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[Phys-l] next-generation nuclear reactors



1) Tomorrow is National Triskaidekaphobia Day.


2) Definition of lose/lose situation: More than half the population
is mad at the ISI for protecting Osama bin Laden, and more than half
is mad at them for not protecting him enough.


====================================

This is sort of a "heads-up" about a potentially interesting topic.

I emphasize that I don't know much about this. There could be all kinds
of crucial considerations that I have overlooked. All I can say is that
it might be an interesting topic of discussion.

The topic is "next-generation" nuclear reactors.

Quoting http://www.world-nuclear.org/info/inf08.html :

Several generations of reactors are commonly distinguished.
Generation I reactors were developed in 1950-60s, and outside the UK
none are still running today. Generation II reactors are typified
by the present US and French fleets and most in operation elsewhere.

In particular, the Three Mile Island and Fukushima reactors were
evidently 2nd generation designs.

(3rd generation) advanced reactors have been operating in Japan since
1996. Late 3rd generation designs are now being built.

The "next generation" will be called the 4th generation. AFAICT
the topic is still amorphous and open-ended, such that whatever
gets built that doesn't look like 3rd generation will be called
4th generation.

We are all scientists here, and we are supposed to uphold the rules
of scientific integrity. For example, if we are proposing a new
theory, scientific integrity requires us to evenhandedly discuss
all the relevant evidence for /and against/ the theory.

We need to beware because not everybody in the world plays by the
same rules. In particular:

The people who have been speaking for the nuclear industry for the
last 50 years evidently do not have this kind of integrity. They
have touted the good points of their reactor designs ("defense in
depth") but have been much less forthcoming about the weaknesses
("so-called depth notwithstanding, station blackout is a single-mode
failure that predictably leads to breaching all of the containment
and spewing radioactivity far and wide").

Reading the generation-to-generation comparisons is interesting because
it tells us the weaknesses of earlier generations.

Advantages of 3rd-generation reactors include:
* a standardised design for each type to expedite licensing, reduce capital cost and reduce construction time,
* a simpler and more rugged design, making them easier to operate and less vulnerable to operational upsets,
* higher availability and longer operating life - typically 60 years,
* further reduced possibility of core melt accidents,*
* resistance to serious damage that would allow radiological release from an aircraft impact,
* higher burn-up to reduce fuel use and the amount of waste,
* burnable absorbers ("poisons") to extend fuel life.

* The US NRC requirement for calculated core damage frequency is
1x10-4, most current US plants have about 5x10-5 and Generation III
plants are about ten times better than this. The IAEA safety target
for future plants is 1x10-5. Calculated large release frequency (for
radioactivity) is generally about ten times less than CDF.

The greatest departure from second-generation designs is that many
incorporate passive or inherent safety features* which require no
active controls or operational intervention to avoid accidents in the
event of malfunction, and may rely on gravity, natural convection or
resistance to high temperatures.

* Traditional reactor safety systems are 'active' in the sense that
they involve electrical or mechanical operation on command. Some
engineered systems operate passively, eg pressure relief valves. They
function without operator control and despite any loss of auxiliary
power. Both require parallel redundant systems. Inherent or full
passive safety depends only on physical phenomena such as convection,
gravity or resistance to high temperatures, not on functioning of
engineered components, but these terms are not properly used to
characterise whole reactors.

I believe the units on CDF are "meltdowns per reactor per year".
Given the large number of operating reactors, we would like the CDF
to be a very small number.

Evidently the actual observed large-release frequency is an order of
magnitude greater than the industry's "calculated" frequency. And
they wonder why nobody trusts them.



Back to the main point: Reading between the lines of the list quoted
above tells us /some/ of the weaknesses of the currently operating
reactors:
-- difficulty of operation
-- vulnerability to "operational upsets"
-- "possibility of core melt accidents"
-- vulnerability to aircraft impact
-- lots of waste
-- glaring unsolved problems dealing with the waste
-- bad economics


We can continue this by looking at the "4th generation" documents, e.g.
https://netfiles.uiuc.edu/mragheb/www/NPRE%20457%20CSE%20462%20Safety%20Analysis%20of%20Nuclear%20Reactor%20Systems/Fourth%20Generation%20Reactor%20Concepts.pdf

The goals of the generation IV initiative cover the areas of sustainability,
econpmic competitiveness, safety and reliability and security against weapons
proliferation.

