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Information Notice No. 83-46: Common-mode Valve Failures Degrade Surry's Recirculation Spray Subsystem
SSINS No.: 6835 IN 83-46 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C., 20555 July 1, 1983 Information Notice No. 83-46: COMMON-MODE VALVE FAILURES DEGRADE SURRY'S RECIRCULATION SPRAY SUBSYSTEM Addressees: All nuclear power reactor facilities holding an operating license (OL) or a construction permit (CP). Purpose: The primary purpose of this notice is to inform licensees and holders of CPs of the apparent common-mode failures that affected the valves which admit service water to the recirculation spray coolers at the Surry Power Station. Seven of eight motor-operated, 30-in. butterfly valves (four on Unit 1 and three on Unit 2) failed to open during surveillance tests of the recirculation spray subsystem. (See Figure 1, "Service Water System" for the valves that failed to open). The recirculation spray subsystem not only cools and depressurizes the containment following a postulated loss-of-coolant accident (LOCA), it also removes heat from water which is injected into the core by the low pressure safety injection system. These failures, therefore, jeopardized the plant's ability to mitigate the effects of a LOCA. (See Figure 2, "Engineered Safeguards Systems" for the interfacing of the recirculation spray subsystem with the emergency core cooling system.) A secondary purpose of this notice is to alert licensees and holders of CPs of the susceptibility to common-mode failures of other components or systems using brackish and/or silty service water. Such service water can cause components to fail by plugging resulting from marine growth or silt deposit, by leaking resulting from corrosion or erosion, or by a combination of these effects. Failures of components using such service water have been experienced at several facilities. For example, Salem has experienced about 75 service water related events since 1980. In addition, the issuance of IE Bulletin 80-24 was precipitated by an Indian Point 2 event in 1980 which flooded the containment building with service water. (See Table 1 for a partial listing of LERs issued since 1980 involving failures or degradation of components attributed to hostile service water systems.) System Description: The recirculation spray subsystem at the Surry Power Station is designed to mitigate the effects of a postulated LOCA during the recirculation phase of the recovery (i.e., after the water in the refueling water storage tank has 8306270401 . IN 83-46 July 11, 1983 Page 2 of 4 been nearly depleted). This is accomplished by returning the containment pressure to a subatmospheric value following a LOCA and by providing for long term heat removal and maintaining the containment at subatmospheric conditions. The extended loss of the recirculation spray subsystem subsequent to a LOCA, therefore, could result in the loss of the ultimate heat sink. Primary coolant water and emergency core cooling water spilled from a postulated LOCA and the water from the containment spray system would collect in the containment sump. While in the recirculation mode, the containment sump water would be diverted to two subsystems: (1) the low head safety injection subsystem, and (2) the recirculation spray subsystem. Water from the low head safety injection subsystem would be returned to the reactor to cool the core. Water from the recirculation spray subsystem would cool and depressurize containment by the heat removal function of the four recirculation spray coolers. The recirculation spray coolers would not only cool the containment spray water but would also cool the water being returned to the reactor. However, before these coolers can cool the containment and remove the decay heat, at least one of the four normally closed valves that admit service water to the coolers must be opened. Description of Circumstances: On February 9, 1983, the Surry Unit 1 recirculation spray subsystem was being tested while the unit was shut down with the reactor coolant temperature and pressure less than 350
