Japan Nuclear Coverage

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Gawd
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Re: Japan Nuclear Coverage

Post by Gawd » Sun Mar 13, 2011 7:57 am

Warren Dew wrote:
Gawd wrote:I don't know what kind of idiots design nuclear power plants, but requiring persistent power to ensure that there isn't a meltdown or explosion is monumentally dumb. When power is cut, the nuclear reactor should have fail safe mechanisms to cool the core down for a duration needed to reach safe temperatures. Requiring mechanical pumps that use power to do so and are prone to hiccups is a death sentence. What should be required is a water tower that stores water at elevation. It would be connected to the cooling system of the core but would be held back by solenoid values that require power to stay closed. When the power goes out, the solenoid valves open and the water from the water tower pours in to cool the reactor. The valves are sized so that a persistent rate of flow is obtained for the time needed. THIS IS WHAT IT MEANS TO BE FAIL SAFE.
Nuclear power plants generate a considerable amount of residual heat - initially several percent of their operating power level - for days after they are shut down. Passive cooling methods are simply not adequate for most commercial nuclear plants. It might be possible to design plants around that requirement, but they might well be uneconomically expensive.
Dead wrong. Passive cooling works as shown by different reactor designs such as the Westinghouse Electric Company's AP1000 reactor:

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Power reactors of this general type continue to produce heat from radioactive decay products even after the main reaction is shut down, so it's necessary to remove this heat to avoid meltdown of the reactor core and possible escape into the containment or, very unlikely, beyond the containment. In this design Westinghouse's Passive Core Cooling System (PCCS) uses less than twenty explosively operated and DC operated valves which must operate within the first 30 minutes. This is designed to happen even if the reactor operators take no action.[7] The electrical system required for initiating the passive systems doesn't rely on external or diesel power and the valves don't rely on hydraulic or compressed air systems.[4][8]
If the active process to turn on the passive system works the design is intended to passively remove heat for 72 hours, after which the PCS gravity drain water tank must be topped up for as long as cooling is required.
http://en.wikipedia.org/wiki/AP1000

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Re: Japan Nuclear Coverage

Post by FBM » Sun Mar 13, 2011 8:07 am

I think it would be better to design a system that required electricity to keep the rods within effective distance of each other. Lose power and gravity makes half the rods slide down a rail, for example, far enough to stop the reaction. But I imagine the engineers know more about it than I do.
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Re: Japan Nuclear Coverage

Post by Gawd » Sun Mar 13, 2011 8:10 am

FBM wrote:I think it would be better to design a system that required electricity to keep the rods within effective distance of each other. Lose power and gravity makes half the rods slide down a rail, for example, far enough to stop the reaction. But I imagine the engineers know more about it than I do.
The rods are already designed like that.

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Re: Japan Nuclear Coverage

Post by FBM » Sun Mar 13, 2011 8:12 am

Gawd wrote:
FBM wrote:I think it would be better to design a system that required electricity to keep the rods within effective distance of each other. Lose power and gravity makes half the rods slide down a rail, for example, far enough to stop the reaction. But I imagine the engineers know more about it than I do.
The rods are already designed like that.
Oh. So...why didn't the reaction stop when power was lost? I suppose I shoul've read up more on it before now.
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Re: Japan Nuclear Coverage

Post by Gawd » Sun Mar 13, 2011 8:16 am

FBM wrote:
Gawd wrote:
FBM wrote:I think it would be better to design a system that required electricity to keep the rods within effective distance of each other. Lose power and gravity makes half the rods slide down a rail, for example, far enough to stop the reaction. But I imagine the engineers know more about it than I do.
The rods are already designed like that.
Oh. So...why didn't the reaction stop when power was lost? I suppose I shoul've read up more on it before now.
The main reaction did stop but nuclear fuel have byproducts of which some have short half lives and give off heat as they decay over a few days to a couple of weeks. They need to be cooled during this period as the short term byproducts die off. The problem is that the back up water pumps failed.

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Re: Japan Nuclear Coverage

Post by FBM » Sun Mar 13, 2011 8:19 am

Oh. OK. Thanks for the info, Gawd. :tup:
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Re: Japan Nuclear Coverage

Post by JimC » Sun Mar 13, 2011 10:03 am

Gawd wrote:
FBM wrote:
Gawd wrote:
FBM wrote:I think it would be better to design a system that required electricity to keep the rods within effective distance of each other. Lose power and gravity makes half the rods slide down a rail, for example, far enough to stop the reaction. But I imagine the engineers know more about it than I do.
The rods are already designed like that.
Oh. So...why didn't the reaction stop when power was lost? I suppose I shoul've read up more on it before now.
The main reaction did stop but nuclear fuel have byproducts of which some have short half lives and give off heat as they decay over a few days to a couple of weeks. They need to be cooled during this period as the short term byproducts die off. The problem is that the back up water pumps failed.
Perfectly correct. In fact, something like 6 % of the heat energy released in the fuel rods comes from radioactive decay of short-lived fission products and various trans-uranics, rather than fission. The rapid insertion of the neutron-absorbing control rods halts the fission reaction, but the other continues unabated for some time.

Intelligent engineering solutions, anticipating a major quake, should have included more back-up cooling options than diesel generators that failed too easily...
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Re: Japan Nuclear Coverage

Post by Gawdzilla Sama » Sun Mar 13, 2011 11:25 am

Must have been a frantic google session.
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Re: Japan Nuclear Coverage

Post by Warren Dew » Sun Mar 13, 2011 1:51 pm

Gawd wrote:Dead wrong. Passive cooling works as shown by different reactor designs such as the Westinghouse Electric Company's AP1000 reactor:
Still requires electricity to operate valves after shutdown, and still requires power to fill the water tank. It's advertised as "passive", but it really isn't.

