UPDATE 1-Valero says shutting Corpus Christi HCU for work

(Adds background on west plant unit, paragraph 3)

HOUSTON Oct 22 (Reuters) - Valero Energy Corp (VLO.N) said it was shutting the west plant hydrocracking unit at its 315,000 barrel per day (bpd) Corpus Christi, Texas, refinery on Thursday to repair a leak.

The leak was discovered after the unit restarted Sunday following an unplanned shutdown due to a small fire on Oct. 7. Valero said it was unknown on Thursday how long the unit would be shut to repair the leak.

The west plant unit is a gasoil hydrocracker and has throughput capacity of 36,000 bpd. A hydrocracker uses hydrogen under high pressure to increase the yield of motor fuel from feedstocks. (Reporting by Erwin Seba; Editing by David Gregorio)