Future Energy Sources 1.9.1.2 CanDU Reactors

Dear masu,

Other than "...can also burn spent PWR fuel, since the U-235 content in this fuel is still slightly enriched over natural fuel...", in section #9 of their document, I could hardly find other clues, not to mention a description of the fission's isotope transmutation-chain, to visualise what materials are involved.

It was only mentioned that the moderator used is D₂O (Dideuterium monoxide type of heavy water), and not a whisper as to the materials resulted off the process.

The claim that it can use spent (not depleted!), enriched uranium, is indeed some relatively good news since no feasible fusion power-production is anywhere near, but no effort is likely made to relax environmental freaks like myself.

More description is needed on the physics and enviro-logistics of the process, and unless they publish some, no else one is gonna.

problems with both normal operations and refurbishment that have contributed to the extent and severity of wide-scale power outages in Canada and the northeast of the USA.

Problems with refurbishment could not have contributed to the power outages because when a reactor is being refurbished it is already off-line.

For another look at the CANDU system, look at www.nuclearfaq.ca .Many of the problems of the nuclear power industry in Ontario have been as the result of mismanagement and meddling by the Ontario Government. These plants have been privatized and the future is looking much better. I don't believe that you will find that the CANDU is a flawed design.

"Problems with refurbishment could not have contributed to the power outages because when a reactor is being refurbished it is alread off-line."

While having the reactor off line doesn't contribute directly it dose compound the situation as there is les surplus generating capacity in the system. In fact having a major portion of your generating capacity off line can actually be one of the factors that triggers a cascading blackout.

With a big chunk of your generating capacity off line, for refurbishment, the remaining systems must take up the slack and therefore, is under a greater load than normal. This means they have taken up a portion, if not all, the surplus generating capacity in the plants that are on line and generating power. The result is a system that is less robust and more prone to failure due to short transient overloads.

Her is an example, imagine you have a system that consists of ten 100 Mw plants that normally run at 80% capacity. If you take one of the plants off line the 80 Mw that that plant generates must be made up frthe surplus capacity in the remaining 9 plants. This means that each plant now needs to increase its output from 80 Mw to 88 Mw and the surplus capacity has dropped from 20% to 12%. A failure of any of the remaining 9 plant will chew up all the remaining surplus and leaves all the plants running at 100% capacity. Any short term transient will now overload the system and can start a cascading failure that results in the shutdown of the entire generating and distribution system.

So having plants off line for extended periods severely affect the robustness of the system and makes the system more prone to failure. Whilst not directly contributing to a cascading failure the fact that the capacity is not there may have been the critical factor. We will never know, but if the plant was on line the cascading failures that were experienced may not have occurred at all.

It's a case of the straw that broke the camel's back, remove a single straw and the camel's back doesn't break.

"There have also been problems with both normal operations and refurbishment that have contributed to the extent and severity of wide scale power outages in Canada and the north east of the USA."

I live in Ontario, Canada. What wide scale power outages are you referring to?

The last power outages were due to environmental causes. We had a severe ice storm in Eastern Canada/NE USA which the weight of ice caused power lines to go down. The last "man-made" outage in 2004 was caused by a relay station in Cincinnati, Ohio going down and since our system is tied in to the US system to sell them power, that outage cascaded to our system.

So what is your complaint about CANDU's?????

...what is your complaint about CANDU's...

Please Address your question: Who's complaint? Problems you might have with any introduction of technology. The point is at having some foresight to examine the principles behind the "clockwork" and see if it generally betters the possible co-existence with human habitat.

Otherwise, why bother? Ecological trouble we already have in abundance.

You can hardly expect people, to automatically swallow any offer on the table, just because it can generate some corporate profit.

While CANDU and Thorium power-plants are offered as a waste-gobbling reactors which might be good news, they may present other problematic issues, we not yet posses the knowledge and experience to tackle.

Should this be your desire?

