Posted on 05/19/2008 5:59:37 AM PDT by Straight Vermonter
Give me one pebble, and I will build a car around it.
Thanks. I’m glad it made sense. Considering that it’s been twenty-two years since I flunked out of Nuke School, I’m surprised I can still write a coherent sentence on the topic!
This a very nice description of Pebble Bed Reactors. Thank you for posting this.
NNPTC?
Not far from where I live......
http://www.hillsdale.edu/hctools/imprimis_archive/2008/02/2008_02_Imprimis.pdf
NNPS Orlando, 1985
Better yet, we need to let the free market decide. When “we” decide what needs to be done in advance, in a rush to solve the problem with the solution that appears to be the best one this week, “we” rush into things using other people’s money and the armed agents of government to enforce what “we” have decided. Almost always we later regret our decision, such as converting food grains to ethanol, and find we have thus wasted precious time and money.
My son’s a glowworm. Graduated from NNPTC in Goose Creek last year.
I stray from P.B.R. and prefer Corona.
Makes sense. I’m more familiar with fast neutronics, and in a Godiva, the reaction is limited by Doppler too.
How do you shut down the reactor? Funnel pellets out until the reactivity drops?
One potential problem, very unlikely to occur- what if the reaction bed becomes flooded with water?
Only because Bam-Bam taught her how....
Bump
Which graphic represents sustainable nuclear energy.
Nuclear is as renewable as any other form of energy.
As I understand it, the pebbles are constantly in motion. As they reach the bottom of the core, they are extracted, subjected to an automated inspection process, then replaced at the core top. The whole core is wrapped in a beryllium reflector can. My guess is that you go subcritical by simply removing a given number of pebbles from the core using this process; once enough are outside the "can", there's not enough left inside to keep the rest of the pile going.
As far as flooding, I'm not sure what would happen. There's no water in the cycle, if I understand the schematics correctly; it's gas-cooled. I guess a flood or something could happen, but even in the worst case I don't think it's a problem. Keep in mind that this RX runs at a much higher temperature (and lower pressure) than a PWR or BWR; my guess is that any water in the core would be flashed to steam, which would poison the reaction ( = negative void coefficient) and take the core subcritical.
If I remember correctly, the test reactors based on this design also came with control rods that could be inserted into the pebble bed to scram the reactor. I may be wrong about that, however.
By the way, I'm sorry for the lame answers. While I have a shallow, basic knowledge of the principles behind this system, I am not an expert on PBR/HTGRs; my experience is entirely with PWRs of the A5W class (1950s tech!), and I'm afraid that the inner workings of these babies are outside my knowledge base. I wish we had a real nuclear engineer here on FR who could supply us all with detailed technical information on this system.
Nuclear Bump 8-)
The pebble bed reactors have about 1/10th the output, but disposal at the back end of production is simpler and cleaner. Not too sure about the processes which make the pebbles in the first place though. Developed in Germany, which later caved on its entire nuclear power program because of politics related to high-level waste disposal.
McCain calls for 700+ new nuclear plants costing $4 trillion
grist.org | 06 May 2008 | Joseph Romm
Posted on 05/19/2008 9:54:02 AM PDT by Tailgunner Joe
http://www.freerepublic.com/focus/f-news/2018144/posts
Thanks for the ping...good article.
Lame answers? You cut through the fog (well, my fog anyway) and gave me the keys to go and learn more. Thanks!
There are “real” nukies here, I’ll need to go back in time and see who they are.
You served on a nuke boat! Wow, thanks for that too!
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.