Actually changing the fuel every 90 days is more like what is necessary to produce weapons grade Plutonium. Iran cannot produce fuel fast enough to use the VVER for weapons production. The Busher reactor is light-water moderated, and uses very low enriched fuel. There are sound reasons why folks wising to use manufacture weapons use heavy water or graphite moderated reactors.
Report: Palestinian, 18, killed in clashes with IDF in West Bank (Haaretz)
from the article: Russia to begin loading fuel into Iran's nuclear reactor next week