Talk:CANDU reactor

Article Bias

The article reads very biased. Looks as though it was written by the AECL publicity department! Needs to be more NPOV. Nfitz 00:40, 13 January 2007 (UTC)

The NPOV dispute process requires that you "clearly and exactly explain which part of the article does not seem to have a NPOV and why. Make some suggestions as to how one can improve the article. Be active and bold in improving the article."

Please proceed. Whitlock 20:12, 13 January 2007 (UTC)

Whole thing needs a rewrite. Technical information is good, but there are little NPOV bits in, that should go, or need references. I can't reference comments like "Some CANDU plants suffered from cost overruns during construction, primarily due to external factors so I would just delete everything after the comma if I was doing a rewrite. And the whole nuclear nonproliferation section seems perhaps unnecessary. Not to mention, I don't have the time; but the article is now tagged, so people looking at the article are aware of the issue. Nfitz 17:40, 14 January 2007 (UTC)

The statement you refer to ("Some CANDU plants suffered from cost overruns...") was referenced at the end of the subsequent sentence. However, I've added a second reference for good measure. I've also added a reference to the statement about the China build that follows.

The "Non-proliferation" section is there because someone figured it was important to discuss with regards to CANDU. I'm okay taking it out but I gather others (including whoever first authored it) feel otherwise. It is true that misperceptions exist in this subject area, so perhaps this is as good a place as any to set things straight.

As for other "bits", you'll have to be more specific. An NPOV challenge means you are aware of contrary, verifiable information which isn't reflected in the article. Therefore, if you can identify such situations, we can address them. A blanket claim will not suffice, and the tag will be removed if a dispute is determined to not exist. Whitlock 02:45, 15 January 2007 (UTC)

Since two weeks have now passed without further substantiation of NPOV, I've removed the tag. Whitlock 14:02, 31 January 2007 (UTC)

Safety

The reference being used to support the statement that CANDU reactors are not more more safe than other reactors in earthquakes is inadequate. The statement implies the reference would contain a comparison to other rectors. The reference does not. The statement sounds biased.

I suggest the safety section be rewritten and expanded upon by experts, and better referenced. Davemody (talk) —Preceding undated comment added 15:10, 12 March 2011 (UTC).

The AECL lobby at work ladies and gentlemen. How subtle of you guys, really, to come edit this section in the wake of the Fukushima fiasco. And you have the nerve to call others biased, who is on the AECL payroll again? That's right, GTFO of here dude, go spread your disinformation and your orwellian sophisms elsewhere. - 216.144.124.59 (talk) 14:37, 14 March 2011 (UTC)

Forgetting about the staunch anti-nuclear activist above, I assume that the CANDU's higher seismic safety is related to the nuclear processes inside of the reactor. Whereas the Fukushima reactor needed to continuously cool the nuclear cores once the shut-down rods have been inserted (because of residual fission and extreme heat), the CANDU reactors more or less completely shut-down once the control rods are inserted because of the low-grade uranium used and the greater ability of the heavy-water to cool the system passively. Because the system is "less" complex, there are less components that have the potential of failing. Mind you, an earthquake could cause the control rods to get bent in both reactors, preventing them from being inserted into the core to shut-down the reactions. This is related to the physical "seismic-proofing" construction of the building, though. I don't think the control rods got bent at Fukushima because of the building's good seismic design; the cooling mechanism that were necessary at Fukushima failed, the same cooling mechanisms which aren't as critical a component in the CANDU design. I am no expert though, so I do agree that the safety section requires an expert rewrite.

New Plants

The text said:

"In Summer 2006, Turks protested against plans for building nuclear reactors, erroneously believing that all designs are as dangerous as the RBMK (involved in the Chernobyl accident), when in fact all other designs have fail safe features."

I changed the last phrase to "when in fact other commercial reactor designs have better safety records." My reasons:

• "all other designs" All other designs include SL-1, which had a bad design that killed three people. All other designs is overly broad.
• "fail safe features" The term "fail safe" is slippery. It is debatable as to whether the ECCS works, and whether Three Mile Island failed safe or not. SL-1 did not fail safe.

