How long is A-bomb valid??

As i remember from my physics leasons every radioactiv material is slowly falling a part.So anyone have some info how long is A-bomb valid??
I will be thankfull about links also!!

I seem to recall reading somewhere about 15 years. Then they get dismantled. I may be mistaken, but I think the go to Almagordo for dismantling.

Found this on the web. Don't know if this is reassuring or not?????

Washingtonpost.com

The National Nuclear Security Administration said yesterday that studies have concluded that the plutonium used to trigger U.S. nuclear warheads and bombs will remain reliable for about 100 years, far longer than had been believed.

How long is a A-bomb valid??

That depends on iff you reffer to a nuclear warhead or the actual Uranium/Plutonium.

In the case off the warhead: If you leave it storaged then the parts that are vital could start to rust (like bolts who tension the sphere containing the Ur/Plu.) But if you maintain them and do regular check ups and replacing vital parts (like that bolt) then you could stretch the life time off the device much much longer.

In the case off the Ur/Plu: If you leave the material alone then dust could pile up. Moisture could cause rust off the matrial and making the material less powerfull and less stable.
But if you maintain the Ur/Plu by cleaning it on regular bases and leave it in a cleanroom without moisture then the material is much more stable and keeps its power and increases his lifetime.

Conclusion: If you do not maintain it then it will be over within 50 Years +-
But if you maintain them then they will last as long as you wish

It is very unlikely that there are 'rustable' components, and I'd hope they keep them stored in dry inert atmospheres.

However, weapons have quite a number of components of various chemical compositions which could degrade in a number of ways which affect the performance. They are much more complex than the descriptions of the early 1940's style bombs.

But above all of these is the requirement in contemporary weapons for tritium, usually in gas, for boosting in the primary. This involves complex pumps and containers and some such, and tritium decays with a half life of 11 years. Remember it's hydrogen so it is quite volatile and hard to contain and causes embrittlement of metallic materials.

Renewing the tritium and validating the gas storage is the primary maintenance item. Then there are the neutron generators and the electronics themselves which could be degraded from the radiation emitted from the plutonium.

Then there's high explosives, the beryllium and various plastics which have specific physical roles in the detonation. Chemical changes could result in physical changes.

Personally, I don't want to maintain nuclear weapons and I'd rather have many fewer.

The one thing which is clear---actual decay of Pu and U would have almost no effect except on the OTHER nearby items, since the half lives are so long.
One exception: the Pu and U decay would create daughter products which themselves would be radioactive, and this may hurt other components with time.
[edit on 29-6-2007 by mbkennel]

[edit on 29-6-2007 by mbkennel]

In terms of the nuclear material itself, how viable is the Plutonium after 15 years ?

Someone mentioned to me about contamination by Pu240 contaminating North Korea's nuclear bomb. In terms of shelf life won't transuranics and Pu240 contaminate the fissile material aswell ?

On another tack, I realise Uranium is rarely used for warheads but because I am working on a novel where it interests me, how long would bomb grade Uranium be viable in a gun type device ?

Pu240 has a halflife of 6500 years so I wouldn't worry about it going kaput anytime soon.

Uberarcanist, warheads use Pu239...

Pu240 is an unwanted contaminant which inhibits a nuclear explosion.

The question which I am asking is over 15 years or some similar period, will part of the Pu239 degrade or change to another element destroying the bomb's viability ?

For example some Pu239 may absorb neutrons to become Pu240. Since the neutrons in a warhead will be fast neutrons absorbtion may not occur, but some transuranics may occur. Any takers ?

Likewise can anybody here also advise me how long HEU is viable in a gun type bomb ?

[edit on 29-6-2007 by sy.gunson]

Originally posted by sy.gunson
Uberarcanist, warheads use Pu239...

Pu240 is an unwanted contaminant which inhibits a nuclear explosion.

The question which I am asking is over 15 years or some similar period, will part of the Pu239 degrade or change to another element destroying the bomb's viability ?

For example some Pu239 may absorb neutrons to become Pu240. Since the neutrons in a warhead will be fast neutrons absorbtion may not occur, but some transuranics may occur. Any takers ?

