Information Notice 2004-21, Additional Adverse Effect of Boric Acid Leakage: Potential Impact on Post-Accident Coolant pH
| ML043280614 | |
| Person / Time | |
|---|---|
| Issue date: | 11/24/2004 |
| Revision: | 0 |
| From: | Hiland P L NRC/NRR/DIPM/IROB |
| To: | |
| Hodge, CV, NRR/DIPM/IROB, 415-1861 | |
| References | |
| IN-04-021 | |
| Download: ML043280614 (7) | |
November 24, 2004
NRC INFORMATION NOTICE 2004-21:ADDITIONAL ADVERSE EFFECT OF BORICACID LEAKAGE: POTENTIAL IMPACT ON POST-
ACCIDENT COOLANT pH
ADDRESSEES
All holders of operating licenses or construction permits for pressurized water reactors (PWRs),except those who have ceased operations and have certified that fuel has been permanentlyremoved from the reactor vessel.
PURPOSE
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to informaddressees of potential adverse effects of boric acid leakage that may not have been previously considered and to reemphasize concerns regarding boric acid accumulations on reactor plant equipment inside containmen The primary concern regarding boric acid leakage is corrosion of ferritic steel component However, if boric acid deposits of sufficient magnitude are present in containment, dissolution of these deposits may also affect the pH of the reactor coolant in the containment sum The NRC anticipates that recipients will review the information for applicability to their facilities and consider appropriate action However, suggestions containedin this IN do not constitute NRC requirements; therefore, no specific action or written responseis required.DESCRIPTION OF CIRCUMSTANCES During refueling outages throughout the 1990s, personnel at the Davis-Besse nuclear powerplant performed visual inspections of the reactor pressure vessel (RPV) head surface that was accessible through the service structure weep hole Visual inspections performed below the RPV head insulation found some accumulation of boric acid deposits on the RPV hea The boric acid buildup was due to leaking control rod drive mechanism flanges and reactor coolant pressure boundary leakag Many areas of the RPV head were not visible because of persistent boric acid deposits that the licensee did not clean. In addition to the significantbuildup of boric acid on the reactor pressure vessel head, a substantial amount of boric acid built up inside the containment at Davis-Bess After a loss-of-coolant accident (LOCA) at a pressurized water reactor, chemical agents wouldbe used to ensure that the reactor coolant pH is kept neutral or slightly basi At the Davis-Besse plant, trisodium phosphate (TSP) is use The TSP is kept in designated storage baskets in the containment buildin However, large deposits of boric acid in containment may adversely affect the pH of the reactor coolant in the containment sum DISCUSSION Boric acid deposits can occur inside a pressurized water reactor containment as a result ofreactor coolant system leakag The deposits typically accumulate at any point where moisturecondenses inside containment (e.g., cooling water pipes, ventilation systems, containment linersurfaces). If these deposits are not promptly identified and routinely removed, they couldaccumulate and impact the sump p Therefore, it is important to have procedures and programs to routinely identify and remove boric acid deposits.After a LOCA, the iodine released from the damaged core is removed from the containmentatmosphere by spraying borated water accumulated in the containment sum To keep iodine in solution, the pH of the sump water should be at least Maintaining a pH of 7 or slightly greater is also necessary to minimize chloride stress corrosion cracking in austenitic stainless steel components exposed to the sump wate The amount of TSP depends on how much boric acid from all sources has accumulated in the containmen Failure to control and remove accumulations of boric acid deposits inside containment may challenge whether the reactor coolant in the containment sump is chemically neutral or slightly basic.Boron concentration in the reactor coolant and the impact on containment sump pH arediscussed in NRC Bulletin 77-04, ?Calculational Error Affecting the Design Performance of aSystem for Controlling pH of Containment Sump Following a LOCA," available at ADAMS Accession No. ML031200570 and on the NRC Web site at