The Pros and Cons of Nuclear Power

[garytse86]

What do you think about nuclear power?

How dangerous is nuclear power plants?
and from a physics point of view, how efficient is nuclear power c.f. coal-powered plants etc.?

and what about the advantages? There are no greenhouse gases released but what about nuclear waste?

 

[russ_watters]

There are quite a number of threads here on the subject, but briefly.

What do you think about nuclear power?

It is the only large scale, currently viable future source of power in use. In other words, with any luck, in 50 years, we won't be using coal, oil, gas, windmills, solar cells, etc. With any luck, we'll have fusion by then, but even if we don't, nuclear fission can handle our needs.

How dangerous is nuclear power plants?

So safe that statistics are meaningless when discussing nuclear safety. If you ever hear someone say "if this nuclear plant has a meltdown...", ask "how likely is that?" The answer is: so unlikely that the chance can't even be measured.

...and from a physics point of view, how efficient is nuclear power c.f. coal-powered plants etc.?

Slightly less efficient than other types of power plants. This question has little meaning though: consider that gas heat for your house is 80% efficient, heat pumps are about 30% efficient, and electric is 100% efficient. Which should you use? (answer: usually gas, sometimes heat pump).

and what about the advantages? There are no greenhouse gases released but what about nuclear waste?

Nuclear power produces small quantities of waste (orders of magnitude less than coal or oil) and is not released into the environement, ie. it produces no pollution.

 

[theCandyman]

I think nuclear power is a great step foward in both protecting our environment and producing energy. As for its dangers, it is just like fire, the more carelessly it is used, the more likely it will be dangerous. I'm no physict so I can't comment much on efficency of plants. The waste? That is the only problem I see in using it, but it is the lesser of two evils considering other energy sources.

 

[Astronuc]

Nuclear power is as safe as the designers, manufacturers and operators make it. There were safety margins built in the original designs, and with a gain of experience, some of the margins have been used to improve performance. However, if operators get sloppy, then nuclear power can become unsafe. (This is an overly simplist answer - but it is essentially accurate).

Nuclear plants are comprised of reinforced concrete structures (e.g. containment building), which contain the reactor system. These structures are more robust than the structures housing fossil plants of similar capacity.

Commercial nuclear power plants use fission (nuclear process) to generate thermal energy, which in turn is converted either through gas or steam turbines to produce mechanical energy, which in turn drives an electrical generator which produces electrical energy.

Most commercial reactors are light water reactors LWRs (PWRs and BWRs) which use the Rankine cycle to convert thermal to mechanical energy in steam turbines. CANDUs (heavy water reactor) also use the Rankine cycle, and so do the Gas Cooled Reactors in UK.

The efficiency of the Rankine cycle is temperature limited in order to limit coolant pressure or prevent corrosion (prolong life of components in radiological areas). For most nuclear plants using the Rankine cycle this means efficiencies of 32-34%. Coal plants can use superheated steam which can provide efficiencies in the high 37-38%, and modern supercritical coal plants may have efficiencies of up to 45% gross. High temperature gas-cooled reactors have been designed with theoretical effiencies of about 42%.

Gas-fired plants based on aircraft (jet) turbines (so-called aeroderivative turbines) can achieve thermal efficiencies of 42-45%, and if they feed a steam cycle (as in a combined-cycle plant), then the plant can achieve up to 60% thermal-to-mechanical conversion efficiency.
====================================

As for the waste (backend) - the long term storage solution in the US depends on the resolution of Yucca mountain as the final repository of the spent fuel from the US.

In the case of fossil plants, many (particularly coal) plants have filter systems to filter ash, otherwise the waste is discharged to the atmosphere (green house gases, and traces of Hg, U and whatever ash is not collected). Some old plants may have less efficient filtering systems - but that is a political-economic issue (i.e. we have the technology, but if it costs too much, we may not use it).

As for the front end - both uranium and coal come from the ground and mining it means lots of waste. That's another political-economic issue.

 

[Morbius]

What do you think about nuclear power?

How dangerous is nuclear power plants?
and from a physics point of view, how efficient is nuclear power c.f. coal-powered plants etc.?

and what about the advantages? There are no greenhouse gases released but what about nuclear waste?

Gary,

Nuclear power plants are VERY SAFE!

Compare the US experience of nuclear power with other activities.

Do you think airliners are safe? Every few years an airliner crashes and
kills a couple hundred people. Is anyone calling for the shutdown of the
air travel industry?

How about cars? Each year automobile accidents kill on the order of
50,000 people. Are cars safe? Is anyone calling for the elimination of
cars?

