# What improvements have the latest generation of nuclear reactors? **URL:** \ **Category:** Factual Questions\ **Created:** [May 23, 2006, 5:25pm UTC](https://boards.straightdope.com/t/what-improvements-have-the-latest-generation-of-nuclear-reactors/357926 "2006-05-23T17:25:32Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Carnac\_the\_Magnificent](https://avatars.discourse-cdn.com/v4/letter/c/ccd318/32.png) [@Carnac\_the\_Magnificent](https://boards.straightdope.com/u/Carnac_the_Magnificent)\ **Post date:** [May 23, 2006, 5:25pm UTC](https://boards.straightdope.com/t/what-improvements-have-the-latest-generation-of-nuclear-reactors/357926/1 "2006-05-23T17:25:32Z")
Sen. John McCain has added his name to the rising chorus of politicians advocating more US reliance on nuclear power. Comparisons are inevitably made with the crippled reactors at Three Mile Island. Long question short, what improvements have the latest generation of reactors, over those of the 1960s - 1970s? Proponents say they are better in every way. How so? ---
**Author:** ![LiveOnAPlane](https://avatars.discourse-cdn.com/v4/letter/l/3d9bf3/32.png) [@LiveOnAPlane](https://boards.straightdope.com/u/LiveOnAPlane)\ **Post date:** [May 23, 2006, 8:39pm UTC](https://boards.straightdope.com/t/what-improvements-have-the-latest-generation-of-nuclear-reactors/357926/2 "2006-05-23T20:39:30Z")
I am not particularly knowledgeable on this topic, but take a look at [this thread](http://boards.straightdope.com/sdmb/showthread.php?t=371250&highlight=candu+reactor) for some thoughts on the CANDU reactor. One of the threads there also has a link to a site providing more info. Hope this helps, even if only a little. ---
**Author:** ![LiveOnAPlane](https://avatars.discourse-cdn.com/v4/letter/l/3d9bf3/32.png) [@LiveOnAPlane](https://boards.straightdope.com/u/LiveOnAPlane)\ **Post date:** [May 23, 2006, 8:40pm UTC](https://boards.straightdope.com/t/what-improvements-have-the-latest-generation-of-nuclear-reactors/357926/3 "2006-05-23T20:40:41Z")
Dagnabit, I meant one of the posts there has a link… ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [May 24, 2006, 1:34am UTC](https://boards.straightdope.com/t/what-improvements-have-the-latest-generation-of-nuclear-reactors/357926/4 "2006-05-24T01:34:55Z")
I am mostly knowledgable about the pebble bed reactors. But their main safety features are that - they use helium to cool, so if there is a leak only non-polluting helium gets out - the geometry and casing of the nuclear fuel prevents a meltdown from occuring Instead of fuel rods which older reactors use the pebble bed reactors use billiard ball sized balls of uranium cased in graphite. When the balls become too hot (aroudn 1600 C) the geometry changes to prevent them from heating any further so they cannot be heated past 1600 C. A meltdown requires temperatures of 2000 C, so they are meltdown proof. “When a pebble-bed reactor gets hotter, the more rapid motion of the atoms in the fuel decreases the probability of neutron capture by 235U atoms by an effect known as Doppler broadening. When the uranium is heated, its nuclei move more rapidly in random directions, and therefore see and generate a wider range of relative neutron speeds. 238U, which forms the bulk of the uranium in the reactor, is much more likely to absorb fast-moving neutrons.[3] This reduces the number of neutrons available to cause 235U fission, reducing the power output by the reactor. This natural negative feedback places an inherent upper limit on the temperature of the fuel, without any operator intervention.” wikipedia has good articles on these reactors as well as the older light water and heavy water ones. pebble bed > **[Pebble-bed reactor | Safety features](https://en.wikipedia.org/wiki/Pebble_bed_reactor#Safety_features)** > > Pebble-bed reactors have an advantage over conventional light-water reactors in operating at higher temperatures. A technical advantage is that some designs are throttled by temperature, not by control rods. The reactor can be simpler because it does not need to operate well at the varying neutron profiles caused by partially withdrawn control rods.\[citation needed\] > Pebble-bed reactors are also capable of using fuel pebbles made from different fuels in the same basic design of reactor (though pe... CanDU > **[Candu](https://en.wikipedia.org/wiki/Candu)** > > Candu or CANDU may refer to There is a debate going on on the subject right now too > **[Is it time for nuke power?](https://boards.straightdope.com/sdmb/showthread.php?t=372399)** > > In my younger days I was strongly anti-nukewith good reason I believe, but I’ve found my opposition softening lately. Tonight I read this article which points to a side I hadn’t really considered - global warming. The author makes a pretty good case....