ENS 39714

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v t e ENS Event
11:00 Mar 29, 2003
Title
Event Description	DEGRADED CONDITION DUE TO LEAKAGE AT SMALL BORE INCONEL 600 PENETRATION The following information was received from the licensee via facsimile "The following event description is based on information currently available. If through subsequent reviews of this event, additional information is identified that is pertinent to this event or alters the information being provided at this time, a follow-up notification will be made via the ENS or under the reporting requirements of 10CFR50.73 "On March 29, 2003, at approximately 04:00 Mountain Standard Time (MST) engineering personnel performing preplanned visual examinations of reactor coolant System (RCS) piping in accordance with procedure requirements discovered boric acid residue on three RCS small bore Inconel 600 penetrations. One location was the RCS hot leg in-service thermowell 3JRCBTW0112HB. The visual observation was characterized as a small white trail of boron residue running down the hot leg approximately 2 inches. There were no signs of dripping, spraying, puddles of liquid, or liquid running down the nozzle or hot leg. The residue appeared dry. The other two were on pressurizer heater sleeves (nozzles) A-4 and A-18. The visual observation at these two locations was characterized as a small white buildup of boron residue around the heater sleeve as the sleeve enters the pressurizer bottom head. There does not appear to be residue running down the outside of the sleeves. There were no signs of dripping, spraying, puddles of liquid, or liquid running down the nozzle or [pressurizer]. The residue appeared dry "Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.4.14 permits no reactor coolant system (RCS) pressure boundary leakage and therefore, the discovery of leakage (presumed boric acid residue) from the hot leg thermowell and the pressurizer heater sleeves was a degradation of a principal safety barrier. Therefore, the ENS notification of this event is in accordance with 10CFR50.72(b)(3)(ii). The control room personnel entered LCO 3.4.14 Condition B and are continuing to place the plant in Mode 5. The RCS was being cooled down in preparation for Unit 3's tenth refueling outage. At the time of discovery, the RCS was at approximately 520 degrees F and 2218 psia "An investigation of this event will be conducted in accordance with the PVNGS [Palo Verde Nuclear Generating Station] corrective action program. The cracking of Alloy 600 components both at Palo Verde and industry-wide has been attributed to axially oriented, primary water stress corrosion cracking (PWSCC). PWSCC is not considered a significant threat to the structural integrity of the RCS boundary, thermowell, or heater sleeves as this type of cracking typically results only in small leaks "The bases for this conclusion is that if PWSCC occurred at Palo Verde, the cracks would be predominately axial in orientation. As in this case, the cracks would result in visibly detectable leakage that would be apparent during visual examinations, performed as part of walkdown inspections, before significant damage to the reactor coolant boundary occurred "Palo Verde has a program for replacing the Alloy 600 hot leg thermowells. This thermowell was scheduled for replacement during this refueling outage. The plans to replace the thermowell remain unchanged "A mechanical nozzle sleeve assembly (MNSA) will be installed on each of the pressurizer heater sleeves "No ESF actuations occurred and none were required. There were no structures, systems, or components that were inoperable at the time of discovery that contributed to this condition. There were no failures that rendered a train of a safety system inoperable and no failures of components with multiple functions were involved. The event did not result in the release of radioactivity to the environment and did not adversely affect the safe operation of the plant or health and safety of the public. The licensee has informed the NRC Resident Inspector.

ENS 39714 +/-
Where
Palo Verde Arizona (NRC Region 4)
Reporting

10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded
Time - Person (Reporting Time:+2.68 h0.112 days <br />0.016 weeks <br />0.00367 months <br />)
Opened:	Dan Marks 13:41 Mar 29, 2003
NRC Officer:	Howie Crouch
Last Updated:	Mar 29, 2003
39714 - NRC Website Loading map... {"minzoom":false,"maxzoom":false,"mappingservice":"leaflet","width":"350px","height":"250px","centre":false,"title":"","label":"","icon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"zoom":6,"defzoom":14,"layers":["OpenStreetMap"],"image layers":[],"overlays":[],"resizable":false,"fullscreen":false,"scrollwheelzoom":true,"cluster":false,"clustermaxzoom":20,"clusterzoomonclick":true,"clustermaxradius":80,"clusterspiderfy":true,"geojson":"","clicktarget":"","imageLayers":[],"locations":[{"text":"\u003Cdiv class=\"mw-parser-output\"\u003E\u003Cp\u003E\u003Ca class=\"mw-selflink selflink\"\u003EENS 39714\u003C/a\u003E - \u003Ca href=\"/Palo_Verde\" title=\"Palo Verde\"\u003EPalo Verde\u003C/a\u003E\n\u003C/p\u003E\u003C/div\u003E","title":"ENS 39714 - Palo Verde\n","link":"","lat":33.386894444444444,"lon":-112.86263333333333,"icon":"/w/images/9/93/Arizona_Public_Service_icon.png"}],"imageoverlays":null}
v • d • e

v t e Emergency Notification System
Palo Verde with 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded
WEEKMONTHYEAR2023-10-09T22:07:00 [Table view]
[ENS list for Palo Verde]

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