In the 47 years that we've had nuclear power in the US - we have had
one major accident - Three Mile Island - which did not injure the public.
[ There was major damage to the reactor - but the public was not
injured. The amount of radiation release was trivial ]

[ Some point to Chernobyl. Chernobyl was a flawed design - one that
US scientists pointed out was unsafe to the Soviets - who did nothing.
The operators were running a poorly planned experiment on the
reactor - and then didn't follow the plan. Chernobyl is an anomaly
that bespeaks more about the flawed Soviet system, than it does
about nuclear power as practiced in Western countries.]

When you talk about efficiency - do you mean the thermodynamic
efficiency of converting heat to electricity? In that case, coal plants
are somewhat more efficient because fossil fueled boilers are allowed
to run hotter than we let nuclear reactors run. The hotter the heat
source, the more efficient. However, the comparison between the
two is really "apples and oranges". The heat sources are different.
Might one be a little less efficient with the cleaner nuclear heat
source than a dirtier coal source in order to realize the advantages
of that cleaner nuclear energy source?

Additionally, coal plants put more RADIOACTIVITY into the air than
nuclear plants. Coal contains trace amounts of uranium and thorium.
Because we burn billions of tons of coal - we put thousands of tons of
radioactive uranium and thorium into the air. See the following from
scientists at Oak Ridge National Laboratory:

http://www.ornl.gov/info/ornlreview/rev26-34/text/colmain.html

which states:

"Americans living near coal-fired power plants are exposed to higher
radiation doses than those living near nuclear power plants that meet
government regulations"

As far as nuclear waste is concerned, the amount of nuclear waste
that has accumulated in nearly 50 years of operating nuclear power
plants, as well the waste from the Manhattan Project and defense
uses of nuclear energy - would fit in a volume the size of a high school
gymnasium. That's really trivial compared to the mountains of slag
from coal power plants.

Scientists from our national laboratories and the National Academy of
Sciences say we can safely dispose of nuclear waste in an underground
depository like Yucca Mountain. The opposition is basically political.

The waste can be safely transported to Yucca Mountain. Sandia National
Laboratory has done lots of testing on the casks used to ship the waste,
including putting them on a truck parked across a railroad track, then
putting rockets on a locomotive and slamming it at high speed into the
cask:

http://www.sandia.gov/recordsmgmt/ctb1.html

I think the case for expanded use of nuclear power is well made.

Dr. Gregory Greenman
Physicist

 

[CharlesP]

Give up nuclear power - see my post on radioactive material.

 

[russ_watters]

No offense, but your post in the reprocessing thread ignores everything said before it. Its quite simply, wrong.

 

[CharlesP]

No offense, but your post in the reprocessing thread ignores everything said before it. Its quite simply, wrong.

I keep up with Physics Today and mainline scientists have determined that reprocessing is too hazardous. One Rocky Flats is enough. I doubt that even a Republican government will permit it any time soon. Long term storage is on hold because of contrary reports. This is a very serious impediment to any long term continuation of nuclear power. A survey of previous posts shows that some folks are not doing their homework. Three mile Island demonstrated the same horrible irresponsibility in US power companies that Chernobyl demonstrated in the USSR.

 

[Morbius]

I keep up with Physics Today and mainline scientists have determined that reprocessing is too hazardous. One Rocky Flats is enough. I doubt that even a Republican government will permit it any time soon. Long term storage is on hold because of contrary reports. This is a very serious impediment to any long term continuation of nuclear power. A survey of previous posts shows that some folks are not doing their homework. Three mile Island demonstrated the same horrible irresponsibility in US power companies that Chernobyl demonstrated in the USSR.

LIAR LIAR LIAR!

The Physics community is very supportive of Nuclear Power and has
made no such statement that reprocessing is too hazardous.

If you've been reading Physics Today and you make the statement above,
then either you are a liar or you didn't understand what you read.

Contrary to your assertion above, there is no consensus by "mainline
scientists" that reprocessing is too dangerous.

If anyone is not doing their homework - it is YOU!

There is absolutely NO comparison between Three Mile Island and
Chernobyl. At TMI, the release of radioactivity was trivial - much less
than the natural radioactivity. The containment system worked very
well.

I think the Judge who heard the TMI lawsuits summarized the case very
well when she summarily dismissed the complaints against the utility
which operated TMI:

http://www.pbs.org/wgbh/pages/frontline/shows/reaction/readings/tmi.ht

Judge Sylvia Rambo states:

"Defendants, proffer of evidence and that put forth by Plaintiffs in both
volume and complexity are vast. The paucity of proof alleged in support
of Plaintiffs, case is manifest. The court has searched the record for any
and all evidence which construed in a light most favorable to Plaintiffs
creates a genuine issue of material fact warranting submission of their
claims to a jury. This effort has been in vain. ..Those standards combined
with the scarcity of evidence of record to support Plaintiffs, claims
mandate the result reached by the court today. "

You demonstrate your ignorance further when you try to connect
nuclear power with Rocky Flats. Rocky Flats was a nuclear weapons
facility run by the Government - and doesn't have anything whatsoever
to do with the commercial nuclear power industry.

