Direct proof of use
The Vulcain-class record in the 1990 Gulf War rests on Pluton, the class member attached to French mine-warfare forces during the Kuwaiti-coast clearance effort. Dominique Guillemin's naval history of the French Navy in the Gulf War identifies the force as a French, Belgian, and Dutch mine-countermeasures group and names Pluton as the French bâtiment-base de plongeurs-démineurs reinforcement alongside the minehunter Orion and the 3rd clearance-diver group.
A first-person account published by Gulf University for Science and Technology places Pluton with the French support ship Loire at Kuwait City on February 24, 1991, and describes French mine-warfare units as taking part in mine-clearance operations off the Kuwaiti coast. The same account describes the force as composed of French, Belgian, and Dutch minehunters, one mine-clearance support ship, and two logistics support ships.
Sources: La marine nationale et la guerre du Golfe, French Naval Campaign off the Kuwaiti Coasts
Campaign timeline
The French naval mine-clearance role followed Iraq's maritime mine threat and Kuwait's liberation. The GUST account says French minehunters and support ships took part in mine-clearance operations off Kuwait from January 30, 1991; it then dates Loire's call at Kuwait City with Pluton to February 24, 1991.
Guillemin's article places the larger Southern Breeze mine-countermeasures operation after the February 28 ceasefire. It says Kuwait requested assistance neutralizing minefields laid by Iraqi forces, that coalition forces found six minefields and four mine lines off the coast, and that the French-Belgian-Dutch force destroyed 530 of 1,240 neutralized mines before the operation ended on July 16, 1991.
Sources: La marine nationale et la guerre du Golfe, French Naval Campaign off the Kuwaiti Coasts
Mine-countermeasures role
Pluton's role was support for clearance divers rather than minehunting by ship-mounted sonar. The French Navy describes its groupe de plongeurs-démineurs mission set around mine warfare, port security, maritime-approach security, and explosive-ordnance neutralization, with Vulcain-class BBPD ships listed as support vessels for those diver groups.
In the Gulf War context, that placed Pluton in a force-protection and maritime-access mission after Iraqi forces had mined the Kuwaiti approaches. The sources support Pluton's presence and support role in the French mine-warfare force; they do not identify a specific mine disposal by Pluton alone.
Sources: La marine nationale et la guerre du Golfe, French Naval Campaign off the Kuwaiti Coasts, Groupe de plongeurs-demineurs