow it with this tripe. 🙄

Anyone who thinks the all too frequent releases of radioactivity has no significant effect is burying their head in the sand

Get real TJ.

Go and have a look at the ecological and human damage anthropogenically-driven climate change is already having, never mind its predicted impacts. Then come back here with cold, hard, peer-reviewed data (not your self-important myopic views) showing me that the impacts of radiation from civilian nuclear power generation is even on the same scale.

Your bias is ridiculous.

the very rare releases of harmful radiation

all too frequent. Not very rare at all.

a disaster such as Fukushima is minor compared to the destruction that would be caused by a large barrage or hydro scheme

Utter ridiculous assertion. NO TIDAL BARRAGES ARE PROPOSED OR NEEDED

You equate large scale release of radiation with building a dam?

How about your shifting of the goalposts to fossil fuel free electricity generation? You total refusal to acknowledge that significant energy / CO2 production reduction is possible

Just a ridiculous set of baseless assertions from you.

It is only proposed to build 16 gw of new nukes. Still leaves that gap. How are you going to fill the other 40 GW needed?

we can significantly increase the use of renewables – these measures combined will mean we meet the targets for CO2 reduction

What’s the timescale for CO2 reduction, and how much real baseload renewables will we have online by then? More importantly, given all the old stuff needing shutting down, what new baseload capacity should we be getting to replace it?

Anyone who thinks the all too frequent releases of radioactivity by coal fired power stations has no significant effect is burying their head in the sand.

FTFY

Look at the state the Irish sea.

What about it?

People are still dying from the release at Chernobyl.

Reference or it’s untrue.

Teh releases from Fushiyama are still unknown but clearly getting worse still and will kill people for decades – how many we don’t know

You’ve been strangely quiet recently regarding news from Japan – not noticed that they’ve now stopped a lot of the leaks? Got any evidence for your completely unsubstantiated assertions about deaths? I suppose “we don’t know” is at least accurate, as that covers 0.

How are you going to fill the other 40 GW needed?

How are you going to fill the 16GW (when tidal will be 2.5GW max by 2020 for the whole of Europe according to your own link)?

How quickly do you think you can get nukes built – not a shred of a chance of getting any new nukes on line by 2020 ( or do you really think they can be built in 8 1/2 years} whereas 5 + GW of tidal is at planned and installation has started. and will be online in 2020. Planned, costed, planing consents given, funding in place.

News from Japan? I have been following it. Have you? They are having to empty a containment pool of “mildy radioactive water” into the sea so they can fill the pond with highly radioactive water from the reactors where containment is cracked.

They still don’t know how much of the cores are damaged and how much containment is breached. deaths are absolutely certain from the amount of radioactivity being released could be dozens could be thousands – we don’t know as they have not stopped the releases. The leaks you refer to are from containment into groundwater. They are hopeful they have stopped or slowed this – however that is not the only source of radioactivity releasead they don’t know how many cracks there are – and the leak pluggng is not permanent solution. permanent meaning needs to last for thousands of years

I have repeadedtly said how the 16 GW can be covered. renewables,energy efficiency in all energy consuming sectors means we can reduce CO2 release as a country.

Now you tell me how you are going to get new reactors built in 8 1/2years.

deaths are absolutely certain from the amount of radioactivity being released

More unsubstantiated assertions. How much radioactivity is being released exactly? How harmful is that to human health?

you tell me how you are going to get new reactors built in 8 1/2years.

I refer you to Sizewell B. Not sure if you’ve heard of that? Have we mentioned it on here before? Construction started August 1987, sychronised to grid February 1995. I make that 7.5 years 🙄
(of course I could mention Calder Hall being built in 3 years, but unlike you I wouldn’t rely on data from 50 year old power stations to support my arguments).

I have repeadedtly said how the 16 GW can be covered.

You’ve never got anywhere close to costing it out – just lots of handwaving.

Got any hard data on where that 5GW (presumably peak, so needs a bit of derating even if it’s true) of tidal is going to be? You’ll have to forgive me for being dubious given your own links suggest Tidal stream and wave generation deployment could account for 1 to 2.5 GW of installed capacity in Europe by 2020 and By around 2015 Scotland will host 17.1 GigaWatts ( GW) of renewable capacity. At that stage only a minority of the capacity (3.0W) is likely to be from marine sources – noting that their marine source capacity includes 2.4GW of wind, and the only significant capacity beyond 2015 it mentions is “ten exclusivity agreements for six wave and four tidal projects with a potential capacity to generate 1.2 GW of marine energy in the Pentland Firth”.

