United States Nuclear Regulatory Commission - Protecting People and the Environment

IE Circular No. 79-25 - Shock Arrestor Strut Assembly Interference



CR79025 

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                          WASHINGTON, D. C. 20555 
                                     
                             December 14, 1979 
                                (Corrected) 

MEMORANDUM FOR:     B. H. Grier, Director, Region I 
                    J. P. O'Reilly, Director, Region II 
                    J. G. Keppler, Director, Region III 
                    K. V. Seyfrit, Director, Region IV 
                    R. H. Engelken, Director, Region V 

FROM:               Harold D. Thornburg, Director, Division of Reactor 
                      Construction Inspection, IE 

SUBJECT:            IE CIRCULAR NO. 79-25 - SHOCK ARRESTOR STRUT ASSEMBLY 
                    INTERFERENCE 

The subject circular should be dispatched for action to all licensees and 
holders of power reactor construction permits no later than December 20, 
1979. The text of the circular and draft letter to licensees are enclosed 
for this purpose. 


                                   Harold D. Thornburg, Director 
                                   Division of Reactor Construction 
                                     Inspection 
                                   Office of Inspection and Enforcement 

Enclosures
1.   Draft transmittal letter
2.   IE Circular No. 79-25

CONTACT:  W. Laudan, IE 
          49-27551 
.

                                                 SSINS: 6830 
                                                  Accession No: 7910250514 

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                   OFFICE OF INSPECTION AND ENFORCEMENT 
                          WASHINGTON, D.C. 20555 
                                     
                             December 20, 1979 

                                                      IE Circular No. 79-25 

SHOCK ARRESTOR STRUT ASSEMBLY INTERFERENCE 

The Bergen Paterson Pipesupport Corporation reported to the NRC a potential 
problem with their mechanical shock arrestor - "Strut Assembly." The Bergen 
Paterson, Part 2540 Strut Assembly, is being used as a rear bracket for 
different sizes of Pacific Scientific Company (PSCO) mechanical shock 
arrestors. Some of these shock arrestor sizes may not function as intended 
due to insufficient clearances. The following problems were identified: 

For PSCO shock arrestors sizes 15 and 50, the Bergen Paterson Part 2540 
strut Assembly does not provide sufficient clearance for the shock arrestor 
to function freely, when installed at an off axis angle greater than 
83. 

For PSCO shock arrestor size 120 there is insufficient clearance throughout 
the 180 installation angle. 

For PSCO shock arrestor sizes 50 and 120 with Bergen Paterson Adaptor Part 
2103 the shock arrestor unit may sustain functional damage when the adaptor 
unit comes in contact with the rear of the snubber, causing distortion of 
the end dust cover. 

PSCO shock arrestors sizes -.35, -.65, 1.5 and 6 do not have this 
interference condition and therefore are not part of the potential problem 
of this circular. 

Bergen Paterson stopped shipment as of October 1979 of all Part 2540-15, 
2540-50, and 2540-120 strut assemblies and is reviewing all applicable 
design detail drawings, to identify all affected items and the facilities to 
which those items have been delivered. 

Licensees and holders of construction permits are advised to proceed with 
the inspection of Pacific Scientific Mechanical Shock Arrestor installations
with Bergen Paterson Part 2540-15, 2540-50 and 2540-120 Strut Assemblies and
determine whether any of the following conditions are applicable: 

1.   The shock arrestor installation orientation presents a possible 
     interference problem. 

2.   Inspection of shock arrestors 50 and 120 with adaptor show damaged or 
     deformed snubber. 

Corrective action should be coordinated with the Strut Assembly supplier 
(Bergen Paterson) and appropriate resolutions promptly implemented. 
.

(Corrected)
(Draft letter to all licensees and holders of construction permits) 

IE Circular No. 79-25 

Gentlemen: 

The enclosed Circular 79-25, is forwarded to you for information. No written
response to this Circular is required. If you require additional information
regarding this subject, please contact this office. 

                                        Sincerely, 


                                        Signature 
                                        (Regional Director) 

Enclosures:
1.   IE Circular No. 79-25
2.   List of IE Circulars
       Recently Issued


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