v3.26.1
REVENUE AND GRANT INCOME RECOGNITION - Additional Information (Details) - USD ($)
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Dec. 31, 2025
Disaggregation of Revenue [Line Items]      
Direct costs $ 65,359,000 $ 28,724,000  
Deferred revenue recognized 0 1,100,000  
Deferred Revenue 18,045,000   $ 15,153,000
Deferred revenue 21,900,000   15,300,000
Deferred revenue 3,835,000   132,000
Unbilled receivables and contract assets 51,159,000   41,529,000
Due From Related Parties (399,000) (8,213,000)  
Deferred Revenue, Noncurrent      
Disaggregation of Revenue [Line Items]      
Deferred Revenue 18,000,000   15,200,000
Accrued Liabilities      
Disaggregation of Revenue [Line Items]      
Deferred revenue 3,900,000   100,000
Unbilled Accounts Receivable and Contract Assets      
Disaggregation of Revenue [Line Items]      
Contract assets 1,000,000   7,500,000
Related Party      
Disaggregation of Revenue [Line Items]      
Direct costs [1] 1,196,000 9,083,000  
Deferred Revenue 2,285,000   2,353,000
Deferred revenue 2,300,000   $ 2,400,000
Advanced Reactor Demonstrator Program ("ARDP")      
Disaggregation of Revenue [Line Items]      
Grant income 3,200,000 1,300,000  
Direct costs $ 2,700,000 $ 1,100,000  
[1] Expenses relating to subcontracting services are reflected within Direct costs in the condensed consolidated statements of operations and comprehensive loss.