Dr. Gregory Greenman
Physicist

 

[Astronuc]

There are some physicists in organizations such as Union of Concerned Scientists and Nuclear Control Institute who actively oppose the use of Nuclear Energy. However, they seem to be in the minority.

As for the premier organization of Physicists, The American Physical Society, please refer to the policy statement 00.3 ENERGY STATEMENT (Adopted by the Council, 19 November 2000), "Energy Policy for the Twenty-first Century", which states -

"The Council of the American Physical Society believes that the use of renewable energy sources, the adoption of new ways of producing and using fossil fuels, increased consideration of safe and cost effective uses of nuclear power, . . . " and yes they do call for energy-efficient technologies. No where to they call forelimination of nuclear energy.

http://www.aps.org/statements/00_3.cfm

BTW - my personal experience in dealing with UCS and NCI is that they sometimes miss the mark or are completely wrong, and some individuals lack sufficient expertise to make credible assertions regarding the consequences of nuclear power.

 

[CharlesP]

Nuclear power faces three serious challenges even not counting the public mistrust of the industry.
1. Disposal. A recent report on the Yucca site has caused a stir in Congress. Failures which it outlines may cause a serious slip in schedules.

2. Building reactors with safety sufficient to avoid more crises. The present administration has the same attitude as the Rocky Flats management and lowered standards will not help the industry.

3. There is a quickly closing window of opportunity. Unless construction gets underway in a few short years the available funds will evaporate in the expected economic collapse.

 

[Atom-Go-Boom!]

Hey Guys,
Here's my point of view in the nuclear world:
Nuclear Fission is not very effecient because of the waste its produces. In'till we create a stable, effecient fusion reactor, we will be buried up to our knees in radioactive waste and all die.

 

[enigma]

As opposed to pumping much more radioactive C-14 into the atmosphere by burning coal, and getting the added benefit of giving everyone asthma?

I think you're seriously overestimating the quantity and seriously underestimating the containability of nuclear waste.

Welcome to the forums, BTW

 

[Morbius]

Hey Guys,
Here's my point of view in the nuclear world:
Nuclear Fission is not very effecient because of the waste its produces. In'till we create a stable, effecient fusion reactor, we will be buried up to our knees in radioactive waste and all die.

Atom-Go-Boom,

What about the waste from other forms of power generation?

Because nuclear power plants derive energy from the nuclear force which
is ONE MILLION times more powerful than the Coulomb force on which
chemical reactions - the source of energy for fossil fuels - are based -
pound for pound, nuclear power plants produce one million times more
energy than fossil fuels.


Or to turn that around - for a given amount of energy - nuclear power
produces ONE-MILLIONTH the amount of waste as chemical processes!

You hear a lot of talk about the nuclear waste problem - but do you have
any idea of the amount of nuclear waste the USA has?

All the nuclear waste - from about 50 years of nuclear power - will fit
in a building the size of the gymnasium at your local high school!

The waste from coal plants - a MILLION times as much. A lot of the
waste from coal plants goes into the air for people to breathe -
including the RADIOACTIVITY!

Yes - coal has trace amounts of Uranium and Thorium in it. Because we
burn BILLIONS of tons of coal each year - coal plants are putting
THOUSANDS of TONS of radioactive Uranium and Thorium into the air
for you to breathe and be exposed to the radioactivity!

See the following report from the Oak Ridge National Laboratory:

http://www.ornl.gov/info/ornlreview/rev26-34/text/colmain.html

As the report states, Americans get 100 times the radiation exposure
due to coal as they do from nuclear plants - 100 TIMES!

That additional radiation exposure is brought to you by the idiots in the
environmental movement that have opposed nuclear power at every
turn.

Good scientists, like the those in the American Physical Society; have
been trying to get out the message for years that nuclear power is more
friendly to the environment than the alternatives.

http://www.aps.org/statements/93_7.cfm

But I'm afraid it's hard for the American Physical Society and their
official "position papers" to compete with the so-called
"environmentalists" with their "No Nukes" rock concerts.

Dr. Gregory Greenman
Physicist

 

[Morbius]

Nuclear power faces three serious challenges even not counting the public mistrust of the industry.
1. Disposal. A recent report on the Yucca site has caused a stir in Congress. Failures which it outlines may cause a serious slip in schedules.

