Historical accounting and plutonium
A SUMMARY REPORT BY THE MINISTRY
OF DEFENCE ON THE ROLE OF HISTORICAL ACCOUNTING FOR FISSILE MATERIAL IN THE
NUCLEAR DISARMAMENT PROCESS, AND ON PLUTONIUM FOR THE UNITED KINGDOM'S DEFENCE
NUCLEAR PROGRAMME
Introduction
1. The Government is committed to transparency
and openness about the defence nuclear programme when compatible with continuing
national security requirements and the United Kingdom's international obligations
under Article I of the Nuclear Non-Proliferation Treaty (NPT). The Government
is also committed to work towards the goal of the global elimination of nuclear
weapons As the Strategic Defence Review stated, eliminating nuclear weapons
will require States which have had nuclear programmes outside international
safeguards to account for the fissile material that they have produced. This
contributes to the process of nuclear disarmament by developing confidence that
as States reduce and eventually eliminate their nuclear weapons, they have not
retained concealed stocks of fissile material outside international supervision
with which to construct clandestine nuclear weapons. Such accounting was crucial
to the International Atomic Energy Agency's initial verification of the comprehensive
safeguards agreement signed by South Africa when it eliminated its nuclear weapons
programme and joined the Nuclear Non-Proliferation Treaty as a non-nuclear-weapon
State. The United States has produced a comprehensive report on its production
of plutonium for defence purposes, and is working on a similar study on its
production of High Enriched Uranium.
2. It is important not to overestimate the
contribution such historical accounting can make to the verification of the
reduction and elimination of nuclear weapons. By its very nature it is dependent
on the records still available today. It is an unfortunate reality that in the
early days of nuclear programmes records were not kept to the standards required
today, nor have all the records that were kept survived. Furthermore, the technology
and equipment did not exist to conduct technical assessments and measurements
to the level of sensitivity available today. In the light of the Ministry of
Defence's work on this issue over the last eighteen months, and taking account
of the conclusions of the South African and the continuing US historical accounting
programmes, the Government does not believe that it will ever be possible for
any of the relevant States to be able to account with absolute accuracy and
without possibility of error or doubt for all the fissile material they have
produced for national security purposes.
3. A further complication is that technical
information about the early years of the defence nuclear programmes of the Nuclear
Weapon States is likely to be of particular value to any aspiring proliferator
seeking to build a low-level, unsophisticated nuclear capability. The Nuclear
Weapon States therefore have to consider the implications of declassification
in this area very carefully in the light of their obligations under Article
I of the Nuclear Non-Proliferation Treaty.
4. However, even taking these complications
and restrictions into account, the Government continues to believe that accounting
as far as possible for the United Kingdom's past production of fissile material
for nuclear weapons is a necessary and appropriate process. The Government is
committed to transparency about the defence nuclear programme, past and present,
where possible. Historical accounting has a role here in its own right. Moreover,
the Government believes that while it will never be possible to create an exact
and absolute final account, in the United Kingdom or elsewhere, such accounting
has an important confidence-building role, both as a demonstration that any
figures declared for defence stockpiles of nuclear material are consistent with
past declared production, and as an important indicator of good faith and commitment
to the process of working for the elimination of nuclear weapons.
5. In this context, and mindful of its transparency
objectives, the Government therefore set in hand in the Strategic Defence Review
a process of declassification and historical accounting with the aim of producing,
by the Spring of 2000, an initial report of defence fissile material production
since the start of the United Kingdom's defence nuclear programme in the 1940s.
This work complements and, for plutonium, expands on the SDR publication of
the size of the defence stockpile of fissile material. This accounting has been
a labour intensive process involving detailed scrutiny of a wide range of records
by the staff of the Assistant Chief Scientific Adviser(Nuclear), the Defence
Procurement Agency, and civil and defence nuclear facilities. In the first instance,
to make the best use of the available resources for this work, the Ministry
of Defence has therefore concentrated on a historic review of plutonium production
for the United Kingdom's defence programme. The main conclusions of this review
are set out below. The full report by the Ministry of Defence's Assistant Chief
Scientific Adviser (Nuclear) is published on the Ministry of Defence website
at www.mod.uk.
Historical Background
6. The United Kingdom's nuclear weapons programme
was formally sanctioned in January 1947. In its early years it was carried out
in parallel with the development of the civil nuclear programme, firstly under
the Ministry of Supply until 1954, and then under the United Kingdom Atomic
Energy Authority (UKAEA) until the creation of British Nuclear Fuels Limited
(BNFL) in 1971 to take over the UKAEA's production activities. Nuclear weapons
design work was moved from Fort Halstead to Aldermaston in 1950. This site transferred
to Ministry of Defence ownership in 1973. The wide-ranging nature of the UKAEA
organisation meant that in the early years there was an inevitable blurring
of the distinctions between the military and civil nuclear programmes and sites.
Some civil nuclear development work was carried out at nuclear weapons fabrication
facilities and some plutonium was shipped to Aldermaston for civil applications.
This was not seen as significant at the time.