http://www.nrc.gov/reading-rm/doc-collections/gen-comm/bulletins/1977/bl77004.html.During recent years, the nuclear power industry has become more sensitive to leakage ofborated water from the reactor coolant system or auxiliary system The NRC issued severalgeneric communications to inform the industry of the serious consequences of such leakage and took other actions to ensure that such leakage is addressed if and when it occur Several actions to address boric acid leakage are described in Attachment 1 of Regulatory Issue Summary (RIS) 2003-13, "NRC Review of Responses to Bulletin 2002-01, <Reactor PressureVessel Head Degradation and Reactor Coolant Pressure Boundary Integrity.'" This RIS is available at ADAMS Accession No. ML032100653 and the NRC Web site at http://www.nrc.gov/reading-rm/doc-collections/gen-comm/reg-issues/2003/ri200313.pd
CONTACT
This information notice requires no specific action or written respons If you have anyquestions about the information in this notice, please contact one of the technical contactslisted below or the appropriate project manager from the NRC's Office of Nuclear ReactorRegulation (NRR). /RA/Patrick L. Hiland, Chief Reactor Operations Branch Division of Inspection Program Management Office of Nuclear Reactor RegulationTechnical Contacts:K. Parczewski, NRRC. Vernon Hodge, NRR301-415-2705301-415-1861 E-mail: kip@nrc.gov E-mail: cvh@nrc.gov
Attachment:
List of Recently Issued NRC Information Notices
CONTACT
This information notice requires no specific action or written respons If you have anyquestions about the information in this notice, please contact one of the technical contactslisted below or the appropriate project manager from the NRC's Office of Nuclear ReactorRegulation (NRR). /RA/Patrick L. Hiland, Chief Reactor Operations Branch Division of Inspection Program Management Office of Nuclear Reactor RegulationTechnical Contacts:K. Parczewski, NRRC. Vernon Hodge, NRR301-415-2705301-415-1861 E-mail: kip@nrc.gov E-mail: cvh@nrc.gov
Attachment:
List of Recently Issued NRC Information NoticesDISTRIBUTION:ADAMS IN FileADAMS ACCESSION NUMBER: ML043280614DOCUMENT NAME: G:\DIPM\OES\Staff Folders\Hodge\vern cmt IN TSP3-25.wpdOFFICEOES:IROB:DIPMTECH EDITOREMCBEMCBC:EMCB:DENAMECVHodgePKleeneKIParczewskiALLundWHBatemanDATE11/09/200411/09/200411/09/200411/09/200411/10/2004OFFICERIIILD3:DLPMDLPMA:SC:IROB:DIPMC:IROB:DIPMNAMEJAGrobeJAHopkinsACMcMurtrayTHBoycePLHilandDATE11/02/200411/17/200411/16/200411/23/04 / /2004OFFICIAL RECORD COPY
______________________________________________________________________________________OL = Operating License CP = Construction PermitAttachment LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICES_____________________________________________________________________________________
InformationDate of Notice N SubjectIssuanceIssued to
_____________________________________________________________________________________2004-20Recent Issues Associated withNRC Medical Requirements forLicensed Operators11/24/2004All holders of operating licensesfor nuclear power reactors and research and test reactors, except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor vessel.2004-19Problems Associated withBack-up Power Supplies to Emergency Response Facilities and Equipment11/04/2004All holders of operating licensesfor nuclear power reactors, except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor vessel.2004-18Recent Safety-related Event atPanoramic Wet-source- storage Irradiator10/26/2004All licensees authorized topossess and use sealed sources in panoramic wet-source-storage irradiators, and irradiator vendors.2004-17Loose Part Detection and Computerized Eddy Current Data Analysis in Steam Generators08/25/2004All holders of operating licensesfor pressurized-water reactors (PWRs), except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor.2004-16Tube Leakage Due to aFabrication Flaw in a Replacement Steam Generator08/03/2004All holders of operating licensesfor pressurized-water reactors (PWRs), except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor.Note:NRC generic communications may be received in electronic format shortly after they areissued by subscribing to the NRC listserver as follows:To subscribe send an e-mail to <listproc@nrc.gov >, no subject, and the followingcommand in the message portion:subscribe gc-nrr firstname lastname