Charles,

Why do you only give "part" of the story. Every report to Congress
critical of Yucca Mountain has been thoroughly "shot down" by the
scientists of the National Labs on whom Congress calls for technical
support.

If you would be specific about which report you are referring - I can
tell you specifically what's WRONG with it!

2. Building reactors with safety sufficient to avoid more crises. The present administration has the same attitude as the Rocky Flats management and lowered standards will not help the industry.

Why do keep confusing commercial nuclear power with a defense
program?

You are also LYING when you say the present administration is lowering
standards. There has been absolutely NO lowering of standards for the
nuclear industry! The industry is perfectly able to live with, and thrive
in the current regulations on operating reactors.

Personally, I would make a change from the 2 step to a 1 step licensing
process. At present, there is a whole process of hearings and court
cases when a utility applies for a permit to build the plant. Once the
permit is issued, then the utility can build the plant.

After the plant is built - there's a whole second process hearings and
court cases when the utility applies to operate the plant. This second
step is a rehash of the first step.

A better solution is a single step process - like when you apply to build
a home. Everything is considered and adjudicated BEFORE construction.
Once a decision is made, construction starts, and upon completion - with
a determination by the building inspector that the house was constructed
properly - obeying all building codes and restrictions in the building
permit - you get to move in.

The same should be true for nuclear power plants. Make all the decisions
up front - and if the plant is constructed as per the construction permit -
then allow the utility to operate the plant.

Nuclear power has an enviable safety record - the SINGLE serious
accident in 50 years - Three Mile Island - injured nobody.

Can any other industry make that claim? Take the airline industry.
Airline travel is one of the safest, if not THE safest form of travel - yet
every few years a plane crashes and a couple hundred people are killed.

Or take automobiles. Each and every year 50,000 people are killed by
automobile accidents.

If you really were concerned about saving the lives of the maximum
number of people - THAT'S where you should spend your efforts.

3. There is a quickly closing window of opportunity. Unless construction gets underway in a few short years the available funds will evaporate in the expected economic collapse.

As far as I see - the USA will always have a demand for energy - so
whatever funds the USA is willing to spend on energy generation - are
available to fund nuclear power. There's no impending crisis.

Dr. Gregory Greenman
Physicist

 

[NEOclassic]

What? really is in a spent reactor fuel rod?

The Uranium-235 that I handled at LANL was truly Weapon-grade - over 90% enriched. Not only that but three crits were the fuel of the so-called "25" gun gadget. I think the enrichment of reactor-grade U-235 was perhaps more like 5% and that means that 95% of the fuel was inert U-238 - or was it? Truth is that U-238 has a 2.7 barn probability of capturing a neutron from the persistent neutron flux in the reactor thus producing, in fairly short order, a couple of beta electrons and a weapons-grade plutonium-239 atom. There are many folk who think that those atoms just sit there awaiting some North Korean to go on an Easter egg hunt and retrieve all that stuff for a Korean Bomb - Recently the press declared that a single spent fuel rod had some 60 pounds Pu-239 - that's about twice the 30.8 pounds of Pu-239 in the US Nagasaki Weapon. Lest the reader forget, that weapons fuel continues for the several weeks or months in that same neutron flux where there is a statistical competition between two main reactions. Some of the Pu-239 atoms do fission but some become Pu-240. Now then what could possibily happen to that Pu-240? It too has its own propensity to fission vs to become Pu-241 and so on and on. Below is a table that shows that more than 90% of the originally created Pu-239 has been burnt with the remaining being mostly Pu-242, and Pu-244. If the reader finds this unbelievable I suggest that he ask google about plutonium-242. After the mid 70s LANL, used real Pu-242 in four-pi full-scale implosion models and they didn't go nuclear.

Pluton- Cross Sections in barns (probabilities) Original Number E+9
ium Neutron, Gamma Neutron, Fission Number Number
Isotope Pu-n> N >Pu-n+1 Pu-n> N >Frags Held Fisssioned
Over
Pu-239 286 barns 742 barns 2.653 E+8 7.347 E+8
Pu-240 250 0.03 2.650E +8 3.2 E+4
Pu-24l 390 1010 7.382 E+7 1.912 E+8
Pu-242 19 2 6.67 E+7 7.0 E+5
Pu-243 170 0 6.6 E+7
Pu-244 1.8 0 7. E+5

Remember that a vast majority of fragments are beta emitters and that there is one, strontium-90 with half life of 29 years that needs to be avoided since it is likely responsible for breast cancer epidemic and two iodine isotope one is so long lived that the intensity is inconsequential and the other is so weak that the problem is the gamma that accompanies the beta emission.
Cheers, Jim Edit! The table above was constructed with 5 columes but it got jammed together. J Edit -2 1st Col if isotope, 2nd is gamma cross section, 3rd is fission CS 4th the the numbr remaining unburnt and the 5th is number burned at each stage. The original sample was E+9 Pu-239 created.

