Projects / prj-ucri-ien
UCRI critical unit for the Brazilian microreactor programme at IEN
Planned critical test reactor at IEN’s Argonauta building in Rio de Janeiro, separate from the existing Argonauta reactor and from a commercial microreactor deployment. IEN is responsible for implementation, commissioning and operation. CNEN reports that IEN sent a letter to ANSN on 2 December 2025 seeking permission to construct the critical unit and conduct tests at Argonauta. The letter itself was not opened; acceptance and authorization are not established. CNEN describes power at the scale of 100 W without an explicit thermal/electrical basis, so no numeric rating is assigned. The 9 December ceremony was a licensing event, not evidence of physical construction. The programme’s commercial design relationship to HARPIA and conflicting 5 MWth/5 MWe descriptions remains unresolved.
What this record says
Last verified 2026-10-13. This is a record review date, not proof of current activity. An announcement records the announcement, not necessarily the physical step it describes.
Site and deployment
UCRI critical unit for the Brazilian microreactor programme at IEN is recorded at IEN Argonauta building, UFRJ campus, Rio de Janeiro, Rio de Janeiro, Brazil. Operator: Instituto de Engenharia Nuclear (IEN/CNEN). Vendor for a linked design: No selected-design vendor is recorded. Stage: Licensing. Location precision: undisclosed. Other documented relationships: Project proposer: Diamante Energia.
Capacity
Electrical output is not recorded on this project. Module count is not recorded. Thermal output is not recorded on this project.
Permission recorded
- Reported IEN request to construct the UCRI critical unit — ANSN; Construction permission sought; Application received; submitted 2 Dec 2025 · actual · day. CNEN reports an IEN letter to ANSN dated 2 December 2025 seeking construction permission and use of Argonauta facilities for the critical experiment. This is a reported submission; the letter, acceptance and a permission decision are not recorded.
- An application under review is not a permit.
Latest supported development
No actual dated development is recorded.
Next documented milestone
No next milestone date is recorded.
Material unknowns
- Electrical output is not recorded.
- Thermal output is not recorded on this project.
- No map pin is shown for this record.
View on map and table · Permissions and applications · Sources and check dates
- Design
- Design profile not linked (Microreactor)
- Technology
- Not recorded on a linked design profile — see the description
- Operator(s)
- Instituto de Engenharia Nuclear (IEN/CNEN)
- Vendor for linked design
- No selected-design vendor recorded
- Other documented relationships
- Project proposer: Diamante Energia · source
- Location
- IEN Argonauta building, UFRJ campus, Rio de Janeiro · Brazil · precision: undisclosed
Named facility; coordinates not recorded. No map pin. - Coordinates
- undisclosed / not plotted
- Electrical capacity
- Not recorded · scope: plant
- Thermal capacity
- Not recorded
- Inclusion basis
- microreactor_labeled
- Confidence
- medium
- Last verified
- 2026-10-13 (publication/verification date)
Milestones & dated events
- No dated milestones recorded yet.
Regulatory actions
Construction applications and decisions
- Reported IEN request to construct the UCRI critical unit
Construction permission sought · Application received · ANSN · submitted 2025-12-02
CNEN reports an IEN letter to ANSN dated 2 December 2025 seeking construction permission and use of Argonauta facilities for the critical experiment. This is a reported submission; the letter, acceptance and a permission decision are not recorded.
Sources: CNEN: reported licensing request for the UCRI critical unit
Selected jurisdiction context
Browse related records by location. A jurisdiction measure does not by itself approve this project, and location alone does not establish eligibility for funding or support.
Sources
- ANSN: Brazilian microreactor critical-unit pre-licensing meeting (regulator_primary, published 9 Oct 2025, accessed 2026-10-13)
- IEN: Brazilian microreactor programme and critical-unit responsibilities (government_primary, published 11 Nov 2025, accessed 2026-10-13)
- CNEN: reported licensing request for the UCRI critical unit (government_primary, published 15 Dec 2025, accessed 2026-10-13)
- Diamante: Brazilian microreactor development project (company_primary, accessed 2026-10-13)