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When people talk about hydrogen loss in a generator and say so-and-so number of cubic meters per day or a total hydrogen charge of so-and-so cubic meters, do they mean STP or actual cubic meters? Because, I heard some pretty big numbers...
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Sep 17, 2011 17:19
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| # ¿ May 3, 2024 05:42 |
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squeakygeek posted:Where is this hydrogen coming from? AGA, you putz.
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Sep 18, 2011 02:01
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Frozen Horse posted:I think the steam in a boiling-water-reactor would be throttled to the condenser, bypassing the turbine. The interesting problem becomes how one keeps the coolant pumps going to re-inject the condensate into the reactor and flow outside water through the condenser. However, it's possible that the condenser pressure rises too quickly (it's not meant to take the rated steam flow for very long at all), dump blocking is enabled, and steam pressure builds in the reactor pressure vessel until one of the reactor pressure relief values is reached. Then, steam is dumped to the suppression pool. As far as the coolant pumps go, there are feedwater/condensate pumps (same thing, as far as a reactor engineer is concerned, since they're in series) controlling flow into the reactor, as well as circulation pumps controlling flow circulating within the reactor through the core. A generator trip will lead to a scram condition of some sort getting fulfilled, and both circulation and feedwater/condensate are intended to be brought down on painstakingly developed ramps (e.g. 100% to 0% in 5 s). These ramps assume continuous external power, even in the case of a generator trip. The plant's pumping systems are designed to consume power just like the farm houses, the gas station and the outage workers' temporary brothel down the road--that is, everything is pretty much business as usual. A dump condition would just result in continued circulation dump->condenser->condensate->feedwater->RPV. If there is a mass imbalance, something will, for example, run into a low tank level condition and kill some pumps or close some valves, just like normal. The real interesting problem is that this event is somewhat hard on the fuel, as the sudden closure of the valves going to the turbine will cause a pressure spike, a void collapse, and a reaction increase. This isn't exactly the kind thing that happens every year, but it's probable enough that the reactor is run with enough margin (think underclocking the reactor) to avoid damaging (overheating) the fuel in the event that such a thing would happen. For the record: In the event that the fuel was damaged by an event of this nature, it usually means that you have to shut down for a week and replace a handful of the several hundred fuel elements. Expensive, but not especially more radioactive than normal.
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Sep 20, 2011 22:01
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Three-Phase posted:Is it correct that the reactor "physics" changes over the life of the fuel? So a reactor with fresh fuel that has more pure uranium will behave differently than a reactor where half of it's uranium has been depleted and replaced with other isotopes and compounds? Absolutely. Estimating how the fuel will behave one day/month/quarter/etc into the fuel cycle is a large part of the job of core design (you're not just refueling the reactor each year, you're making a whole new machine with different behavior). Your uranium isn't just going to turn into fission products, which are radioactive and (more importantly) generate heat after the reaction is halted, but also new fuel (plutonium), which doesn't behave the same as uranium. The same [BWR] fuel element will have drastically different changes in composition take place at the bottom than at the top. Three-Phase posted:I'm also assuming the pump ramp-down over five seconds is to reduce the effect of water hammer, right? No, but god knows water/steam hammer is on everybody's mind in the design process... (Attention: only BWR) Fundamentally, the feedwater (which goes into the reactor pressure vessel to be turned into steam) can't fill up the tank forever. If you close the steam valves, you've got a tank partially filled with water, partially with steam, which has no outlet. If you know the outlet (i.e. steam valves) are closing, you might as well shut off the flow into the vessel. Water level in the vessel too high? Another good reason to shut off the flow into the tank. The circulation pumps (which move the water around in a loop inside the vessel) ramp down because:
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Sep 21, 2011 22:04
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Three-Phase posted:Is it just me, or are BWRs a little "scarier" than PWRs? Radioactivity going into the turbine in a BWR plant has two components:
The irradiated water is massively radioactive, but only while the plant is running. After a matter of minutes after shutdown, it will have decayed into nothing. The other stuff lasts longer, and is closely monitored (see below). PWRs have plenty of scary things to keep track of. For example, a BWR has very simple water chemistry: pure water. Just like any old coal plant boiler... A PWR, on the other hand, is constantly adding and removing boron-bearing acid from its reactor water to control the reaction rate. This can cause problems if done improperly: http://en.wikipedia.org/wiki/Davis-Besse_Nuclear_Power_Station#Reactor_head_hole PWRs separation between systems, the steam generators, consist of thousands upon thousands of small, tightly packed tubes bearing a pressure difference of ca 85 bar. The potential for a leak is big, and so is the time it takes to fix it if you can't just plug the bastard. helno posted:Yeah it never seemed like a great idea. As soon as you have failed fuel your entire system is contaminated with fission products. Yeah, popping a fuel rod will contaminate your turbine -> condenser -> feedwater system, but there are sensors for measuring the radioactivity and (IIRC) radiation alarm signals which can shut down and seal off the reactor from the rest of the plant in a matter of seconds. The radioactivity passing through the turbine and condenser is constantly monitored, and poking a pinhole in just one of the 50,000-100,000 fuel rods in your BWR core can actually be detected and dealt with before things get out of hand. Even though the steam has been passing through it from the core all year long, people can still climb into the turbine housings and work the whole outage without space suits.
