# How difficult is it to distinguish a thermonuclear explosions? (NK's "still not clear" one, e.g.) **URL:** \ **Category:** Factual Questions\ **Created:** [September 15, 2017, 12:57am UTC](https://boards.straightdope.com/t/how-difficult-is-it-to-distinguish-a-thermonuclear-explosions-nks-still-not-clear-one-e-g/796370 "2017-09-15T00:57:24Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [September 15, 2017, 12:57am UTC](https://boards.straightdope.com/t/how-difficult-is-it-to-distinguish-a-thermonuclear-explosions-nks-still-not-clear-one-e-g/796370/1 "2017-09-15T00:57:24Z")
See query. Decades ago it was announced upon first news of a bang that India had thermonuclear as opposed to fission. It seems to me unbelievable that we (one, if one is the Pentagon) can be in doubt about that; the political or sources/technology-security issues for saying one thing or another is another topic, of course. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [September 15, 2017, 2:26am UTC](https://boards.straightdope.com/t/how-difficult-is-it-to-distinguish-a-thermonuclear-explosions-nks-still-not-clear-one-e-g/796370/2 "2017-09-15T02:26:35Z")
If the bang is big enough, it has to be thermonuclear, because fission bombs max out at about 1 MT. If there’s an airburst, it’s a lot easier, since sniffers can pick up residual tritium and deuterium. ---
**Author:** ![Duckster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/duckster/32/1244_2.png) [@Duckster](https://boards.straightdope.com/u/Duckster)\ **Post date:** [September 15, 2017, 2:56am UTC](https://boards.straightdope.com/t/how-difficult-is-it-to-distinguish-a-thermonuclear-explosions-nks-still-not-clear-one-e-g/796370/3 "2017-09-15T02:56:18Z")
[How do scientists determine if a nuclear blast has occurred?](http://science.howstuffworks.com/nuclear-detection.htm) [http://blogs.discovermagazine.com/crux/2016/01/06/how-scientists-detect-nuclear-explosions-around-the-world/](http://blogs.discovermagazine.com/crux/2016/01/06/how-scientists-detect-nuclear-explosions-around-the-world/) ---
**Author:** ![SamuelA](https://avatars.discourse-cdn.com/v4/letter/s/c77e96/32.png) [@SamuelA](https://boards.straightdope.com/u/SamuelA)\ **Post date:** [September 15, 2017, 3:04am UTC](https://boards.straightdope.com/t/how-difficult-is-it-to-distinguish-a-thermonuclear-explosions-nks-still-not-clear-one-e-g/796370/4 "2017-09-15T03:04:55Z")
Well, instead of pretending the government has magic or satellite sensors using no known technology, let’s talk about what they could reasonably do. 1. The explosion itself creates a shock wave that can be heard through the ground. As beowulff points out, if the explosion is above a certain magnitude, it pretty much has to be a nuke. Above a certain level above that, and it pretty much has to be a thermonuclear device. 2. _If_ some of the products of the explosion leak to the atmosphere, they could be sampled with a spy plane and from the isotope mix, it could be determined what type of nuclear reaction occurred. 3. If the explosion weren’t hidden underground but were clearly visible, from the fireball I suspect it’s possible to tell from timing and temperature, _if_ a very large and expensive camera were aimed at it. Which would be difficult to mount on a satellite, wouldn’t have enough resolution from space, and so on. 4. There may be exotic particle physics you can detect, but the detection equipment would probably have to be pretty close. ---
**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:** [September 15, 2017, 5:18am UTC](https://boards.straightdope.com/t/how-difficult-is-it-to-distinguish-a-thermonuclear-explosions-nks-still-not-clear-one-e-g/796370/5 "2017-09-15T05:18:20Z")
There was a second delayed seismic signal that may have indicated a tunnel collapse. > **[North Korea nuclear test: 'Tunnel collapse' may provide clues](https://www.bbc.com/news/41139740)** > > It's the biggest test yet for North Korea, but what can we hope to learn about its nuclear progress? > [@](#): > > The US Geological Survey recorded a second event approximately eight minutes after the test. The USGS, as well as China, have assessed this event as a “collapse” of the cavity. > Why would the tunnel collapse? It could be that the tunnel was not constructed sufficiently to handle an explosion of that size. It’s also possible that they intended for this collapse to occur - a way of signalling to the world that this was an authentic test through radionuclide release, a serious advance. It is still too early to tell. And spy satellite pics of the site showed that a landslide had occurred. > **[North Korea nuclear crisis: Test 'caused landslides'](https://www.bbc.com/news/world-asia-41170940)** > > Satellite images show "more numerous and widespread" disturbances at the test site than before. So there may be sufficient leakage of radionuclides to analyze the event. This could prove definitively that it was thermonuclear. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [September 15, 2017, 2:15pm UTC](https://boards.straightdope.com/t/how-difficult-is-it-to-distinguish-a-thermonuclear-explosions-nks-still-not-clear-one-e-g/796370/6 "2017-09-15T14:15:20Z")
[Air Force Gen. John E. Hyten, commander of Strategic Command], on whether the NK bomb was thermonuclear]: I have to make that assumption. What I saw equates to a hydrogen bomb. I saw the event. I saw the indications that came from that event. I saw the size, I saw the reports, and therefore to me I’m assuming it was a hydrogen bomb.” [Cite.](https://www.timesofisrael.com/us-nuclear-commander-assumes-north-koreans-tested-h-bomb/) Well, so much for the political embargo. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [September 15, 2017, 2:27pm UTC](https://boards.straightdope.com/t/how-difficult-is-it-to-distinguish-a-thermonuclear-explosions-nks-still-not-clear-one-e-g/796370/7 "2017-09-15T14:27:44Z")
