Information Papers

Plutonium

(July 2008)

In practical terms, there are two different kinds of plutonium to be considered: reactor-grade and weapons-grade.  The first is recovered from typical used fuel from a nuclear reactor, which has been irradiated ("burned") for about three years.  It is a by-product of electricity generation.  The second is made specially for the military purpose, and is recovered from uranium fuel which has been irradiated for only 2-3 months in a production reactor.  The two kinds differ in their isotopic composition.

Plutonium, both that routinely made in power reactors and that from dismantled nuclear weapons, is a valuable energy source in the nuclear fuel cycle. Over one third of the energy produced in most nuclear power plants comes from plutonium which is created there as a by-product and burned before the used fuel is discharged.

Plutonium isotopes 

Like all other heavy elements, plutonium has a number of isotopes, differing in the number of neutrons in the nucleus.  All 15 plutonium isotopes are radioactive, because they are to some degree unstable and therefore decay, emitting particles and some gamma radiation as they do so.  Most decays emit relatively weak alpha radiation which can be blocked even by a sheet of paper (but which is hazardous if within the body - see below).

The main isotopes of plutonium are:

Half-life is the time it takes for a radionuclide to lose half of its own radioactivity. The fissile isotopes can be used as fuel in a nuclear reactor, others are capable of absorbing neutrons and becoming fissile (ie they are "fertile"). Alpha decays are generally accompanied by gamma radiation.

Plutonium-238, Pu-240 and Pu-242 emit neutrons as a few of their nuclei spontaneously fission, albeit at a low rate. They and PU-239 also decay, emitting alpha particles and heat. The decay heat of Pu-238 (0.56 W/g) enables its use as an electricity source in the radioisotope thermoelectric generators (RTGs) of some cardiac pacemakers, space satellites, navigation beacons, etc. Plutonium has powered 24 US space vehicles and enabled the Voyager spacecraft to send back pictures of distant planets. These spacecraft have operated for 20 years and may continue for another 20. The Cassini spacecraft carries three generators providing 870 watts power as it orbits aroound Saturn.

In commercial power-plants and research applications plutonium generally exists as plutonium oxide (PuO2), a stable ceramic material with an extremely low solubility in water or body fluids and with a high melting point (2 390° C).

In pure form plutonium exists in six allotropic forms or crystal structure - more than any other element. As temperature changes, it switches forms - each has significantly different mechanical and electrical properties. One is nearly twice the density of lead (19.8 g/cm3). It melts at 640°C into a very corrosive liquid. The alpha phase is hard and brittle, like cast iron, and if finely divided it spontaneously ignites in air to form PuO2. Beta, gamma and delta phases are all less dense. Alloyed with gallium, plutonium becomes more workable.

Apart from its formation in today's nuclear reactors, plutonium was formed by the operation of the natural reactors in a uranium deposit at Oklo in west Africa some two billion years ago.

Plutonium: a fission energy source

Plutonium is a by-product of the fission process in nuclear reactors, due to neutron capture by uranium-238 in particular. When operating, a typical 1000 MWe nuclear reactor contains within its uranium fuel load several hundred kilograms of plutonium, with plutonium-239 being the most common isotope. Pu-239 is fissile, yielding much the same energy as the fission of a U-235 atom, and complementing it.

Well over half of the plutonium created in the reactor core is "burned" in situ and is responsible for about one third of the total heat output of a light water reactor (LWR). Of the rest, one sixth through neutron capture becomes Pu-240 (and Pu-241), the balance emerges as Pu-239 in the used fuel.

An ordinary large nuclear power reactor (1000 MWe LWR) gives rise to about 25 tonnes of used fuel a year, containing up to 290 kilograms of plutonium. Plutonium, like uranium, is an immense energy source. If the plutonium is extracted from used reactor fuel it can be used as a direct substitute for U 235 in the usual fuel, the Pu-239 being the main fissile part, but Pu-241 also contributing.

In order to extract it for recycle, the used fuel is reprocessed and the recovered plutonium oxide is mixed with depleted uranium oxide to produce mixed-oxide (MOX) fuel, with about 5% Pu-239. Plutonium can be used on its own in fast neutron reactors, where all the plutonium isotopes fission, and so function as a fuel (along with U-238). Isotopes of uranium and plutonium which fission in a fast neutron environment are said to be "fissionable", as distinct from fissile.  As with uranium, the energy potential of plutonium is more fully realised in a fast reactor.

