ML060950250
| ML060950250 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee  |
| Issue date: | 03/22/2006 |
| From: | Morgan M NRC/NRR/ADRO/DLR/RLRC |
| To: | Office of Nuclear Reactor Regulation |
| morgan M NRR/NRC/DLR/RLRC, 415-2232 | |
| Shared Package | |
| ML060950189 | List:
|
| References | |
| %dam200611, TAC MC9668 | |
| Download: ML060950250 (9) | |
Text
AUDIT WORKSHEET GALL REPORT AMP PLANT: ______________________________
LRA AMP: __________________________ REVIEWER: ______________________
GALL AMP: XI.E3, Inaccessible Medium-Voltage Cables Not Subject to 10 DATE: __________________________
CFR 50.49 Environmental Qualification Requirements Program Auditable GALL Criteria Documentation of Audit Finding Element Program A. Most electrical cables in nuclear power plants are located in Consistent with GALL AMP: Yes No Description dry environments. However, some cables may be exposed to Document(s) used to confirm Criteria:
condensation and wetting in inaccessible locations, such as conduits, cable trenches, cable troughs, duct banks, underground vaults or direct buried installations. When an energized medium-voltage cable (2KV to 35 KV) is exposed to Comment:
wet conditions for which it is not designed, water treeing or a decrease in the dielectric strength of the conductor insulation can occur. This can potentially lead to electrical failure.
B. The purpose of the aging management program described Consistent with GALL AMP: Yes No herein is to provide reasonable assurance that the intended Document(s) used to confirm Criteria:
functions of inaccessible medium-voltage cables that are not subject to the environmental qualification requirements of 10 CFR 50.49 and are exposed to adverse localized environments caused by moisture while energized will be Comment:
maintained consistent with the current licensing basis through the period of extended operation. An adverse localized environment is a condition in a limited plant area that is significantly more severe than the specified service environment for the cable. An adverse variation in environment is significant if it could appreciably increase the rate of aging of a component or have an immediate adverse effect on operability. This program considers the technical information and guidance provided in XI.E3 Inaccessible Medium-Voltage Cables Not Subject To 10 CFR 50.49 EQ Requirements 1
Program Auditable GALL Criteria Documentation of Audit Finding Element NUREG/CR-5643, IEEE Std. P1205, SAND96-0344, and EPRI TR-109619.
C. In this aging management program periodic actions are taken Consistent with GALL AMP: Yes No to prevent cables from being exposed to significant moisture, Document(s) used to confirm Criteria:
such as inspecting for water collection in cable manholes, and draining water, as needed. The above actions are not sufficient to assure that water is not trapped elsewhere in the raceways.
For example, if duct bank conduit has low points in the routing, Comment:
there could be potential for long-term submergence at these low points. In addition, concrete raceways may crack due to soil settling over a long period of time and manhole covers may not be watertight. Additionally, in certain areas, the water table is high in seasonal cycles and therefore, the raceways may get refilled soon after purging. Furthermore, potential uncertainties exist with water trees even when duct banks are sloped with the intention to minimize water accumulation. Experience has shown that insulation degradation may occur if the cables are exposed to 100 percent relative humidity. The above periodic actions are necessary to minimize the potential for insulation degradation. In addition to above periodic actions, in-scope, medium-voltage cables exposed to significant moisture and significant voltage are tested to provide an indication of the condition of the conductor insulation. The specific type of test performed will be determined prior to the initial test, and is to be a proven test for detecting deterioration of the insulation system due to wetting, such as power factor, partial discharge, or polarization index, as described in EPRI TR-103834-P1-2, or other testing that is state-of-the-art at the time the test is performed.
D. As stated in NUREG/CR-5643, "The major concern with Consistent with GALL AMP: Yes No cables is the performance of aged cable when it is exposed to Document(s) used to confirm Criteria:
accident conditions." The statement of considerations for the final license renewal rule (60 Fed. Reg. 22477) states, "The major concern is that failures of deteriorated cable systems XI.E3 Inaccessible Medium-Voltage Cables Not Subject To 10 CFR 50.49 EQ Requirements 2
Program Auditable GALL Criteria Documentation of Audit Finding Element (cables, connections, and penetrations) might be induced during Comment:
accident conditions." Since they are not subject to the environmental qualification requirements of 10 CFR 50.49, the electrical cables covered by this aging management program are either not exposed to harsh accident conditions or are not required to remain functional during or following an accident to which they are exposed.
- 1. Scope of A. This program applies to inaccessible (e.g., in conduit or direct Consistent with GALL AMP: Yes No Program buried) medium-voltage cables within the scope of license Document(s) used to confirm Criteria:
renewal that are exposed to significant moisture simultaneously with significant voltage. Significant moisture is defined as periodic exposures to moisture that last more than a few days (e.g., cable in standing water). Periodic exposures to moisture Comment that last less than a few days (i.e., normal rain and drain) are not significant. Significant voltage exposure is defined as being subjected to system voltage for more than twenty-five percent of the time. The moisture and voltage exposures described as significant in these definitions, which are based on operating experience and engineering judgment, are not significant for medium-voltage cables that are designed for these conditions (e.g., continuous wetting and continuous energization is not significant for submarine cables).
