United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 79-24, Overpressurization of Containment of a PWR Plant after a Main Steam Line Break

IN79024 

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                          WASHINGTON, D. C. 20555 
                                     
                            September 23, 1979 

MEMORANDUM FOR:     B. H. Grier, Director, RI 
                    J. P. O'Reilly, Director, RII 
                    J. G. Keppler, Director, RIII 
                    K. V. Seyfrit, Director, Region IV 
                    R. H. Engelken, Director, RV 

FROM:               Norman C. Moseley, Director, Division of Reactor 
                      Operations Inspection, IE 

SUBJECT:            Information Notice No. 79-24, OVERPRESSURIZATION OF 
                    CONTAINMENT OF A PWR PLANT AFTER A MAIN STEAM LINE BREAK

The enclosed information notice should be dispatched October 1, 1979 to all 
power reactor facilities holding operating licenses and to facilities with a 
construction permit. 


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

Enclosures: 
1.   Information Notice No. 79-24 
2.   Draft Transmittal Letter 

CONTACT:  H. A. Wilber, TP 
          49-28180 
.

(Draft letter to all power reactors facilities with operating licenses and 
construction permits.) 

                                           Information Notice No. 79-24 

Gentlemen: 

The enclosed Information Notice provides information with regard to an 
analysis that identifies an event that could result in overpressurization of
containment at a pressurized water reactor. 

                                        Sincerely, 


                                        Signature 
                                        (Regional Director) 

Enclosures: 
1.   Information Notice 79-24 
2.   List of IE Information 
       Notices Issued in the 
       Last Six Months
.

                                                              SSINS:  6870 
                                                              Accession No: 
                                                              7908220123   

                              UNITED STATES  
                       NUCLEAR REGULATORY COMMISSION 
                   OFFICE OF INSPECTION AND ENFORCEMENT 
                         WASHINGTON, D. C. 20555  
                                     
                             October 1, 1979  

                                           Information Notice No. 79-24 

OVERPRESSURIZATION OF CONTAINMENT OF A PWR PLANT AFTER A MAIN STEAM LINE 
BREAK 

Virginia Electric and Power Co. submitted a report dated September 7, 1979 
that identified a deficiency in the original analyses of containment 
pressurization as a result of a steam line break for North Anna Power 
Station, Units 3 and 4. 

Stone and Webster Engineering Corporation performed a reanalyses of 
containment pressure following a main steam line break and determined that, 
if the auxiliary feedwater system continued to supply feedwater at runout 
conditions to the steam generator that had experienced the steam line break,
containment design pressure would be exceeded in approximately 10 minutes. 
The long term blowdown of the water supplied under runout conditions by the 
auxiliary feedwater system had not been considered in the earlier analyses. 
The corrective action is now under review by the owner, architect engineer, 
and NSSS supplier. 

This Information Notice is provided as an early notification of a possibly 
significant matter that is still under review by the NRC staff. 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 NRC evaluations so indicate, further licensee 
actions may be requested or required. 

No written response to this Information Notice is required. If you have any 
questions regarding this matter please contact the Director of the 
appropriate NRC Regional Office. 

Enclosure:
List of Information Notices 
  Issued in the Last Six Months 
.
Page Last Reviewed/Updated Thursday, November 13, 2014