One kilogram of Pu-239 being slowly consumed over three years in a conventional nuclear reactor can produce sufficient heat to generate nearly 10 million kilowatt-hours of electricity.

Plutonium-240 is the second most common isotope, formed by occasional neutron capture by Pu-239. Its concentration in nuclear fuel builds up steadily, since it does not undergo fission to produce energy in the same way as Pu-239. (In a fast neutron reactor it is fissionable, which means that such a reactor can utilise recycled LWR plutonium more effectively than a LWR.)

The approximately1.15% of plutonium in the spent fuel removed from a commercial LWR power reactor (burn-up of 42 GWd/t) consists of about 53% Pu 239, 25% Pu-240, 15% Pu-241, 5% Pu-242 and 2% of Pu-238 which is the main source of heat & radioactivity. Comparable isotopic ratios are found in the spent fuel of CANDU heavy-water reactors at much lower burnups (8 GWd/t), due to their use of natural uranium fuel and high thermal neutron spectrum. (From gas graphite Magnox reactors the plutonium has more Pu-239 - about 65%, plus 25% Pu-240, 5% Pu-241, 1% Pu-242 and negligible Pu-238.) Reactor-grade plutonium is defined as that with 19% or more of Pu-240.

Plutonium stored over several years becomes contaminated with the Pu-241 decay product americium-241 (see paper on Smoke detectors & Americium), which interferes with normal fuel fabrication procedures. After long storage, Am-241 must be removed before the Pu can be used in a normal MOX fabrication plant because it emits intense gamma radiation (in the course of its alpha decay to Np-237).

While of a different order of magnitude to the fission occurring within a nuclear reactor, Pu-240 has a relatively high rate of spontaneous fission with consequent neutron emissions. This makes reactor-grade plutonium entirely unsuitable for use in a bomb (see below).

Recovered plutonium can only be recycled through a light water reactor once or twice, as the isotopic quality deteriorates. However, fast neutron reactors can then use this material and complete its consumption. Such reactors can also be configured to be net breeders of plutonium (as originally envisaged), which is important for the long-term sustainability of nuclear energy. Meanwhile research on fast neutron reactors is focused on maximising consumption of plutonium and incineration of actinides formed in the light water reactors.

Resources of plutonium

Total world generation of reactor-grade plutonium in spent fuel is some 60 tonnes per year. About 1300 tonnes have been produced so far, and most of this remains in the used fuel, with some 370 tonnes extracted. About one third of the separated Pu (130 t) has been used in MOX over the last 30 years. Currently 8-10 tonnes of Pu is used in MOX each year.

Three US reactors are able to run fully on MOX, as can Canadian heavy water (CANDU) reactors. All Western and the later Russian light water reactors can use 30% MOX in their fuel.

Some 32 European reactors are licensed to use MOX fuel, and several in France are using it as 30% of their fuel. Areva's new EPR is capable of running a full core load of MOX.

About 22 tonnes of reactor-grade plutonium is separated by reprocessing plants in the OECD each year and this is set to double by 2003, by which time its usage in MOX is expected to outstrip this level of production so that stockpiles diminish.

At the end of 2007 the UK had 77 tonnes of separated plutonium and this stockpile is expected to grow to 106 tonnes by 2012 - some 81t from Magnox fuel and 25t from AGR fuel.  It also held 27 tonnes on behalf of foreign utilities which had had their used fuel reprocessed at Sellafield.  Using all of UK's plutonium in MOX fuel rather than immobilising it as waste is expected to yield a £700-1200 million resource cost saving to UK, along with 300 billion kWh of electricity (about one year's UK supply).  The 106t Pu could be consumed in two 1000 MWe light water reactors using 100% MOX fuel over 35 years.

At the end of 2006 France held nearly 50 tonnes of separated plutonium and Russia 41 tonnes. Worldwide stocks were estimated as just over 250 tonnes.

See also Appendix on plutonium recycling.

Plutonium and Weapons

It takes about 10 kilograms of nearly pure Pu-239 to make a bomb. Producing this requires 30 megawatt-years of reactor operation, with frequent fuel changes and reprocessing the 'hot' fuel. Hence weapons-grade plutonium is made in special production reactors by burning natural uranium fuel to the extent of only about 100 MWd/t (effectively 3 months), instead of the 45,000 MWd/t typical of LWR power reactors (or even the 7000 - 10,000 MWd/t in CANDU or Magnox reactors used for power).