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Sep 22, 2011 23:28
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helno posted:Boiler tube inspection and plugging is a massive outage job and I am sure it is similar at all PWR reactors. How bad does Canada want the Bomb that they still deal with these?
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Sep 23, 2011 20:17
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movax posted:What's a good nuclear engineering textbook you guys used in school? Wikipedia's nice, but I'd like a book I can read to improve my knowledge of the reactor types and keep them straight in my head. I don't think I had a single generally available nuclear engineering textbook my entire program! What are you interested in? Mechanical engineering? Physics?
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Sep 24, 2011 10:55
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Ossetepo posted:You work at a CANDU, right? I didn't know you guys had gas turbines as backup power. I imagine that's a lot easier to deal with than the care and feeding of thirty-year old marine diesel engines. I really need to convince my employer to send me on a benchmarking trip up there just to poke around. We had some radiation protection guys from Bruce down here with WANO last year and actually got some useful information out of it. Turbines are assholes. Diesels all the way...
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Oct 2, 2011 21:31
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Three-Phase posted:I had heard about people trying to see if there was a way to somehow "reverse" the smelting to store and regenerate electricity. Sounds odd though. You aren't of proposals (there was something on Slashdot a while ago) to use aluminum-oxidizer batteries as a way of storing surplus electricity via aluminum production?
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Dec 29, 2011 23:01
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grover posted:Ah, OK, I see what you're talking about now; I thought you were trying to recapture energy "lost" during smelting. Given the energy density, though, I can see how it would be useful as a chemical battery, too. But since the end state is a solid, it would be very difficult to do outside of a lab. Iceland and others (Hoover Dam was a similar situation in its day) are of course already doing that in a way, by smelting imported aluminum ore and exporting the refined (can't think of the word) metal.
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Dec 30, 2011 22:46
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stealthdozer posted:I just stumbled across this: What the hell is this video?
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Nov 5, 2012 00:32
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FrozenVent posted:Wait, H2 as in hydrogen? I worked at a plant that had a significant hydrogen leak, and the main concern was running out.
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May 4, 2013 02:38
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grover posted:Works pretty good on AC; not sure how it would be on DC controls.
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Sep 17, 2013 13:44
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afen posted:Why do you guys talk about motor power in HP? I've always used kW when talking about electric motors. The kilo-watt (KW) is a unit of electrical energy in the US.
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Dec 23, 2013 17:39
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Enilev posted:Watts are a measure of power. Energy is power over a certain amount of time. Energy is measured in kWh (as in, one kilowatt for one hour), J, or BTU depending on the context. No, I'm pretty sure you're mistaken.
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Dec 23, 2013 19:19
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Noctone posted:Do tell. It's a U.S. Customary unit: 1 kilowatt x 1 hour = 1 kilo-watt Groda fucked around with this message at 20:34 on Dec 23, 2013 |
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Dec 23, 2013 20:32
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NihilismNow posted:BTU is not in the SI and therefore unholy and shall never be used. Also, having six definitions and being used as a unit of power in the US...
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Dec 24, 2013 13:51
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Three-Phase posted:Groda don't take this the wrong way, but you are absolutely wrong here. Like red flag illuminated with flashing lights level wrong. Papercut posted:HP is voltage-independent, which allows mechanical engineers to just specify a HP and then feign ignorance to this crazy concept called "voltage" and wipe their hands clean.
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Dec 27, 2013 05:22
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| # ¿ May 3, 2024 05:42 |
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original sin
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Jan 7, 2016 22:25
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