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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, D.C. 20555 April 5, 1989 INFORMATION NOTICE NO. 89-38: ATMOSPHERIC DUMP VALVE FAILURES AT PALO VERDE UNITS 1, 2, AND 3 Addressees: All holders of operating licenses or construction permits for nuclear power reactors. Purpose: This information notice is being provided to alert addressees to potential failures of main steamline atmospheric dump valves (ADVs). It is expected that recipients will review the information for applicability to their facil- ities and consider actions, as appropriate, to avoid similar problems. However, suggestions contained in this information notice do not constitute NRC require-ments; therefore, no specific action or written response is required. Description of Circumstances: On March 3, 1989, Palo Verde Unit 3 experienced a large load rejection and a subsequent automatic reactor power decrease from 98 percent to 45 percent power. The turbine bypass valves opened but the bypass valve controller malfunctioned, causing excessive steam relief and overcooling of the reactor coolant system (RCS). A main steamline isolation and reactor trip were caused by low pressure in the number 2 steam generator. Safety injection and containment isolation activated upon low RCS pressure. Following steamline isolation, the ADVs remained closed after operators attempted to open them first from the control room and then from the remote shutdown panel. The valves do not receive an automatic signal to open. After the ADVs failed to open remotely, auxiliary operators experienced difficulty in opening the ADVs using the handwheels because of the lack of lighting (including emergency lighting), poor labeling of ADV equipment, poor procedures and training, a disengaged handwheel, and considerable noise caused by the opening of the main steamline safety relief valves. The operators partially opened two ADVs. The pneumatic operators on the ADVs are actuated by using either plant instru- ment air or a stored, pressurized nitrogen supply. The valves were manufactured by Control Components, Inc. (CCI). CCI indicated that previous problems had been experienced in the testing of ADVs at Palo Verde Unit 1 and other facil-ities. Excessive bonnet pressure caused by abnormally high leakage past the main valve plug piston ring is suspected to have contributed to these problems. Foreign particles from the steamlines in the clearance areas and under the piston ring sealing surfaces may produce the high piston ring leakage. CCI has developed design modifications to address this problem. 8903300021 . IN 89-38 April 5, 1989 Page 2 of 2 Following the failures of the ADVs to open remotely at Palo Verde Unit 3, the licensee tested the ADVs at the other two Palo Verde units. Four of the eight valves failed the functional tests. Preliminary results indicated that there were problems with valve positioners, possible valve stem binding problems, and calibration problems with nitrogen pressure regulators. The licensee for Palo Verde is continuing to investigate the cause of valve failures but has not yet identified a root cause. Contributing to the simultaneous ADV failures at Palo Verde is the lack of in- service testing under hot steam conditions. The valves are routinely tested during refueling outages with the steamlines cold and depressurized. For testing, the pneumatic operators are actuated with plant air rather than with the pressurized nitrogen supply. Licensees may wish to reassess the frequency of ADV testing and to evaluate their ADV surveillance test procedures and consider performing the tests under conditions that better simulate inservice conditions. No specific action or written response is required by this information notice. If you have any questions about this matter, please contact one of the technical contacts listed below or the Regional Administrator of the appropriate regional office. Charles E. Rossi, Director Division of Operational Events Assessment Office of Nuclear Reactor Regulation Technical Contacts: Horace Shaw, NRR (301) 492-0906 Walton Jensen, NRR (301) 492-1190 Attachment: List of Recently Issued NRC Information Notices . Attachment IN 89-38 April 5, 1989 Page 1 of 1 LIST OF RECENTLY ISSUED NRC INFORMATION NOTICES _____________________________________________________________________________ Information Date of Notice No._____Subject_______________________Issuance_______Issued to________ 89-37 Proposed Amendments to 4/4/89 All U.S. NRC 40 CFR Part 61, Air licensees. Emission Standards for Radionuclides 89-36 Excessive Temperatures 4/4/89 All holders of OLs in Emergency Core Cooling or CPs for nuclear System Piping Located power reactors. Outside Containment 88-86, Operating with Multiple 3/31/89 All holders of OLs Supp. 1 Grounds in Direct Current or CPs for nuclear Distribution Systems power reactors. 89-35 Loss and Theft of Un- 3/30/89 All U.S. NRC secured Licensed Material byproduct, source and special nuclear material licensees. 89-34 Disposal of Americium 3/30/89 All holders of an Well-Logging Sources NRC specific license authorizing well- logging activities. 89-33 Potential Failure of 3/23/89 All holders of OLs Westinghouse Steam or CPs for PWRs. Generator Tube Mechanical Plugs 89-32 Surveillance Testing 3/23/89 All holders of OLs of Low-Temperature or CPs for PWRs. Overpressure-Protection Systems 89-31 Swelling and Cracking 3/22/89 All holders of OLs of Hafnium Control Rods or CPs for PWRs with Hafnium control rods. 89-30 High Temperature 3/15/89 All holders of OLs Environments at or CPs for nuclear Nuclear Power Plants power reactors. _____________________________________________________________________________ OL = Operating License CP = Construction Permit ..
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