So evidently the known problems with 3rd-generation (and earlier) reactors
include
-- bad economics
-- inability to "follow the load" on any reasonable timescale
-- problems with safety and reliability
-- lack of sustainability
-- problems with proliferation

I don't pretend to understand the whole situation, but it seems to me
that any one of those problems (not to mention all of them collectively)
would be a sufficient reason for not building any more reactors until
the problems have been dealt with.

In particular: The industry has heretofore seriously downplayed the
sustainability issue. A lot of people are surprised to hear that the
supply of 235U is neither renewable nor plentiful. The energy content
of the known reserves of 235U is comparable to the energy content of the
known reserves of coal or petroleum. And all 3rd-generation reactors
are fueled by 235U.

The original meaning of the word "fossil" refers to something dug up
from the ground. It does not refer to prehistoric life forms. From
the same root we have the word "fossorial" referring to an animal
that digs in the ground, such as a badger.

Therefore uranium must be considered a fossil fuel. It's not fossil
carbon, but it is fossil fuel.

I am not opposed to nuclear power in principle. OTOH I am opposed to
bad engineering and bad economics. Also I think that anybody involved
with something as dangerous as multi-ton quantities of radioactive
materials should be held to the highest standards of integrity.

We also need regulators who take their job seriously.

By way of analogy:
The FAA is far from perfect, but I mostly trust them to regulate
the aviation industry. They will suspend or revoke an air-carrier
certificate if they think something unsafe or dishonest is going
on. They can also impose million-dollar fines. They don't do
it often, but they have done it.

The aviation industry benefits from regulation, and they know it.
A rogue operator would be bad for the industry as a whole, and those
who play by the rules would take a very dim view of anyone who didn't.

I have much less faith in the nuclear regulators in the US or
Japan.
http://allthingsnuclear.org/post/4814761753/susquehanna-spent-fuel-pool-concerns-and-how-i-ended

Given the general lack of integrity in the industry, I hesitate to
recommend that anybody get involved in it. On the other hand, the
upside potential is enormous. I'm not sure that the problems with
nuclear power can be solved ... but I'm not sure that they can't.
If they could be solved, it would go down as the one of the greatest
achievements of all time.

As the proverb says: We won't know unless we try. OTOH I don't know
how hard we should try. There might be some obvious reason why this
topic is not worth pursuing. I don't know.

One idea that might be worth another look is the idea of a breed-and-burn
reactor. This idea has been around for 50 years, and nobody has been
able to make it work, which suggests that there are tremendous unsolved
problems. On the other hand, if it could be made to work, it would
dramatically change the sustainability issue. It would alleviate the
waste problem (and that part of the safety problem). It might also
alleviate the proliferation problem.

The point is that 238U is 200 times more abundant than 235U. Therefore
a 50-year supply of energy from 235U translates to a 1000-year supply of
energy from 238U. All breeder reactor designs so far have made the
safety problems worse and made the proliferation problems worse, which
explains why almost none have been built. OTOH a non-expert such as
myself can at least imagine a 4th-generation breed-and-burn reactor
that would somehow get the job done.

http://www.google.com/search?q=breed-and-burn+reactor

The wikipedia article on traveling wave reactors seems full of wishful
thinking and full of contradictions, but there are plenty of better
documents that you can find by googling.

The idea of breed-and-burn is that (almost) everything happens within
the reactor, so that no reprocessing is required. A reprocessing
plant is a proliferation nightmare. Even if a breed-and-burn reactor
requires occasional "reconditioning" of the fuel, that is supposedly
much less of a proliferation threat than full-blown reprocessing.

It seems to me that 3rd-generation (and earlier) reactors are a high
risk / no reward proposition. There is no point in having a nuclear
power industry unless it is economical, sustainable, and proliferation-
resistant. I don't know that the 4th-generation goals can be achieved,
... but I don't know that they can't. This seems like a high risk /
potentially-high reward proposition.

I emphasize that I don't know much about this. There could be all kinds
of crucial considerations that I have overlooked. All I can say is that
it might be an interesting topic of discussion.