Cxbrx 20:18, 10 February 2007 (UTC)

All other designs is quite broad, but I meant those commercially available. Also, small accidents (the RBMK in Chernobyl exploded) do happen in all kinds of power plants. If a reactor is as safe as a coal-fired plant, then it is safe. Q43 09:08, 2 July 2007 (UTC)

Turkey currenlty has simmering disputes with all its neighbors. Before the catastrophic earthquake of some years ago, Turkey even planned to purchase an aircraft carrier and was set back on that. So, one wonders whether they pursue Candu in order to follow India's path. Q43 09:11, 2 July 2007 (UTC)

"India's path" did not make use of CANDU reactors. See discussion in article under "Nuclear Nonproliferation". Whitlock 02:44, 3 July 2007 (UTC)

Historical Technological Confusion

In the late 1960’s we students were told that the WWII Western Allies divided nuclear technologies into three components: 1) USA was to develop light water technology 2) Canada was to develop heavy water technology 3) Europe was to develop breeder technology. After a period of 20 years or so, these countries were supposed to get back together and freely exchange technical information with the intent that all countries would eventually migrate to the best technology. Today, it seems like these countries compete against each other and have no intention of ever changing. So here’s my question: Is what I learned in school correct or was it my professor's wishful thinking? Has anyone got any historical information they could add which would clarify this postition? An new article would also be helpful. --Neilrieck 12:48, 8 April 2007 (UTC)

I don't believe there was any international agreement of this type. Some confusion may arise from the distribution of development tasks during WWII, when the British-Canadian program located in Montreal, Canada was given the responsibility of pursuing heavy-water plutonium production technology (culminating in the post-war startup of the NRX reactor at Chalk River in 1947).

This Canadian expertise in heavy water reactors lead twenty years later to the heavy-water CANDU power reactor, whereas other countries pursued other designs. Breeder technology, on the other hand, was universally embraced at first, since everyone recognized the need to extend uranium resources then thought to be in short supply. However, the degree to which different countries invested in breeder R&D programs depended on various economic and political factors, with the U.S., for example, eventually scrapping its program in the 1970s due to proliferation concerns associated with plutonium separation.

In Canada, the post-war discovery of significant uranium resources in Ontario and, later, Saskatchewan reduced the incentive to invest in costly breeder development, along with the fact that CANDU reactors themselves are near-breeders (and potentially breeders) under a thorium fuel cycle, due to their significant neutron economy, online refuelling, and highly thermalized neutron spectrum (all necessary for the burning of natural uranium rather than enriched uranium).

Now, that said, the essence of what you remember being taught in the 1960's about international development/convergence of technology sort of happened in an ad hoc fashion: The USA adapted light-water technology from its naval propulsion program and this design eventually went on to dominate the world power reactor market (although not all supplied by the USA); Canada developed the heavy-water CANDU reactor that today comprises roughly 5% of the installed plant around the world (but nevertheless is the only commercial reactor concept competing with light-water reactors, in recent years achieving a comparable new-build record with light-water designs); breeder reactor development has continued outside the USA (mainly in France and Japan), but recently has seen a resurgence of Amercian and international interest as an end-point "burner" technology for closing the fuel cycle. However in order to economically and efficiently get to the fast breeder processing stage it may be necessary to provide a "bridge" technology that can reduce the volume of high-level light-water reactor spent fuel, using a sort of "intermedate burner" reactor. By virtue of its existing ability to burn diverse fuel types, and its demonstrated commercial success, the CANDU reactor may just be a convenient off-the-shelf product that can fulfil that "intermediate burner" role.

--Whitlock 16:34, 8 April 2007 (UTC)

Active Candu Reactors

In this section of the article, it is mentioned that India pursued Candu derivatives so that it could develop nuclear weapons. This resulted in Canada terminating its nuclear dealings with India. Did the same scenario happened with Pakistan as well? Q43 09:02, 2 July 2007 (UTC)

Also, in this section of the article, Argentina is shown to operate one Candu reactor. It's interesting that this country, according to Wikipedia List Of Nuclear Reactors also operates a PHWR that was built before its Candu and is also constructing another PHWR originally began with Siemens in 1980. Are these two reactors different designs by other vendors, or is AECL also involved? Q43 09:02, 2 July 2007 (UTC)

India did not use its CANDU reactors in its nuclear weapons program; it used a production reactor (like every other country that has developed a plutonium-based weapon). It was because they misused a Canadian-supplied research reactor (CIRUS) in this manner, not because of any ties to CANDU technology, that sanctions were placed in on international trade with India after its 1974 test explosion.