 

[Morbius]

The Uranium-235 that I handled at LANL was truly Weapon-grade - over 90% enriched. Not only that but three crits were the fuel of the so-called "25" gun gadget. I think the enrichment of reactor-grade U-235 was perhaps more like 5% and that means that 95% of the fuel was inert U-238 - or was it?

Jim,

The enrichment for fresh fuel in U.S. LWRs [ Light Water Reactors - both
Pressurized Water Reactors (PWRs) and Boiling Water Reactors (BWRs)]
is about 3% to 4%.

Truth is that U-238 has a 2.7 barn probability of capturing a neutron from the persistent neutron flux in the reactor thus producing, in fairly short order, a couple of beta electrons and a weapons-grade plutonium-239 atom. There are many folk who think that those atoms just sit there awaiting some North Korean to go on an Easter egg hunt and retrieve all that stuff for a Korean Bomb.

The Pu-239 is, of course, fissile - so if it sits in the neutron flux of the
reactor, it can fission. In fact, about 40% of the energy that you get
from a new fuel assembly during the ~3 years that the assembly spends
in the reactor, comes from fissioning Pu-239 that was created in situ.

- Recently the press declared that a single spent fuel rod had some 60 pounds Pu-239 - that's about twice the 30.8 pounds of Pu-239 in the US Nagasaki Weapon.

The press got that wrong - a single rod doesn't weigh anywhere near
60 pounds. What they probably meant was that the total of ALL the
rods gives you the 60 pounds. The reports that I have read have said
that the North Koreans got enough Pu-239 for about 2 weapons in this
latest batch.

Lest the reader forget, that weapons fuel continues for the several weeks or months in that same neutron flux where there is a statistical competition between two main reactions. Some of the Pu-239 atoms do fission but some become Pu-240. Now then what could possibily happen to that Pu-240? It too has its own propensity to fission vs to become Pu-241 and so on and on. Below is a table that shows that more than 90% of the originally created Pu-239 has been burnt with the remaining being mostly Pu-242, and Pu-244. If the reader finds this unbelievable I suggest that he ask google about plutonium-242. After the mid 70s LANL, used real Pu-242 in four-pi full-scale implosion models and they didn't go nuclear.

The table you give Jim is appropriate for a reactor that is operated
as a power reactor. However, a production reactor - one whose purpose
is to produce weapons grade plutonium is not operated in the same
manner as a power reactor. In a production reactor, you don't leave
the fuel assemblies in the reactor as long as in a power reactor. In fact,
you leave the fuel assemblies in about 1/5 as long.

As you say - once one creates the Pu-239 in the reactor - it is subject to
being fissioned, and to creating the heavier [ and unwanted ] Pu-240 and
Pu-242.

But when you are operating the reactor as a production reactor - you
take the fuel assembly out of the reactor earlier in order to avoid just
the problem you outlined above.

That's the difference between so-called "reactor-grade" Plutonium and
"weapons-grade" Plutonium. You get "reactor-grade" Plutonium from
a reactor that was operated as a power reactor and the fuel was
subjected to a high "burnup". When you operate the reactor as a
production reactor, such that the fuel is subjected to low "burn-up",
then you get "weapons-grade" Plutonium.

I'm not sure what the point you were trying to make was - but one most
certainly can get "weapons-grade" Plutonium if one has a reactor, and
knows how to operate it to maximize the amount of weapons usable
Plutonium produced.

Dr. Gregory Greenman
Physicist

 

[NEOclassic]

Thanks Gregory,
I am aware that the total time in the reactor has a lot to do with production. My main emphasis here was meant to show that whatever Plutonium that remained after retirement from a power reactor would statistically be mostly 242 and 244 and useless as weapon fuel. Cheers, Jim

 

[kapton]

One problem with fission is;
If a high powered neutron flux pulse gun fired N's at u235 then;
the initial wave of neutrons would fission the initial surface of the u235. However as the energy expands and increases, especially multiplies in small areas where fission is commonley exerting, then the energy will combine and wipe out the N and carry the uranium material away, dissallowing for a highly efficient neutron fission of the entire core. what i mean is that the speed of combining nuclear fission carries across an area much faster that a neutron takes to combine with a nucleus and fission. so therefor increasing the density of the uranium in not always going to work in greater power? Also are the neutrons kinetic?. because the binding energy of a nucleus is enough to fission pu239, u235 and u233. but u238 and th232 require kinetic N's.?

so chain reaction is a problem here?

