United States Nuclear Regulatory Commission - Protecting People and the Environment

Resolution of Generic Safety Issues: Issue 104: Reduction of Boron Dilution Requirements ( NUREG-0933, Main Report with Supplements 1–34 )


In the prioritization of Issue 22, "Inadvertent Boron Dilution," it was found that inadvertent boron dilution events during cold shutdown operation do not constitute a significant risk to the public. Further work by DSI confirmed this assertion and the issue was deemed to be resolved without additional requirements. Based upon these findings, it was recommended that SRP11 Section 15.4.6 be considered for deregulation.694

As was verified by the studies associated with the resolution of Issue 22, the public risk from inadvertent boron dilution events during cold shutdown operations under current requirements is insignificant. As a result, some of the conservatism included in SRP11 Section 15.4.6 may be unduly excessive. Studies may be justified to investigate the results of deregulation and its effect upon public risk. In such studies, consideration must also be given to the potential for worker injury, should an inadvertent criticality event occur during work on the refueling deck with the reactor vessel head removed.


To prevent an increase in the likelihood of an inadvertent criticality due to a boron dilution event which is considered an unacceptable state under any circumstances, even at minimal public risk, this issue was a DROPPED from further consideration.

Page Last Reviewed/Updated Thursday, March 29, 2012