A comparison was made of after-shutdown primary piping radiation levels between Shipping-port PWR first core and second core operation. Due to changes in materials of construction, a higher power core, and other design parameters, it was thought that the radiation buildup would be different during second core operation. It was found that the radiation level due to 58Co was greater during second core than first core due to the use of NiCrFe Alloy 600 steam generator tubing. All the other factors were found to essentially cancel each other.