For weapons use, Pu-240 is considered a serious contaminant and it is not feasible to separate Pu-240 from Pu-239. An explosive device could be made from plutonium extracted from low burn-up reactor fuel (ie. if the fuel had only been used for a short time), but any significant proportions of Pu-240 in it would make it extremely hazardous to the bomb makers, as well as unreliable and unpredictable. Typical plutonium recovered from reprocessing used power reactor fuel has about one-third non-fissile isotopes (mainly Pu-240)*.  This is known as reactor-grade plutonium.

* In 1962 a nuclear device using low-burnup plutonium from a UK power reactor was detonated in USA. The isotopic composition of this plutonium has not been officially disclosed, but it was evidently about 85% Pu-239 - what would since 1971 have been called "fuel-grade" plutonium.

Plutonium for weapons is made differently, in simple reactors (usually fuelled with natural unenriched uranium) run for that purpose, with frequent fuel changes (ie. low burn-up). This, coupled with the application of international safeguards, effectively rules out the use of commercial nuclear power plants for weapons material.

International safeguards arrangements applied to traded uranium extend to the plutonium arising from it, ensuring constant audits even of reactor-grade material. This addresses uncertainty as to the explosive potential of reactor-grade plutonium - some authorities say that it could be used for an explosive device in the one kiloton range, though others disagree.  (All we know for sure is that it has never been made to explode.)

The International Atomic Energy Agency (IAEA) is conservative on this matter so that, for the purpose of applying IAEA safeguards measures, all plutonium (other than plutonium comprising 80% or more of the isotope Pu-238) is defined by the IAEA as a 'direct-use' material, that is, 'nuclear material that can be used for the manufacture of nuclear explosives components without transmutation or further enrichment'.  The IAEA is not saying that all plutonium is suitable for making weapons, simply that on the basis of calculations and under certain technically-demanding conditions it might be made to explode.  The 'direct use' definition applies also to plutonium which has been incorporated into commercial MOX fuel, which certainly could not be made to explode.

Disarmament will give rise to some 150-200 tonnes of weapons-grade plutonium, over half of it in former USSR. Discussions are progressing as to what should be done with it. The main options for the disposal of weapons-grade plutonium are:

In June 2000, the USA and Russia agreed to dispose of 34 tonnes each of weapons-grade plutonium by 2014, and since then the US government has released further surplus weapons plutonium.  The US government planned to pursue the first two options above, though it has since dropped the first one for any significant amount of material.  The UK is also using it for five tonnes of impure plutonium. 
In the USA the MOX option is proceeding, and the first trials of MOX made with weapons plutonium are under way in South Carolina.  Developments under the Global Nuclear Energy partnership (GNEP) make it very likely that the some military plutonium will be used in fast reactors in USA.  Meanwhile the USA has developed a "spent fuel standard", which means that plutonium, including weapons Pu, should never be more accessible than if it is incorporated in used fuel. 

Europe has a well-developed MOX capacity and this suggests that weapons plutonium could be disposed of relatively quickly. Input plutonium in facilities such as Sellafield's new MOX plant would need to be about half reactor grade and half weapons grade, but using such MOX as 30% of the fuel in one third of the world's reactor capacity would remove about 15 tonnes of warhead plutonium per year. This would amount to burning 3000 warheads per year to produce 110 billion kWh of electricity.

Canada was promoting the use of its CANDU heavy water reactors as having very flexible fuel requirements and hence as suitable for disposing of military plutonium. Various mixed oxide fuels have been tested in these reactors, which can be operated economically with a full MOX core.

Russia is strongly committed to using its plutonium in mixed-oxide fuel, burning it in both late-model conventional reactors and BN series fast neutron reactors.

The only use for "reactor grade" plutonium is as a nuclear fuel, after it is separated from the high-level wastes by reprocessing. It is not and has never been used for weapons, due to the relatively high rate of spontaneous fission and radiation from the heavier isotopes such as Pu-240 making any such attempted use fraught with great uncertainties.

Toxicity and Health Effects

Despite being toxic both chemically and because of its ionising radiation, plutonium is far from being 'the most toxic substance on earth' or so hazardous that 'a speck can kill'. On both counts there are substances in daily use that, per unit of mass, have equal or greater chemical toxicity (arsenic, cyanide, caffeine) and radiotoxicity (smoke detectors).

