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23 comments on A Dam failure in Missouri

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Whitehall on December 15, 2005 - 3:26pm Permalink | Subthread | Parent | Comments top
How much longer until you get your engineering degree?

You seem to have a pretty good handle on these issues!

Yes, net load rejection is a difficult transient for a big nuke.  BWRs with this capacity have to have oversized condensers and integrated and anticipatory control systems on the reactor, the turbine control valves, the generator, and the turbine bypass valves.

On PWRs, they can blow off steam to the atmosphere and dump heat into the condensate system.  The first time we tried this transient in a test at Diablo Canyon, when the relief valves opened, the jets of steam were so strong that the siding panels on the turbine building got sucked off and flew a mile through the air!  Imagine dumping 3500 megawatts of thermal energy into the air - a million pounds/hr of high pressure steam (850 psig) - talk about loud!

For both designs, xenon buildup is accomodated with initial excess reactivity.  It can be a problem if one is near the end of a fuel cycle and is in coast down mode. One may have to start a refueling outage early but this sensitivity is limited to the last month or so of an 18 month fuel cycle.

As to the success rate, it's definitely not 100%.

One can have lots of wind on a grid - you just have to pay for it in spinning reserve, grid remote controls, and transmission line upgrades.  Above a few percent, it is definitely has  declining marginal utility.

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Magnus Redin on December 15, 2005 - 3:56pm Permalink | Subthread | Parent | Comments top
Next year, I realy should work more with my dynamics then read The Oil Drum. The closest problem is to find practice work and do more math.

I got what I concider technical general knowledge and since most things are built with the same physical building blocks its only to piece together the puzzle och perhaps put togheter an new one with the pieces on hand. I can bet you a beer on being able to describe the overall function of more then 50% of any random system in a powerplant. But I might need a dictionary to do it in english.

Understanding a process, its components and how everything is interrelated is the easy part. The hard part is to describe it in math and then optimise it.

A PWR can have as large a condenser as a BWR but why build it if you can dump non radioactive steam to the atmosphere?  Its not acceptable for a BWR since there is no heat exchanger between the reactor core and the turbine island. (I dident think about that option for PWR:s, this is not a throughly overworked texts. )

Perhaps you can tell med why PWR:s dont have a steam condensing pool?

BWR:s have steam dump pools where steam from an insulation vale closure of the get blown thru overpreassure alves into a pool of cold water inside the containment where it condenses. (I write this to keep it intresting for the general reader. Did you get my email? )

As far as I know PWR:s have a larger containment withouth such a pool and dump the steam inside the containment. The containments preassure can then be lowered by pumping sump water from the bottom of the containment thru sprinklers in the roof.  The size of the containmnet is probably due to the need to have the heat exchangers, that is steam generators inside it and to be able to lift components for service.

Do this automatically give enough volume to make blowdown into a pool unneceserry?  It seems like it would be a nice passive system to keep the preassure buildup down and give less wear on installations inside the containment.

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Whitehall on December 15, 2005 - 4:58pm Permalink | Subthread | Parent | Comments top
A PWR has a smaller reactor system volume and so in case of a LOCA (loss of coolant accident), a pressure containment (the "big round thing" or BRT) is the more economical solution although a few plants have racks of ice inside to condense the steam from the flashing coolant.  They've shown themselves more hassle than they are worth.

A BWR has a much larger volume of water within the vessel so the added complexity of a "suppression chamber" is worthwhile and much cheaper than a pressure containment.  That allows the flashing steam bubble through an internal pond of water and condense.

Note that these are separate from the steam condenser under the main turbine which is part of the power production cycle.  We can make use of it for safety issues like net load rejection.

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23 comments on A Dam failure in Missouri

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