ENS 41783
ENS Event | |
|---|---|
18:00 Jun 17, 2005 | |
| Title | Potential Degraded Condition Due to Pressurizer Heater Element Non-Conformance |
| Event Description | 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 June 15, 2005, Palo Verde Nuclear Generating Station was informed by Framatome that Thermocoax pressurizer heater elements provided for, and installed in Unit 3, were in non-conformance with specifications. Specifically, the active heating portion of the element was approximately 8 inches lower than design. The result of this error is that the active (heating) portion of the element extended into the nozzle area of the pressurizer heater sleeve and the heating effect on the pressurizer sleeve exceeded design, and possibly code-allowable temperature. Unit 3 operators entered Technical Requirements Manual LCO 3.4.103, Structural Integrity, Condition A for a ASME Code Class 1 component not conforming with requirements. The pressurizer can not be isolated and RCS temperature was already more than 50 degrees F above the minimum temperature required by NDT consideration when the condition was discovered. TLCO 3.0.100.3 is not applicable in Mode 5 and Technical Specification 3.4.9, Pressurizer, is not applicable in Mode 5. The RCS is in Mode 5 at approximately 190 degrees F and 350 psia. Engineering personnel are evaluating the code acceptability and potential for significant degradation resulting from the temperatures experienced by the pressurizer heater sleeves. On June 17, 2005, at approximately 11:00 AM MST, Palo Verde was informed that based on x-ray results of a PVNGS failed Thermocoax heater that revealed the active portion of the heater is longer than previously assumed, the metal temperatures exceeded ASME code allowable values. Stress levels are still under evaluation. This report is conservatively being placed per 10CFR50.72(b)(3)(ii)(A) based on the potential that the RCS pressure boundary may be seriously degraded, and 10CFR21(d)(3)(i) based on a defect in the pressurizer heater, a basic component, that may affect its safety function necessary to assure the integrity of the reactor coolant pressure boundary. An investigation of this condition will be conducted in accordance with the PVNGS corrective action program. The Thermocoax heater elements were installed in November 2004, when all heaters in the Unit 3 pressurizer were replaced. Due to the increased failure rate all Thermocoax heater elements have been replaced in the last 30 days with General Electric style pressurizer heater elements that were used previously. The heaters, which were also provided to SONGS 2&3 and Waterford 3, had a design variance (480 VAC single phase instead of 480 VAC 3-phase) which made them unique to Palo Verde. The impact of this variance is currently being evaluated. The licensee notified the NRC Resident Inspector.
The licensee is retracting this event based on the following: This is a retraction of ENS 41783, placed with the Headquarter Operations Center on 06/17/2005 at 1839 EDT. On June 15, 2005, Palo Verde Nuclear Generating Station was informed by Framatome that the Thermocoax pressurizer heaters provided for, and installed in Unit 3, were in non-conformance with the applicable design specification. Specifically, the heating section of the heater was manufactured approximately 8 inches longer than cited in the specification. The result of this error was that the heating section extended into the pressurizer lower head. Engineering analysis concluded that the pressurizer lower head exceeded design and ASME Code allowable temperatures. This condition was reported on June 17, 2005 (ENS 41783). Further Engineering analysis concluded that the RCS pressure boundary (pressurizer lower head) was not significantly degraded. APS has requested NRC approval for a relief request (reference letter to the NRC dated June 19, 2005). The proposed alternative discussed in this relief request provided an acceptable level of quality and safety since no significant creep effects were introduced into the Unit 3 pressurizer lower head as a result of the design non-conformance. Therefore, APS has requested that the proposed alternative be authorized pursuant to 10 CFR 50.55a(a)(3)(i). The NRC provided verbal approval for Unit 3 to continue operation. Based on the above information the "Degraded Operation" ENS notification made on June 17, is being retracted. The heater supplier, FRAMATOME ANP, INC, reported the defect in accordance with10CFR Part 21 on July 22, 2005 (ENS 41864). The licensee has retracted both the 10CFR Part 50.72(b)(3)(ii)(A) degraded condition notification and their 10 CFR Part 21 notification. Retraction of the 10 CFR Part 21 notification is based on the fact that the vendor reported the same condition. The licensee notified the NRC Resident Inspector of the retraction. Notified R4DO (D. Powers). |
| Where | |
|---|---|
Palo Verde  Arizona (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded 10 CFR 21.21 | |
| Time - Person (Reporting Time:+0.65 h0.0271 days <br />0.00387 weeks <br />8.9037e-4 months <br />) | |
| Opened: | Dan Marks 18:39 Jun 17, 2005 |
| NRC Officer: | Jeff Rotton |
| Last Updated: | Aug 1, 2005 |
| 41783 - NRC Website | |
Unit 3 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Cold Shutdown (0 %) |
| After | Cold Shutdown (0 %) |
Palo Verde with 10 CFR 21.21, Notification of failure to comply or existence of a defect and its evaluation, 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | |
WEEKMONTHYEARENS 567852023-10-09T22:07:0009 October 2023 22:07:00
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