AM Best assigns B++ to Nuclear Industry Reinsurance Association

AM Best assigned a B++ (Good) financial strength rating and a "bbb+" (Good) long-term issuer credit rating to Nuclear Industry Reinsurance Association, a Luxembourg mutual, with a stable outlook, the agency said Nov. 5.

NIRA's risk-adjusted capitalization is at the strongest level on AM Best's BCAR measure. Available capital more than fully covers two full nuclear limit losses with a liquid, high-quality portfolio. The agency also cites adequate operating performance, a limited business profile and appropriate enterprise risk management. It notes limited financial flexibility to recapitalize after a full limit loss.

For advisors using the rating to size reinsurance counterparty exposure, the constraint is limited flexibility to recapitalize after a full limit loss, not current capital, which covers two such losses.

NIRA's combined ratio reached 439% in 2025 on unfavorable development on two large conventional non-nuclear energy third-party liability claims, against 35% to 66% in the prior four years. Average return on capital and surplus was 2.1% over the five years to 2025. AM Best expects prospective performance to remain adequate but volatile given the risks underwritten.

AM Best rates NIRA's business profile limited: a small mutual reinsurer writing mainly third-party liability and material damage cover for members, plus conventional non-nuclear energy property and liability risks. Strong demand for nuclear insurance capacity and geographic diversification of reinsured assets partially offset that profile and the high-risk nature of the business.