05000331/LER-2006-002
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No. 05000 | |
| Event date: | |
|---|---|
| Report date: | |
| 3312006002R00 - NRC Website | |
FACILITY NAME (1) DOCKET NUMBER 12) 1 � LER NUMBER (6) PAGE 13)
I. Description of Event:
On March 18, 2005, while operating at 84% power, it was determined that the installed configuration of the Containment Vent Purge Exhaust line did not account for thermal movement of the Drywell. Specifically, theca ct-h—riraliiiirasociAted-Writh the-Containment-Vent-Purge Exhaust-line did-not accountioriheihermaLor pressure related movement of the Drywell in its stress model. The model did not start at the Drywell shell and there were no thermal anchor movements (TAM) or pressure anchor movements (PAM) applied. The failure to account for TAM or PAM did not meet the design requirements for Drywell penetrations. As a result of the identified discrepancy, an immediate operability determination was made that concluded that the penetration was operable based on ASME Section 1.11, Appendix F acceptance criteria. As a result of an extent of condition review into this issue, all Drywell penetrations were reviewed. This review resulted in 14 other Drywell penetrations, for a total of 15, being identified requiring modifications to restore the Drywell penetrations to their original design requirements and 16 Drywell penetrations requiring further analysis. The 15 Drywell penetrations requiring modifications were modified during RFO 19, which concluded on May 3, 2005.
As of the date of this LER, of the 16 Drywell penetrations requiring further analysis, 8 were subsequently identified as requiring modifications. Formal operability determinations for these 8 drywell penetrations have concluded that no current or past operability concerns exist.
Ats of the date of this LER, no past operability concerns with the first 15 Drywell penetrations that were niodified during RFO 19 have been identified. However, as noted below, additional actions are underway to determine if any past operability concerns existed with these 15 Drywell penetrations. As documented in FPL Energy Duane Arnold's letter to the NRC, dated April 3, 2006, these additional actions are being taken based on the conclusion that the original basis for operability was non-conservative due to the fact that they , titilized-AipindEFP OT-SiCtiarill of the–ASICIE–Codel 1 071-Edition/ 1 918 SinnmeiAddenda) for —� determination of past operability. However, we have concluded that past operability reviews of the affected Drywell penetrations need to utilize a newer version of ASME Section III, Appendix F which would require c nsideration of TAM and PAM.
ere was no other inoperable equipment at the start of this event that affected this event.int,
II. Assessment of Safety Consequences:
Since there are no current or past operability issues identified associated with the Drywell penetrations, there are no safety consequences associated with this event. This conclusion could change based on the results of the past operability analysis currently being performed as discussed in the corrective actions section of this LER.
FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3) Duane Arnold Energy Center 05000 331
III. Cause of Event:
Plant design documents did not adequately account for TAM or PAM for mechanical piping systems interfacing with Drywell penetrations. Since the calculations were performed as long ago as 25 or more years; i � iiiiiitFiliibrelirdeterTnifirkieraercause ofthis event. --
IV.Corrective Actions:
As stated above, the first 15 Drywell penetrations that were identified were modified during RFO 19 to restore them to their original design requirements. For the 8 penetrations identified subsequent to RFO 19 that require modifications, a modification plan is currently being developed. These modifications are scheduled to be completed prior to the completion of RFO 20 which is scheduled to commence in February 2007.
To preclude further occurrences similar to what caused this event; Engineering Design Guide DGC-M100 "Stress Analysis and Support Design of Seismic Category I Piping System" was revised to include guidance to account for Drywell shell movement due to thermal and pressure loading at accident conditions.
Additionally, actions are underway to determine if any past operability concerns existed for the 15 drywell penetrations that have already been modified. The past operability evaluations are to be completed by Optober 31, 2006.
V.Additional Information:
Previous Similar Occurrences:
A review of LERs at the DAEC over the last 3 years identified no LERs with similar events.
MIS System and Component Codes:
N/A Reporting Requirements:
This report is being submitted as a voluntary LER.