 

[Morbius]

Thanks Gregory,
I am aware that the total time in the reactor has a lot to do with production. My main emphasis here was meant to show that whatever Plutonium that remained after retirement from a power reactor would statistically be mostly 242 and 244 and useless as weapon fuel. Cheers, Jim

Jim,

Your final statement is incorrect.

Nuclear weapons scientists conducted a nuclear test in 1962 to show
that you CAN make nuclear weapons with reactor grade plutonium.

In fact, I believe it was your former employer, Los Alamos, that conducted
this test. This fact has been known to nuclear weapons designers since
the 1960s - but was only declassified in July 1977.

Courtesy of the U.S. Department of Energy:

http://www.osti.gov/html/osti/opennet/document/press/pc29.html

which states specifically:

"A successful test was conducted in 1962, which used reactor-grade
plutonium in the nuclear explosive in place of weapon-grade plutonium.

The yield was less than 20 kilotons."


There's more Pu-239, and not as much Pu-240 and Pu-242, as you think
in reactor grade plutonium. The point is that, althought tricky; you
CAN make a weapon from reactor grade plutonium.

Dr. Gregory Greenman
Physicist

 

[cwbiii]

Nuclear power is generally as safe as those in charge of operating it. The proceedures are in place to operate it safely. Problems happen when the operating agencies (power companies) try to cut corners by hiring high school grads and train them to operate them as a cost saving measure. I once held an operators license for an open pool research reactor... it took quite a bit of work to get there, and the work needed to operate a power reactor is quite a bit more. Attention to detail is a necessity.
Actual operation is very boring... watching guages and readouts while making tiny adjustments to the control rods from time to time.

 

[russ_watters]

Nuclear power is generally as safe as those in charge of operating it. The proceedures are in place to operate it safely.

Ideally, it's even safer than that: newer reactors are truly "idiot proof" - it would take a conscous effort to cause an "accident." One feature used in Navy reactors, for example, is magnetic support for the control rods. If the plant malfunctions and power is lost, the rods drop into the reactor on their own and stop the reaction.

Pebble-bed reactors, iirc, are physically incapable of meltdown.

Reactor safety really is extrordinarily high.

 

[Morbius]

Ideally, it's even safer than that: newer reactors are truly "idiot proof" - it would take a conscous effort to cause an "accident." One feature used in Navy reactors, for example, is magnetic support for the control rods. If the plant malfunctions and power is lost, the rods drop into the reactor on their own and stop the reaction.

Russ,

I think you'll find that magnetic support of control rods is universal for
ALL reactors that have control rods that enter from the top - and drop
down into the core.

For example, see the following URL courtesy of the M.I.T. Nuclear Reactor
Laboratory:

http://web.mit.edu/nrl/www/reactor/core_description.htm

In the first photo of the core, the caption reads:

"The electromagnets used to "scram" the reactor can be seen in the
upper areas of the photo."

Those shiny discs that surround the rod followers - a good example
is seen at the top edge of the photo at about the 11:30 o'clock position;
are the electromagnets that when de-energized will cause the control
rods - or blades, in the case of the M.I.T reactor; to drop into the core
by gravity.

The only reactors that do not use electromagnets to support the control
rods are BWRs - Boiling Water Reactors. BWR control rods enter from
the bottom of the reactor vessel, and have to be pushed UP in order to
scram the reactor. This is ensured by using the pressure of the water
inside the reactor to drive the piston that drives the control rod.

Dr. Gregory Greenman
Physicist

 

[rdt2]

The problem with nuclear power (and, Dubya, it's 'nu-clear' not 'noo-kyu-lar') is more political than technical. A largely innumerate public (I'm in the U.K but it's probably true worldwide) have no concept of risk and will always fall for the 'Chernobyl' argument. However, that same public is unlikely to want to accept the drastic change of lifestyle that will come if we don't develop nuclear power. Whether one likes it or not, it's coming. Most of our respective politicians simply won't admit it.

 

[Morbius]

The problem with nuclear power (and, Dubya, it's 'nu-clear' not 'noo-kyu-lar') is more political than technical. A largely innumerate public (I'm in the U.K but it's probably true worldwide) have no concept of risk and will always fall for the 'Chernobyl' argument. However, that same public is unlikely to want to accept the drastic change of lifestyle that will come if we don't develop nuclear power. Whether one likes it or not, it's coming. Most of our respective politicians simply won't admit it.

rdt2,

Yes - it always amazes me that people can be so phobic about nuclear
power; claiming that they are afraid of some fantasy accident concocted
by the anti-nuclear crowd; yet they still fly on airliners!

