Talk:A4W reactor

Useless Links
The reason I reverted here is because the links don't exist and in my opinion shouldn't, at least in Wikipedia. Those links are better suited in the Wiktionary instead. -- RevRagnarok  Talk Contrib Reverts 12:50, 17 June 2006 (UTC)


 * It seems to me that the links could point to quite interesting articles, with a number of details about the fuel and core lifespans, and about neutron shields. I would hardly call them "useless links". modify 12:54, 17 June 2006 (UTC)

Mis-Information
The shaft horsepower does not have anything to do with the A4W reactor. The shaft horsepower is determined by the turbines that are on the various Nimitz class aircraft carriers. The specification that is on all of the US Navy VNimitz Class Carriers is 260,000, but even that is incorrect. I do not think that the Navy will disclose the actual #s, so citing reliable references is going to be nearly impossible.

The fuel lifespan is not set for each of the A4W reactors in the US Navy fleet. Most are rated at 30 years, but they all vary due to different designs. The reactors themselves do not have a rating for lifespan.

In the design section, I took out all of the metals and percentages because they are just plain wrong. The design of the fuel is not correct either.

I also do not believe that BAPL or KAPL actually built the reactors. I believe that Westinghouse actually built them, with technical input from BAPL and KAPL, but I can not prove that. Nly8nchz 11:24, 15 October 2006 (UTC)


 * In the past, we have -when possible- tried to put information on shaft horsepower in the reactor article. This is in part because while any particular reactor design may be used on a variety of ship classes, the reactor normally produces a certain amount of steam which is then fed into the steam turbines designed for that particular reactor.  Hence why the D2G reactor produces 30,000 shp regardless of if it is installed on the Bainbridge, Truxtun, California, or Virginia class cruisers.  As long as the information in question is properly cited and from a reliable source, I am sure we are fine.  Thanks for removing the incorrect info on the reactor lifespans and composition.  BAPL was operated by Westinghouse until 1999, when Bechtel took over the government contract.  --Kralizec! (talk) 12:41, 16 October 2006 (UTC)

Kralizec, you are 100% wrong in your statement "This is in part because while any particular reactor design may be used on a variety of ship classes, the reactor normally produces a certain amount of steam which is then fed into the steam turbines designed for that particular reactor." The reactor does indeed exchange heat to make steam, but the actual SHAFT HORSEPOWER is dedicated to the steam turbines, not the Reactor. Shaft horsepower is driven from the design of the turbines, which any reactor can drive the steam production. This is not to say that just any reactor can keep up with the steam demands of the 140KShp that the turbines "might" make.

Please stop putting the power that the reactor can make. Not only is the # cited a guess, the website that it is supposed to cite does not even have a MW rating. The website that is cited only has the shaft horsepower referenced at 140KShp, it does not mention the power that the reactor can make.

Once again, the shaft horsepower HAS NOTHING TO DO WITH THE POWER OF THE REACTOR. If you are going to talk about shaft horspower, talk about the steam side of the power plant, not the reactor.

On another note, if you do the calculations, the 140KShp is not equal to the 550MW that was cited on this page. www.onlineconversion.com

The power that each reactor can produce IS NOT ON THE WEBSITE IN THE LINK. If you are going to cite references, make sure that the info on the website is actually there. I operated an A4W reactor for 4 years in the Navy, I know what I am talking about, but it seems that Kralizec does not. This is not a slam, just making sure that people do not put up information that is not properly cited.Nly8nchz 04:51, 24 March 2007 (UTC)
 * Note: 71.118.174.88's edits to the above paragraph were reverted, but you may want to take a look at them, it was possibly a response. &mdash; RevRagnarok  Talk Contrib 12:10, 25 March 2007 (UTC)

Nly8nchz, thank you very much for your work to ensure accuracy in this article. People working together on topics they have interest in is one of the best ways to improve our encyclopedia. However while I share some of your frustrations on this topic, I would caution you to remember our rules on civility. Statements like "Kralizec, you are 100% wrong" and "I know what I am talking about, but it seems that Kralizec does not" do nothing to resolve what is essentially a content dispute and only serve to ratchet up emotions on all sides.

