# “Hot” coffee cup **URL:** \ **Category:** Factual Questions\ **Created:** [January 20, 2024, 7:45pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406 "2024-01-20T19:45:03Z")\ **Posts on this page:** 20\ **Page:** 4
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 21, 2024, 2:32pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/61 "2024-01-21T14:32:10Z")
> [@abcdefghij](#): > > geothermal relies on the relatively stable temperature of the thermal mass of earth in the first tens of meters below the surface Not if you’re dipping a cup in a hot spring at Yellowstone to warm up your coffee. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 21, 2024, 2:36pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/62 "2024-01-21T14:36:06Z")
> [@Chronos](#): > > natural uranium isn’t noticeably warm That reminds me of this weird thing… > **[Natural nuclear fission reactor](https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor)** > > A natural nuclear fission reactor is a uranium deposit where self-sustaining nuclear chain reactions occur. The conditions under which a natural nuclear reactor could exist were predicted in 1956 by Paul Kuroda. The remnants of an extinct or fossil nuclear fission reactor, where self-sustaining nuclear reactions have occurred in the past, are verified by analysis of isotope ratios of uranium and of the fission products (and the stable daughter nuclides of those fission products). This was firs Ok... ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [January 21, 2024, 2:36pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/63 "2024-01-21T14:36:55Z")
> [@DPRK](#): > > Strontium-90 will produce a lot of secondary radiation via bremstrahlung. I’m not sure DPRK’s correct and relevant observation got the attention it so richly deserves. Beta radiation may be fairly easy to stop, but for more energetic Beta emitters, stopping it creates Gamma rays. They’re much harder to stop. A few years I built a Sr-90 source into a machine, and felt encouraged to do a fair bit of extra work to avoid possible operator exposure to this secondary radiation. ---
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [January 21, 2024, 2:41pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/64 "2024-01-21T14:41:10Z")
“Jim never has an extra dose of bremsstrahlung when I make coffee” ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 21, 2024, 2:41pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/65 "2024-01-21T14:41:28Z")
If you want to heat your coffee _quickly_, you need to think outside the box of mundane nuclear processes. X-ray laser is the way to go. > **[Scientists Turn X-ray Laser Into World’s Fastest Water Heater | SLAC National...](https://www6.slac.stanford.edu/news/2018-05-15-scientists-turn-x-ray-laser-worlds-fastest-water-heater)** > > Experiments at SLAC heated water from room temperature to 100,000 degrees Celsius in less than a millionth of a millionth of a second, producing an exotic state of water that could shed light on Earth’s most important liquid. ---
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [January 21, 2024, 2:43pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/66 "2024-01-21T14:43:32Z")
But how long does it take to recharge that thing to blast again? The goal is to _keep_ the coffee hot, not to get it hot in the first place. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 21, 2024, 3:03pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/67 "2024-01-21T15:03:11Z")
Sorry, did not read the thread carefully enough - I just realized that you had already posted a link to a different account of the Oklo natural reactor. ---
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [January 21, 2024, 3:03pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/68 "2024-01-21T15:03:53Z")
No worries! It should be on everyone’s reading list. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 21, 2024, 3:41pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/69 "2024-01-21T15:41:20Z")
> [@LSLGuy](#): > > anti-matter annhilator or whatever I feel like this deserves more attention. The heat capacity of water is 4 J/g/K, so if we assume that our insulated container cools by about 1K every 400s, we need an energy input of 10^-2 J/g/s. If we take the obvious approach of using half anti-water to make our coffee (containment and modulation of the annihilation is left as an exercise for the reader), and noting recent expert commentary that we can probably get 92% efficiency… [Nuclear fission / fusion? - #45 by Pasta](https://boards.straightdope.com/t/nuclear-fission-fusion/996046/45) …we have 8 x 10^13 J/g available. So we can keep our coffee warm for 8 x 10^15 s, or 250 million years as a rough approximation. Of course, the volume of coffee would steadily decrease, which is a drawback to this method. ---
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [January 21, 2024, 4:32pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/70 "2024-01-21T16:32:43Z")
> [@abcdefghij](#): > > I wasn’t trying to achieve criticality If, despite best efforts, you do happen to achieve criticality, you’ll want to have a hafnium stir stick or access to borated creamer to keep things in check. We don’t want to boil off the coffee, after all. Don’t remove the stir stick too rapidly or you risk [prompt criticality](https://en.m.wikipedia.org/wiki/Prompt_criticality) and splattering coffee absolutely everywhere. ---
