United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 81-23: Fuel Assembly Damaged Due to Improper Positioning of Handling Equipment

                                                            SSINS No.: 6835 
                                                            Accession No.: 
                                                            8103300403     
                                                            IN 81-23       


                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                           WASHINGTON, D.C. 20555
                                     
                               August 4, 1981

Information Notice No. 81-23:   FUEL ASSEMBLY DAMAGED DUE TO IMPROPER 
                                   POSITIONING OF HANDLING EQUIPMENT 

Description of Circumstances: 

On June 19, 1981, a spent fuel assembly at the D. C. Cook Unit 1 facility 
was damaged while being transferred in the refueling cavity when the lower 
end of the assembly struck a ledge outside of the reactor vessel. During 
lifting of the fuel assembly from the core, the two air lines and the 
electric cable serving the gripper tangled and caught the gripper-tube-up 
position switch, closing it before the gripper tube and attached fuel 
assembly were in the full-up position inside the canister. Closing the 
switch cleared the interlock and allowed lateral movement of the manipulator 
crane. The lower end of the fuel assembly protruded below the canister and 
it struck the ledge on the refueling cavity floor just outside the reactor 
vessel area. Several rods in the fuel assembly were damaged, and one rod was 
dislodged and fell from the assembly onto the refueling cavity floor. No 
release occurred as a result of the damaged rods, even though the dislodged 
rod was severely bent. However, considerable time was lost due to efforts to 
recover the dislodged rod and to move the damaged fuel assembly out of the 
refueling cavity. Discussions with refueling personnel indicate that 
tangling of the air lines and electric cable is not an uncommon occurrence. 
For example, manipulator crane operators frequently must shake the gripper 
tube lines and cables to obtain a signal that the gripper has correctly 
engaged the fuel assembly. 

Stearns Roger, manufacturer of the manipulator crane, has previously 
proposed modifications to improve the cranes, especially the earlier models. 
One of these modifications was the addition of the Z-axis tape that provides
positive indication of the vertical position of the gripper tube assembly 
(and thus the fuel assembly). The D. C. Cook manipulator cranes have the 
Z-axis tapes, but the operator(s) involved in the subject event apparently 
did not check the tape to verify the position of the assembly before 
initiating lateral movement. 

The licensee has revised the fuel handling procedure to require the 
manipulator crane operators to check the Z-axis tape in addition to the 
limit lights to verify the fuel assembly is in the full-up position before 
the crane is moved. (It has always been required by D. C. Cook procedures to 
utilize the tape to verify that the fuel assembly is in the full-down 
position before the gripper is disengaged.) 

A related event involving improper vertical positioning of the gripper tube 
assembly occurred at the Point Beach Unit 2 facility during the April-May 
1981 refueling outage. The gripper fingers were extended in the latch 
position underneath the leaf spring of the fuel assembly rather than under 
the top plate of the top nozzle. Again, the problem could have been avoided 
by checking the Z-axis tape. 
.

                                                             IN 81-23      
                                                             August 4, 1981 
                                                             Page 2 of 2   

All licensees and construction permit holders, particularly those with 
similar manipulator cranes, may wish to make equipment modifications to 
reduce the potential for this type of event. In addition, operating 
procedures should be reviewed to assure that all available indications are 
fully utilized (i.e., the Z-axis tapes, visual observation of the air lines 
and electrical cables, underwater visual observation using binoculars of 
movement of the fuel assemblies) to prevent this type of occurrence. 

This Information Notice is provided as a notification of a possible generic 
problem. It is expected that recipients will review the information for 
possible applicability to their facility. It is also expected that copies of
this Information Notice will be provided to personnel involved in fuel 
handling operations. No special action or response is requested at this 
time. If you have any questions regarding this matter, please contact the 
director of the appropriate NRC Regional Office. 

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