The following statement comes from my contact within Atomic Energy of Canada Limited, the company the gave the world the CANDU system.

"Four of the operating CANDU units (three at Bruce, one at Darlington) were able to step back to a lower-power mode that left them immediately available to re-supply the grid when requested. Unfortunately it took several more hours for this request to be established, due to other logistical problems involving the grid operator. When reconnection was eventually established these four units played a vital role in the return of supply to millions of customers that evening. The ability to step back to lower power and maintain availability in such circumstances is a unique feature of CANDU reactors."

Needless to say the folks at AECL were somewhat offended to see their child blamed for the problem. This is not an official statement from AECL but the words of a very knowledgeable employee of the company. He is currently trying to if the comapny has made an official statement refuting the claims of culpability in the cause of the original blackout.

"There have also been problems with both normal operations and refurbishment that have contributed to the extent and severity of wide scale power outages in Canada and the north east of the USA."

This statement is patently false and perhaps libelous. How could a reactor that is in the process of being refurbished cause a power failure? This statement obviously came from someone who wanted to find someone to blame and foreign technology made a convenient scapegoat. I heard that it was a switching problem somewhere in the American part of the grid. Does anybody know the real truth?

What I still know from the time I was in nuclear business is that the reactors are shut down as soon as serious anomalies are detected (eg earth quake of +4 triggers an automatic shut down, to prevent alternator damage if the connection with other supply points should get lost), this to prevent damage or worse. Nuclear reactors have a high latency and as stated somewhere else: an emergency shut down would require weeks to be able to start up again.

And why would a US organisation take the responsibility when you can blame Canada?

Hi The_curious_one,

"How could a reactor that is the process of being rfurbished cause a power failure?"

This is a good question and several people have already asked it. The answer is, while it cant directly cause the problems it can be a major contributing factor. Here is the answer I gave to the question elsewhere.

This is a valid query and you are the second person to ask this question. Basically what happens is that if you have a sizable chunk of your generating capacity off line for refurbishment, it decreases the systems overall tolerance to short term transients. The result is that a fault that would normally not caused any problems pushes the system over the edge and results in a cascading failure that knocks out a large portion of the grid. You can read my detailed response by following this link.

Power distribution grids are normally very tolerant systems and while there is surplus generating capacity any sudden increase in the load will be accommodated by distributing it over all the stations that are on line. If you have a reduced surplus capacity due to a plant being off line for maintenance, you can hit a point when demand outstrips supply. When this happens the grid tries to spread the increased load over the existing power stations and the inevitable happens when a plant shuts down due to an overload. The grid now distributes the load that this station was covering to all the other fully loaded power stations on the grid and bingo you have a cascading power failure. The only way to stop the cascade is to create a type of fire wall by isolating the cascading failure from the rest of the grid and letting that isolated region fail completely. You then need to shut down all the inter-connectors inside that shut down region and start bring sections back on line one at a time. Once a region has been brought back on line and is stable it can be connected back to the grid by starting up the inter-connectors again.

If any of the power stations has been damaged then there will be regions that can't be brought back on line until there is a enough surplus generating capacity to cover the load in that region.

A power grid is a very fault tolerant system only while the generating capacity is greater that demand. If demand exceeds capacity then they are prone to cascading failures like the one seen in Canada and the north west USA.

Put simply if you reduce the surplus generating capacity because you have a plant off line for refurbishment you make the entire power grid more unreliable. If the spare generating capacity drops to zero because of failures of equipment that is on line you have set the stage for a cascading failure that can shut the entire grid down. It is critical with a power distribution grid that you keep demand lower than generating capacity. If you live in the north east USA or south east Canada you have more than likely seen what happens when demand exceeds supply.

I hope that answers your question.

Hi,

does anyone know the price of heavy water and how much is needed per GW of electricity production in these CANDU reactors?

And: is there enough capacity to have more if a substantial amount of heavy water reactors are built?

