Iran has begun decommissioning uranium enrichment centrifuges under the terms of the nuclear deal struck with six world powers in July, Tehran’s nuclear chief was quoted as saying on Monday during a visit to Tokyo.  We have started the preliminary work” on implementing the agreement, Iran’s Atomic Energy Organization chief Ali Akbar Salehi was quoted as saying by Japan’s Kyodo news agency, adding that the measures include reducing the number of active centrifuge machines.  Under the July 14 agreement, Iran is to curb its nuclear program under United Nations supervision to ensure it cannot be used to make a nuclear weapon, in exchange for the removal of sanctions that have isolated Tehran and hobbled its economy.