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Old May 1st, 2012, 02:42 PM   #41
Squirrelking
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Just to address a few points:

Since Fukushima there has been a full review of the AGR and PWR fleet in the UK (and I'm sure the remaining Maxnox reactors have had one too) which is available to view via EDF Energy. Disaster management has been thoroughly looked at and there are several upgrades taking place across the fleet in order to address immediate concerns. Further to that there has been an ongoing seismic upgrade programme for a number of years now across all sites.

Submerging a reactor is bad news, aside from anything else you then need to submerge the turbine hall and deal with the knock-on effect of local water table seepage into the buildings. Then there's the added cost of lifting gear used to perform maintenance and such. As they are usually build in coastal areas that's also going to be really bad news in the event of flooding.

On the subject of remote locations, there are two reactors in Hartlepool and four in Heysham. The main problem with building near built up areas is the issue of exacuation and crisis management should an off-site nuclear emergency ever occur which is a hugely varying term for the degree of danger the surrounding area may be in. Basically, any site incident that releases or has the potential to release any amount of radiation across the site boundary must be declared as an off-site nuclear emergency. Imagine the panic that could be caused from a potentially very minor event.

CHP is certainly possible as it has been done in Russia but it's also the issue of trying to get people to accept it having come from a nuclear power station. You can seperate streams all you like but some people will still be convinced that it will give them cancer because their mate with the tinfoil hat said so. There is also the issue of electrical efficiency being lost with CHP being utilised (steam is bled off at a higher temperature so cannot be used for generation) however that is usually made up for by overall efficiency being improved.
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Old May 7th, 2012, 04:04 AM   #42
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Japan has shut down its last operational reactor now, they were supposed to be restarted after inspections but no local authorities have granted permissions for restarts.

Back in the UK theres been a huge number of bidders for the Horizon site and reactor project EON cancelled from Russia, the Middle East, China, USA. In all theres been five bids for the future reactor with the winner to be the one which can build it the fastest.
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Old May 7th, 2012, 06:22 AM   #43
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Japan is being absolutely ridiculous. I'm dreading summer, electricity is going to be super unreliable.

Annoys me so much how over blown the Fukushima stuff was. The media loved to rant and rave about nuclear apocolypse whilst ignoring the real major disaster of the tsunami .
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Old May 7th, 2012, 10:14 AM   #44
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Quote:
Originally Posted by Squirrelking View Post
Since Fukushima there has been a full review of the AGR and PWR fleet in the UK (and I'm sure the remaining Maxnox reactors have had one too)
Surely just Sizewell B then?


Japan's knee jerk reaction is amazing. They sustained a good track record with nuclear power generation. Rather than learn from operational experience on the event (which the Nuclear industry relies heavily upon) they'd rather shut perfectly operable stations down.

Reading a scientific report earlier, it was argued in a situation like the one faced by Japan a PWR may have had a lesser side effect to the tsunami. However I'm tad skeptical - emergency diesel generators for a PWR would be under the same risk as those for a BWR if they aren't located in the correct place.

In the UK when considering locations Squirrelking has it spot on. The low risk of an off site nuclear event must be taken into consideration.
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Old May 8th, 2012, 02:20 AM   #45
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Generally considered safer as the opposite effect to Fukushima, if there was a failure and the water boiled off unlike Fukushima theres no chance of a meltdown as without water the reaction actually stops (it even slows down the hotter the water). So unless it was submerged in heavy water it would fail safe.
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Old May 8th, 2012, 10:41 AM   #46
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Quote:
Originally Posted by WatcherZero View Post
Generally considered safer as the opposite effect to Fukushima, if there was a failure and the water boiled off unlike Fukushima theres no chance of a meltdown as without water the reaction actually stops (it even slows down the hotter the water). So unless it was submerged in heavy water it would fail safe.
In a PWR/BWR if there is a loss of coolant accident (LOCA) there will be a partial meltdown at least.