To my knowledge the today supply of heavy water is coming from the electrolysis of ordinary water where the heavy water is split into hydrogen and oxygen much slower than the ordinary water. So I suppose that we will have a shortage and heavy price rises if there is more demand.

Iran is building one heavy water reactor now - I don't know details - but towards their way to nuclear weapons it is one possibility to get the plutonium without external help and without a lot of centrifuges working.

Happy Easter for everybody

RHABE

I have attempted on several occasions to reply to various forums but when I try to submit the reply I get the message "couldn't process this form" What unknown sin am I guilty of?

You could start to create yourself a user name.

The content of what you write is of coarse checked by the CIA and counter checked by the KGB, if they both agree on it it can be published.

I thought that I was logged on, I will try again

When the Ontario Government was running things there was a lot of meddling going on and the result was over budget, over schedule projects. Several of the reactors had been shut down for some time. A major refurbishment is currently occuring at several locations which will extend the life of the reactors for 25-30 years.

Canada has the ability to meet its domestic need for heavy water with enough left over for export.

The DUPIC fuel cycle can use spent reactor fuel from light water reactors because there is more U235 in the spent fuel than in the natural uranium that the reactor usueally uses, combine that with the reactor grade plutonium in the "spent" fuel and you a very rich diet for the CANDU. Therefore a group of light water reactors and CANDU reactors could operate symbiotically.

The ACR-1000, an advanced concept CANDU will use slightly enriched uranium (SEU) and heavy water as the moderator with light water as the coolant. The use of SEU will actually reduce the fuel costs. It will also retain the multi-fuel cycles of the current generation.

As for the role the CANDU played in the blackout, I have sent an e-mail to a contact in Atomic Energy of Canada asking for their version of the story.

I will try to find out the cost of heavy water. I am not sure how meaningful it will be because even though it is an expensive item in the cost of a plant, it may be more than offset by savings in other areas, such as on-poer refueling, the use of pressure tubes rather than a presssure vessel, the use of unenriched or SEU uranium rather than the more expensive LEU, etc.

For an excellent description of the Advanced Concept Reactor, ACR, the next Generation of CANDU contact AECL and ask for a copy of the ACR-1000 Technical Summary. You will get a 40 page booklet with lots of explanations, diagrams, and tables. It is quite a nice document and it is free.

...and counter checked...

A nice one .

Gwen

With respect to being logged on. It appears that there is some sort of timer associated with being logged on. On more than one occasion I have logged on and by the time I had finished composing a particularly long post, I was no longer logged on and the post was rejected.

As a defensive act before I attempt to submit a long post I copy it to notepad before I post it and if I run into a problem I login again, copy the message back from notepad and then submit it. It is a pain in the you know where.

You were right about being signed on though, there seems to be a limit to how large a post a guest can make.

I may be wrong about all of this but the symptoms seem to fit my conclusions.

Gidday The_curious_one,

You may find the technique that I use to create and edit posts useful.

Basically I do the whole thing using Microsoft^® Word^® cutting any quotes that I wish to use from the posts in the thread. You can use the word features like hyperlink creation & editing, bold, underline, italic, numbering, bullet points, symbols ØΩΔπ , ^superscript, _subscript etcetera.

Once I have completely finished the post I then start up the CR4 editor and cut the entire post from the Word^® document directly into the CR4 editor. All you need to do then is to preview it and submit it. What you see in the preview screen is pretty much what you will end up with.

Equations and images are a little different and you need to use the image button on the CR4 editor toolbar (see image at left) to and insert them one at a time. This can be a hassle if you have a post with heaps of images or equations in it but that sort of post is rare.

Could this help?

Thank you Yuval for this really very interesting link about cold fusion.

But did you really want to send this link or someting else because I was asking about heavy water supply and prices and the amount needed.

Back to your link and the measurement of fusion products and heat generated in simple electrolysis:

The measurement is done carefully but I still don't believe the results.