Like smoking, you can’t ascribe any one cancer sufferer’s disease to radiation exposure, it could just be chance. However, when dealing with larger samples then you can ascribe higher incidences of cancer to various lifestyle choices and risk factors including radiation exposure. There’s enough data from nuclear testing, nuclear bombing and nuclear accidents to predict roughly how many excess deaths per 100 000 you’ll get from a given dose.

So, Aracer, given the level of exposure of Fukushima workers being reported (repeated yearly doses in a few hours according to Eins Extra) you need to use something like “there will be deaths due to radiation exposure resulting from the Fukushima accident”. The death toll won’t be zero and will be measured in units, tens, hundreds or thousands depending on how many people have been exposed to how much radiation.

Interesting piece in yesterdays Guardian, not sure if it’s already been posted. I make no comment on the truthfulness or otherwise of what it says.

Nuclear comment

given the level of exposure of Fukushima workers being reported

Which is what, Edu? You’ll need to give us actual doses, not relative ones. The numbers I’ve seen reported might be a lot larger than they’re supposed to get normally (they raised the radiation dose limit), but not enough to likely even cause one extra death due to cancer amongst the number of workers involved.

The death toll won’t be zero and will be measured in units, tens, hundreds or thousands

Why, are there thousands of workers there they’ve not reported on? 😯

Of course sad as it is, workers get killed in almost every industrial situation – coal mining, hydroelectric, windmills… TJ of course is busy trying to imply people other than the workers are at risk 🙄

Your bias is ridiculous.

In what way, in that I’m reporting facts and you’re doing some myopic arm-waving?

No tidal barrages are needed. Did you not bother to read all the links on this

Really? So we’re simply going to plant tidal turbines everywhere just like that, when there’s 5-10 GW on offer in the Severn. By using the same reasoning you have as to why nuclear apparently competes with renewables, surely large, capital projects win though in the real world, regardless of merit? Or is there another reason why nuclear is competing with small-scale renewables?

so zokes – you are going a lot further than anyone in power with saying all fossil fuel must be replaced with something that produces minimal CO2?

This is because I happen to believe that the damage this is currently being caused, and which will continue to increase due to anthropogenically-driven climate change is more than a little more worrying on a global scale than a Chernobyl or Fukushima once every 25 years. Our thirst for energy will always cause some damage to the world, but screwing up weather patterns, rainfall, ocean currents, and sea levels strikes me as something to be a damned sight more concerned about than a once-every-25-years major nuclear event, that mostly harms only humans. How much damage has been caused by oil exploration? Do you not recall a few years ago large swathes of forests being decimated by acid rain? These things happen in normal operation of fossil-fuel driven energy cycles

If you want to ignore all this and simply carry on your idiotic stance that radiation trumps everything else, well, I’d suggest you write an open letter to the residents of Cornwall and advise them on leaving. You’d also better never eat any bananas or other K-rich food (lots of natural K-40 in there you’re ingesting). Guess what, that UV from the sun that gives you a tan – radiation too. Then if you’re ill – the doses become staggering rather quickly compared to simply living near a nuclear power station.

But then what do I, or many scientists with a much greater knowledge of this field than either of us know? It appears very little, we must all listen to the all-knowing TJ

Nice moving of the goalposts. so from a position of looking to replace the existing nukes and the old worn out power generation capacity with new and reducing CO2 output you have now gone to a totally ridiculous position of a zero emmisions power generation. That would require 50+ new nuclear stations and is completely unfasable anyway as nukes cannot be turned on and off quickly as demand alters. One of the issues they are finding in France with their 75~% nukes generation. 100 % is completly impossible to do

I didn’t really move the goal posts. Just I worked out that as I was arguing correctly that coal power causes far more environmental damage than nuclear, it seemed a logical progression.

