The Iranian government has promised to provide information on detonators as one of seven steps aimed at allaying fears over its nuclear programme.
It reached agreement after two days of talks with the UN nuclear watchdog, the IAEA, in the Iranian capital Tehran.
All seven promised measures are due to be completed by 15 May.
A BBC correspondent says the detonator promise is potentially significant as it is related to suspicions that Iran researched nuclear weapons technology.
The IAEA is investigating possible military dimensions to Iran's nuclear work, a charge which Iran denies.
Its investigation into these suspicions has been deadlocked for years, the BBC's Bethany Bell reports from Vienna, where the IAEA is based.
Saying its nuclear work was purely peaceful, Iran committed itself to co-operate with the IAEA in order to clear up any "ambiguities".
Another confidence-building step is a commitment to provide "managed access" to the Saghand uranium mine in Yazd, which is said to produce some 60 tonnes of yellowcake annually.
The talks in Tehran are separate from Iran's negotiations over its nuclear programme with six world powers, which called on Tehran to allow the IAEA free access to its Parchin military site.
Parchin was not included in the five other confidence-building steps, which are listed on the website of the IAEA as
*Managed access to the concentration plant near Ardakan
*Submission of an updated design information questionnaire for the IR-40 Reactor near Arak
*Work on agreeing a safeguards approach with the IAEA for the IR-40 Reactor
*A "technical" visit to the laser centre at Lashkar Ab'ad
*Information on nuclear source material, including imports and uranium extracted from phosphateshttp://www.bbc.co.uk/news/world-middle-east-26109994