CFO Etheridge said the Didcot site, at which one person has already died as a result of Tuesday's explosion "reminds me of Chernobyl with the sheer extent of what we're dealing with".
At the time of writing, it was reported that it was "highly unlikely" three missing people would be found alive.
CFO Etheridge told BBC Radio Oxford: "I hope that they felt that was a way of understanding the enormity of the challenge that we are facing, but we won't step back from that challenge.
"I have been in the fire service for 30 years and undoubtedly the incident we are facing at the moment this is the most technically challenging incident I have ever come across."
The area being searched is 55m (180ft) long, 30m (98ft) wide and 25m (82ft) high, and "unstable".
Thermal imaging cameras, drones with audio sensing equipment, sniffer dogs and military remote-controlled vehicles are already being used in the search with heavy engineering cranes and lifting equipment arriving today (25 Feb).
The demolition of the decommissioned Didcot A power plant was being carried out by Coleman and Company.
Oxfordshire's coal-fired Didcot A Power Station was turned off in 2013, after 43 years in service. The station included six cooling towers, measuring 375ft (114m) in height, which dominated the skyline of the town.