A few items of note on this issue:
 * The "550 MW" number was added to the article by an anonymous editor earlier this month and no one caught the vandalism.  Before that change, the article listed 104 MW, which is the correct metric conversion of 140,000 shp.
 * Official wikipedia policy (WP:VER) is verifiability, not truth. The power produced by the A4W reactor is properly cited from the Federation of American Scientists website, which clearly indicates that the "power per reactor" is "140,000 shp."
 * You stated "I operated an A4W reactor for 4 years in the Navy, I know what I am talking about." While I have no doubt that you are an expert on A4W reactors, please remember that official wikipedia policy states that original research (including personal experience) is strictly forbidden.  Wikipedia articles should only contain verifiable content from reliable sources.

Thanks again for your interest and hard work on the article. Between the two of us, I am sure we will make this article the best, most accurate article it could possibly be! --Kralizec! (talk) 13:47, 26 March 2007 (UTC)

[I hope I'm in the right place.]

ANYTIME you see a ship's reactor power rating based on the ships Shaft Horse Power it is a BOGUS number based on defective reasoning.

The number you are seeing is the shaft's power rating given in watts. That has nothing to do with the reactor's ratings.

- - If you want to 'verify' that then use basic math and a grain of common sense.

The shafts are FAR from the only load on the reactor. The shafts [shaft turbines specifically] only utilize PART of the reactor's available/rated power. Further, Shaft HP is the output at the shafts, not the power put into the shaft turbines.

When the shafts are at 100% the reactors still have 30-70% power available. [Depending on the ship class/type.]

Using Shaft HP as sole consideration as to the the reactor's power capacity disregards the power that goes to electrical generation [huge load], steam heat, steam that operates pumps, and on a carrier the steam sent to the catapults. [Catapults are a HUGE steam load comparable to what is used by the shafts.]. Additionally it disregards the efficiency [heat losses] of the main engine steam turbines and the steam plant. Reactor power lost to heat losses is extensive in the steam side of the plant.

The numbers given by the Federation of American Scientists are DELIBERATE misinformation.

Federation of American Scientists probably knows this, but they don't know what the 'real' numbers are.

The Navy won't give out the 'real' numbers for reactor power. They never have. Further, the Navy doesn't even give the same numbers for SHP every time. That's deliberate too. [Misrepresenting Shaft HP I hides how fast the ship can go. - DUH!]

- 'Verifiable' does NOT make it 'correct' no matter how many places you 'verify' it.

- Deliberate misinformation is still misinformation.

- The fact that someone Publishes something doesn't make it correct or the source 'reliable'.

140,000 SHP is reasonable [though not necessarily correct] for ONE PAIR of shafts from ONE plant. The ships have TWO pairs of shafts and EITHER reactor can power all 4 shafts to their maximum HP -AND- still provide all the other steam loads with the other plant shut down. It is a design basis for Nuclear Warships. So, the ship's total SHP would be 280,000 SHP [which is consistent with what numerous other sources give as the ship's total SHP.] That is already 208 MW -JUST- for the shafts if your SHP-MW conversion factor is correct.

I was also an Operator on A4W. [Also A1W, A2W, D1G-2 at different times.]

The correct power rating for the A4W plant is 550 MW. [That is for each reactor. There are two reactors.]

That is the correct number and the truth but it's doubtful you will be able the verify it.

- However -

It would be nice if Wikipedia would at least abstain from repeating the WRONG and obviously INCORRECT information in their web pages.

104 MW for a pair of A4W plants is blatantly incorrect. That is barely enough steam to run the ship's electric plant, let alone move the ship through a harbor.

I was also in the Navy and operated on an A4W as a reactor operator for just over 4 years. I agree with most of what the person above me said except for one minor thing- I think that it's a very bold statement to say "When the shafts are at 100% the reactors still have 30-70% power available" or "The shafts are FAR from the only load on the reactor."

