Abstract: A method for sealing cracks adjacent stub tube attachment welds in a reactor pressure vessel of a nuclear reactor is described. The reactor pressure vessel includes at least one stub tube through which a control rod housing extends. The control rod housing is attached to one end of the stub tube with an upper stub tube attachment weld. A sidewall of a control rod drive housing is cut at a location below the upper stub tube attachment weld to separate an upper portion of the control rod housing from a lower portion of the control rod housing. The lower portion of the control rod drive housing is removed from the bottom head opening, and a replacement lower portion is positioned in the bottom head opening proximate to the remaining upper portion. The replacement lower portion then is secured to the reactor pressure vessel without securing the replacement lower portion to the remaining upper portion of the control rod drive housing.