F and 450 psig. This test involved the flushing of the four recirculation spray heat exchangers by opening four normally closed motor-operated valves. Opening these 30-in. butterfly valves permits service water to flow through the recirculation spray heat exchangers. However, during this particular test, all four valves failed to open. Because of these failures, the Unit 2 valves that admit service water to the recirculation spray coolers were also tested on February 9, 1983 while Unit 2 was operating at 100% power. Three of the four normally closed motor-operated valves failed to open during this test; however, since opening of only one valve will provide service water to all four coolers, the recirculation spray subsystem was operable. After the four Unit 1 valves failed to open, each was manually opened by using the valve's hand wheel. Significant torque was required to lift the butterfly discs off their seats. The fact that each valve's failure to open resulted in the tripping of its motor overload device indicates that significant torque would be required to open the valves. After the valves had been manually opened, two responded to the electrical signals from the control room and two failed to respond. As a consequence, the licensee was unable to determine the exact causes of the initial failures for those valves that subsequently responded to the electrical signals. The cause of failures of those that did not respond to the electrical signals was listed as corrosion (one bad a corroded motor, the other a corroded torque switch). Although the exact cause or causes for these failures has not been determined, they have been attributed to several factors, or a combination thereof, including: . IN 83-46 July 11, 1983 Page 3 of 4 o Marine growth - barnacles, shells, silt and seagrowth were found on the valve seats and discs; o Corrosion - two valves failed to open because of a corroded motor and another because of a corroded torque switch. The corrosion appears to be due to either the flooding of the valve bit area that occurred several years ago or to the high moisture content in the valve pit area; o Infrequent testing - these valves had been only stroke-tested during refueling outages (i.e., approximately every 18 months); o Low torque switch settings - two Unit 2 valve operators "torqued out" when tested; and o Marginally sized motors and/or improperly geared valve operators. Corrective actions taken by the licensee include: o Cleaning the piping and valve internals; o Applying marine inhibitor paint on the valve discs; o Testing the valves quarterly rather than during refueling outages. (Note: The Unit 1 valves operated properly during subsequent testings, but one Unit 2 valve failed to open during subsequent testing because of a low torque switch setting.); o New motor operators having increased torque output have been engineered and one such operator is being tested at the plant before installing eight such operators. In the interim, the torque switch settings of the installed operators have been increased; and o Administrative controls - responsibility for the proper operation of these valves has been specifically assigned to a knowledgeable person on each shift. This person is responsible for ensuring the proper operation of these valves during accident conditions by going to the valve pit area and manually opening the valves, if so required. In addition, prior to this event but subsequent to the above mentioned flooding of the valve pit area, metal dikes had been constructed, around the valve pits and water level detectors had been installed to prevent or detect flooding of these valves. No written response to this notice is required; however, it is suggested that licensees and holders of construction permits review this information for applicability at their facilities. . IN 83-46 July 11, 1983 Page 4 of 4 If you have any questions regarding this matter, please contact the Regional Administrator of the appropriate NRC Regional Office, or the Technical Contact listed in this notice. Edward L. Jordan Director Division of Emergency Preparedness and Engineering Response Office of Inspection and Enforcement Technical Contact: I. Villalva, IE (301) 492-9365 Attachments: 1. Figure 1, Service Water System 2. Figure 2, Engineered Safeguards Systems 3. Table 1 4. List of Recently Issued Information Notices . Attachment 3 IN 83-46 July 11, 1983 Page 1 of 8 TABLE 1 Abstracted List of LERs Issued Since 1980 Involving Component Failures or Degradation Due to