Again you take one half of my argument without the other – why can’t we have some energy reductions equating 20%, renewables at 20% and nukes taking the other 60%. You also state that nukes can’t be turned on and off easily, which in the older designs is true. In the newer designs this is getting better – who’s to say a little R&D won’t improve things further? As ever, I am not the one suggesting that it’s renewables vs nukes, only the short-sighted-to-the-point-of-blind posters are doing that.

Now what I was arguing for was a reduction in CO2 output in line with Kyoto and similar agreements. Electricity generation is only a part of what produces CO2 in the UK.

And what I am arguing for is that we generate our energy by the least-damaging means. I thought this was your argument against nukes, until most people proved you wrong.

Energy conservation in all energy using sectors has the potential to reduce CO2 output significantly as does renewables energy production.

And so would nuclear power. We save 20 %, we use renewables to take up at least 20%, we use nukes for the remainder – U-fission initially, and as Th becomes more viable, we replace as plant age dictates. Either way, if we don’t suss fusion soon enough, the entire argument will become academic.

So we can reduce the total amount of electricity used easily, we can reduce the amount of energy used to heat homes and businesses and that used in transport, we can significantly increase the use of renewables – these measures combined will mean we meet the targets for CO2 reduction.

But still leave coal and gas belching out emissions. The Kyoto protocol was agreed nearly 15 years ago, based on old science, and by the time its targets are met, it will be older science. Why are you objecting to my suggestion that we can reduce our emissions by more than the Kyoto targets, if you want to be pious about being ‘green’?

Reneawables include tidal, wind, wave, solar as heating and photovoltaics. other measures that increase efficiency are such things as combined heat and power at a local level, increased insulation.

Well I never – education 🙄

Now would you like me to state the blindingly obvious about how not all nuclear generation is the same?

Cuts in energy consumption can be made easily across the UK

But quantify this statement for it to be meaningful. You turning off your PC would be an energy saving. We both agree that 20% seems a reasonable aim. But by not supporting nukes, you leave a huge energy gap that will only be filled with coal – either existing or new. To consider burning coal as less damaging than nuclear power is quite simply wrong if you have any grasp of climate science. No IMO needed there – that statement is backed by a large body of peer reviewed evidence, some of which I have posted, that you still refuse to read.

What utter rubbish

TURN IT DOWN FOR ****’S SAKE!

Be nice or it’ll become a stupid row again, and I can’t stand it any more 🙁

Aracer – /zokes – I suggest you actually read the links on the amounts of tidal being proposed and what is proposed. Just in Scotland there is far more planned and than you claim. If England joined in as well there would be much more. However while all the money is being spent on Nukes there won’t be.

You also totally discount the amount of energy available from other sources

I was only every arguing for a modest and sustainable reduction in CO2 from a mixed bag of practical measures not elimination entirely – which is a totally ridiculous position.

So now you want what – 40 new nukes in the UK?

How many world wide? You want to see multiple nukes in areas of political and geological instability? there is not enough uranium to power the world. You are also again arguing for the use of tech that does not exist

Go my way we might well need some new fossil fuel plants. I propose CHP on a local scale – this of course has a huge efficient advantage in that effectively you are heating homes and businesses from the waste heat that currently is lost. Massive CO2 savings there. However given the efficiency savings possible in all sectors we can still reduce CO2 output significantly even if some new more efficinet conventional fuel is used

Herein lies one of your fallacies. a once in 25 years nuclear accident – increase the numbers of reactor exponentially as you suggest then these accidents will be far more frequent.

Climate change is not the only consideration in looking at the safety record – and you continue to do what you accuse me of – comparing the data from 40 yr old conventional power plants with your theoretical new nukes.

And finally – it is an either or situation to major extent. Both new nukes and large scale reneawables require massive investment. We will find it very hard to do one. We will not do both – again the history shows this. Investment in remnewables R&D is minuscule compared to nuclear. its only since we got holyrood that is not blindly wedded to nuclear that we have had some progress on renewables but only in Scotland. Westminster still does almost none.

Remember the 5 gw of tidal that is going to be on line by 2020 is only in Scotland.

So haow many new reactors worldwide? How are you going to fuel them?

zokes – Member

“Your bias is ridiculous”.

In what way, in that I’m reporting facts and you’re doing some myopic arm-waving?

