Information Notice No. 85-83: Potential Failures of General Electric PK-2 Test Blocks

                                                         SSINS No.:  6835
                                                            IN 85-83 

                               UNITED STATES 
                          WASHINGTON, D.C. 20555  

                              October 30, 1985 

                                   PK-2 TEST BLOCKS 


All nuclear power reactor facilities holding an operating license (OL) or a 
construction permit (CP). 


This information notice is to alert recipients of a potentially significant 
problem involving fractures of PK-2 test block terminal posts that could 
lead to inoperability of essential electrical equipment. It is expected that 
recipients will review this information for applicability to their 
facilities and consider actions, if appropriate, to preclude a similar 
problem occurring at their facilities. However, suggestions contained in 
this information notice do not constitute NRC requirements; therefore, no 
specific action or written response is required. 

Description of Circumstances: 

The Tennessee Valley Authority (TVA) reported to General Electric (GE) and 
the NRC that the Sequoyah Nuclear Power Plant experienced fracture failure 
of terminal posts on some PK-2 test blocks during routine testing of a cir-
cuit that was not safety related. TVA subsequently tested PK-2 blocks at the
Watts Bar Nuclear Plants and found that terminal post fractures could be in-
duced, in some cases, by wiggling by hand. No failures were identified by 
TVA on PK-2 safety-related applications. GE is investigating to determine 
the root cause of the failures. However, because of the broad usage of the 
test blocks, GE has notified the NRC that GE is unable to determine all of 
the possible PK-2 class IE installations and therefore is unable to assure 
specific notification of the problem to each utility. 


Failure of PK-2 test blocks could occur either during testing or at other 
times. Failure during circuitry testing could result in the inoperability of
essential electrical equipment. In this case, the loss of the electrical 
equipment would be detected during the testing. The possibility also exists 
for the fracture failure to occur at the completion of the circuit testing 
or as the result of bumping during other maintenance. Such an occurrence 



                                                          IN 85-83 
                                                          October 30, 1985 
                                                          Page 2 of 2 

result in an open circuit and the unavailability of the associated 
electrical equipment could go undetected in certain applications. Though the 
failures noted by TVA were not safety related, the usage of PK-2 test blocks 
includes safety related equipment such as emergency diesel generator relay 
boards. In addition to the possible loss of safety related equipment there 
is a potential personnel safety concern if an open circuit is developed on a 
current transformer circuit during testing. 

General Electric has recommended that, in addition to visual inspection, a 
force of about five pounds in any direction perpendicular to the terminal 
posts can be applied to detect incipient failures. 

No specific action or written response is required by this information 
notice. If you have any questions about this matter, please contact the 
Regional Administrator of the appropriate regional office or this office. 

                                   Edward L. Jordan,Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  James C. Stewart, IE 
                    (301) 492-9061 

Attachment:  List of Recently Issued IE Information Notices 

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