The U.S.-based Natural Resources Defense Council (NRDC) estimates that Pakistan has built 24-48 HEU-based nuclear warheads with HEU reserves for 30-52 additional warheads.[9][10] The US Navy Center for Contemporary Conflict estimates that Pakistan possesses between a low of 35 and a high of 95 nuclear warheads, with a median of 60.[11].But these are outdated sources.

The NRDC's and the Carnegie Foundation's estimates of approximately 50 weapons are from 2002-3 estimations. In 2000, US Military intelligence estimated that Pakistan's nuclear arsenal may be as large as 100 warheads.[12]. The actual size is hard for experts to gauge owing to the secrecy which surrounds the program in Pakistan. In recent developments, retired Brig. General Feroz Khan, previously second in command at the Strategic Arms Division of Pakistans' Military told a Pakistani newspaper the nation has "about 80 to 120 genuine warheads"-and also revealed that Pakistan has decoy or dummy warheads to complicate any designs by aggressors. [13][14]

Pakistan already tested plutonium capability in the sixth nuclear test of May 30, 1998 at Kharan. In this test, the latest and most sophisticated bomb design made to be carried by missiles was tested. And it was a very compact, yet powerful device. Secondly, compactness is also an issue with F-16s and other fighter-bomber aircraft of the same class, unless the platform happens to be a dedicated strategic bomber. F-16s have limits to the size and weight of the bombs they can carry.

Now the critical mass a bare mass sphere of 90 % enriched Uranium-235 is 52 kg. Correspondingly, the critical mass of a bare mass sphere of Plutonium-239 is 8-10 kg. The bomb that destroyed Hiroshima used 60 kg of U-235 while the Nagasaki Pu bomb used only 6 kg of Pu-239. And that was in 1945! Since all Pakistani bomb designs are implosion-type weapons, they will typically use between 15-25 kg of U-235 for their cores. Reducing the amount of U-235 in cores from 60 kg in gun-type devices to 25 kg in implosion devices is only possible by using good neutron reflector/ tamper material such as beryllium metal, which increases the weight of the bomb. And the uranium like plutonium is only usable in the core of a bomb in metallic form. Add about 50 or so chemical high-explosive lenses, triggering circuits, and outer aluminum casing, all this adds to the overall weight of the device. Therefore if a bomb has to use only U-235, it will impose serious restrictions on the amount of U-235 that can be used, and the size of the bomb itself, thus restricting its explosive yield. True PAEC did develop bomb designs that could be carried by all PAF aircraft, but after years of effort and R & D, and then too, there were serious limitations on the further extent of miniaturization of the bombs. If Uranium is used as bomb fuel, it cannot be miniaturized beyond a certain point.

On the other hand, only 2-4 kg of plutonium is needed for the same device that would need 20-25 kg of U-235. Add a few grams of tritium (a by-product of plutonium production reactors and thermonuclear fuel) and you can increase the overall yield of the bombs by a factor of three to four.

A whole range and variety of weapons using Pu-239 can be easily built, both for aircraft delivery and especially for missiles (in which U-235 cannot be used). So if Pakistan wants to be a nuclear power with an operational deterrent capability, both first and second strike, based on assured strike platforms like ballistic and cruise missiles (unlike aircraft), the only solution is with plutonium, which has been the first choice of every country that built a nuclear arsenal.

As for Pakistan's plutonium capability, it has always been there, from the early 1980s onwards. There were only two problems. One was that Pakistan did not want to be an irresponsible state and so did not divert spent fuel from the safeguarded KANUPP for reprocessing at New Labs. This was enough to build a whole arsenal of nuclear weapons straight away. So PAEC built its own unsafeguarded plutonium and tritium production reactor at Khushab, beginning in 1985. The second one was allocation of resources.

Ultra-centrifugation for obtaining U-235 cannot be done simply by putting natural uranium through the centrifuges. It requires the complete mastery over the front end of the nuclear fuel cycle, which begins at uranium mining and refining, production of uranium ore or yellow cake, conversion of ore into uranium dioxide UO2 ( which is used to make nuclear fuel for natural uranium reactors like Khushab and KANUPP), conversion of UO2 into Uranium tetrafluoride UF4 and then into the feedstock for enrichment (UF6).

All this also needs the complete mastery over fluorine chemistry and production of highly toxic and corrosive hydrofluoric acid and other fluorine compounds. Then this UF6 is pumped into the centrifuges for enrichment and afterwards it has to go through the same process, but in reverse till UF4 is produced which leads to the production of uranium metal, the form in which U-235 is used in a bomb.

It is estimated that there are about 10000 centrifuges in Kahuta. This means that with P2 machines, they would be producing between 75-100 kg of HEU since 1986, when full production of weapons-grade HEU began. Also the production of HEU was voluntarily capped by Pakistan between 1991 and 1997, and the five nuclear tests of May 28, 1998 also consumed HEU. So it is safe to assume that between 1986 and 2005 (prior to the 2005 earthquake) , KRL produced 1500 kg of HEU. Now accounting for losses in the production of weapons, it is safe to assume that each weapon would need 20 kg of HEU. This is sufficient for 75 bombs, produced in 20 years!.

