Talk:A4W reactor

message: 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)
replies: text: 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)
thread_title:  Useless Links 

message: 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)
replies: text: 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)
thread_title:  Mis-Information 

message: 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)
replies: text: 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)
thread_title:  Ratings 

message: 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)
thread_title:  Megawatt amount 

message: 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)
thread_title:  So many problems remaining