ちょうど私が話しているとき、大爆発が起こった。

Just as we are talking, there was a loud explosion.

ちょうど私(わたし)が話(はな)しているとき、大(だい)爆発(ばくはつ)が起(お)こった。

Chōdo watashi ga hanashiteiru toki, dai bakuhatsu ga okotta.

丁度 (ちょうど)

just; right; exactly

私 (わたし、わたくし)

I; me; private affairs; personal matter; secrecy; selfishness

が (が)

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

話す (はなす)

to talk; to speak; to converse; to chat; to tell; to explain; to narrate; to mention; to describe; to discuss; to speak (a language)

とき (とき)

regular (stops at every station) Jouetsu-line Shinkansen

大 (おお)

big; large

爆発 (ばくはつ)

explosion; detonation; eruption

起こる (おこる)

to occur; to happen

Readings: シ、わたくし、わたし

Meanings: private, I, me

Readings: ワ、はな.す、はなし

Meanings: tale, talk

Readings: ダイ、タイ、おお-、おお.きい、 -おお.いに

Meanings: large, big

Readings: バク、は.ぜる

Meanings: bomb, burst open, pop, split

Readings: ハツ、ホツ、た.つ、あば.く、おこ.る、つか.わす、はな.つ

Meanings: departure, discharge, publish, emit, start from, disclose, counter for gunshots

Readings: キ、お.きる、お.こる、お.こす、おこ.す、た.つ

Meanings: rouse, wake up, get up