PWRs are designed such that the hot and cold legs of the reactor are above the fuel, meaning the reactor cavity and internals are always submerged in water. However when there is loss of pressure (due to a LOCA), thermodynamics states the boiling temperature will plummet. At an operating temperature of over 300 degress C, the reactor will quickly boil off any remaining coolant, and a meltdown may start. However before anything becomes a LOCA the defence in depth will stop it. For example the station automatic control system (SACS) will automatically trip the reactor if ideal operating conditions are not met.
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Old May 8th, 2012, 12:59 PM   #47
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In a PWR reactor water is required to act as a moderator and stop the reaction burning out by containing the neutrons, as the density of the water falls (either from heating, boil off or replacing heavy water with light water) the reaction rate falls. Remember in a PWR theres two seperate water systems, the steam in a closed loop which produces power and the flooded reactor bed.
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Old May 8th, 2012, 05:25 PM   #48
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Quote:
Originally Posted by WatcherZero View Post
In a PWR reactor water is required to act as a moderator and stop the reaction burning out by containing the neutrons, as the density of the water falls (either from heating, boil off or replacing heavy water with light water) the reaction rate falls. Remember in a PWR theres two seperate water systems, the steam in a closed loop which produces power and the flooded reactor bed.
You're correct. What you've just described is a negative moderator temperature coefficient, which a PWR has - it's an inherent and passive safety system, it'll always be there.

I also fully understand that a PWR has primary and secondary circuits. However no matter how negative the moderator-temperature coefficient is, when there is a LOCA some/most of that coolant will be boiled off. Which is why PWRs have an ECCS (emergency core cooling system). Heck Sizewell has a RUHS (reserve ultimate heat sink) as a last resort.
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Old May 9th, 2012, 01:04 AM   #49
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The ocean?
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Old May 9th, 2012, 05:34 AM   #50
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^ Whenever you trip a reactor the heat previously generated within the fuel will continue to be generated for a substantial time afterwards. If your coolant is lost then the fuel will go into partial meltdown unless the temperature is controlled hence the huge problems they were having with the Fukushima cooling ponds.

eXSBass - when I was referring to the fleet I was referring to both collectively (ie. EDF Energy)

Not sure on Japans track record either, they've had a few incidents over the years including some fuel going critical mid fabrication and falsification of safety inspections. All in all pretty shonkey and not a bit of previous OPEX learnt.
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Old May 16th, 2012, 02:03 PM   #51
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Attended a talk by GE Hitachi last night on PRISM rector tech and possible deployment as a measure to reduce our plutonium stockpiles.

They reckon that with 45 day fuel cycles they could have all 112 tonnes of Pu that we hold irradiated to the point of inviable for nuclear proliferation (1000 REM/ Hr) in 5 years (provided Sellafield can keep up with store emptying).

Sounds great but I ended up leaving with more than a few unanswered questions that occurred to me on the drive home. The costing for one thing (they want to charge the government for every kilo that they irradiate and use that money to pay off the capital costs in those 5 years!) and the long term storage of the fuel for another. They do say that they want to burn it for electricity but in the last breath they had said that the US export licence wouldn't allow then to reoptimise it for best efficiency (breeding). Sounds a bit pointless really, yes you get rid of the Pu stockpile and the transuranic products are safe within 300 years (as opposed to 300,000 years with present tech) but once it's gone it's gone. Never mind the insane costs of paying for a reactor over 5 years.

Breeder/ burners, when they are proven, are the future but I'm not sure this is a model that will give the best benefit.
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Old May 22nd, 2012, 12:32 PM   #52
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That's quite interesting SquirrelKing. I share your sentiments about breeder reactors. If I recall correctly there is a large program of research in India into breeder reactors.

With regards to getting rid of the Pu stockpile, how to Sellafield propose to do so with their current fleet of evaporators? It's my understand evap C is on it's way out and evap D is facing delays?