Regarding Argentina, its non-CANDU PHWR design is not of AECL origin. Whitlock 02:41, 3 July 2007 (UTC)

My mistake. I misread the "Active CANDU Reactors" section of the article and thought that India built Candu derivatives to develop nuclear weapons. Can AECL take India to court since the latter is essentially using the former's work? Q43 19:13, 3 July 2007 (UTC)

There is nothing illegal about India's reverse-engineering of CANDU, and in fact one of the attractions of CANDU trade deals is their high technology-transfer content, to a wide vareity of economies (for the same reason that Canada was able to construct a CANDU using its domestic industry). This is particularly attractive today since much of the world lacks the ability to build the large forged components of a PWR. Whitlock 13:17, 4 July 2007 (UTC)

OK, but this means that essentially Canada's sanctions hurt AECL --that is, Canada-- while they are ineffective against the other side. But I guess this is the subject of a different article! Q43 11:12, 10 July 2007 (UTC)

Does Gentilly-1 (BHWR) really belong on this list (counted under Canada, shut down, as far as I can tell)? It seems it would not meet the all descriptions of CANDU given on this page.Revr J (talk) 20:20, 3 July 2008 (UTC)

It's a good question. G-1 was a prototype direct-cycle (boiling) light-water-cooled CANDU variant. I believe it does belong in the list as it represented a developmental arm of the CANDU program that explored alternate coolants (like WR-1 at Whiteshell in Manitoba). Whitlock (talk) 02:07, 4 July 2008 (UTC)

Statement about Turkey

As I was wikifying, correcting spelling and such, I placed a fact tag after the sentence, "In the summer of 2006, Turks protested against plans for building nuclear reactors, erroneously believing that all designs are as dangerous as the RBMK (involved in the Chernobyl accident), when in fact other commercial reactor designs include fail safe features and better control giving them much better, almost perfect, safety records." I do not think that references are necessary for things that are self evident or that are known by anyone with a little knowledge of the topic, but I think references are needed to support the assertion that Turks believe "that all designs are as dangerous as the RBMK" and that "other commercial reactor designs include fail safe features and better control giving them much better, almost perfect, safety records." Also, it is ambiguous as to what a perfect safety record is in this instance. For example, it could refer to only to radiation releases, only to deaths, or only to accidents (with or without deaths) involving the reactor and/or radiation, which could exclude things like the steam explosion at the Mihama Nuclear Power Plant in Japan that killed five people. Also, it could exclude accidents at non-commercial plants, like the SL-1 Reactor. Finally, it is unclear what would constitute a design. Would all light water reactors be grouped together or would smaller divisions be made? If the divisions are small enough, only a few plants of many designs would probably exist, and in some cases there might only be one (I say "probably" because I am not familiar with specific models, just divisions like pressurized light water reactor, boiling water reactor, graphite moderated reactor and so on). This would make it easy to have an excellent safety record, especially if the reactors have not been operating for very long yet or were shut down after operating only 10 or 20 years, as a problem may only show up after many years. An example is the hole found in a reactor vessel at the Davis-Besse Nuclear Power Station, which began operation in 1977, in 2002. The problem was discovered before there was an accident, but it was a close call and could have been very serious. -- Kjkolb 11:22, 27 July 2007 (UTC)

I would just remove the statement, it doesn't add anything to the statement of fact it's attached to, and is likely to be bogus anyway. People around the world protest against nuclear power, they don't need a reason as difficult to believe as this one! Maury 11:57, 27 July 2007 (UTC)

Citations?

there are hardly any citations on the entire page (less than 5), and most of the information lacks a citationVarunC777999 (talk) 00:46, 18 May 2008 (UTC)

