A mid-sized startup working to develop nuclear microreactors filed for bankruptcy Tuesday, raising more questions about the future of advanced nuclear power.

Ultra Safe Nuclear (USNC), based in Oak Ridge, Tennessee, filed for Chapter 11 bankruptcy in the U.S. District of Delaware, leaving its more than 1,000 creditors including Hyundai, the University of Illinois, the government Canadian, the Massachusetts Institute of Technology, Siemens and Oracle in limbo to recover its investments.

“After carefully considering all available options, we decided that this court-supervised sale process provided the best path forward while ensuring continuity of our key technology initiatives,” said Kirk Edwards, Chairman of the Board of Trustees. administration of the USNC. said in a press release.

The filling is part of a back-and-forth series of good and bad news for advanced nuclear technology.