Why there was no gamma-ray counter?

Why there was no switching on and off the electrolysis and catching the gamma rays on the fotografic film shielded by some moving pattern so that the effect of the gamma rays can be seen on the film as a series of exposures?

If it is known that the palladium electrodes can store the suspected He than why not a superthin electrode some nanometers thick instead of the bulky and scratched one?

And: if the cold fusion is real than there seems to be no theory behind and the yield is so low that we would have to make the process many orders of magnitude better than now.

Do you really believe in this effect?

Happy holidays

RHABE

Dear RHABE,

...did you really want to send this link or something else ...

Look at the paper. It's a Discussion offer from 1991. To the best of my knowledge prior to the Tokamak experiment (which Hailed as a breakthrough but dismantled by it's creators as a failure).

You stated in #6: "To my knowledge the today supply of heavy water is coming from the electrolysis of ordinary water where the heavy water is split into hydrogen and oxygen much slower than the ordinary water"

- sending this paper, was my humble reference.

Here, you ask for my opinion: "...if the cold fusion is real...",

well:

You judge: the longest continuous sustenance of active plasma in a British (Tokamak) toroid chamber was less than 10 milliseconds, hardly documented on hyper-speed video transcriptor, and the experimenters argued for about a month about the validity of the expected temperature versus the captured few frames they managed to document.

Does this seem like a sustainable process?

Their conclusion was that the confined gas' hydrodynamics was not likely to be controllable within the toroid's electromagnetic-confinement.

Does this seem like a sustainable process?

From toroid confinement they moved to spherical.

I'm still waiting for the tie-breaker, longer than a minute. Not forever, not a year long, not a month long.

You can wait with me, and let time be the judge.

Besides, "Cold-Fusion" sounds like an oxymoron .

Then again, maybe I'm just too short-sighted.

Yours, Yuval

The current price of heavy water in the quantities required for a CANDU reactor is $300US per kilogram. A CANDU-6 required 457 Mg of the stuff but the ACR-1000, the next generation CANDU only requires 250 Mg.

Canada has several mothballed heavy water plants that could be activiated if the demand was there.

Here I go again.

The CANDU is capable of both a plutonium fuel cycle and a mixed oxides (MOX) fuel cycle and a thorium fuel cycle. Both MOX and thorium fuel bundles have been tested, if not in CANDU reactors then in reactors with features designed for testing CANDU fuel bundles.

The Indians who have some genuine CANDUs as well as some home grown CANDU clones also have a lot of thorium. They are using some thorium fuel bundles in their production reactors in order to flatten or balance the reactivity in the reactor when using fresh uranium fuel.

A question remains. When all of the required international agreements are signed allowing the production use of MOX fuel in Canadian CANDU reactors, will we have to pay for the plutonium component or will the US and Russia pay us for getting rid of their nasty weapons grade plutonium?

About CANDU reactors:

Given that CANDUs do not go through an enrichment process, does this affect their output in comparison with the output of reactors which use enriched fuel (with and without the advantages of not having to shut down for refueling etc)?

I have a few estimates of the SWUs for enrichment with gaseous diffusion and with centrifuge, both very energy costly although the latter much less so.

Since CANDU doesn't use anything except uranium 238 and heavy water, … um…why doesn't everyone? Or, to put it another way, what are the advantages (if any) in going through the separation processes? Were they perhaps just derived from nuclear facilities which also wanted to produce weapons plutonium?

Any views?

Neutrino

I wondered about these questions myself. Thanks for bringing it up so clearly.

Anyone to meet the challenge?

Hi Yuval,

Thanks.

I sort of came to some conclusions myself, after the question, and put them in a reply to (?)Ramal's comment about new CANDUs where he asked about enrichment costs.

cheers,

Neut

I noticed on a very early stage, we do have a rare collection, of some very informed people here.

It must have something to do with the reputation of this here site...

It makes me feel like a part of a modern-time royalty...