**Author:** ![Common\_Tater](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/common_tater/32/13846_2.png) [@Common\_Tater](https://boards.straightdope.com/u/Common_Tater)\ **Post date:** [January 21, 2024, 5:07pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/71 "2024-01-21T17:07:04Z")
Is Borated creamer a requirement?? Frankly, it sounds awful. I’m partial to Half & Half myself. Milk is too thin, Cream is too thick. “Arf and Arf” is just right. I’m almost certain Carly Simon noticed this, too. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [January 21, 2024, 7:18pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/72 "2024-01-21T19:18:51Z")
Radioactive power sources are a waste stream nightmare. ---
**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:** [January 21, 2024, 7:41pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/73 "2024-01-21T19:41:09Z")
Which is why we’d only make these nuclear-thermal coffee cups as a reusable design, not as disposable to-go coffee containers. Gotta control that waste stream. ---
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [January 21, 2024, 8:07pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/74 "2024-01-21T20:07:32Z")
> [@Common\_Tater](#): > > Is Borated creamer a requirement?? Frankly, it sounds awful. I’m partial to Half & Half myself. I think as long as you start with borated cows, you can have borated half&half ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 21, 2024, 9:03pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/75 "2024-01-21T21:03:18Z")
> [@abcdefghij](#): > > I think as long as you start with borated cows, you can have borated half&half I think you’d struggle to make a Boron (VI) ion when it only has 5 electrons, but if you did it would probably react with Neon. (Okay, to be pedantic I guess I need some Oxygen in there too.) ---
**Author:** ![Beckdawrek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beckdawrek/32/3647_2.png) [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)\ **Post date:** [January 21, 2024, 9:06pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/76 "2024-01-21T21:06:03Z")
Yep. If it happens in Vegas, it needs to stay in Vegas. ---
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [January 21, 2024, 9:10pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/77 "2024-01-21T21:10:18Z")
Sorry. I don’t know anything about animal husbandry. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 21, 2024, 9:12pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/78 "2024-01-21T21:12:35Z")
> [@Riemann](#): > > I think you’d struggle to make a Boron (VI) ion when it only has 5 electrons, but if you did it would probably react with Neon. (Okay, to be pedantic I guess I need some Oxygen in there too.) OK, I’m not getting this one. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 21, 2024, 9:15pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/79 "2024-01-21T21:15:14Z")
You’re not missing anything, it was a weak attempt to do something with Bovine. Perhaps “farm structure constant” has more mileage. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [January 21, 2024, 9:46pm UTC](https://boards.straightdope.com/t/hot-coffee-cup/996406/80 "2024-01-21T21:46:12Z")
An insulated mug obviously doesn’t solve the problem, but it _does_ make it substantially more tractable. In fact, the _lid_ on an insulated mug is an enormously important factor. See the [measurements here](https://protonsforbreakfast.wordpress.com/2018/11/12/mug-cooling-the-lid-effect/): [![](https://protonsforbreakfast.files.wordpress.com/2018/11/slide6-e1542059480181.png) ](https://protonsforbreakfast.files.wordpress.com/2018/11/slide6-e1542059480181.png) If room temperature is 20 C, and we want the coffee to be 55 C, then we have a 35 C delta, which according to this chart only requires about 2.5 W of heat input to sustain, as long as we use a lid. That’s only about 5 grams of Pu238. Just 0.25 cm^3. And 2.5 W is small enough that it shouldn’t be particularly unsafe while sitting in a closed cabinet, etc. I can imagine some passive safety measures to help as well. Consider a small button of material attached to the bottom of the mug. Since the mug is stainless steel, which isn’t particularly conductive as far as metals go, it might get unsafely hot around the button after a while–probably not enough to start a fire, but enough to burn a finger if you touched it, or melt plastic that got dropped in. One possible measure is to have bimetallic heat conductors within the vacuum area. When they get unsafely hot, they bend outwards, touching the outer surface of the mug. There’s now a shortcut path for excess heat to the outside, and 2.5 W over the outer surface of a mug is not very much to dissipate. When there’s coffee in the mug, the liquid moderates the temperature. There are many other possibilities; that’s just the first that came to mind. I think it’s a fairly straightforward engineering problem aside from the acquisition and disposal of the material. [Previous page](https://boards.straightdope.com/t/hot-coffee-cup/996406.md?page=3) [Next page](https://boards.straightdope.com/t/hot-coffee-cup/996406.md?page=5)