Iran – new developments: Exploding Bridge Wire (EBW)

The following are excerpts from IAEA Safeguards reports since 2008 posted for the assistance of journalists covering the newest developments in the Iran file following talks in Tehran 8 and 9 February.

They were compiled for Atomic Reporters by Tariq Rauf, former Head, Verification and Security Policy Coordination, Office reporting to the IAEA Director General, 2002-2012, who worked on high priority safeguards issues including, Iran, Iraq, Libya, North Korea, South Korea,  and Syria.

“While the IAEA-Iran track on implementation of Iran’s comprehensive safeguards agreement is a separate one,” said Rauf, “now it is somewhat related to the EU3+3 and the Iran track.”

“There  needs  to be better coordination between the EU3+3 & Iran and the Agency. In its work, the IAEA’s normal practice is to go about its business in accordance with its confidentiality rules and requirements of safeguards and the Agency’s Statute and report developments to the Board of Governors”

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EBW references from IAEA Board of Governors’ reports


39. During the meetings on 3–5 February 2008, the Agency made available documents for examination by Iran and provided additional technical information related to: the testing of high voltage detonator firing equipment; the development of an exploding bridgewire detonator (EBW); the simultaneous firing of multiple EBW detonators; and the identification of an explosive testing arrangement that involved the use of a 400 m shaft and a firing capability remote from the shaft by a distance of 10 km, all of which the Agency believes would be relevant to nuclear weapon R&D
. Iran stated that the documents were fabricated and that the information contained in those documents could easily be found in open sources. During the meetings mentioned above, the Agency also described parameters and development work related to the Shahab 3 missile, in particular technical aspects of a re-entry vehicle, and made available to Iran for examination a computer image provided by other Member States showing a schematic layout of the contents of the inner cone of a re-entry vehicle. This layout has been assessed by the Agency as quite likely to be able to accommodate a nuclear device. Iran stated that its missile programme involved the use of conventional warheads only and was also part of the country’s space programme, and that the schematic layout shown by the Agency was baseless and fabricated.


E. Possible Military Dimensions

17. One aspect of the alleged studies refers to the conversion of uranium dioxide to UF4, also known as green salt. A second aspect concerns the development and testing of high voltage detonator firing equipment and exploding bridgewire (EBW) detonators including, inter alia, the simultaneous firing of multiple EBW detonators; an underground testing arrangement (GOV/2008/4, para. 39); and the testing of at least one full scale hemispherical, converging, explosively driven shock system that could be applicable to an implosion-type nuclear device. A third aspect of the studies concerns development work alleged to have been performed to redesign the inner cone of the Shahab-3 missile re-entry vehicle to accommodate a nuclear warhead.

20. Concerning the alleged work to design and build an EBW detonator and a suitable detonator firing unit, Iran acknowledged that it had conducted simultaneous testing with two to three EBW detonators with a time precision of about one microsecond. Iran said, however, that this was intended for civil and conventional military applications. Iran further stated, inter alia, that there was no evidence in the documents presented to it to link them to Iran.

A. Documents shown to Iran in connection with the alleged studies

A.2. High Explosives Testing Document 1: “Analysis and Review of Exploding Bridgewire (EBW) Detonator Test Results” dated January–February 2004, comprising 11 pages in Farsi reporting on work carried out by “Project 3.12” to design and construct an EBW detonator and a suitable detonator firing unit, including testing of about 500 EBW detonators.

B.1. Questions addressed in Agency letters of 8 and 12 February 2008

1. The Agency asked about the possible involvement of an Institute of Applied Physics (IAP) staff member in Iran’s work on EBW detonators; procurement attempts by this person for borehole HP (Ge) gamma spectrometers (GOV/2008/4, para. 40); and Iran’s procurement attempts for spark gaps by another entity (GOV/2008/4, para. 40)
. Iran stated that the person concerned was not involved in work related to EBWs and that the procurement requests were related to well logging for the oil ministry. Iran denied that attempts were made to procure spark gaps by another entity. The Agency continues to assess the information provided by Iran.


C.5. Detonator development

38. The development of safe, fast-acting detonators, and equipment suitable for firing the detonators, is an integral part of a programme to develop an implosion type nuclear device. Included among the alleged studies documentation are a number of documents relating to the development by Iran, during the period 2002–2003, of fast functioning detonators, known as “exploding bridgewire detonators” or “EBWs” as safe alternatives to the type of detonator described for use in the nuclear device design referred to in paragraph 33 above

39. In 2008, Iran told the Agency that it had developed EBWs for civil and conventional military applications and had achieved a simultaneity of about one microsecond when firing two to three detonators together,37 and provided the Agency with a copy of a paper relating to EBW development work presented by two Iranian researchers at a conference held in Iran in 2005. A similar paper was published by the two researchers at an international conference later in 2005.38 Both papers indicate that suitable high voltage firing equipment had been acquired or developed by Iran. Also in 2008, Iran told the Agency that, before the period 2002–2004, it had already achieved EBW technology. Iran also provided the Agency with a short undated document in Farsi, understood to be the specifications for a detonator development programme, and a document from a foreign source showing an example of a civilian application in which detonators are fired simultaneously. However, Iran has not explained to the Agency its own need or application for such detonators.

40. The Agency recognizes that there exist non-nuclear applications, albeit few, for detonators like EBWs, and of equipment suitable for firing multiple detonators with a high level of simultaneity
. Notwithstanding, given their possible application in a nuclear explosive device, and the fact that there are limited civilian and conventional military applications for such technology, Iran’s development of such detonators and equipment is a matter of concern, particularly in connection with the possible use of the multipoint initiation system referred to below.

C.10. Conducting a test

58. The Agency has information provided by a Member State that Iran may have planned and undertaken preparatory experimentation which would be useful were Iran to carry out a test of a nuclear explosive device. In particular, the Agency has information that Iran has conducted a number of practical tests to see whether its EBW firing equipment would function satisfactorily over long distances between a firing point and a test device located down a deep shaft. Additionally, among the alleged studies documentation provided by that Member State, is a document, in Farsi, which relates directly to the logistics and safety arrangements that would be necessary for conducting a nuclear test. The Agency has been informed by a different Member State that these arrangements directly reflect those which have been used in nuclear tests conducted by nuclear-weapon States.

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