It was part of the fleet that took part in the investigation of the Ring. The ship was severely damaged after a bomb planted by Clarissa Melpomene Mao under the guise of Melba, detonated inside one of its maintenance corridors.
Its crew dumped their core and evacuated the ship.
In "Delta-V", the UNN Seung Un is a Fleet support Ship sent as part of the Fleet to investigate the Ring. A bomb is placed onboard by Melba, a civilian mechanic working for Savage Industries, a company contracted for repair work by the United Nations Navy.