NSLS ESH Highlight #45

Human Performance Analysis of Liquid Nitrogen Spill

Date: January 15, 2009
Editors: Lori Stiegler

A review of a recent incident at NSLS, as well as historical events, shows that communication and self checking are crucial to avoiding Human Performance Error Traps.

During commissioning of the X-ray lines last week, a seemingly small change was made in equipment in a hutch, and not communicated to all other workers that may work on that beamline. In a protein crystallography hutch, the inside dewar was disconnected from the fill line for maintenance. In this particular hutch, the inside dewar is not visible from the door. The next day a worker hooked up a full dewar to the fill line outside the hutch and opened the valve. After hearing the familiar sound of the line venting, he left the area. Consequently, about 75 liters of liquid nitrogen spilled inside the hutch before being noticed by others in the area who closed the valve. Fortunately, there was no injury or equipment damage, however some floor cleanup was necessary. This could have been avoided by communicating the changed equipment status either by a tag on the outside line, or verbal or written communication to the other workers.

Another way to avoid this error trap is by using the Human Performance tool 'STAR'. You should always STOP before performing the task step, and focus on attention to detail. THINK before taking any action, and verify the action is correct. It may help to touch or verbalize the intended action. ACT – perform the intended action. And then you should REVIEW to verify that the actual response was the expected response.

NSLS has undertaken Human Performance Improvement training for staff so that we can all be more aware of error traps and error –likely situations. It’s up to us to implement changes in order to help eliminate the errors that can affect our facility.