Pakistan's first nuclear tests were made in May 1998, when six warheads were tested. It is reported that the yields from these tests were 12 kT, 30 to 35 kT and four low-yield (below 1 kT) tests. From these tests Pakistan can be estimated to have developed operational warheads of 20 to 25 kT and 150 kT inshape of low weight compact designs and may have 300-500kt large size warheads. The low-yield weapons are probably in nuclear bombs carried on F-16 Fighting Falcon aircraft and fitted to Pakistan's short-range ballistic missiles, while the higher-yield warheads are probably fitted to the Shaheen and Ghauri ballistic missiles.

Notes
1^ Global Security
2^ "Pakistan Nuclear Weapons". Retrieved on 2007-02-22.
3^ "Uranium Institute News Briefing 00.25 14 - 22 June 2000". Uranium Institute (2000). Retrieved on 2006-05-07.
4^ Key Issues: Nuclear Energy: Issues: IAEA: World Plutonium Inventories
5^ BBC NEWS | World | South Asia | Pakistan nuclear report disputed
6^ Pakistan Expanding Nuclear Program - washingtonpost.com
7^ BBC NEWS | World | South Asia | Pakistan 'building new reactor'
8^ U.S. Group Says Pakistan Is Building New Reactor - New York Times
9^ Federation of American Scientists
10^ Center for Defense Information
11^ "US Navy Strategic Insights. Feb 2003". US Navy (2003). Retrieved on 2006-10-28.
12^ Pakistan's Nuclear Arsenal Underestimated, Reports Say
13^ Impact of US wargames on Pakistan N-arms ‘negative’ -DAWN - Top Stories; December 03, 2007
14^ Calculating the Risks in Pakistan - washingtonpost.com
15^ "U.S. Secretly Aids Pakistan in Guarding Nuclear Arms", The New York Times (2007-11-18). Retrieved on 2007-11-18.
16^ [http://www.nytimes.com/2007/11/18/washington/18nuke.html New York Times/18 November 2007

As stated in the article, a lot of the sources are dated. The most recent estimates put our nuclear arsenal at around 120 warheads give or take 10.

Not long ago Christian Science was crediting with Pakistan having more war heads than India, estimating between 150 - 200!

The exact number will only be known to our strategic defence planners and the highest ranks of the military. It is probably best to assume that the total is somewhere in the middle, that of 120-130 warheads. What we should concentrate our efforts on now is to deliver them over far greater distances, i.e. ICBM’s.

Pakistan has easily over 100 nuclear weapons.

As far as calculating the number of weapons we have goes, nobody can be really sure. We could be buying weapons grade material, we could be selling it.

What I do know is that we don't have an adequete number, you need several thousand nuclear weapons, mounted on icbm's to be totally secure.

I think 200 nukes are enough. This along with 80 to 100 ICBMs is enough to ensure security. I mean which country would want even one Nuke Equipped ICBM heading its way??

Country Warheads active/total* Year of first test



Other known nuclear powers


Undeclared nuclear weapons states




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It is interesting to see that UK and China have 200 and 160 estimate. It just shows that we really dont need more than 100-150. It is pointless to have more than that.

^^^Not really. The more weapons you have, the more powerful weapons you have, the greater the strength you have.

Assuming during a hypothetical attack we got to this point of needing to fire nuclear weapons; 50 nuclear missiles would not wipe out the USA. At our current yield, they'd probably only wipe out 50 cities/stratgic sites. Now if they were the size of some the Russian bombs (where only the fireball has a 5km radius, let alone the radiation), then it would be a different matter.

Assuming we were on the brink of defeat, would you launch a strike as a last resort, a goodbye present? If not, then we shouldn't have nukes at all. I would. Would 50 small nukes cause enough damage to cause a truely determined enemy to not attack you, no. would 500, well they have 10 times the chance.

I think 150-200 are enough.

We should be working on the delivery system (reducing CEP on our current missiles) and second strike capability (SLBM).

It is simple mathematics how many are required for complete destruction of enemy?

Well I still believe in the MAD doctrine. I think that in this day and age, even one nuclear weapon used is too many. It is for the survival of the mankind that we only have them as a deterrent and not actually think of destroying a country by launching hundreds of nuclear weapons. I believe no sane man will contemplate using hundreds to make sure a country is destroyed. Ofcourse, we always dont know if the person sitting by the button is a sane man or an idiot.

Whatever it takes to destroy the world a few times over. That is a true deterrent. No one in their right mind would mess with you (nor would other countries let them) if they knew you could easily destroy the world if it came to it.