There are three principal routes by which plutonium can reach human beings:

Ingestion is not a significant hazard, because plutonium passing through the gastro-intestinal tract is poorly absorbed and is expelled from the body before it can do harm.

Contamination of wounds has rarely occurred although thousands of people have worked with plutonium. Their health has been protected by the use of remote handling, protective clothing and extensive health monitoring procedures.

The main threat to humans comes from inhalation. While it is very difficult to create airborne dispersion of a heavy metal like plutonium, certain forms, including the insoluble plutonium oxide, at a particle size less than 10 microns, are a hazard.

If inhaled, much of the material is immediately exhaled or is expelled by mucous flow from the bronchial system into the gastro-intestinal tract, as with any particulate matter. Some however will be trapped and readily transferred, first to the blood or lymph system and later to other parts of the body, notably the liver and bones. It is here that the deposited plutonium's alpha radiation may eventually cause cancer.

However, the hazard from Pu-239 is similar to that from any other alpha-emitting radionuclides which might be inhaled. It is less hazardous than those which are short-lived and hence more radioactive, such as radon daughters, the decay products of radon gas, which (albeit in low concentrations) are naturally common and widespread in the environment.

In the 1940s some 26 workers at US nuclear weapons facilities became contaminated with plutonium. Intensive health checks of these people have revealed no serious consequence and no fatalities that could be attributed to the exposure. In the 1990s plutonium was injected into and inhaled by some volunteers, without adverse effects.

Plutonium is one among many toxic materials that have to be handled with great care to minimise the associated but well understood risks. In the 1950s Queen Elizabeth was visiting Harwell and was handed a lump of plutonium (presumably Pu-239) in a plastic bag and invited to feel how warm it was.

Plutonium

Type Composition Origin Use
Reactor-grade from high-burnup fuel 55-70% Pu-239, >19% Pu-240, typically about 30% non fissile Comprises about 1% of spent fuel from normal operation of civil nuclear reactors used for electricity generation As ingredient (c5%) of MOX fuel for normal reactor
Weapons-grade Pu-239 with >7% pu-240 From military "production" reactors specifically designed and operated for production of low burn-up Pu. Nuclear weapons (can be recycled as fuel in fast neutron reactor or as ingredient of MOX)

See also paper on Military warheads as a source of nuclear fuel in this series.

Sources:
''Plutonium: blessing or curse?' Henderickz, HV, Copper Beech 1998.
'Management of separated plutonium' OECD/NEA Paris 1997.
'Plutonium Fuel: An Assessment' OECD/NEA Paris 1989.
'Plutonium Management in the Medium Term' OECD/NEA Paris 2003.
'Plutonium: The Myths and the Facts' USCEA (NEI), Washington June 1993.
NATO ASI series, Managing the Plutonium Surplus: Applications and Technical Options, 1994.
'The Toxicity of Plutonium' Medical Research Council, London HMSO 1975.
Plutonium articles in Revue Generale Nucleaire, June 1995.
Fishlock, D 2005, Drama of Plutonium, Nuclear Engineering International.

Appendix: From the 1999 Annual Report of the Australian Safeguards and Non-Proliferation Office, DFAT:

Appendix:  PLUTONIUM RECYCLING: THE USE OF 'MOX' FUEL 

(from 1999 ASNO Annual Report)

With the transport and use of MOX (mixed oxide) fuels attracting increasing public attention, readers may find the following background information useful.

Plutonium is formed in uranium fuel during the operation of a reactor. Plutonium has substantial potential as a source of energy, and in fact is a significant contributor to the energy produced in a uranium-fuelled reactor.

The use of MOX fuel reduces inventories of separated plutonium, and is likely to assume increasing importance for degrading weapons-grade plutonium released by disarmament.

Why recycle?

The concept of plutonium recycling involves reprocessing of spent fuel from a reactor, in order to separate the plutonium produced in the fuel, fabricate it into fresh fuel, and use it for further energy production. When uranium is used to fuel a reactor, energy is produced primarily from the fissile isotope U-235, which constitutes only around 0.7% of natural uranium. Plutonium recycling offers substantially greater efficiency, because energy is produced from the most abundant uranium isotope, U-238 (which constitutes around 99.3% of natural uranium), through conversion of U-238 to plutonium. In theory therefore plutonium recycling offers some 150 times as much energy from a given quantity of uranium as the 'once-through' cycle (i.e. use of uranium without reprocessing). Practical factors prevent this theoretical maximum from being reached, but a very substantial increase appears to be practicably attainable. Plutonium recycling would therefore be extremely attractive if uranium were in short supply and high-priced.

