# Is there a 'small' reactor? **URL:** \ **Category:** Factual Questions\ **Created:** [February 6, 2004, 12:30pm UTC](https://boards.straightdope.com/t/is-there-a-small-reactor/227827 "2004-02-06T12:30:47Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![LowerLip](https://avatars.discourse-cdn.com/v4/letter/l/839c29/32.png) [@LowerLip](https://boards.straightdope.com/u/LowerLip)\ **Post date:** [February 6, 2004, 12:30pm UTC](https://boards.straightdope.com/t/is-there-a-small-reactor/227827/1 "2004-02-06T12:30:47Z")
If I wanted to produce 2 kilowatts (two thousand watts) of electricity per hour, continuously, what would be the physical size of the reactor? ---
**Author:** ![N9IWP](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/n9iwp/32/3154_2.png) [@N9IWP](https://boards.straightdope.com/u/N9IWP)\ **Post date:** [February 6, 2004, 1:22pm UTC](https://boards.straightdope.com/t/is-there-a-small-reactor/227827/2 "2004-02-06T13:22:46Z")
The Navy has the NR-1 research sub which is probably the smallest mobile reactor. I couldn’t find the power output specs (classified???) but this article [http://www.fas.org/man/dod-101/sys/ship/docs/nr\_1.htm](http://www.fas.org/man/dod-101/sys/ship/docs/nr_1.htm) mentions twing 50 HP motors, so the reactor has to produce at least 74,570 watts. Some universities have research reactors – UW-Madison’s is currently at 1 Megawatt. [http://www.engr.wisc.edu/ep/newsletter/2001\_springsummer/nuclear.html](http://www.engr.wisc.edu/ep/newsletter/2001_springsummer/nuclear.html) Brian wants to build a nuclear truck (I’m thinking a semi with the reactor in the trailer) ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [February 6, 2004, 2:01pm UTC](https://boards.straightdope.com/t/is-there-a-small-reactor/227827/3 "2004-02-06T14:01:44Z")
The [CANDU SLowpoke](http://www.nuclearfaq.ca/cnf_sectionH.htm#g3) was rated at 20kW. Pretty small too > [@](#): > > SLOWPOKE-2 core is only about 22 cm diameter by 22 cm high, and sits in a pool of regular (“light”) water, 2.5 m diameter by 6 m deep, which provides cooling via natural convection. In addition to passive cooling, the reactor has a high degree of “inherent safety”; that is, it can regulate itself through passive, natural means, such as the chain reaction slowing down if the water heats up or forms bubbles. These characteristics are so dominant, in fact, that the SLOWPOKE-2 reactor is licensed to operate unattended overnight . Maybe drop into a few universities having going out of business sales. 😉 ---
**Author:** ![Ranchoth](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranchoth/32/1066_2.png) [@Ranchoth](https://boards.straightdope.com/u/Ranchoth)\ **Post date:** [February 6, 2004, 2:22pm UTC](https://boards.straightdope.com/t/is-there-a-small-reactor/227827/4 "2004-02-06T14:22:49Z")
You could check with Ford, and see what they were going to use on the [Nucleon.](http://www.velocityjrnl.com/jrnl/1958/vmd1210ov.html) And you thought the PINTO’s crash tests were bad…:eek: 😃 ---
**Author:** ![Ranchoth](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranchoth/32/1066_2.png) [@Ranchoth](https://boards.straightdope.com/u/Ranchoth)\ **Post date:** [February 7, 2004, 3:29am UTC](https://boards.straightdope.com/t/is-there-a-small-reactor/227827/5 "2004-02-07T03:29:33Z")
Oh, BTW, the Russians had a couple of [space-based reactors](http://www.tbs-satellite.com/tse/online/mis_spec_radioactive.html) they’ve used on satellites, occasionally. The “Topaz II” reactor was rated at 6KW, and would have weighed about 1 Ton. (I can’t find any details about it’s size, though.) ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [February 7, 2004, 2:52pm UTC](https://boards.straightdope.com/t/is-there-a-small-reactor/227827/6 "2004-02-07T14:52:37Z")
As folks have said, the minimum capacity of a traditional reactor is driven by critical mass and all that and is a lot bigger than 2KW. You could build a 2KW radioisotope thermoelectric generator (RTG), which is not a true reactor. You put some radioactive material inside a shield and as it decays it makes heat, which you convert to electricity using a thermocouple. These can be made with as tiny a capacity as you want. Here’s some info about a unit used for powering space probes from [http://www.qmetrics.com/radioisotope\_thermoelectric\_generato.htm](http://www.qmetrics.com/radioisotope_thermoelectric_generato.htm). > [@](#): > > Nuclear technology has been used in the U.S. space program over the past 25 years to provide power for more than 20 NASA spacecraft. The power source has been an ingenious device called a radioisotope thermoelectric generator, or RTG. RTGs use the natural decay of plutonium-238 to produce heat, which is directly transformed into electricity through a thermocouple device. A typical RTG produces about 230 watts of electricity and will operate unattended for years. It is ideal for interplanetary travel, not only because of its long power-generating life span, but also its compactness. A typical RTG measures 45 inches in height, 18 inches in diameter, and weighs only about 123 pounds. Procuring the plutonium would seem to be your biggest hurdle in your quest for an unlimited backyard powerplant. ---
**Author:** ![aerodave](https://avatars.discourse-cdn.com/v4/letter/a/f08c70/32.png) [@aerodave](https://boards.straightdope.com/u/aerodave)\ **Post date:** [February 7, 2004, 3:36pm UTC](https://boards.straightdope.com/t/is-there-a-small-reactor/227827/7 "2004-02-07T15:36:21Z")
[nitpick] You can’t really produce 2kW _per hour_. Watts are already a measure of the rate at which energy is produced. A Watt is equivalent to 1 Joule (energy) per second. Adding another time division could only measure the rate of change of _that_ rate. So a 2kW generator or reactor will make (2000 W \* 3600 sec) 7,200,000 Joules of energy every hour. [/nitpick] ---
**Author:** ![LowerLip](https://avatars.discourse-cdn.com/v4/letter/l/839c29/32.png) [@LowerLip](https://boards.straightdope.com/u/LowerLip)\ **Post date:** [February 8, 2004, 7:24am UTC](https://boards.straightdope.com/t/is-there-a-small-reactor/227827/8 "2004-02-08T07:24:55Z")
Thank you **LSLGuy** for the qmetrics link and RTG. Yor’re probably right about the slight hurdle procuring the 238 for my backyard powerplant. The RTG would be ideal because it comes with a thermocouple. Thanks **Grey** The Slowpoke 2 is still small enough, but would have to be monitored. That would take me away from my computer!! That was funny **Ranchoth** on the Nucleon.