Disallowed Key Characters/daily-news/archive/2015/09/The_head_of_the_U_N__nuclear_agency_pushed_back_on_Thursday_against_critics_questioning_the_wisdom_of_letting_Iranian_experts_take_samples_meant_to_help_determine_whether_their_own_country_clandestinely_worked_in_the_past_on_atomic_arms,_saying_he_is_convinced_the_process_was_faultless