Terra Innovatum has submitted all 18 chapters of the Preliminary Safety Analysis Report (PSAR) for its SOLO microreactor to the US Nuclear Regulatory Commission. The company announced the milestone on November 4, 2026, opening the readiness review phase that precedes the formal construction permit application.
Progress has been swift. In mid-October the company, listed on Nasdaq under the ticker NKLR, had shared 12 of the 18 chapters, a figure that rose to 14 in the following update. On October 19 came the last documented batch before completion, with the stated goal of finishing the submission by the end of the month. The readiness review assesses the completeness and quality of the materials before the official filing of the Construction Permit Application (CPA).
The NRC describes this phase as a voluntary opportunity to identify information gaps and technical or policy issues before an application is submitted. It does not amount to acceptance of the application or authorization to build. The next milestone in the review is expected by the end of November 2026, depending on the agency’s schedule. The complete CPA, including the PSAR, will be filed at the end of the process.
The PSAR is the document that describes the reactor design and the safety analysis supporting the license. Submitting it in full and ahead of the formal application allows the NRC to raise comments before the application is formalized. According to Cesare Frepoli, co-founder and head of licensing activities, engagement with the regulator is proceeding through regular technical interactions, with the aim of a thorough and efficient review.
On the industrial side, Terra Innovatum is advancing engineering, component procurement and production preparation in parallel. The company says it has sufficient funds to cover all remaining activities through deployment of the first-of-a-kind reactor, scheduled for 2027. CEO Alessandro Petruzzi described a supply chain under construction as production and installation are prepared. The co-founder is Italian, and the SOLO project has its roots in Italy’s nuclear research, a detail of particular interest to Italian readers.
If the readiness review concludes without obstacles, the formal permit application could be filed in the first months of 2027. From that point the NRC will begin its substantive review, and the timeline for the first SOLO unit will depend on the agency’s pace. For microreactors it is a test case: demonstrating that the move from design to construction site can happen on timescales compatible with the needs of those seeking low-emission energy for remote and industrial sites.