Tritium emissions

Regarding user Eiland's submission on 2008 Sept. 21 regarding tritium emissions, please see discussion at http://www.nuclearfaq.ca/cnf_sectionD.htm#tritium, and in particular the complete debunking of Dr. Ian Fairlie's scaremongering Greenpeace item at http://www.nuclearfaq.ca/ReviewofGreenpeacereport_Final.pdf. Whitlock (talk) 22:46, 21 September 2008 (UTC)

i dont think its a more reliable source then GP's [1] -- eiland (talk) 09:14, 22 September 2008 (UTC)

Oh, I see, it's your own :) -- eiland (talk) 09:16, 22 September 2008 (UTC)

The Greenpeace report by Dr. Ian Fairlie has been reviewed and debunked by Dr. Richard Osborne at the above link; it is not my report. If you would like to author additional objective material on the health hazards of tritium, please go ahead (but it probably belongs in the Tritium article). Also, the CANDU 6 reactors in Canada (similar to Cernavoda) do not remove tritium from their moderators. Whitlock (talk) 12:44, 22 September 2008 (UTC)

Well, Then there are two contradicting views - one of a Greenpeace commissioned scientist, and one with AECL liaisons - on CANDU and tritium, and I dont think its too much work to properly include both of them in the article. Will you, or shall I? My proposal still stands, and I wonder what are your exact issues?

== Health risk of tritium ==

CANDU reactors have a large output of Tritium. In Darlington, Canada, large part of Tritium is recovered by the Tritium Removal Facility (see above), but in Cernavodă, Romania, Tritium is released into the environment. This gives rise to health concerns for the local population, especially for young children and pregnant women.

Hm, Its not at all about Romania, the report, and I don't know, I think if dr. em. Osborne, "the AECL author", would talk about dr. Fairlie, instead of continuously referring to him as the "Greenpeace author", I would be more willing to read on.

-- eiland (talk) 13:10, 22 September 2008 (UTC)

The facts can be related in a section on Tritium Emissions, as follows:

== Tritium Emissions ==

CANDU reactors generate more tritium in their coolant and moderator than light-water designs, due to neutron capture in heavy hydrogen. Some of this tritium escapes into containment and is generally recovered; however a small percentage (about 1%) escapes containment and constitutes a routine radioactive emission from CANDU plants. Operation of a CANDU plant therefore includes monitoring of this effluent in the surrounding biota (and publishing the results), in order to ensure that emissions are maintained below regulatory limits. In some CANDU reactors in Canada the tritium concentration in the moderator is periodically reduced by an extraction process, in order to further reduce this risk. Typical tritium emissions from CANDU plants are Canada less than 1% of the national regulatory limit, which is based upon the international guideline of the ICRP (for example, the maximum permitted drinking water concentration for tritium in Canada corresponds to 1/10 of the ICRP's public dose limit).

In general there is significant public controversy associated radioactive emissions from nuclear power plants, and for CANDU plants one of the main concerns is tritium. In 2007 Greenpeace published a critique of tritium emissions from Canadian nuclear power plants by Dr. Ian Fairlie. This report was reviewed by Dr. Richard Osborne and found to be in significant error.

Whitlock (talk) 14:35, 22 September 2008 (UTC)

Okay we're getting there. Do you maybe know the quantities of Tritium being emitted from LWRs and CANDU's? Then it is easier comparing. And there should still be smt about Romania, and other CANDU sites. -- eiland (talk) 18:01, 22 September 2008 (UTC)

Moved to article, with modifications. Whitlock (talk) 02:01, 23 September 2008 (UTC)

Use of Uranium

I would assume from the context that the CANDU reactor is more efficient at the use of uranium. However, the the statement "However, by avoiding the uranium enrichment process, overall utilization of mined uranium in CANDU reactors is significantly less than in light-water reactors, about 30-40% less, using current designs." is not clear. It could mean that CANDU utilizes 30-40% less of energy in the uranium supplied (is less efficient) or that CANDU requires 30-40% less uranium to be mined for the same energy output. Would someone more confident in the actual meaning fix this. I would recommend the word "consumes" or "requires" rather than "utilizes". —Preceding unsigned comment added by Bdentremont (talk • contribs) 02:16, 18 October 2008 (UTC)

Changes made. Other contributing factors added as well. Whitlock (talk) 01:54, 19 October 2008 (UTC)

Error in the rector schematic

There is a problem with reactor schematic Image:CANDU Reactor Schematic.svg above. The pressurizer (4) should not be linked directly into the boiler pressure vessel (5). I don't have any svg editing program or experience (or time for that matter). So just throwing that out there, that the error exists.