Although the shafts are only part of the load on an A4W reactor plant (which is the specific class in question), if the shafts are at full rated speed (which fluctuates based on ship's displacement and is probably classified- I'm not sure and I'm not going to test it), the reactor will have FAR less than 30% power remaining. Actually, the limiting factor in these situations would usually BE reactor power. Of course, I'm talking about the shafts being at a speed that very rarely is asked for, unless during drills.

Another, more simple way to make the same point is to bring to attention the fact that if the shafts are not receiving steam in any way, the highest reactor power ever would be was always under 30% (which is assuming the rest of the entire steam plant is online and some very rare situations). Normally, with everything running save the shafts, it would be closer to half that.

I know there are some exceptions to what I'm talking about, and honestly, the situation I was addressing is a pretty rare one. I purposely left out certain situations that wouldn't apply to normal, day-to-day operations (i.e. steam dumping).

. —Preceding unsigned comment added by 1FreeRadical (talk • contribs) 19:02, 29 September 2010 (UTC)

Ratings
First, let me point out why rating a reactor's power by Shaft Horsepower, as is done on the FAS website, is fallacious. How many reactors do NIMITZ-class carriers have? Two. How many shafts does it have? FOUR! So simply converting SHP to watts and multiplying by two reactors just does not work. Furthermore, the reactors provide steam to many other loads besides the main engines. There are turbine-generators for shipboard electrical power, steam-powered pumps, steam catapults, and so on. The reactors must generate much more power than that which is required for propulsion. This means that not only is 104 MW an incorrect power rating for the A4W plant, it is not even in the right ballpark. I would think that it would be better to have no number than an obviously incorrect number. Second, to say that the fuel lifespan is not set for naval reactors is incorrect. Each reactor core has a certain amount of fuel and burnable poison, and the laws of physics determine very clearly what the end-of-life of any given reactor will be. A reactor core lifespan is expressed in units of Effective Full Power Hours, and this is very closely monitored during reactor operation. The problem in determining exactly how long -- in years -- a naval reactor core will last, is that the reactor power varies greatly during its lifetime. Very rarely is a naval reactor actually operated at 100% full power. So while it is easy to calculate how long a reactor will last if it is run at full power all the time, it is not a practical or useful value. Only operational experience can determine the lifespan of a NIMITZ-class carrier reactor, and that has been shown. In a book published by RAND corporation's National Defense Research Institute, for the U.S. Navy, titled "Refueling and Complex Overhaul of the USS Nimitz (CVN 68): Lessons for the Future," I found the following quote in the summary (p. xiii): "At some point, the nuclear reactors that power an aircraft carrier run out of the fuel with which they were provided when the carrier was built. For the current Nimitz-class carriers, fuel depletion occurs after about 23 years." 129.6.122.174 02:00, 21 September 2007 (UTC)


 * Thank you for pointing out that oversight- you beat me to the punch there! Not to mention the fact that the max core rating stated in the various manuals is with the throttles cracked wide open and Average Coolant Temperature at the top of the band. Seeing as the reactor doesn't always operate at that temperature (and during sea trials on the Reagan, we ran the full power speed trial at an even higher elevated band personally approved by NAVSEA08, who was onboard at the time), there's even more evidence to shoot down the argument above. A note about the lifetime of the cores- while fuel depletion for Nimitz, Ike, and Vinson was around 23 years, with the increased tempo of operations of the CVN fleet (surges, longer, more frequent deployments, etc), shouldn't that be reflected in the article as well? Rumor in the fleet is that TR and Lincoln have been put on restricted EFPH because they're nearing the end of their core lives too fast for NGNN to be able to keep up with the pace of carriers requiring refueling. Anybody have any word about that?

Tspencer227 02:21, 16 November 2007 (UTC)

Megawatt amount
In this article is written:

''The only ships to use these nuclear reactors are the Nimitz class supercarriers, which have two reactors rated at 550MWt each. These each generate enough steam to produce an 100 MW electricity supply plus 140,000 shaft horsepower (104 MW).''