Seismic waves from a nuclear explosion are very distinctive … unfortunately the USGS seismographic network isn’t “tuned” to register these waves … however the USAF maintains a similar network that is explicitly “tuned” to these waveforms; mainly by setting up the military seismometers away from earthquake prone areas … here’s a blurb about [AFTAC](http://www.25af.af.mil/Units/AFTAC.aspx) and what they do … What I don’t know is if there are different waveforms for fission and fusion devices … or if we’re relying on **beowulff’s** comment about the size of the explosion … keep in mind that much of what AFTAC is doing is, you know, classified … so even if the military could tell the difference, they’re not going to be telling us they can … ---
**Author:** ![Blakeyrat](https://avatars.discourse-cdn.com/v4/letter/b/ecd19e/32.png) [@Blakeyrat](https://boards.straightdope.com/u/Blakeyrat)\ **Post date:** [September 15, 2017, 6:59pm UTC](https://boards.straightdope.com/t/how-difficult-is-it-to-distinguish-a-thermonuclear-explosions-nks-still-not-clear-one-e-g/796370/8 "2017-09-15T18:59:32Z")
> [@SamuelA](#): > > Well, instead of pretending the government has magic or satellite sensors using no known technology, let’s talk about what they could reasonably do. > > 1. The explosion itself creates a shock wave that can be heard through the ground. As beowulff points out, if the explosion is above a certain magnitude, it pretty much has to be a nuke. Above a certain level above that, and it pretty much has to be a thermonuclear device. > > 2. _If_ some of the products of the explosion leak to the atmosphere, they could be sampled with a spy plane and from the isotope mix, it could be determined what type of nuclear reaction occurred. > > 3. If the explosion weren’t hidden underground but were clearly visible, from the fireball I suspect it’s possible to tell from timing and temperature, _if_ a very large and expensive camera were aimed at it. Which would be difficult to mount on a satellite, wouldn’t have enough resolution from space, and so on. > > 4. There may be exotic particle physics you can detect, but the detection equipment would probably have to be pretty close. 1. They might have reliable human intelligence assets (aka spies) on the ground that say it was thermonuclear, and they just say it was detected by technology in the public release as to not give them away. ---
**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:** [September 16, 2017, 1:02pm UTC](https://boards.straightdope.com/t/how-difficult-is-it-to-distinguish-a-thermonuclear-explosions-nks-still-not-clear-one-e-g/796370/9 "2017-09-16T13:02:25Z")
The commander of Strategic Command pretty much has to assume that it’s a real H-bomb whether it is or not, if there’s even the slightest chance that it might be. It’s his job to plan for the worst-case scenario. He also has to assume that it’s not just a bomb, but a weapon, even though we’ve never had any evidence that North Korea has any sort of nuclear weapon. But they _might_, and that’s enough to get people (especially people like Gen. Hyten) to lose sleep. ---
**Author:** ![AK84](https://avatars.discourse-cdn.com/v4/letter/a/85e7bf/32.png) [@AK84](https://boards.straightdope.com/u/AK84)\ **Post date:** [September 16, 2017, 2:40pm UTC](https://boards.straightdope.com/t/how-difficult-is-it-to-distinguish-a-thermonuclear-explosions-nks-still-not-clear-one-e-g/796370/10 "2017-09-16T14:40:57Z")
There are basically four\* kinds of nuclear devices **Pure Fission** Achieved from the fission of nuclear material; U-235/U-238 **Boosted Fission** A small amount of Tritium is used just as fission starts, which increases the amount of materal which undergos fission; it also produces a small amount of fusion, but its a fraction of the total explosive force. **Layer Cake Fission/Fusion** A fission core, surrounded by layers of fusion followed by fission layer (U-238 not U-235). The Fission of the core starts a reaction in the fusion layer, which starts a reaction in the fission layer; about 15-25% of the explosive force comes from fusion, rest from the increased efficiency of the fission reaction. \*\*True Multi stage \*\* A fission primary sets off a fusion secondary. The size of an explosion can give an indication, a high KT range weapon is likely to be a Boosted fission or layer cake device, a multi-megaton one, a Multi-stage one. The NORK device was 120KT. The largest pure fission bomb tested was [Ivy King](https://en.wikipedia.org/wiki/Ivy_King), 500KT. The largest pure fission bomb ever deployed was the French [MR-31](https://en.wikipedia.org/wiki/MR_31), at 120 KT (and this was deployed on a missile so was not particularly clunky). So the tested weapon is within range for pure fission bombs. Its also within range for boosted fission/layer cake and although on the lower scale, Multi-Stage. You can tell the difference between pure fission and the rest pretty easily by checking the particles produced. You might be able to tell the difference between boosted fission and Layer Cake/Multi-Stage. AFAIK, there is no way to tell the difference between Layer Cake and Multi Stage, except the larger yield ones will probably be Multi-Stage \*Ignoring neutron bombs.