--metta, The Sunborn 22:39, 27 October 2008 (UTC)

I brought your comment to the attention of inductiveload, the creator of the schematic and he has changed the diagram. 192.75.48.150 (talk) 18:41, 17 June 2009 (UTC)Daley

Pros and Cons of CANDU technology for Iran

Should the world be pushing Iran to accept CANDU nuclear technology which does not require enrichment? After reading the economic and proliferation sections, I was still unclear. Does CANDU technology affectively address the nuclear weapons proliferation fears, or only shift them? 96.252.103.113 (talk) 20:42, 13 August 2009 (UTC)

requesting more references

I placed two {{cn}} after two statements I thought needed references -- namely:

"At the time of its design, Canada lacked the heavy industry to cast and machine the large, heavy steel pressure vessel used in most light water reactors..." "Canada also lacked access to uranium enrichment facilities, which were then extremely expensive to construct and operate..."

WRT the second assertion -- surely this was true for every nation that developed a nuclear industry?

WRT the first assertion -- this may very well be correct. But it is not what I remember when I first read about the CANDU design.

Cheers! Geo Swan (talk) 16:19, 20 March 2010 (UTC)

I don't know about the 1st, but as to the 2nd, no, I think the other nations working on nuclear power had already developed enrichment capability as part of their nuclear weapons programs.

—WWoods (talk) 04:34, 24 March 2010 (UTC)

Both assertions are true - and in fact are still true for most of the world. Whitlock (talk) 12:33, 25 March 2010 (UTC)

Pressurized or not?

I dont know if this is really an error, but I was confused when I got to this part..

"The heavy water is unpressurized, and a cooling system is required to keep it from boiling.

At the time of its design, Canada lacked the heavy industry to cast and machine the large, heavy steel pressure vessel used in most light water reactors.[citation needed] Instead, the pressure is contained in much smaller tubes, "

It seems rather contradictory. 24.141.10.136 (talk) 06:31, 17 March 2011 (UTC)

The moderator is heavy water in a large tank (calandria) at atmospheric pressure which must be kept cool by the moderator heat exchangers.

The primary fuel coolant (also heavy water) is pressurised but flows through tubes containing the fuel which run horizontally through the calandria. These tubes are a lot easier to fabricate than the thick walled pressure vessels used in Pressurised water Reactors which contain both the fuel and light water which acts as a moderator and coolant. Dabbler (talk) 14:35, 17 March 2011 (UTC)

Picture of fuel bundle.

I believe that the picture of the fuel bundle with text that states '"Two CANDU fuel bundles: Each about 50 cm in length and 10 cm in diameter, and generating about 1 GWh of electricity during its time in the reactor. Photo courtesy of Atomic Energy of Canada Limited.' has a problem.

I think it should say 1 GW or 1 GWe.

1 GWh is worth about $ 80.00 ( at $ .08/KWh retail ).

Could someone who knows more check and make the change if I am correct please.

Thank you,

Rob Walker. RS Walker (talk) 17:30, 31 March 2011 (UTC)

1 GWh(e) is correct:

nominal CANDU burnup = 7500 MWd/Te

1 CANDU bundle = 20 kg U (roughly)

therefore, 1 CANDU bundle's energy output = 7500 * 20/1000 = 150 MWd = 3.6 GWh ~ 1 GWh(e)

Also, at $ 0.08/kWh 1 GWh(e) would be $80,000, not $80

Whitlock (talk) 05:59, 1 April 2011 (UTC)

Thank you for clearing that up. It makes sense now.RS Walker (talk) 19:31, 1 April 2011 (UTC) — Preceding unsigned comment added by RS Walker (talk • contribs) 19:29, 1 April 2011 (UTC)