You continually refute the potential of renewables despite the hard data. You continually propose that there is no possibility of any energy saving, you gloss over the difficulties in building new nukes, you downplay the dangers of nukes conveniently forgetting that the danger are more than climate change and that nukes are not carbon zero anyway

You latest one is to claim that there is some mysterious way round the issue of being able to alter the output of nukes to match demand. Apparently some new tech will come along to allow that.

Quote the numbers you’ve seen reported then Aracer. Mine (heard not seen) from Eins Extra are pretty clear : more than a year’s dose each time they went in. Don’t forget that three had serious radiation burns. After that kind of dose Tchernobyl experience says they will die prematurely.

yes, we could change the ‘severn barrage plan’ to a ‘severn lagoon plan’

but then instead of 10GW, we’ll only get 2 or 3 GW.

(this is actually my preferred option – a barrage would be very destructive)

you can’t just dump a turbine in the sea, and expect it to work – producing 5MW every day. there are site conditions to consider, and they need to be right.

(speed and duration of current, condition of the seabed, shipping lanes, ecological concerns, etc.)

maybe there are thousands of suitable sites, maybe there aren’t… i don’t know, but to get 10gigawatts, we’ll need thousands of turbines.

Look at the state the Irish sea.

Looks alright to me.
I swim in it and eat Morecombe Bay shrimp.

I can’t be bothered to read back the whole way but it is clear that some of the workers left on site have now taken doses which health physics tells us will result in higher incidence of cancer later in life. How many will suffer and whether they will die from it are not yet known. But I don’t think it’s wide of the mark to say that ‘people will die as a result of this incident’. To say thousands will is well wide of the mark. As I see it to date the main risk to human health is to the workers on site. The discharges into the sea due to the isotope mix and the vast dispersal in the Pacific are not likely to have any lasting effect. I wouldn’t go swimming or fishing round there right now though.

some of the workers left on site have now taken doses which health physics tells us will result in higher incidence of cancer later in life.

Which is what they’re paid to do. There’s a reason nuclear workers are pretty well paid, which is that if it all goes wrong, they will be required to do potentially dangerous clean up work. They will have known exactly what they were potentially getting into when they signed up.

They will have known exactly what they were potentially getting into when they signed up.

Very revealing, Sobriety. Soldiers should expect to get blown up, coal miners buried alive and nuclear workers to suffer radiation burns. Serious leaks are to be expected then.

Very revealing, Sobriety. Soldiers should expect to get blown up, coal miners buried alive and nuclear workers to suffer radiation burns. Serious leaks are to be expected then.

Potentially, yes. Which is the point that you seem to have missed.

I belive they are currently operating ‘above and beyond’ and should be commended.

I belive they are currently operating ‘above and beyond’ and should be commended.

I’d agree with that, it takes a lot to keep going back in to do the clean up. I certinally wouldn’t work on a PWR/BWR reactor plant, as having the moderator double up as a coolant has always struck me as a bit silly.

Has anyone got any idea of what exposure the Fukushima 50 have actually received?

Best I can see so far is that three were sent to hospital after receiving an exposure of 180 millisieverts. another got about 150 millisieverts

No, in the grand scheme of things – thats equivalent to the dose of someone at Hiroshima, and there is no evidence of any lifelong damage to people exposed to that dose – in fact, they reckon that lifetime increase in cancer can be measured at about 5% increased risk of cancer per sievert – so these guys would have a potential increase in cancer risk of about 1-2%, and thats if the relationship is a linear non-threshhold one, (ie. there is a threshhold below which exposure does not increase risk of cancer),

by way of comparison – the workers who died from exposure at Chernobyl were exposed to in excess of 4 sieverts, in fact many got over 5 sieverts and survived – so, 20 times the dose these guys got – and they were working highly, highly radioactive stuff like graphite core material emitting equivalent 1000 sieverts…

so, when we’re supposing that these people will surely die – the data really doesn’t support the conclusion!

Has anyone got any idea of what exposure the Fukushima 50 have actually received?

Yes and no – I saw it in an article I was reading the other day but can’t find again. If I’ve remembered it correctly it said that close to 30 of them had now received a dose that will give them a cancer risk that is (i) higher than the population and (ii) statistically/scientifically attributable to the dose.

But I try not to state things as fact without being able to back them up – that’s TJ’s job.