I've been to a few talks on nuclear hosted by the IMechE and IChemE. Whilst informative the talks have always ended in a "but..." or "maybe...". That is there is never a positive definate conclusion to these nuclear presentations. Perhaps this is an inherent culture associated with the nuclear industry.
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Old May 22nd, 2012, 02:07 PM   #53
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A Prototype Fast Breeder Reactor(PFBR) of 500 MW is U/C in India and almost 86% of the work is complete. The whole project is expected to be completed by 2012 to mid 2013.

Source: 86 Percent Work on Kalpakkam N-plant Complete: Official
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Old May 22nd, 2012, 04:10 PM   #54
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Congratulations, welcome to 50 years ago, theres been dozens of fast breeder reactors around the world and India was the sixth country to develop the technology two decades ago.
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Old May 23rd, 2012, 03:48 PM   #55
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Quote:
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Congratulations, welcome to 50 years ago, theres been dozens of fast breeder reactors around the world and India was the sixth country to develop the technology two decades ago.

Yes there have been but it's only now that Gen IV is becoming commercially viable. PRISM was developed from a 1970's/1980's design!

Not sure on whats going on at Sellafield but GE Hitachi seem more confident in PRISM than MOX conversion.
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Old March 6th, 2013, 09:37 PM   #56
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Report Casts Doubt on Britain’s Nuclear Electricity Strategy

By STANLEY REED
Published: March 4, 2013

Britain’s plans to build a fleet of nuclear power plants by 2025 are “ambitious” at best and “unrealistic” at worst, according to a report to be released Monday by a committee of the House of Commons.

“It is worrying that the government does not have any contingency plans in place for the event that little or no nuclear is forthcoming,” the Energy and Climate Change Committee wrote in its report.

Replacing the country’s aging network of nuclear power stations is a major component of the government’s strategy to lower 1990 levels of greenhouse gas emissions by 80 percent by 2050. While nuclear power has disadvantages, particularly the production of radioactive waste, it emits virtually no greenhouse gases.

The French utility EDF and the British government are negotiating the terms for developing new nuclear plants. EDF has proposed constructing two plants at Hinkley Point on the Severn Estuary in southwest England, where the company operates two nuclear stations built in the 1970s. The new plants would be the first for Britain since 1995.

But cost estimates for the project have soared. Analysts say that in order for the project to be viable, EDF needs the government to guarantee it will buy electricity from the plants at prices substantially higher than the current market rates.

Read more: http://www.nytimes.com/2013/03/04/bu...tegy.html?_r=0
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Old March 6th, 2013, 10:46 PM   #57
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The whole nuclear waste thing is annoying me, modern alchemy* techniques have already demonstrated that the half-life of nuclear waste can be cut down to as little as 10 years. This isn't just theoretical, it has been done. Nuclear is safer than ever, and with more research into Thorium** based reactors, it is only getting safer.

* I mean the literal term of alchemy, altering the atomic structure of something. Not turning scrap into gold.

** The only reason Thorium wasn't used in the first place, is that it is useless for Nuclear Weapons.
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Old March 7th, 2013, 02:09 AM   #58
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But alas people are ignorant and nuclear is a scary word
A few weeks back I read about the big stockpile of nuclear material we have and how we're failing to do anything with it. Just ridiculous.
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Old March 11th, 2013, 12:23 AM   #59
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Quote:
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** The only reason Thorium wasn't used in the first place, is that it is useless for Nuclear Weapons.
And that will continue to be the reason that it won't be used (or even thought about much) now.
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Old March 11th, 2013, 05:13 PM   #60
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Quote:
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And that will continue to be the reason that it won't be used (or even thought about much) now.
You evidently aren't aware thet the UK govt. performed a consultation a few years ago with regards to what the hell we are supposed to do with our plutonium stockpile.

Options were - irradiate, vitrify and bury it, convert it to MOX fuel or save it for breeder reactors.

We have more than enough plutonium for military use, we certainly don't need more making your argument completely invalid.
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