United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 79-17 - Source Holder Assembly Damage from Misfit Between Assembly and Reactor Upper Grid Plate

IN79017 

                               June 18, 1979 

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:               Norman C. Moseley, Director, ROI:IE 

SUBJECT:            Information Notice No. 79-17 - SOURCE HOLDER ASSEMBLY
                    DAMAGE FROM MISFIT BETWEEN ASSEMBLY AND REACTOR UPPER 
                    GRID PLATE 

The subject Information Notice is transmitted form issuance on June 20, 
1979. The Information Notice should be issued to all holders of Reactor 
Operating Licenses and Construction Permits. Also enclosed is a draft copy 
of the transmittal letter for this purpose. 


                                        Norman C. Moseley, Director 
                                        Division of Reactor Operations 
                                          Inspection 
                                        Office of Inspection and Enforcement

Enclosure:
1.   IE Information Notice
2.   Draft Transmittal Letter

CONTACT:  C. J. DeBevec, IE
          49-28180 
.

(Draft letter to all holders of Reactor Operating Licenses and Construction 
Permits) 

                                            Information Notice No. 79-17 

Addressee: 

This Information notice is provided as an early notification of a possibly 
significant matter. It is expected that recipients will review the 
information for possible applicability to their facilities. No specific 
action or response is requested at this time. If further NRC evaluations so 
indicate, an IE Circular or Bulletin will be issued to recommend or request 
specific licensee actions. If you have questions regarding this matter, 
please contact the Director of the appropriate NRC Regional Office. 

                                        Sincerely, 


                                        Signature 
                                        (Regional Director) 

Enclosure:
IE Information Notice
  No. 79-17
.

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

                                            Information Notice No. 79-17 

SOURCE HOLDER ASSEMBLY DAMAGE FROM MISFIT BETWEEN ASSEMBLY AND REACTOR UPPER
GRID PLATE 

Description of Circumstances: 

Recently, the NRC was informed of a problem at two Westinghouse PWR 
facilities resulting from an apparent misfit between secondary source holder
assemblies and the reactor upper grid plate. 

The misfit problem was first identified by Carolina Power & Light, licensee 
for H. B. Robinson Unit 2, who informed the NRC on May 6, 1979, of the 
circumstances. During the current refueling outage at H. B. Robinson 2, CP&L
determined that two secondary source holder assemblies had been damaged 
during the previous refueling in February 1978, by a misfit between the 
assembly and the reactor upper grid plate. The misfit resulted from 
insufficient clearance (i.e. 1/2 to 3/4 inch) between the source holder 
assembly hub and the grid plate at the core locations containing 
thermocouple mixing vanes. This lack of sufficient clearance caused minor 
deformation of the upper grid plate components at the core location and of 
the source holder assemblies. The deformation also resulted in some bending 
of the fuel rods in the assembly, however, in no case did this bending 
result in fuel cladding perforation. 

On May 16, 1979, the licensee of D. C. Cook Unit 1 informed the NRC that the
present refueling outage would be extended 15 to 20 days to remove the 
reactor head, which had already been reinstalled following completion of 
refueling, to correct this misfit problem. They learned of the problem from 
Westinghouse Subsequently, the licensee's inspection revealed that the 
source holder assembly hubs were in contact with the vanes. The source 
holder was removed from one assembly readily with no apparent damage while 
in the other the source holder was found stuck in the assembly. The problem 
was corrected prior to return to operations. 

The secondary source assembly rods are normally inserted into rod cluster 
control assemblies and placed at symmetrical locations in the core. Each 
such assembly contains a symmetrical grouping of four secondary source rods 
and between zero and twenty burnable poison rods. Locations in the assembly 
not filled with a source or burnable poison rod contain a thimble plug. The 
lack of sufficient clearance for these source holder assemblies apparently 
exists only at the core locations which contain thermocouple mixing vanes. 
.

Information Notice No. 79-17                              June 20, 1979 
                                                             Page 2 of 2  

This Information Notice provides the details of a significant occurrence 
that is still under review by the NRC staff. If further NRC review 
indicates, an IE Circular or Bulletin may be issued to recommend or request 
specific licensee actions. 

No written response is required. If you desire additional information 
regarding this matter, please contact the Director of the appropriate NRC 
Regional Office. 

Enclosure:
List of Information Notices
  Issued in 1979 

Page Last Reviewed/Updated Tuesday, November 12, 2013