Another nuclear test by NK?

GopherT

Joined Nov 23, 2012
8,012
My grandfather owned a store in Indian Springs and my mother and aunt both worked at the Nevada Test Site (Mercury Labs) in the 1950s.

They had a secret clearance and were not allowed to discuss anything that went on in the place. However, the details of bomb making were well known by outsiders and one guy who came into my grandfather's store seemed to be willing to talk about the advantages and disadvantages of the fission process and here's his explanation.

Fission works best at low temperatures (in the lower 1000s of degrees (F) when the velocity of the neutrons is equal to the ambient temperature. This is the so called "moderating" process and it is done by surrounding the fissionable material with graphite. These "thermalized" neutrons have the best chance of creating a critical or supercritical reaction. However once the temperature starts to rise from 1000s of degrees to hundreds of 1000s, then to up in the millions, the graphite melts and vaporizes so the neutrons are no longer moderated.

At millions of degrees, moderation becomes negligible and the reaction eventually stalls. Therefore attempting to build a fission bomb above a certain energy output becomes a case of diminishing returns. However a fusion bomb works very well at high temperatures and there's no limit on the energy output. In 1962, the Soviet Union detonated the largest fusion bomb ever built called Big Ivan which had an energy yield of 50 Megatons.

So, the graphite only starts to melt at the 100s of thousands of degrees?
 

nsaspook

Joined Aug 27, 2009
6,933
I don't really care what type of bomb they have, what worries me is the command and control system that tells some 'Joe' on the line when to fire. Who is really in charge there and how can anyone be sure that a sane person is running the show. We (Nuclear Command, Control, and Communications PRP personnel) trained at the Nuclear Weapons Center at North Island as authenticators of "lawful orders" for deployed US nuclear weapons where we also talked about Soviet and Chinese control systems. In our system the president is the only individual with the authority to order the use of nuclear weapons but he can't send the order unless it's approved by a separate authority to jointly authenticate the order and the order won't be executed unless authenticated in the field even with the Gold Codes unless our operational message unlock keycodes match/verify that only we (with two man control outside of the normal ships command on afloat vessels and subs today) had access to limit the presidents capability to launch. Russia and China have similar systems and I hope like hell China is still in the authenticator loop for NK.
 

Glenn Holland

Joined Dec 26, 2014
705
Graphite melts at the temperature for a given pressure and at normal pressure, that temperature may be only several 1000 degrees (F).

However the time scale for the detonation process is only microseconds and the internal pressure is great enough so that the components can remain intact long enough to act as a moderator.
 

markdem

Joined Jul 31, 2013
113
My grandfather owned a store in Indian Springs and my mother and aunt both worked at the Nevada Test Site (Mercury Labs) in the 1950s.

They had a secret clearance and were not allowed to discuss anything that went on in the place. However, the details of bomb making were well known by outsiders and one guy who came into my grandfather's store seemed to be willing to talk about the advantages and disadvantages of the fission process and here's his explanation.

Fission works best at low temperatures (in the lower 1000s of degrees (F) when the velocity of the neutrons is equal to the ambient temperature. This is the so called "moderating" process and it is done by surrounding the fissionable material with graphite. These "thermalized" neutrons have the best chance of creating a critical or supercritical reaction. However once the temperature starts to rise from 1000s of degrees to hundreds of 1000s, then to up in the millions, the graphite melts and vaporizes so the neutrons are no longer moderated.

At millions of degrees, moderation becomes negligible and the reaction eventually stalls. Therefore attempting to build a fission bomb above a certain energy output becomes a case of diminishing returns. However a fusion bomb works very well at high temperatures and there's no limit on the energy output. In 1962, the Soviet Union detonated the largest fusion bomb ever built called Big Ivan which had an energy yield of 50 Megatons.
Hmm. I might be wrong, but I thought all (I think there was a test using slow neutrons that did not work but can't be bothered to look it up) nuclear weapons used fast neutrons.
The idea here is quite simple. While it is true that modulation will increases the adsorption cross section making it more likely that the neutron will cause another nucleus to undergo fission, it will also slow down the rate of the reaction. This is what you want in a reactor, but in a weapon you want the reaction to be as fast as possible. You only have about 100us to try to burn up as much material as you can before the bomb "blows" up and reduces the density of the fuel below the level required to sustain criticality.
You will find that nuclear weapons will use neutron reflectors to reflect the fast neutrons to give them more chances to collide with fuel.

In saying all this, I have some major doubts if NK could make a thermonuclear weapon. This device, unlike a fission weapon, takes great care to make the reaction work. It is, at the end of the day, a nuclear bomb been set off by using a nuclear bomb. (Interestingly tzar bomba (is Big Ivan a US name?) was a 3 stage design. One fission bomb would be set off that would then have the required pressure and temperature to start a fusion reaction, then that energy would then be used to compress more fuel to make a bigger fusion reaction.)
NK looks like this at night - http://static.independent.co.uk/s3fs-public/thumbnails/image/2014/02/25/08/v4-North-Korea-at-night.jpg (That black space is NK). Something tells me a country like that would have some issues setting off a multistage weapon.
 

markdem

Joined Jul 31, 2013
113
Isn't that dependent on the North Korean leadership's priorities?
Only to a point. Just because the guy with the bad haircut wants to have a fusion weapon does not mean he will have the resources (raw material, electricity, equipment and ,most importantly, knowledge) to build one.
This is not to say that it is not possible, just unlikely.
 

Papabravo

Joined Feb 24, 2006
12,910
I had to scroll back a long way to understand that connection!
The only reason I mentioned it in the first place was the attempt by American mobsters, Giancana, Trafficante, and Roselli to assassinate Fidel Castro at the behest of the CIA. Despite numerous attempt which all failed, I guess Fidel has had the last laugh and outlived all of them.
 

JoeJester

Joined Apr 26, 2005
4,188
Only to a point. Just because the guy with the bad haircut wants to have a fusion weapon does not mean he will have the resources (raw material, electricity, equipment and ,most importantly, knowledge) to build one.
This is not to say that it is not possible, just unlikely.
Maybe he's saving the pennies from the countries electricity account to fund it. After all, except for a couple of places on that map, the vast majority of the country is darkened.
 
Oh my... View attachment 97955 MY COVER'S BEEN BLOWN!... now the NSA, CIA, FBI, CBS and HEB are going to know that english is not my birth language!! I'm gonna get deported back to.... wait a minute, I'm already here! :p:D

Major it is then, thank you. I stand corrected... and btw, I'm going to leave my previous typo as it is, for posterity's (and humor's) sake.
Good for you , some people have nothing better to do that show they went to primary school, big thinkers!
 
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