Here we need to understand the dynamics of our much hyped,"Minimum Strategic Detterence" policy.

Detternce
Gentlemen for being a detterence there are four basic necessities as stated below.
A detternce should be:
1- Credible
2- Communicable
3- Controlable
and
4- Capable

Minimum Strategic Detternce
It implies that Pakistani Armed Forces draw various contegency plans and then calculate the number of nuclear devices that would be needed to come out of that contegency. From best case to worst case scenerios various number of nuclear devices required to break enemy on ground and decimate enemy's war waging potential are calculated and a minimum possible number as per requirement is agreed upon. Then our stretegic institutions are given the task of producing the said number of nuclear devices. That is how we achieve a minimum strategic detyterence.

Restrained Efforts
This isn't an all out effort to produce as much nukes as you can but as much as you need.

Conclusion
Over time we may have not run on our 100% capacity as it may have over shoot our needs. We have a very calculated and sound stretgic detterence system. One thing which we keep very secret is our "Nuclear Threshold". As long as enemy does not know it, it will not dare put agressive designs into action.

Saad

If a nuclear explosion of 350Kt occurs 300 miles above in atmosphere, can send an EMP that can wipe out any electric grid stations and communcations around 600 miles radius.. i will post the link about it. Pakistna shoul dwork on MIRV with plutonium and tritium based missiles.

Here something to share on yield of nuclear bombs

Calculating yields and controversy
Yields of nuclear explosions can be very hard to calculate, even using numbers as rough as in the kiloton or megaton range (much less down to the resolution of individual terajoules). Even under very controlled conditions, precise yields can be very hard to determine, and for less controlled conditions the margins of error can be quite large. Yields can be calculated in a number of ways, including calculations based on blast size, blast brightness, seismographic data, and the strength of the shock wave. Enrico Fermi famously made a (very) rough calculation of the yield of the Trinity test by dropping small pieces of paper in the air and measuring at how far they were moved by the shock wave of the explosion.


Picture of the blast used by G.I. Taylor to estimate the yield of the device detonated during the Trinity testA good approximation of the yield of the Trinity test device was obtained from simple dimensional analysis by the British physicist G. I. Taylor. Taylor noted that the radius R of the blast should initially depend only on the energy E of the explosion, the time t after the detonation, and the density ρ of the air. The only number having dimensions of length that can be constructed from these quantities is:

R= [(E t power 2)/p] 1/5



Using the picture of the Trinity test shown here (which had been publicly released by the U.S. government and published in Life magazine), Taylor estimated that at t = 0.025 s the blast radius was 140 metres. Taking ρ to be 1 kg/m³ and solving for E, he obtained that the yield was about 22 kilotons of TNT (90 TJ). This very simple argument agrees within 10% with the official value of the bomb's yield, 20 kilotons of TNT (84 TJ), which at the time that Taylor published his result was considered highly-classified information. (See G. I. Taylor, Proc. Roy. Soc. London A201, pp. 159, 175 (1950).)

Where this data is not available, as in a number of cases, precise yields have been in dispute, especially when they are tied to questions of politics. The weapons used in the atomic bombings of Hiroshima and Nagasaki, for example, were highly individual and very idiosyncratic designs, and gauging their yield retrospectively has been quite difficult. The Hiroshima bomb, "Little Boy", is estimated to have been between 12 and 18 kilotonnes of TNT (50 and 75 TJ) (a 20% margin of error), while the Nagasaki bomb, "Fat Man", is estimated to be between 18 and 23 kilotonnes of TNT (75 and 96 TJ) (a 10% margin of error). Such apparently small changes in values can be important when trying to use the data from these bombings as reflective of how other bombs would behave in combat, and also result in differing assessments of how many "Hiroshima bombs" other weapons are equivalent to (for example, the Ivy Mike hydrogen bomb was equivalent to either 867 or 578 Hiroshima weapons — a rhetorically quite substantial difference — depending on whether one uses the high or low figure for the calculation). Other disputed yields have included the massive Tsar Bomba, whose yield was claimed between being "only" 50 megatonnes of TNT (210 PJ) or at a maximum of 57 megatonnes of TNT (240 PJ) by differing political figures, either as a way for hyping the power of the bomb or as an attempt to undercut it.

Nuclear testing yields, as in the Tsar Bomba example, can also be used as a way of reflecting upon technical expertise, and claiming higher yields or accusations of lower yields can be used as a way of promoting or disparaging the technical abilities of a nuclear program. When India claimed to have successfully detonated a hydrogen bomb in their 1998 Operation Shakti tests, many Western observers relied on analysis of seismographic data to determine whether the Indian tests reflected a successful hydrogen bomb detonation.

This isn't an all out effort to produce as much nukes as you can but as much as you need.

it doesn't really matter if pakistan has 100 or 120, its agreed that it has got quite a lot n it wouldn b hard for me to think that they wouldn b enough in a war