Several years ago, the PBS show "Frontline" did a show about nuclear
power entitled "Nuclear Reaction" hosted by Pulitzer Prize-winning
author Richard Rhodes. At on point, Frontline interviewed a psychiatrist
concerning the anti-nukes. He states that they are not so much
anti-nuclear; but anti-technology and anti-business. Courtesy of
PBS "Frontline":

http://www.pbs.org/wgbh/pages/frontline/shows/reaction/interviews/dupont.html

Dr. Gregory Greenman
Physicist

 

[theCandyman]

I am puzzled even more that while these people are aginst nuclear power, they would most likely not want to give up the benefits of nuclear technology.

 

[Morbius]

I am puzzled even more that while these people are aginst nuclear power, they would most likely not want to give up the benefits of nuclear technology.

Candyman,

I think they would forego the benefits of nuclear technology.

As the good Dr. DuPont states in his interview linked above; the anti-nuclear
crowd is really an anti-technology crowd.

For them, technology is a scourge upon the planet. Many of them look to
the lifestyles of the Native Americans of a few hundred years ago. They
believe that theirs is/was the one true way that humankind should exist
in harmony with Nature.

They believe that Man should eeke out a primitive agrarian existence -
and not have all the technology that you and I, and many others want.

Frequently, the lifestyles of Native Americans is portrayed in a
"romantic" fashion; without the downsides. People tend to forget that
without our technology; we humans are just another animal on the face
of the planet - and subject to all the harsh realities of life as an animal -
disease, hunger from crop failure, ...

I think we live a much better and longer life today that would be the
envy of any peoples of the past. That's why people developed all this
technology that we have today - to rid us of the strife of the past.

However, in order to continue the lifestyles that the advanced countries
enjoy, and to spread the benefits to those that live in the more primitive
areas of the world; is going to take energy. Energy fuels our modern
technological lifestyle - and it will take more energy for the spread
of a modern lifestyle to the poorer nations of the world.

Nuclear energy holds the promise of being able to deliver the energy
needed. Those that want to turn back the clock and have us live a more
primitive life; know that by opposing nuclear power - they can put a
monkey wrench into the engine that drives the expansion of advanced
technological lifestyles.

By strangling nuclear power, they hope to win the war against technology
and leave us no choice but to pursue their dreams of a primitive culture.

Dr. Gregory Greenman
Physicist

 

[rdt2]

As the good Dr. DuPont states in his interview linked above; the anti-nuclear crowd is really an anti-technology crowd.

For them, technology is a scourge upon the planet. Many of them look to
the lifestyles of the Native Americans of a few hundred years ago. They
believe that theirs is/was the one true way that humankind should exist
in harmony with Nature.

They believe that Man should eeke out a primitive agrarian existence -
and not have all the technology that you and I, and many others want.

Frequently, the lifestyles of Native Americans is portrayed in a
"romantic" fashion; without the downsides...

Indeed so. The first paragraph of http://www.mech.gla.ac.uk/~rthomson/teaching/lecnotes/ch01.htm might strike a chord.

 

[russ_watters]

rdt2,

Yes - it always amazes me that people can be so phobic about nuclear
power; claiming that they are afraid of some fantasy accident concocted
by the anti-nuclear crowd; yet they still fly on airliners!

It does not amaze me (am I too young to be that cynical?). People are afraid of the unknown and most people know little to nothing about the real risk. Ask people how many people died in Chernobyl and the answers you get are in the hundreds of thousands. A lot of the blame goes to the media - they can't pass up a good scare story.

Several years ago, the PBS show "Frontline" did a show about nuclear
power entitled "Nuclear Reaction" hosted by Pulitzer Prize-winning
author Richard Rhodes. At on point, Frontline interviewed a psychiatrist
concerning the anti-nukes. He states that they are not so much
anti-nuclear; but anti-technology and anti-business.

Those would be the so-called "environmentalists". I don't know how big of a group they really are, but they are the ones who are actively anti-nuclear. They are neo-hippies and they are pretty much anti-everything modern. This is the dangerous group as they are able to convince the larger ignorant and impressionable group (described above) of things like 100,000 people died as a result of Chernobyl.

(great link, btw)

 

[Morbius]

It does not amaze me (am I too young to be that cynical?). People are afraid of the unknown and most people know little to nothing about the real risk. Ask people how many people died in Chernobyl and the answers you get are in the hundreds of thousands. A lot of the blame goes to the media - they can't pass up a good scare story. Those would be the so-called "environmentalists". I don't know how big of a group they really are, but they are the ones who are actively anti-nuclear. They are neo-hippies and they are pretty much anti-everything modern. This is the dangerous group as they are able to convince the larger ignorant and impressionable group (described above) of things like 100,000 people died as a result of Chernobyl.

