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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 .
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