Likewise can anybody here also advise me how long HEU is viable in a gun type bomb ?

[edit on 29-6-2007 by sy.gunson]

I thought transmutations were all part of the decay process, and how fast something decayed was determined by its halflife. As far as I know, the halflives of all fuels used in nuclear explosives are measured in the millenia.

Do not hesitate to correct me if I am wrong.

However long the half lives, the issue is the percentage of contaminants which impede, or prevent nuclear detonation. If as low as 2% contamination is an issue then it could be a critical issue. Certainly what I have read previously suggests that 15 years is the viable life and then Plutonium bombs must be dismantled.

Maybe somebody else can give a more specific answer ?

Originally posted by sy.gunson
However long the half lives, the issue is the percentage of contaminants which impede, or prevent nuclear detonation. If as low as 2% contamination is an issue then it could be a critical issue. Certainly what I have read previously suggests that 15 years is the viable life and then Plutonium bombs must be dismantled.

Maybe somebody else can give a more specific answer ?

That's in line with what I've heard, though I would be surprised if the answer is not classified. Furthermore, aren't half lives just a probabilistic estimate anyways? Is there not always a chance that the actual half life will be a little more or a little less?

Originally posted by mbkennel
But above all of these is the requirement in contemporary weapons for tritium, usually in gas, for boosting in the primary. This involves complex pumps and containers and some such, and tritium decays with a half life of 11 years. Remember it's hydrogen so it is quite volatile and hard to contain and causes embrittlement of metallic materials.

Tritium is not stored in modern hydrogen fusion bombs. Lithium Deuteride is the fuel. A small fission nuke is detonated as a trigger. Neutrons and gamma rays cause the Deuterium to transmute into tritium. It only takes a microsecond. Good thing with the blast wave from the nuclear trigger right behind the particles and rays.

Originally posted by Malichai

Originally posted by mbkennel
But above all of these is the requirement in contemporary weapons for tritium, usually in gas, for boosting in the primary. This involves complex pumps and containers and some such, and tritium decays with a half life of 11 years. Remember it's hydrogen so it is quite volatile and hard to contain and causes embrittlement of metallic materials.

Tritium is not stored in modern hydrogen fusion bombs. Lithium Deuteride is the fuel. A small fission nuke is detonated as a trigger. Neutrons and gamma rays cause the Deuterium to transmute into tritium. It only takes a microsecond. Good thing with the blast wave from the nuclear trigger right behind the particles and rays.

It is true that the fusion fuel in the secondary is lithium=6 deuteride.

In fact, there is a small amount of tritium, and I believe not in LiD form, in the core of the fission primary. There is a small amount of fusion in the fission implosion to give it an extra boost of neutrons at the point of maximum density.

Apparently this is necessary to give a "cleaner" primary core detonation which provides more prompt radiation before the blast wave, enabling the secondary implosion before the blast (fluid flow) upsets it and destroys the possibility for secondary fusion.

Tritium boosting was already under research and development in the 1950's.

Using tritium in the core is also a safety/security feature as it permits a more subcritical primary, and therefore arming the bomb requires appropriate sequencing to get the tritium into position. It is conceivable that without the tritium there would be still a substantial detonation, but not enough to ignite the secondary.

Also it is good to protect somewhat against terrorist thefts. A few years after recharge and maintenance, such a nuclear weapon would not be able to operate properly as is with insufficient tritium, because too much has decayed.
Substantial amounts of tritium for nuclear weapons are not easy to procure and it can't be manufactured except in a nuclear reactor.

It raises the technological requirements for a terrorist to use a nuclear weapon by theft. Probably a terrorist group would have to steal a number of "high-tech" nuclear weapons from developed nuclear powers and remanufacture the fissile material into a less sophisticated configuration in fewer bombs, i.e. design and build a bomb 'from scratch'.

This is why I don't really fear the mythical al-Qaeda 'suitcase nukes' rumored to be stolen from the USSR. Such devices would have to be very compact and to get there, the nuclear weapons design would have to be at the edge of feasibility from professional high-end designers. Undoubtably it would require substantial tritium boosting to achieve its small size, and this means that it would likely not function after a few years.