Hi discussion partners,

CANDU is no longer in the debate but the next generation ACR1000 reactor has similar specs.

Different is that it uses slightly enriched uranium (1.5%) in order to make possible a high energy yield per kg of fuel.

This makes it possible to also burn some of high activity nuclear waste and also thorium.

The high energy yield is gained by the fact that a considerable amount of U238 is converted to burnable (fissionable) material.

The redisign is also using less of the costly heavy water (250...300$/kg, 250000kg needed, losses are negligible) and is using ordinary water as coolant.

Along the fuel rods (many rods in a bundle) is streaming the hot pressurised ordinary water, encapsulated by zirconium tubes, outside these a gas shield for thermal insulation and a second tube and outside this second tube the heavy water - cool and only under slight pressure! If any of the tubes bursts there will be mixture of heavy water with light water or loss of heavy water and both will shut down the nuclear chain reaction so to make the reactor inherently safe.

This makes this system very remarkable. Everybody interested should ask for the leaflet at the adress that was given in one of the contributions above.

I got the same judgement from the organisator of the www.icenes2007.org conferencesupplying a scientific paper about possible burning scenarios.

If anybody is interested I can send it as pdf, I don't know if a multi page pdf can be attached here?

Does anyone have the price of the enrichment process or the cost of an initial core at start of a nuclear (conventional 3,5% enriched U235) power plant?

Concerning nuclear weapons there was a notice in the newspaper that IRAN is proceeding towards weapons or other use also with a heavy water reactor designed to produce plutonium, as expected from the Bushir iranium reactor, as any conventional reactor can be used to produce plutonium, bad stuff if operated for more than 9 months but good stuff (in weapon's sense) if burning only 3 months until chemical reprocessing and plutonium extraction.

Greetings

RHABE

...The high energy yield is gained by the fact that a considerable amount of U238 is converted to burnable (fissionable) material...

This may bring us all back a few steps, because it becomes viable for questionable parties, to make use of fissionable materials, once snatched off reactors refuse transport or storage.

?

Hi Yuval,

you are absolutely right,

everybody who is playing with fissionable material is playing with his and others future.

This is especially true with weapon grade material.

RHABE

Sorry, I'm still looking at basic CANDUs as well. Here is my thinking so far. It's not definitive. Some costs for enrichment below, and I also look at CANDU as already using enrichment with its heavy water (enrichment of water, if you like) which turns out to be a heavy cost. Now you say they are talking about using slightly enriched uranium... but... but.. they could always burn plutonium and thorium, I thought, without using enriched uranium.... I thought they would use the heavy water. Maybe I don't understand. See below:

Separation (Enriching) process:

The amount of energy that goes into the separation process needs to be considered when evaluating energy output by a nuclear plant.

CANDU reactors do not expend energy in separating the stronger from the weaker isotopes of uranium. But they do have to separate deuterium, a relatively harmless isotope of hydrogen, from ordinary water, in order to provide about 360 tonnes of heavy water, which lasts the reactor for about 30 years with a loss of about 5%. The deuterium isotope occurs naturally in the ratio 1:4500; thus D₂O is found at the level of about 1 in 20 million water molecules. It is obtained from Canadian lakes and 340,000 pounds of ordinary water is required to produce one pound of heavy water in the distillation process in Canada.[i] During World War 2 the Germans used heavy water to moderate a reactor which used unenriched uranium.

The apparent success of the CANDU method and earlier knowledge that thorium would be as viable and safer than uranium makes you wonder why the nuclear industry has put up with the difficulties inherent with uranium and enrichment.[ii] The only obvious reason would seem to be the weapons connection. Uranium lent itself readily to refinement for deadly weapons, whereas the much more common thorium did not. Could it be that we persist in costly and dangerous technologies mainly because they were initially developed by weapons scientists? Is this why the nuclear power industry carries such a confusing political and environmental load, and the CANDU reactors have remained relatively unheard of, despite their important role in producing power for Canada and their comparatively wide international distribution?

