The Nuclear Regulatory Commission finished its review of FirstEnergy’s investigation into concrete cracking at the Davis-Besse nuclear plant in Ohio and found the company’s conclusions to be sound.Last fall, crews cutting through the external shield building during a reactor pressure vessel head replacement discovered small cracks in its concrete. FirstEnergy determined they were caused by a 1978 blizzard combined with an absence of weatherproof coating—a conclusion the NRC announced it had accepted Thursday.“Our inspectors conducted a thorough and independent review of FENOC’s root cause determination to make sure that the reasons for the internal cracks in the shield building are well understood. We evaluated the effectiveness of the company’s proposed actions to ensure the continued safety of the shield building going forward,” NRC Region III Administrator Charles Casto said in a release.Corrective actions at the plant will include additional testing of the shield building, application of a moisture protection coating and plans to restore the plant’s design and licensing basis, according to the NRC.The Cleveland Plain Dealer reported the plant will be required to apply the coating this summer, and that it faces a December deadline to provide data proving the building can still resist an external impact of 4,000 pounds per square inch.