ENS 45764
ENS Event | |
|---|---|
02:43 Mar 13, 2010 | |
| Title | Control Rod Drive Mechanism Nozzle Indications |
| Event Description | On March 12, 2010, during the Davis-Besse Nuclear Power Station Unit No. 1 (DBNPS) refueling outage, the documented results of planned ultrasonic (UT) examinations performed on the Control Rod Drive Mechanism (CRDM) nozzles penetrating the reactor vessel closure head (RVCH) identified that two of the nozzles inspected to date did not meet the applicable acceptance criteria. Each of these two nozzles have similar indications that appear to penetrate into the nozzle walls from a lack of fusion point at the outer diameter of the nozzle and the J-Groove weld. Leak path detection was performed on both nozzles with the results showing no leak path. Bare metal visual examinations are scheduled to be performed on all nozzles to determine if there is any pressure boundary leakage. Both indications will require repair prior to returning the vessel head to service. There are sixty-nine nozzles and all will be subject to these UT inspections.
It is important to note that this notification is being provided prior to the completion of all of the required UT and VT [Visual Tests] examinations for these two nozzles and the remaining nozzles. The indications were detected with a blade probe used to detect axially-oriented indications. The remaining probe that is used to complete the UT examination in each of these two penetrations is a blade probe that is used to identify circumferentially-oriented indications. The examinations are being performed to meet the requirements of 10CFR50.55a(g)(6)(ii)(D) and ASME Code Case N-729-1, to identify potential flaws/indications well before they grow to a size that could potentially affect the structural integrity of the reactor vessel head pressure boundary. The licensee notified the NRC Resident Inspector and will notify the State of Ohio and both Lucas and Ottawa Counties.
On March 13, 2010, additional Control Rod Drive Mechanism nozzles (4 and 59) were identified that did not meet the applicable acceptance criteria. The indications on these nozzles are similar in nature and location to the indications previously reported for nozzles 28 and 33. These indications will also require repair prior to returning the vessel head to service. Like the two previously reported nozzles, this notification is being provided prior to the completion of all of the required examinations for the nozzle and the remaining nozzles. The indications were detected with a blade probe used to detect axially-oriented indications. The remaining probe that will be used to complete the examination in this penetration is a probe sensitive to circumferentially-oriented indications. Additionally, during the bare metal visual examination of the outer surface of the reactor vessel closure head, boric acid deposits were found at CRDM nozzles 4 and 33 that are indicative of primary water leakage. The visual examination of the RVCH is continuing. The licensee notified the NRC Resident Inspector, State of Ohio, and local government. Notified the R3DO (Phillips).
Update to Davis-Besse event #45764 initially reported 3/13/2010 at 0445 and adding an additional 10 CFR 50.72 reporting criteria. On March 15, 2010, the FirstEnergy Nuclear Operating Company is issuing a press release regarding the Davis-Besse Nuclear Power Station Unit No. 1 reactor vessel head (RVCH) Control Rod Drive Mechanism nozzles that have indications that do not meet the applicable acceptance regulatory criteria. The results of the ongoing planned ultrasonic (UT) examinations performed on these nozzles penetrating the RVCH have identified indications that will require repair prior to returning the vessel head to service. Currently, there are twelve nozzles which will be repaired, two of which have evidence of primary water leakage found during the bare metal visual examination of the outer surface of the reactor vessel closure head. There are sixty-nine nozzles and all are subject to these UT inspections. It is important to note that this media release is being provided prior to the completion of all of the required examinations for these and the remaining nozzles. The licensee notified the NRC Resident Inspector and will be notifying the State of Ohio and both Lucas and Ottawa Counties. Notified R3DO (Monte Phillips) |
| Where | |
|---|---|
Davis Besse  Ohio (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | |
| Time - Person (Reporting Time:+2.03 h0.0846 days <br />0.0121 weeks <br />0.00278 months <br />) | |
| Opened: | Larry Myers 04:45 Mar 13, 2010 |
| NRC Officer: | Vince Klco |
| Last Updated: | Mar 15, 2010 |
| 45764 - NRC Website | |
Davis Besse with 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | |
WEEKMONTHYEARENS 564132023-03-15T13:50:00015 March 2023 13:50:00
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