the Effects of Hostile Service Water Systems LER NO. Event Cause 82-149 One service water loop inoperable Grassy debris and silt had at Salem 2 plugged the strainer 82-155 Containment fan coil unit (CFCU) Silt buildup in CFCU inoperable at Salem 2 82-136 CFCU inoperable at Salem 2 Tubing eroded by silt 82-091 Numerous SW piping welds fails at Corrosive environment of Salem 1 the service water system 82-130 CFCU inoperable at Salem 2 Silt in control valves 82-135 CFCU inoperable at Salem 2 Tubing erosion due to silt 82-115 Diesel generator inoperable at Erosion of SW pipe due to Salem 2 silt 82-086 SW pump inoperable at Salem 2 Erosion and corrosion of oil cooler 82-075 CFCU inoperable at Salem 2 SW tubing erosion due to silt 82-074 CFCU inoperable at Salem 2 SW tubing erosion due to silt 82-105 CFCU inoperable at Salem 2 Silt buildup in cooling coils 82-109 CFCU inoperable at Salem 2 Coils eroded by silt 82-119 CFCU inoperable at Salem 2 Erosion of coils by silt 82-120 CFCU inoperable at Salem 2 Erosion of tubing by silt 82-098 CFCU inoperable at Salem 2 Silt buildup in cooling coils 82-099 CFCU inoperable at Salem 2 Silt buildup in cooling coils 82-100 CFCU cooling coil leaks at Salem 2 Erosion of coils by silt 82-096 CFCU inoperable at Salem 2 Silt buildup in cooling coils 82-092 CFCU inoperable at Salem 2 Erosion of motor cooling coils 82-091 CFCU inoperable at Salem 2 Coil erosion 82-073 CFCU inoperable at Salem 2 Erosion of cooling coils by silt 82-074 CFCU inoperable at Salem 2 Erosion of cooling coils by silt . Attachment 3 IN 83-46 July 11, 1983 Page 2 of 8 TABLE 1 (CONTINUED) LER NO. Event Cause 82-061 CFCU inoperable due to erratic SW Silt in sensing line flow indication at Salem 1 82-080 CFCU inoperable at Salem 2 Erosion of copper nickel cooling coils 82-084 CFCU Inoperable at Salem 2 Erosion of copper nickel cooling coils 82-070 CFCU inoperable at Salem 2 Erosion of tubing by silt particles 82-065 CFCU inoperable at Salem 2 Valve actuator failed due to corrosion 82-058 CFCU inoperable at Salem 2 Valve plugged by oysters 82-050 3 CFCU's inoperable at Salem 2 Oysters plugged SW valve 82-037 Service water flow to CFCU Valve stuck in closed position insufficient at Salem 1 82-040 SW piping to CFCU leaks at Salem 2 Eroded blank flange 82-041 Low SW flow to CFCU at Salem 2 Oyster plugging tube bundle 82-046 Low SW flow to CFCU at Salem 2 Oyster plugging tube bundle 82-029 CFCU inoperable due to low service Flow control valve stuck closed water flow at Salem 1 82-038 CFCU inoperable at Salem 2 Flow transmitter plugged with silt 82-028 Update on CFCU leak at Salem 2 Leaky flange 82-024 CFCU inoperable at Salem 1 SW flow control valve stuck closed 81-092 CFCU leaks at Salem 1 Coil failure 81-115 Update on CFCU leakage at Salem 2 Coil leakage 81-114 CFCU (motor cooler) leakage Not stated exceeds limit at Salem 2 81-117 Two CFCU's inoperable due to Defective limit switch and silt position and flow sensor problems in line at Salem 2 81-121 SW leak in containment at Salem 1 Leaky spool piece between 2 valves 81-109 CFCU inoperable at Salem 1 Coil failure 81-108 CFCU inoperable at Salem 1 Coil failure 81-119 Charging pump inoperable at Corrosion causes SW line to Salem 1 leak . Attachment 3 IN 83-46 July 11, 1983 Page 3 of 8 TABLE 1 (CONTINUED) LER NO. Event Cause 81-114 CFCU inoperable at Salem 1 Coil failure 81-115 CFCU inoperable at Salem 2 Coil leak 81-094 CFCU leak rate exceeds limit at Two coil leaks Salem 1 81-110 2 CFU's inoperable at Salem 2 Silt in instrument line 81-096 2 CFCUs leak at Salem 1 Coil leaks 81-103 CFCU inoperable at Salem 2 Transmitter plugged with silt 81-086 CFCU service water flow sensor Transmitter plugged with silt fails twice at Salem 1 81-094 CFCU leaks at Salem 2 Primary coil failure 81-099 Low SW flow to CFCU at Salem 2 Flow sensor clogged with silt 81-084 CFCU leaks at Salem 1 Leaky cooling coil 81-083 ECCS subsystem inoperable at SW leak due erosion and Salem 1 corrosion 81-080 CFCU inoperable at Salem 1 Hole in weld on pipe flange 81-090 CFCU leaks at Salem 2 Primary coil failure 81-076 CFCU leaks at Salem 1 Secondary coil failure 81-077 CFCU leaks at Salem 1 Secondary coil failure 81-074 CFCU leaks at Salem 1 Secondary coil failure 81-078 CFCU leaks at Salem 1 Secondary coil failure 81-064 CFCU leaks twice at Salem 2 Weld