Kamalvandi said the accident happened on Thursday morning at one of the industrial sheds under construction on the open-air premises of the Natanz nuclear site.
The accident has not resulted in any human casualties nor has it disrupted the ongoing activities at the site, the spokesperson added.
He also dismissed concerns about possible nuclear pollution in the wake of the accident, saying the industrial shed was not basically in operation.
Expert teams from the AEOI have been deployed to the site of the accident and are conducting an investigation, he added.