ML042090204
| ML042090204 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 03/06/2003 |
| From: | David Pelton Division Reactor Projects I |
| To: | Jenison K Office of Nuclear Reactor Regulation |
| References | |
| FOIA/PA-2004-0267 | |
| Download: ML042090204 (3) | |
Text
David From:
- PeltRR, David Sent:
Th rsday, March 06, 2003 2:26 PM To:
'kfnj~nrc.gov'
Subject:
FW:
Original Message-----
Trom: Underkoffler, Ted Sent: Thursday, March 06, 2003 13:52 To: Pelton, David
Subject:
Technical Position V23-3&4.doc...
1
Position Paper Concerning The As-Found LLRT of V23-3 & V23-4 Ref:
PP 7006, Primary Containment Leak Rate Testing Program (PCLRTP)
ER 2001-0901 History:
Prior to or during RFO-23, V23-3 and V23-4 (HPCI Turbine Exhaust Check Valves) are required to be As-Found Local Leak Rate Tested (LLRT) to fulfill a required action of ER 2001-0901, V23-3 and V23-4 local leak rate test results exceeded acceptance criteria. The event report (Levell) resulted in a Licensee Event Report (LER 01-02). The event report's FOLLOW-UP VERIFICATION requires testing of these valves at the next refueling outage (RFO 23).
When the event report root cause analysis was being conducted, the existing valves were being refurbished and upgraded. Some parts had been determined to be insufficient for the application. The expectation was that the upgrade plus some TLC (tender-loving-care) during the transport of the valves would restore the valves to an acceptance performance level.
Bench testing validated the refurbishment and upgrade restored acceptable seat leakage characteristics.
Following the upgrade, an additional problem was encountered during the post maintenance testing.
The vertically mounted valve failed the As-Left LLRT. This problem was resolved by a reduction in the bolting torque applied on the inlet flange of the outboard check valve. Empirical testing demonstrated that a reduction in applied torque reduced the seat leakage rate and conversely an increase in the applied torque increased the seat leakage rate.
The valve was accepted by the PCLRTP Coordinator since the problem was reproducible and correctable, being predicated on the applied torque to the inlet flange bolting. The acceptance logic was that the valve body or seat base was being distorted/twisted by the increase in applied torque, and that the reduction permitted the valve body or seat base to return to a less distorted/twisted condition.
Once the valve body becomes static, the obturator seating condition should not change except for seat deterioration. The PCLRTP monitors seat leakage (i.e., deterioration).
During RFO 23, V23-3 and V23-4 are being replaced (a modification) with an updated design due to the susceptibility for valve body (seat base) to distortion/twisting. The need for replacement of the existing valves was developed after the event reports were reviewed and approved by PORC and the Vice President of Operations. The development of the replacement modification did not require nor address the testing required by the event report. Presently, VY has no process that drives a re-assessment, the amendment, nor re-presentation of an event report to eliminate or modify pre-determined corrective actions (e.g., the As-Found LLRT requirement).
Discussion:
Primary Containment Isolation Valves V23-3 and V23-4 are local leak rate tested each refueling outage to support the Inservice Testing Program for obturator movement requirements of ASME/ANSI OMa-1988, Part 10, 4.3.2.4(a).
As such, these valves are characterized in the program as Prescriptive (based) Assets. Prescriptive Assets are not required to be As-Found tested prior to maintenance or modification.
Only Performance (based) Assets are required to be As-Found tested.
Satisfactory As-Found testing maintains the basis for the extension testing frequency. There is no technical or
regulatory requirement to As-Found test V23-3 and V23-4 other than those commitments identified in the ER and LER.
Minimal benefits can be derived from'the As-Found testing of the existing valves since:
> Valves are being replaced with an essentially different style valve
> Valves are being discarded
> No autopsy is presently planned
> The testing requires outage time and resources The only benefit that can be envisioned is the validation of Cycle 22 valve operability. However, valve operability is determined as a prerequisite to the mode switch change for start-up. No additional conditions existed prior to start-up from RFO 22, during the operating cycle, or prior to start-up from the MCO that would have compromised V23-3 and/or V23-4 from fulfilling the containment integrity function as tested and accepted during RFO 22.
Recommendation:
The As-Found LLRT and subordinate commitments be deleted from ER 2001-0901.