failures 81-071 Inadequate SW flow to CFCU at Flow transmitter plugged with Salem 1 silt 81-075 CFCU inoperable at Salem 1 SW transmitter filled with silt 81-072 SW leaks found in CFCU at Salem 1 Cooling coil failure 81-055 CFCU SW flow sensor fails at Transmitter clogged with silt Salem 2 81-064 CFCU pipe welds leak at Salem 1 Cracked weld to dissimilar metals 81-039 CFCU leaks at Salem 1 Crack in weld 81-011 CFCU inoperable at Salem 1 Leak in service water pipe weld . Attachment 3 IN 83-46 July 11, 1983 Page 4 of 8 TABLE 1 (CONTINUED) LER NO. Event Cause 81-010 CFCU inoperable at Salem 1 Leak in service water pipe 81-003 Component cooling system Leaky service water pipe welds inoperable at Salem 1 80-049 Charging pump inoperable at Leak in service water piping Salem 1 82-132 RHRSW loop inoperable at Hatch 2 A pin hole leak developed in the valve body via internal erosion 83-014 SW header leaks at North Anna 2 Aggressive water and bacterial reduction 82-064 Containment spray system Heat exchanger fouling due to inoperable at Oyster Creek inadequate service water chlorination 83-001 Car fan cooler leaks at Conn. Corrosion or Erosion of coils Yankee 83-081 SW header inoperable at North Pinhole leak due to aggressive Anna 1 water 82-065 Service water pump fails to Corroded steel stud develop discharge pressure at Surry 2 82-113 RHRSW pump inoperable at Hatch 2 Corroded discharge valve flapper shaft 82-040 Reactor shutdown due to hich CFCU High liquid waste disposal leakage at indian point 2 system burden 82-073 Service water isolation valve Unknown fails to close at Surry 2 82-000S Reactor shutdown due to high Biofouling of containment spray water system delta P at Oyster heat exchangers Creek 82-037 Two containment fan coolers leak Unknown at Indian Point 2 82-050 Low service water system pressure High SW use and a clogged occurs at Surry 2 strainer 82-062 RHR service water pump fails flow Silt in Suction bell test at Hatch 1 82-031 Service water hoses leak in Corrosion containment at Indian Point 82-054 RHRSW pump fails at Hatch 1 Unknown, (silt mentioned) 82-035 Drain valve broken off SW heat Corrosion exchanger line at Calvert Cliffs 2 . Attachment 3 IN 83-46 July 11, 1983 Page 5 of 8 TABLE 1 (CONTINUED) LER NO. Event Cause 82-014 ESW pump fails to meet discharge Mussels, clam, marine growth in pressure at Millstone 1 pump 82-067 Charging pump SW pump fails to Trash in strainer develop sufficient pressure at Surry 1 80-027 Update on river water check valve Pin erosion due to high flow failure at Beaver Valley 1 81-071 Service water supply header leaks Corrosion twice at North Anna 1 82-046 RHRSW pumps fail at Hatch 1 Debris lodged in pump impellers 82-044 RHRSW pump fails to meet flow Crud in pump requirements at Hatch 2 82-047 RHRSW pump inoperable due to high Leaky gland led to bearing vibration at Brunswick 1 corrosion 82-032 Two RHRSW pumps inoperable at Leaky check valve and eroded Arnold set screw allowed hinge pin to loose and valve to move proper seat 82-019 Service water radiation monitor Crud in suction line pump fails at Surry 2 82-053 Two service water radiation Sediment in suction lines monitor pumps inoperable at Surry 1 82-009 AFWS pump cooler service water Silt accumulation valves fail to open at Zion 2 82-010 SW header leaks at Millstone 2 Corrosion 82-006 SW header leaks at North Anna 1 Corrosion 82-008 Letdown cooler leaks at Crystal Tube to shell leak River 3 82-035 RHRSW pressure transmitter fails Corrosion of module diaphragm at Brunswick 1 81-077 Service water radiation monitor Sediment in pump pump fails at Surry 2 82-008 Three valves inoperable due to Service water leak penetrated water leakage at millstone 1 motor control center 82-002 Containment cooling system Marine fouling at SW pump inoperable at Millstone 1 suction . Attachment 3 IN 83-46 July 11, 1983 Page 6 of 8 TABLE 1 (CONTINUED) LER NO. Event Cause 82-035 LPSI pump inoperable at ANO-2 Corrosion products in SW pipe 81-076 Service water inlet valve fails to Unknown operate at Surry 2 82-027 Containment spray heat exchanger Fresh water clams on ERCW inlet inoperable at Sequoyah 1 screen 82-011 Service water piping leaks at Erosion due to valve throttling Cook 2 82-009 Service water piping leaks at Erosion due to valve throttling Cook 1 82-009 Charging pump inoperable at Foreign