ML11186A791
| ML11186A791 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 03/21/2011 |
| From: | Cavey E Detroit Edison |
| To: | Office of Nuclear Reactor Regulation |
| Bedi G | |
| Shared Package | |
| ML11186A384 | List: |
| References | |
| TAC ME1150, NUREG-1482 | |
| Download: ML11186A791 (4) | |
Text
Post Maintenance Test Requirements Following Packing Adjustments or Backseat operations to Correct Active Leakage Code Requirement OM Code ISTC 3.4, ISTC-3310 Effect of Valve or Actuator Replacement, Repair, and Maintenance on Reference Values, states: when a valve or its control system may have been replaced, repaired, or has undergone maintenance that could affect the valves performance, a new reference value shall be determined or the previous values reconfirmed by a an inservice test run before the time it is returned to service or immediately if not removed from service.
Examples of maintenance are provided in a footnote and include: adjustment to stem packing, limit switches, or control system valves, removal of the bonnet, stem assembly, actuator, obturator, or control system components.
ISTOG Guidance During the course of the operating cycle, packing leakage may be observed. Typically, an adjustment to tighten the stem packing is be made or the valve may be placed on the backseat to correct, or stop the active leak. Consequently, a determination must be made as to whether the full stroke, timed measurement test or leak rate test, if applicable, is required.
Normally, a full stroke exercise and stoke time test would be performed following any adjustment to the valve packing since the activity may impact frictional forces acting on the valve stem. Consequently, the ability of the valve to operate in a timely manner may have changed. Some valves may not be capable of being tested due to existing plant conditions. In most cases, this might involve a valve, which if tested at power would result in a plant shutdown. Some valves are more susceptible to change than others.
For example, manual and AC motor operated valves would be unaffected for events, while DC motor, air and solenoid operated valves are more likely to be impacted. Valve design may also be important in the overall assessment (e.g., gate, globe, etc.).
Since this activity must be performed at power, the required testing cannot be performed and additional evaluation may be necessary. Consequently, the maintenance activity cannot be performed unless the valves functional capability and operational readiness can be assured.
Adjustment of the stem packing to eliminate active external leakage is the prudent course of action to take from both a nuclear and personnel safety perspective; however, the maintenance activity may adversely impact the ability of a Category A or B valve to stroke within the time frame required to fulfill its specified safety function.
In addition, Category A valves are required to be leak tight in fulfillment of their specified function. Leak tight integrity is applicable to both the seating surface as well as the exposed packing boundary. Adjustment of stem packing may adversely impact the ability of the obturator to mate with the seating surface, bringing the leak tight integrity of the valve into question.
If it is not appropriate to test the subject valve while at power, then the required testing may be deferred if certain requirements can be met. An engineering analysis of valve performance may be used to determine the impact of the maintenance. The intent of this assessment is to provide assurance that the maintenance activity has not adversely impacted valve performance and that the valve will still be capable of meeting its
Post Maintenance Test Requirements Following Packing Adjustments or Backseat operations to Correct Active Leakage specific function.
This position addresses valves with active packing leakage and is not to be used to perform periodic preventive on-line maintenance. This position weighs the risk of the known detrimental effects of an active packing leak on safety related valves and surrounding equipment and potential personnel hazards against the impact on overall plant safety involved with manipulating the plant to the proper test condition, or electing to bypass corrective maintenance because the desired post maintenance test cannot be performed in the current operating mode.
The following details outline specified requirements for valves in which the desired post maintenance test cannot be completed. The categories are broken down based on the valve function and ability to test or conduct limited tests. As previously noted the type of operator and valve design are important elements that must be considered when using the following guidance. In addition, alternatives to inservice testing may include the use of mock ups that can duplicate the maintenance activity in a controlled test environment.
The categories are defined by:
- 1) Category B valves which cannot be stroke timed in the current plant mode
- 2) Category A valves that can be stroke timed, but not leak tested in the current plant mode,
- 3) Category A valves that cannot be stroke timed or leak tested in the current plant mode.
- 1) A Category B valve that cannot be stroke timed in the current plant operating mode may be assessed for operational readiness provided the following minimum requirements have been met.
- 1. The packing adjustment does not exceed the manufacturers specified tolerance or,
- 2. An analysis of previous activities using similar packing loads on valves with similar or identical designs and operating conditions is completed demonstrates that the activity should not adversely impact the ability of the component to perform its required function,
- 3. The packing adjustment does not deform the valve stem,
- 4. A partial stroke test is performed to obtain further assurance that the valve stem is free to move, if practical, AND
- 5. A full stroke, loss of power, if applicable and stroke time measurement test is conducted at the first available opportunity that demonstrates that the performance parameters have not been adversely affected.
Post Maintenance Test Requirements Following Packing Adjustments or Backseat operations to Correct Active Leakage
- 2) A Category A valve that can be stroke timed, but cannot be leak tested in the current plant operating mode may be assessed for operational readiness provided the following minimum requirements have been met.
For air-operated valves, if the conditions below can be satisfied, a leak rate test is not required.
- 1. The packing adjustment does not exceed the manufacturers specified tolerance or,
- 2. An analysis of previous activities using similar packing loads on valves with similar or identical designs and operating conditions is completed that demonstrates the activity does not adversely impact the ability of the component to perform its required function,
- 3. The packing adjustment does not deform the valve stem,
- 4. A stroke time test is conducted that shows that the performance parameters are not adversely impacted.
- a. This condition may be satisfied if the stroke time test is consistent with the most recent test results and, as a minimum, should be within the established upper and lower code criteria specified in the associated surveillance test.
For motor-operated valves, if the conditions below can be satisfied, a leak rate test is not required.
- 1. The packing torque does not exceed the value established for the existing packing configuration and a successful leak rate test has been previously performed with the existing configuration and,
- 2. The stroke time or diagnostic test results shall be consistent with the most recent test results.
For motor-operated valves, if the conditions above cannot be satisfied, then a leak rate test may be conducted at the first available opportunity to demonstrate that performance parameters have not been adversely affected. The leak rate test may be deferred if the following conditions can be satisfied.
- 1. An engineering analysis of the diagnostic test is conducted that shows that the performance parameters are not adversely impacted. The analysis shall consider the available leakage margin, valve size and any other critical attributes necessary to assure that valve rates are not exceeded.
- 3) A Category A valve that cannot be stroke timed, or leak tested in the current plant operating mode may be assessed for operational readiness provided the following minimum requirements have been met.
- 1. The packing adjustment does not exceed the manufacturers specified tolerance or,
Post Maintenance Test Requirements Following Packing Adjustments or Backseat operations to Correct Active Leakage
- 2. An analysis of previous activities using similar packing loads on valves with similar or identical designs and operating conditions is completed demonstrates that the activity should not adversely impact the ability of the component to perform its required function,
- 3. The packing adjustment does not deform the valve stem,
- 4. A partial stroke test is performed to obtain further assurance that the valve stem is free to move, if practical, AND
- 5. A leak rate test is conducted at the first available opportunity that demonstrates that performance parameters have not been adversely affected.