Programs for the recycling of plutonium were developed in the 1970s when it appeared that uranium would be in scarce supply and would become increasingly expensive. It was proposed that plutonium would be recycled through fast breeder reactors, that is, fast neutron reactors with a uranium 'blanket', which would produce slightly more plutonium than they consume. Thus it was envisaged that the world's 'low cost' uranium resources, then estimated to be sufficient for about 50 years' consumption, could be extended for hundreds of years.

For a variety of reasons, high uranium prices have not eventuated, and future prices are uncertain. Some of the influences on this situation include:

At the moment the consumption of uranium in the world's nuclear energy programs substantially exceeds uranium production (by about 50%), and low cost uranium resources are still equivalent to only about 40 to 50 years' consumption at present levels. These factors might be expected to result in higher uranium prices, but prices remain depressed. In these circumstances there is no impetus to develop fast breeder reactors, particularly since these reactors present major engineering challenges which will be expensive to resolve. Meanwhile, however, around 30% of spent fuel arisings are covered by long-term reprocessing contracts, and the approach of plutonium recycling using light water reactors has been developed as a way of avoiding the accumulation of separated plutonium, and deriving an immediate economic return on this plutonium.

MOX fuel

The term 'MOX' is derived from 'mixed oxides', and refers to reactor fuel made from a mixture of plutonium and uranium oxide. For use in a light water reactor, the proportion of plutonium is about 5%. This is a similar fissile content as low enriched uranium fuel. As is the case with uranium fuel, the MOX is formed into ceramic fuel pellets, which are extremely stable and durable, and which are sealed in metal (usually zirconium) tubes, which in turn are assembled into fuel elements. In most cases about a third of the reactor core can be loaded with MOX fuel elements without engineering or operational modifications to the reactor.

Contrary to suggestions from some commentators, there is nothing unusual in the presence of plutonium in light water reactors. Plutonium is produced during the operation of a reactor. The plutonium content of spent fuel from the normal operation of a light water reactor will be a little less than 1%, usually around 0.8%, when the fuel is unloaded. During the operation of the reactor, plutonium formed in the fuel will contribute an increasing proportion of the overall energy production of the reactor - towards the end of an operating cycle, a substantial proportion of the initial U-235 content of the fuel will have been consumed, and the energy produced by fission of plutonium will be very close to that produced by the remaining uranium.

Use of MOX fuel is expected to significantly reduce plutonium inventories. As an example, the Euratom Supply Agency estimates that the use of a single MOX fuel element consumes 9 kg of plutonium, and avoids the production of a further 5 kg (compared with the use of low enriched uranium fuel). Thus in this example each MOX fuel element used results in a net reduction of 14 kg of plutonium.

Currently plutonium is being recycled with 32 light water reactors in Europe, and this is shortly to commence in Japan. Use of MOX fuels in light water reactors will increase over the next decade. While this will involve mainly reprocessed civil plutonium, the use of MOX fuel to degrade weapons-grade plutonium (There are two ways in which use of weapons-grade plutonium in MOX fuel degrades that plutonium: through the plutonium being associated with highly radioactive fission products in spent fuel (the 'spent fuel standard'); and through changes in isotopic composition during the irradiation process - in normal power reactor useage the plutonium would become reactor-grade), transferred from military programs as part of the disarmament process, will assume increasing importance. By 2010 it is expected that MOX fuels will be used with 45 reactors in Europe, together with 16-18 in Japan, and possibly five in Russia and six in the US, that is, some 15-20% of the world's power reactors.

As noted earlier, plutonium recycling programs were first developed with the breeder cycle in mind. There have been active fast breeder reactor research and demonstration programs in France, Japan and Russia. Future plans for fast breeder reactors are now uncertain, a major factor being economics, especially the price of uranium. At the moment the greatest interest appears to be in operating such reactors, not as breeders, but as net consumers or 'burners' of plutonium and of minor actinides. Clearly of crucial importance here is the future direction of nuclear energy, which will be determined by a complex range of political and economic considerations. If nuclear energy continues to make a significant contribution to world electricity production, and particularly if this contribution increases, plutonium could become an energy source as significant as uranium is today.