(great link, btw)

russ,

One problem seems to be that a lot of the entertainers fall into this
group - hence we have the "No Nukes" concert, etc.

The problem is, as you state above; that the small group can convince
the larger "ignorant and impressionable" group.

For me - the answer to ignorance is education. There too we have a
problem - the quality of education in our schools.

A little anecdote; each year I help out at our local "Expanding Your
Horizons" conference - an annual one day workshop for junior and
senior high girls that showcases women scientists and engineers as role
models.

One of the health physicists at the Lab [ they're the people that ensure
that radiation and radioactivity are handled properly ] had a display
of items that you would find around the house that are radioactive -
smoke detector, fossils, pottery... [ One of the largest radioactive
sources in your house is probably that 50mm lens on the front of your
Nikon, Minolta, or Canon SLR camera as I learned from his display.
Optical glass has thorium in it.]

He told me he also took his little show "on the road" to local [ Bay area ]
schools. At one high school, he was demonstrating the radioactivity in
a fossil shark's tooth. The science teacher asked him what he did to
make the shark's tooth radioactive.

He replied, "Nothing!" and explained that 100 years ago when the shark
was alive and swimming in the ocean, it was injesting the sea water,
removing the minerals from the water, and those minerals were used to
grow the shark's teeth. Some of those minerals are salts of uranium and
thorium - hence they are radioactive.

The high school science teacher asked, "You say that shark's tooth is
100 years old?" He told her, "That's right!". To which she responded,
"Well if that shark's tooth is 100 years old, how could it be radioactive;
since Man didn't invent radioactivity until 1945?"

I was aghast. Somewhere in the Bay Area is a high school science teacher
that is teaching her high school students that Man invent radioactivity
in 1945!

What we need are good teachers that can give our students a good
education. When a well educated person hears one of these "scare
stories"; they will be educated enough to see the inconsistencies and the
untruths of the "scare story" and not believe it.

That's how you immunize people against "scare story" propaganda.

I might also add that online forums like this one are also a part of the
education process - so keep up the good work!

Dr. Gregory Greenman
Physicist

 

[Morbius]

l.
(great link, btw)

Russ,

If you like that one - also check out one of the other interviews; one with
Dr. Charles Till, former Associate Director of Argonne National Lab:

http://www.pbs.org/wgbh/pages/frontline/shows/reaction/interviews/till.html

Dr. Till was one of my bosses 20 years ago when I was at Argonne and
working on the Integral Fast Reactor [ IFR ] that he describes.

Dr. Gregory Greenman
Physicist

 

[russ_watters]

The high school science teacher asked, "You say that shark's tooth is
100 years old?" He told her, "That's right!". To which she responded,
"Well if that shark's tooth is 100 years old, how could it be radioactive;
since Man didn't invent radioactivity until 1945?"

I was aghast. Somewhere in the Bay Area is a high school science teacher
that is teaching her high school students that Man invent radioactivity
in 1945!

I think I'm going to vomit.

I visited Limerick when I was a cub scout (I still live about 15 miles away). I think it should be a part of the curriculum in whatever grade a child is first exposed (pun intented) to radiation (8th or 9th?) that they visit a plant if one is within field-trip range.

 

[theCandyman]

How does someone like that come into a teaching job!?

Yes, education at an early age is probably the best way to prevent them from actually listening to the propaganda about nuclear power and the like, but for that there is a need for people who would want to teach younger children and know sufficient material.

 

[Astronuc]

How does someone like that come into a teaching job!?

Because primary or public school teachers are not necessarily trained (or at least rigorously that is) in the the subject that they teach. Instead they get a degree in education, and consequently many (most?) math/science teachers get little experience in rigorous math, science and engineering courses.

There are exceptions. My chemistry teacher in HS (30+ years ago) had a Master of Science Degree in Chemistry. One of the Physics teachers had a PhD from Caltech, but he only stayed for two years, then went to work for Shell R&D.

Currently, one of the Chemistry (Science) teachers at my daughter's high school is a retired chemist/chemical engineer from one of the development labs of a large oil company.

The American Nuclear Society and DOE/National Labs have outreach programs.

 

[Morbius]

Because primary or public school teachers are not necessarily trained (or at least rigorously that is) in the the subject that they teach. Instead they get a degree in education, and consequently many (most?) math/science teachers get little experience in rigorous math, science and engineering courses.

Astronuc,

Yes - several years ago, a colleague of mine took an early retirement and
wanted to teach high school Algebra.

He was a Ph.D. in Physics - and could have taught at the University level.

However, he couldn't teach high school Algebra until he went back to
school and studied education in order to get his teacher's certification.

Dr. Gregory Greenman
Physicist