- 2. Preventive A. Periodic actions are taken to prevent cables from being Consistent with GALL AMP: Yes No Actions exposed to significant moisture, such as inspecting for water Document(s) used to confirm Criteria:
collection in cable manholes, and draining water, as needed.
Comment:
- 3. Parameters A. In-scope, medium-voltage cables exposed to significant Consistent with GALL AMP: Yes No Monitored/ moisture and significant voltage are tested to provide an Document(s) used to confirm Criteria:
Inspected indication of the condition of the conductor insulation. The specific type of test performed will be determined prior to the initial test, and is to be a proven test for detecting deterioration of the insulation system due to wetting, such as power factor, Comment:
XI.E3 Inaccessible Medium-Voltage Cables Not Subject To 10 CFR 50.49 EQ Requirements 3
Program Auditable GALL Criteria Documentation of Audit Finding Element partial discharge, or polarization index, as described in EPRI TR-103834-P1-2, or other testing that is state-of-the-art at the time the test is performed.
- 4. Detection A. Medium-voltage cables exposed to significant moisture and Consistent with GALL AMP: Yes No of Aging significant voltage that are within the scope of this program are Document(s) used to confirm Criteria:
Effects tested at least once every 10 years. This is an adequate period to preclude failures of the conductor insulation since experience has shown that aging degradation is a slow process. A 10 year testing interval will provide two data points during a 20-year Comment:
period, which can be used to characterize the degradation rate.
The first tests for license renewal are to be completed before the period of extended operation.
B. The inspection for water collection should be performed Consistent with GALL AMP: Yes No based on actual plant experience with water accumulation in the Document(s) used to confirm Criteria:
manhole. However, the inspection frequency should be at least once every two years. The first inspection for license renewal is to be completed before the period of extended operation.
Comment:
- 5. Monitoring A. Trending actions are not included as part of this program Consistent with GALL AMP: Yes No and Trending because the ability to trend results is dependent on the specific Document(s) used to confirm Criteria:
type of method chosen. However, results that are trendable provide additional information on the rate of degradation.
Comment:
XI.E3 Inaccessible Medium-Voltage Cables Not Subject To 10 CFR 50.49 EQ Requirements 4
Program Auditable GALL Criteria Documentation of Audit Finding Element
- 6. A. The acceptance criteria for each test is defined by the specific Consistent with GALL AMP: Yes No Acceptance type of test performed and the specific cable tested. Document(s) used to confirm Criteria:
Criteria Comment:
- 7. Corrective A. An engineering evaluation is performed when the test Consistent with GALL AMP: Yes No Actions acceptance criteria are not met in order to ensure that the Document(s) used to confirm Criteria:
intended functions of the electrical cables can be maintained consistent with the current licensing basis. Such an evaluation is to consider the significance of the test results, the operability of the component, the reportability of the event, the extent of the Comment:
concern, the potential root causes for not meeting the test acceptance criteria, the corrective actions required, and the likelihood of recurrence. When an unacceptable condition or situation is identified, a determination is made as to whether the same condition or situation is applicable to other inaccessible, in-scope, medium-voltage cables. As discussed in the appendix to this report, the staff finds the requirements of 10 CFR Part 50, Appendix B, acceptable to address the corrective actions.
- 8. A. As discussed in the appendix to this report, the staff finds the Consistent with GALL AMP: Yes No Confirmation requirements of 10 CFR Part 50, Appendix B, acceptable to Document(s) used to confirm Criteria:
Process address the confirmation process.
Comment:
- 9. A. As discussed in the appendix to this report, the staff finds the Consistent with GALL AMP: Yes No Administrative requirements of 10 CFR Part 50, Appendix B, acceptable to Document(s) used to confirm Criteria:
Controls address the administrative controls.
Comment:
- 10. Operating A. Operating experience has shown that cross linked Consistent with GALL AMP: Yes No XI.E3 Inaccessible Medium-Voltage Cables Not Subject To 10 CFR 50.49 EQ Requirements 5
Program Auditable GALL Criteria Documentation of Audit Finding Element Experience polyethylene (XLPE) or high molecular weight polyethylene Document(s) used to confirm Criteria:
(HMWPE) insulation materials are most susceptible to water tree formation. The formation and growth of water trees varies directly with operating voltage. Water treeing is much less prevalent in 4kV cables than those operated at 13 or 33kV. Also, Comment:
minimizing exposure to moisture minimizes the potential for the development of water treeing. As additional operating experience is obtained, lessons learned can be used to adjust the program, as needed.
XI.E3 Inaccessible Medium-Voltage Cables Not Subject To 10 CFR 50.49 EQ Requirements 6
EXCEPTIONS Item Program Elements LRA Exception Description Basis for Accepting Exception Documents Reviewed Number (Identifier, Para.# and/or Page #)
1.
2.
ENHANCEMENTS Item Program Elements LRA Enhancement Description Basis for Accepting Enhancement Documents Reviewed Number (Identifier, Para.# and/or Page #)
1.
2.
DOCUMENT REVIEWED DURING AUDIT Document Number Identifier (number) Title Revision and/or Date 1.
2.
3.
4.
XI.E3 Inaccessible Medium-Voltage Cables Not Subject To 10 CFR 50.49 EQ Requirements 7