The first number can be right, I thought it is more since many "Energy" or in this case steam is lost on the way to the 4 steam turbines.. but the Nimitz-Class does not have "only" 104 MW or 140,000 horsepower. There are 4 steam engines (steam comes from thermal nuclear reactors power and seawater) with each 48,500 kW or 48.5 MW or 196 MW (260,000 horsepower) together. Which allows even with the very heavy displacement of over 100,000 metric tons to reach speeds above 30 knots... China and Russia got each a single aircraft carrier, soviet build, the Russian was introduced in Early 1991 only months before the Soviet Unions collapse, the 2nd was already in building (2 others were not started), China however was very interested in the basics already build and bought it, completed it with Russian help, gave its own carrier more modern equipment (radar and so on), these ships have 4 engines too... with 50,000 horsepower each. Which is much lower than Nimitz, but the Kuznetsov-class aircraft carrier got a light displacement of 43,000 tons light, 53,000 – 55,200-tonnes standard and 58,600 – 67,500-tonnes max! Not like Nimitz with over 103,000 tons... the 200,000 horsepower from 4 engines bring the ship to maximum 29 knots at a horrible cost of fuel, which can be seen in the range:

8,500 nmi (15,700 km; 9,800 mi) @ 18 kn (33 km/h; 21 mph) (economic cruise speed) and only

3,800 nmi (7,000 km; 4,400 mi) @ 29 kn (54 km/h; 33 mph) at maximum Speed, which is as you can see I think less than 45% of the 18 knots range... the ship (Russian is in a 3-year modernization from 2015-2018), but the Chinese ship only is driving if "needed" or for exercise since the costs are very high for the Chinese Navy to refuel, even with 18 knots... Greetings Kilon22 (talk) 12:59, 10 March 2016 (UTC)

So many problems remaining
What a mess this article is. Contrast "The A4W designation stands for... W = Westinghouse, the contracted designer" with the next sentence, "These nuclear fission pressurized water reactors (PWRs) were jointly designed by Bettis Atomic Power Laboratory and Knolls Atomic Power Laboratory and built by Westinghouse Electric Company." So W stands for "the contracted builder," I guess, but there's no reference that says so.

The next number is 25, as in 25 years between refueling. For this, an editor cited a piece from FAS, which to begin with is just a website full of unsubstantiated opinions by random people, and this piece is STUNNINGLY random, saying "Current cores for... Nimitz... last on average about 20 years" AND "Nimitz-class carriers are now expected to last 50 years..." AND "versus their original design lifetimes of 30 years." So if I boil that down, that's a citation that would support "50 years" if anything, but here it's being cited to support THE ONE NUMBER that it doesn't even MENTION, "25 years". (I emphasize not to blame anyone but simply to inject some humor, since we're going to need to be in a good mood for the rest of my complaints.)

The 550 MWth figure could be right; (MWe ≅ MWth/5) is reasonable. But who says so?

Some editor chimed in with an external link with a weird note, "correcting for the power output from 500 megawatts to 105", apparently to an essay by Professor M. Ragheb at the University of Illinois at Urbana, Champaign, who may well be a reputable source on this subject (I don't know) but here he does not impress me. He says this type reactor produces either "100 MWth" (Figure 1) or "104 MWth" (in section LARGE SHIP REACTORS) or "104.4 MWth" (Table 1) or "about 105 MWth" (section SURFACE VESSELS), and NONE of these numbers are even remotely reasonable since M. Carnot would tell us, were he not dead, that there's absolutely no way to get 140,000 SHP out of 105 MWth. What kind of "correction" is unreasonable and so extraordinarily inconsistent? We do not need this here.

And then there's the "100 MW of electricity" claim, which isn't in any of the cited references either. Maybe some earlier editor converted 140,000 SHP to about 100 MW and someone else later saw a number in units of MW and helpfully added a note to the effect that MW is a measurement of electrical power? Who knows.

So the bottom line is that there is literally no verifiable fact in this article. Surely someone can help us do better. 67.188.1.213 (talk) 03:15, 29 June 2022 (UTC)