object in valve Surry 2 82-005 RHR shutdown cooling and Plugged sensing lines and suppression pool cooling fails maintenance errors when demanded at Brunswick 2 81-074 RHRSW subsystem inoperable due Crud in motor cooler due to to high pump motor temperature corrosion at Brunswick 1 81-083 Service water supply header leaks Corrosion at North Anna 1 81-123 RHRSW pump inoperable at Hatch 1 Crud in motor cooling water line 81-024 Containment pipeway air cooler Corrosion in coils leaks at Big Rock Point 81-062 Three service water radiation Sediment accumulation monitor pumps fail to operate at surry 2 81-021 SW outlet line from fan cooler Pin hole leak in pipe motor cooler leaks at Indian Point 2 81-089 Plant SW pump fails to maintain Debris lodged in pump flow and pressure at Hatch 1 81-053 SW pump rotates backwards at Check valve failed to seat Surry 2 properly 80-030R Update on displaced RHR heat Accumulation or marine growth exchanger baffle at Brunswick 2 shells 81-084 Plant service water stainer Clogged strainer damaged during at Hatch 1 cleaning 81-023 Service water pump discharge line Corrosion leaks at Millstone 2 81-024 2 service water pumps Inoperable Clogged pump suction bells at Oyster Creek . Attachment 3 In 83-46 July 11, 1983 Page 7 of 8 TABLE 1 (CONTINUED) LER NO. Event Cause 81-066 Standby SW system fails to deliver Crud blocking flow into pump rated flow to diesel at Hatch 2 81-063 RHRSW pump fails test at Hatch 2 Crud lodged in pump 81-041 Recirculation spray SW radiation Service water crud on pump internals monitoring pump fails at Surry 2 81-009 CCW heat exchanger and valve flow Barnacle growth blocked at San Onofre 1 81-011 Exterior surface of SW pump Corrosion discharge piping pitted at Indian Point 2 81-096 SW supply header leaks at North Reducing Bacteria Anna 1 & 2 81-017 Containment spray loop inoperable SW loop out due to sea lettuce at Oyster Creek in canal 81-024 Service water supply header Unknown (suspect leak caused by at North Anna 1 and 2 sulfate reducing bacteria within the SW piping) 81-021 Room chiller removed from service Clogged condenser SW strainer at Surry 2 81-017 Diesel generator trips on high Deposit of impurities in cooling water temperature at Ft. service water on valve stem St. Vrain caused valve to stick closed or nearly closed 81-010 Service water pump develops low Eel lodged in impeller discharge pressure at Surry 2 81-007 RHR service strainer plugs up at Sand lodged in mesh Duane Arnold 81-005 Service water pump suction Clogged pump suction strainer pressure low Oyster Creek 81-007 Generator oil cooler leaks at A sacrificial zinc anode had Millstone 2 corroded resulting in service water leakage 81-010 RHRSW system inoperable at Suction valve would not open Brunswick 2 fully 80-037 Charging pump service water Clogged pump inlet strainer and pressure drops and is not alarmed sensing line at Surry 2 80-029 Service water pump develops low Eel in impeller discharge pressure at Surry 2 . Attachment 3 IN 83-46 July 11, 1983 Page 8 of 8 TABLE 1 (CONTINUED) LER NO. Event Cause 80-006 Screen wash pump discharge valve Corrosion and erosion leaks at Humboldt Bay 3 80-018 Charging pump service water pump Material entrained, on suction inoperable at Surry 2 side of pump 80-035 Insufficient SW flow in reactor Asian clam buildup in service buildup cooling coils at ANO-1 water cooler 80-027 RHRSW check valve fails to seat Degradation of valve internals at Vermont Yankee 80-065 SW valve fails to open at Surry 1 Marine growth suspected 80-052 SW heat exchanger inoperable at Tube leak in #2 saltwater/ Calvert Cliffs 2 service water heat exchanger 80-072 Containment building coolers SW Buildup of Asian clams in SW flow inadequate at ANO-2 side of cooler 80-018 HPSW Pump inoperable at Oconne 1 Motor cooler tube leaks due to erosion and corrosion 80-103 Both SW trains inoperable at Strainers were partially Hatch 1 restricted 80-032 SW heat exchanger outlet valve Corroded piston rod fails to open fully at Calvert Cliffs 1 80-022 High pressure SW pump cooler tube Erosion and corrosion leak at Oconne 1 80-004 High pressure SW pump motor Erosion from flow of Lake water cooler leaks at Oconne 1 80-024 RHR service water pump flow drops Debris drawn into pump suction suddenly at Hatch 2 .
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