7. Plutonium for the nuclear weapons programme
was produced at Windscale until 1957 and reprocessed on site before being shipped
to Aldermaston. Plutonium production at Calder Hall (on the Sellafield site)
for the nuclear weapons programme began in 1956, and at Chapelcross in 1958,
with reprocessing at Sellafield by the same facility used to reprocess spent
fuel from the civil programme, before being shipped to Aldermaston. Both Calder
Hall and Chapelcross were used to produce electricity for the national grid
in addition to supplying material for the defence nuclear programme. The Government
announced in April 1995 that the United Kingdom had ceased production of fissile
material for explosive purposes, and the Calder Hall reactors now operate under
EURATOM safeguards. The Chapelcross reactors are still used to produce Tritium
for the defence programme, and are therefore not subject to international safeguards.
However, in 1998 the Government announced in the Strategic Defence Review that
reprocessing of spent fuel from Chapelcross would henceforth be conducted under
EURATOM safeguards and made liable to inspection by the IAEA.
Records Available
8. Records were raised each time material was
moved between sites (and within sites for local accounting procedures). The
review was therefore conducted primarily from an audit of annual accounts and
delivery records from Sellafield supported by receipt records at Aldermaston
where these are available. Evidence was also sought from available secondary
sources. Records for the early years are inevitably less complete and less detailed
than for more recent years, although Sellafield has maintained good accounts
throughout, which cover the great bulk of material transferred. Overall, confidence
in the completeness and accuracy of the information available is very high for
the 1980s and 1990s, but less so before the mid 1960s.
Results Of The Review
9. The review has drawn up a plutonium balance
and annual breakdown of transfers of plutonium between Aldermaston and other
UK sites. This indicates that some 16.8 tonnes of plutonium were delivered to
Aldermaston for the weapons programme, for onward transfer to the United States
mainly under the Barter arrangements (see paragraph 12 below), and for civil
work.
10. Of this, the records identify the following
subsequent transfers of Plutonium from Aldermaston to other locations:
- 3.9 tonnes to Sellafield;
- 0.2 tonnes to Dounreay;
- 2.8 tonnes to Winfrith;
- 0.5 tonnes to Harwell;
- 0.5 tonnes to the US;
- 0.2 tonnes consumed in weapons tests in Australia
and the US;
- 5.4 tonnes transferred to the US under Barter
arrangements;
- 0.1 tonnes tied up in waste.
The
records indicate a net balance of 3.2 tonnes of plutonium available for the
weapons programme. This compares to a stockpile of 3.5 tonnes identified in
the Strategic Defence Review, including some 0.3 tonnes of weapons grade plutonium
no longer required for defence purposes. The SDR identified in addition some
4.1 tonnes of non-weapons grade plutonium stored at Sellafield, now under EURATOM
safeguards and liable to inspection by the International Atomic Energy Agency.
None of this plutonium has ever been delivered to Aldermaston and it is therefore
not included in the figures above.
11.
These figures show that the weapon cycle stockpile is in fact some 0.3 tonnes
larger than the amount of plutonium the records indicate as available. This
is a positive discrepancy of about 1.7% of total acquisitions. The Ministry
of Defence is confident of the accuracy of the stockpile figure declared in
the SDR. This was established accurately using modern nuclear accounting practices.
The explanation for the discrepancy is therefore likely to lie in the poorer
quality and incompleteness of some of the older records, particularly in the
1950s and early 1960s. As explained in the introduction, such discrepancies
are inevitable when seeking to account for material production and transfers
over a period of over 50 years. Similar discrepancies were identified by the
United States and South Africa in their reports.
Barter Arrangements
12.
As noted above, between 1960 and 1979 the United Kingdom supplied the United
States with approximately 5.4 tonnes of plutonium, from both the civil and defence
programmes, under the 1958 Mutual Defence Agreement. Information on this has
already been released by the US Department of Energy with the agreement of the
Ministry of Defence. The US Government has given assurances that UK plutonium
transferred to the US since 1964 was not used in the US nuclear weapons programme.
It is theoretically possible, but very unlikely, that some UK civil plutonium
may have been transferred to the US and used in the US nuclear weapons programme
before 1964. The Review has established that the records do not exist to determine
this with absolute certainty at this remove.
Conclusion
13.
The Review has conducted a comprehensive investigation of existing records.
This has identified that the defence stockpile of plutonium is some 0.3 tonnes
larger than is indicated by the records examined, or a discrepancy of some 1.7%
of total acquisitions. However, given the long period covered, the less rigorous
accounting standards that applied in the early years of the programme, and the
limited availability of records for the early years, the Government believes
that the review has provided strong corroboration of the defence plutonium holdings
declared in the Strategic Defence Review, and has further reinforced the significant
increase in transparency about the defence nuclear stockpile set out in the
SDR.
14.
In view of its commitment to transparency and the role of historical accountancy
for defence fissile material holdings in the process of nuclear disarmament,
the Government intends to follow this review up in due course with publication
of further material on other elements of the defence nuclear programme, including
production of High Enriched Uranium for the defence programme. However, in view
of the labour-intensive nature of the work involved and the limited resources
available the Government intends now to seek the views of UK academic and non-governmental
experts on their priorities for information in this area before setting any
further internal work in hand.