But heavy water can also be used to make plutonium.[iii]

Other conventional reactors:

For the rest of the reactors, the kind of process for enrichment makes a big difference to the up-front energy costs.

Since uranium isotopes do not differ in their chemical behaviour, enrichment techniques exploit their mass difference as a means for separating them [25].

The most prevalent methods are gaseous diffusions and gas centrifuge. Gaseous diffusion needs 1,000 consecutive separation cascades to approximately 10 consecutive separation cascades required in gas centrifuge. Gaseous diffusions need energy-intensive compression of UF6 at the entry point of each cascade, whereas gas centrifuge only needs only need electrical energy for the rotation of the cylinders,

and some heat to work. Gas centrifuge is taking over from gaseous diffusion for this reason and now about 60-70% of reactors use centrifuge.[iv] Depending on the composition of the original ore more or less work may be required to obtain the requisite mix approaching 3.5% U-235. In the current economic paradigm the cost of the electricity to drive the enrichment process would be weighed up against the cost of yellowcake (uranium 238). Amounts of enriched uranium are frequently described in terms of 'Separative Work Units' – SWUs.

[i] http://www.fas.org/nuke/intro/nuke/heavy.htm

[ii] Re: Future Energy Sources 1.9.1.3 Thorium Reactors, 03/25/2007 2:58 PM, http://cr4.globalspec.com/, "As far as I can remember the phyisist Edward Teller, one of the fathers of the atom bomb had discussed the probability of using 232Th in both a nuclear weapon and as a nuclear reactor way back in 1941. ..I can clearly remember that Teller stated that using 232Th for a nuclear reactor was a lot safer than using 235U. Of course, as it was they had developed the 235U bomb, and it worked, so all thoughts and development since then has been focused on this material to the detriment of 232Th as a nuclear fuel."

[iii] "The importance of heavy water to a nuclear proliferator is that it provides one more route to produce plutonium for use in weapons, entirely bypassing uranium enrichment and all of the related technological infrastructure. In addition, heavy-water-moderated reactors can be used to make tritium." Source: Federation of American scientists, special weapons primer, weapons of mass destruction: "Heavy water production", http://www.fas.org/nuke/intro/nuke/heavy.htm

[iv] Report by ISA of University of Sydney, "Life Cycle Energy Balance and Greenhouse Gas Emissions of Nuclear Energy in Australia" [ Download 2.75 MB PDF ] includes a full cycle energy analysis.

Their spreadsheet is available at www.peakoil.org.au/isa.nuclear-calculator.xls

All nuclear reactors that use a uranium fuel cycle produce plutonium when the ²³⁸U absorbs a neutron and evenutally becomes plutonium. In fact all uranium reactors get as much as 30% of their power from plutonium generated in situ.

Heavy water is not required to generate plutonium, the Hanford reactors which were built for the purpose of generating plutonium used graphite as a moderator.

In a previous post I indicated where to get the information on the new CANDU's as well as a web site on the current CANDU's

²³⁵U is fissile and can be used to produce power, ²³⁸U is not weaker, but it is fertile and will absorb a neutron to eventually become plutonium which is fissile. ²³³Th is also fertile and will become ²³³U which again is fissile. Reactors which breed fissile isotopes from fertile isotopes must have some spare neutrons flying around and most of them do to some extent fast breeder reactors actually produce more fuel than they consume.

Natural uranium has about 0.7% ²³⁵U which is fissionable. As stated before the ²³⁸U is fertile and some of it will become Plutonium which is fertile. The fission of this plutonium adds to the power output of the reactor. a fuel load that is richer in fissionable isotopes would probably produce more power with less total fuel. I could stand to be corrected on this but it seems to make sense.

The CANDU will not speed the decay of weapons grade plutonium, it will burn it just like the ²³⁵U and produce power with it.