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Re: Japan Nuclear Coverage

Post by Gawdzilla Sama » Sun Mar 13, 2011 1:53 pm

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Re: Japan Nuclear Coverage

Post by maiforpeace » Sun Mar 13, 2011 3:33 pm

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Re: Japan Nuclear Coverage

Post by Gawdzilla Sama » Sun Mar 13, 2011 3:36 pm

SNAPSHOT-Developments after major Japan earthquake

(* indicates a new or updated entry)

TOKYO, March 13 (Reuters) - Following are main developments after an 8.9 magnitude earthquake that struck northeast Japan on Friday and set off a tsunami.

- Death toll expected to exceed 10,000 from the quake and tsunami, public broadcaster NHK says. Strong aftershocks persisting in the stricken area.

- Kyodo reports 10,000 people in one town unreachable.

- Tokyo Electric Power Company (TEPCO) says radiation levels at the Fukushima Daiichi nuclear power plant, which is 240 km (150 miles) north of Tokyo, have risen above the safety limit but says this posed no "immediate threat" to human health. An explosion blew the roof off at reactor No. 1.

- Chief Cabinet Secretary Yukio Edano says there is the risk of an explosion at another building housing the No. 3 reactor, although this is unlikely to affect the reactor's core container. He said fuel rods may have been partially deformed but a meltdown is unlikely to have occurred.

* TEPCO is preparing to put sea water into the No.2 reactor at its Fukushima Daiichi nuclear power plant, Jiji news agency says. TEPCO, Japan's largest electric utility, is already injecting sea water into the No.1 and No.3 units at the plant to cool them down and reduce pressure inside reactor container vessels.

- Authorities have set up a 20-km (12-mile) exclusion zone around the Fukushima Daiichi plant and a 10 km (6 miles) zone around another nuclear facility close by. Around 140,000 people have been moved from the area, while authorities prepared to distribute iodine to protect people from radioactive exposure.

- About 300,000 people evacuated nationwide and almost two million households without power in the freezing north, domestic media say.

- Prime Minister Naoto Kan approves power outage plan by TEPCO that begins on Monday to address power shortage. TEPCO says the rollover blackout to affect three million customers, including large factories of all industries, buildings, households.

- Meteorologists say the wind will keep blowing from the south, which could affect residents north of the power plant.

- France recommends its citizens leave the Kanto region that includes Tokyo and six other prefectures in its vicinity, citing the risk of further earthquakes and uncertainty about the situation at its damaged nuclear plants.

- A Japanese official said there were 190 people within a 10-km radius of the nuclear plant when radiation levels rose and 22 people have been confirmed to have suffered contamination.

- Nuclear safety agency rates the incident a 4 on the 1 to 7 International Nuclear and Radiological Event Scale, less serious than Three Mile Island, which was a 5, and Chernobyl at 7.

- Quake triggered tsunami up to 10 metres (30 feet). Waves swept away homes, crops, vehicles and submerged farmland.

- Bank of Japan to hold policy meeting on Monday. It has extended a total of 55 billion yen to 13 financial institutions in the quake-struck northeast of Japan since Saturday.

- Japan's ruling and opposition parties to discuss temporary tax rise to fund quake relief, Kyodo news agency says.

- Toyota Motor Co to suspend operations at all 12 factories on Monday.

- Total insured loss could be up to $15 billion, equity analysts covering the industry say. Disaster-modeling company AIR Worldwide estimates the insured losses from the Japan eathrquake at between $14.5 billion and $34.6 billion.

- Tokyo Stock Exchange to trade as normal on Monday.

- Disaster has sent oil, metals, and grain prices sliding on fears over its impact on demand, deepening their biggest decline in months; yen rose broadly on risk aversion by Japanese investors and expectations of repatriations by Japan's insurance companies; oil prices slide more than $3 a barrel. (Tokyo bureau; World Desk Asia, Singapore +65 6870 3815)
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Re: Japan Nuclear Coverage

Post by Gawd » Sun Mar 13, 2011 4:56 pm

Warren Dew wrote:
Gawd wrote:Dead wrong. Passive cooling works as shown by different reactor designs such as the Westinghouse Electric Company's AP1000 reactor:
Still requires electricity to operate valves after shutdown, and still requires power to fill the water tank. It's advertised as "passive", but it really isn't.
Power is not required to operate the valves, they fail open. And you have a 72 hour water capacity in those tanks. You can refill them with anything that pumps like a fire truck.

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Re: Japan Nuclear Coverage

Post by Seth » Sun Mar 13, 2011 7:46 pm

I would like to know if the Japanese plants have the "China Syndrome" avoidance system I once heard about that puts a cone-shaped divider under the reactor vessel, so that if the core melts down completely and melts through the floor of the vessel, it drops onto a pointed divider that splits the flow up into several different rivers that flow away from each other into pools separated from each other that will help damp the criticality.
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Re: Japan Nuclear Coverage

Post by Seth » Sun Mar 13, 2011 7:53 pm

So the problem is lack of electrical AC power to circulate water, and they are using innovative methods (steam power) and batteries to try to circulate coolant. Where the fuck are the heavy-lift helicopters dropping in portable emergency generators? Where the fuck are the heavy-lift helicopters dropping freshly-charged battery packs by the dozen?

Why the fuck were the emergency generators not placed ON TOP of the containment building, or high enough so they could not be inundated by a tsunami?
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