Is the plutonium in MOX fuel 'weapons-useable'?

Opponents of the use of MOX fuels commonly state that such fuels represent a proliferation risk because the plutonium in the fuel is said to be 'weapons-useable'.' This is a complex subject, where there is no consensus amongst experts, but the short answer is that there would be serious technical difficulties in attempting to make nuclear weapons from plutonium of the quality currently used for MOX (reactor-grade), and none of the countries possessing nuclear weapons has ever made weapons using plutonium of this quality.

'Weapons-useable' is not a technical term, and it is not clear what those using it mean, but if it is supposed to imply that reactor-grade plutonium is a material that could readily find its way into weapons, this overlooks two important facts: that there has been no practical demonstration of the use of such plutonium in nuclear weapons, and that rigorous IAEA safeguards apply to this material in non-nuclear-weapon States party to the NPT. It is misleading to conclude, because this material is subject to safeguards, that it is therefore 'weapons-useable'.

To better understand this issue, it is necessary to appreciate that plutonium exists as several isotopes. As noted earlier, longer reactor irradiation times result in the formation of higher plutonium isotopes, Pu-240, Pu-241 and Pu-242 (and also the isotope Pu-238). The mix of isotopes (isotopic composition) of a particular quantity of plutonium will depend on how the plutonium was produced, that is, its irradiation history. The isotopic composition of plutonium affects its suitability for particular purposes, such as use in a reactor or use in nuclear weapons.

The plutonium isotope most suitable for weapons use is Pu-239. Plutonium used in nuclear weapons, 'weapons-grade' plutonium, comprises at least 92%, usually more, Pu-239. This plutonium is produced in dedicated plutonium production reactors, specially designed and operated to produce plutonium of this quality by removal and reprocessing of fuel after short irradiation times.

The plutonium produced in the normal operation of light water reactors, from which MOX fuel is being made, is what is known as 'reactor-grade' plutonium. Because of the very long time fuel is irradiated in a power reactor (typically 3-4 years), reactor-grade plutonium has a substantial proportion of higher plutonium isotopes. Reactor-grade plutonium typically comprises less than 60% of the isotope Pu-239.

Reactor-grade plutonium contains a large proportion of isotopes which create serious technical difficulties for weapons use, namely Pu-238, Pu-240 and Pu-242. These difficulties include 'pre-initiation' (a high spontaneous fission rate leading to the nuclear chain reaction starting too early), and radiation and heat levels which will adversely affect vital weapons components such as high explosives and electronics. While these difficulties could possibly be overcome, to some extent at least, by experienced weapons designers (e.g. from the nuclear-weapon States, with experience from hundreds of tests to draw upon), ASNO is not aware of any successful test explosion using reactor-grade plutonium, typical of light water reactor fuel (There is some confusion over a 1962 test by the US using what was then described as 'reactor-grade' plutonium, but at that time 'reactor-grade' was much closer to weapons-grade than is currently the case. While the US has never revealed the quality of the plutonium used in that test, there are indications that it was of 'fuel-grade', an intermediate category between weapons-grade and reactor-grade, which has been recognised as a separate category since the 1970s).

IAEA definition of 'direct-use' material

The confusion in the public mind regarding the suitability of reactor-grade plutonium for nuclear weapons appears to arise from the fact that, for the purpose of applying IAEA safeguards measures, all plutonium (other than plutonium comprising 80% or more of the isotope Pu-238) is defined by the IAEA as a 'direct-use' material, that is, 'nuclear material that can be used for the manufacture of nuclear explosives components without transmutation or further enrichment'. In order to understand what this actually means, it is important to appreciate the following:

How does this relate to MOX?

With respect to the use of MOX fuel, arguments about the 'weapons-useability' of reactor-grade plutonium miss the point: as we have seen, MOX is a mixture of uranium and plutonium oxides, with the plutonium being very much in the minority. For light water reactor fuel, the plutonium content is typically around 5%. MOX cannot be used in nuclear weapons or nuclear explosives. To separate the plutonium content from MOX fuel elements would be a major undertaking, similar to reprocessing. IAEA safeguards measures would readily indicate if any attempt were made to process the fuel to separate plutonium.