No eveidence of lifelong damage to hiroshima victims Z-11. The doctor that survived to report didn’t agree:

“We were now able to label our unknown adversary ‘atomic disease’ or ‘radioactive contamination’ among other names. But they were only labels: we knew nothing about its cause or cure… Within seven to ten days after the A-bomb explosion, people began to die in swift succession. They died of the burns that covered their bodies and of acute atomic disease. Innumerable people who had been burnt turned a mulberry color, like worms, and died… The disease,” wrote Dr. Akizuki, “destroyed them little by little. As a doctor, I was forced to face the slow and certain deaths of my patients.”

Please do a little research before replying, you’ll appear less foolish.

p.s. I do understand that there’s a jump from ‘increased risk of cancer’ to ‘people will die’ if the numbers affected are as low as 30 or 50

Edu – he said “no evidence of any lifelong damage to people exposed to that dose”, not that people exposed to (higher doses of) radiation at Hiroshima weren’t adversely affected. Not having a go (given you seem to be trying to work with facts rather than fiction – unlike some on this thread), just correcting where you seem to have misread.

As for dosages at Fukushima, what I’ve read is that their radiation limit was upped from 100mS to 250mS (presumably per year, as that’s how they seem to address risk, hence I’m assuming those who reach that have to stop work) High enough to increase their risk of cancer. Not high enough for there to be even one extra death due to cancer (on balance of probabilities) given the size of the group involved. As mentioned above, Chernobyl workers got doses several orders of magnitude higher. Not nice of course that there is a chance one of them could die of cancer, but that’s a long way from TJ’s “thousands of deaths”, and if we’re really worried about people dieing doing their jobs there are lots of things we should stop before stopping people working on nuclear power stations.

Try reading again Aracer, I read it several times. Whichever way you read it Z-11s statement is incorrect.

Edukator – read again what I wrote before jumping in, that way, you’ll appear less foolish 😉

Thats equivalent to the dose of someone at Hiroshima, and there is no evidence of any lifelong damage to people exposed to that dose

Note that phrase – exposed to that dose!

some people at Hiroshima received more than that, some less! The death rates of nearly 90,000 survivors have been painstakingly studied and compared with people from other cities, so are a valuable source of information!

Most survivors endured an exposure of less than 100 mSv and, for these people, there is no statistically significant increase in cancer risk above background levels when compared with other japanese cities!

Above 200 mSv of total exposure, the effect of the radiation becomes a little more obvious but it is not until the dose was greater than 1,000 mSv that a major increase in cancers occurs.

Over 2,000 mSv, the risk of a survivor of the bombs dying from a solid cancer is approximately twice the level of risk in non-affected cities.

So – Read before jumping in, you might get Edukated…

these workers received less than 200 millisieverts, so, the data days no increased risk!

You’ve completely changed what you originally stated Z-11. People can read and can see that.

Using the data in here.

50 workers exposed to 1Sv and you can expect 4 to die as a direct consequence. 500 exposed to 250mSv and some will die too. The problem is that you can’t prove it statistically because of the statistical noise produced by peole dying of cancer caused by other things. When you start to look at very large populations (and a billion or so people live in eareas so far suffereing low level contamination) but very low levels then you can’t prove anything but common sense exptrapolation tells you people will be dying as a result of the contamination, however, they are hidden by the mass of people dying of cancer anyhow.

The inability to prove a perfect statistical correlation is not proof that there isn’t a cause and effect.

Without wishing to get tied up in Grays and Sieverts (and we should be usings Grays not Sieverts when talking about burns), if someone gets enough Grays to cause radiations burns reported to and by the media within a day then they’ve had a dose of 10s or 100s of Grays and are doomed.

Edukator – I have changed nothing, I specifically stated that I was talking about effects at that dose, and aracer clearly understood my statement in that manner

nobody has actually said the burns were caused by radiation, they’ve said they were being treated as possible radiation burns,

your concept that “50 workers exposed to 1Sv and you can expect 4 to die as a direct consequence. 500 exposed to 250mSv and some will die too” presumes that there is a no threshold linear response, there’s no proof of that, and the data so far seems to not support it, rather the belief is that there is a safe threshold, below which there are no long term effects, due to the body’s miraculous recuperative powers.