ML22075A201
| ML22075A201 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 03/07/2022 |
| From: | Snider S Duke Energy Carolinas |
| To: | Angela Wu NRC/NRR/DNRL/NLRP |
| Wu A, 301-415-2995 | |
| Shared Package | |
| ML22075A196 | List: |
| References | |
| Download: ML22075A201 (10) | |
Text
ONS Subsequent License Renewal NRC Public Meeting (Bolting Integrity)
March 7, 2022
Topic of Discussion TRP 18 - Bolting Integrity (RAI Set #2), RAI B2.1.9-2:
There is misalignment on the approach of how to adequately manage closure bolting in non-pressurized system(s).
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RAI B2.1.9-2 Issue the SLRA does not state how the aging effects associated with closure bolting for components that are not normally pressurized will be detected and managed
..SLRA enhancement no. 4 seems to specifically address the detection of aging effects in submerged closure bolting and in closure bolting where the piping systems containing air or gas. Therefore, it is not clear how closure bolting from systems that are not normally pressurized will be adequately managed, and what alternate means of inspection and acceptance criteria will be implemented...
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SLRA Bolting Integrity Enhancement no. 4 Perform visual inspections of a representative sample of twenty percent of closure bolting where leakage is difficult to detect such as submerged connections or systems containing air/gas or a maximum of seventeen bolts for each material and environment population per unit, whichever is less, during each ten year period. If the minimum sample size is not achieved during a ten year period, then alternative inspections may be performed. For submerged bolting, alternative inspections may include (a) diver inspections or (b) remote video inspections. For systems containing air/gas, alternative inspections may include (a) visual inspection for discoloration when leakage from inside the piping system would discolor the external surfaces of the component; (b) monitoring and trending of pressure decay when the bolted connection is located within an isolated boundary; (c) soap bubble testing on the external mating surface of the bolted component; or (d) thermography, when the temperature of the process fluid is higher than ambient conditions around the component.
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RAI B2.1.9-2 Request 1
- 1. State how the aging effects associated with the closure bolting for components that are not normally pressurized will be detected and adequately managed by the Bolting Integrity program during the subsequent period of extended operation (i.e., inspection methods and acceptance criteria that will be used). Update the SLRA as necessary to include this information.
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RAI B2.1.9-2 Response to Request 1 (General)
Closure bolting in systems that are not normally pressurized will be visually inspected during maintenance activities for degradation including loss of material, visible cracking, and loss of preload (loose or missing bolting)
Bolt heads will be inspected when made accessible and bolt threads will be inspected when joints are disassembled These are opportunistic/direct inspections A representative sample population for each ONS unit will consist of 20% of the population up to a maximum of 17 bolts for each material / environment combination it is expected that sufficient opportunistic inspections will be performed to greatly exceed the representative sample size required by the AMP This statement has been verified per review of the ONS Preventative Maintenance Program From Enhancement no. 4 - If the minimum sample size is not achieved (via maintenance activities) during a ten year period, then alternative inspections may be performed 6
RAI B2.1.9-2 Response to Request 1 (Air or Gas Filled Systems)
Closure bolting in air or gas filled systems that are not normally pressurized (e.g.,
exhaust lines) will be managed consistent with the approach used for closure bolting on normally pressurized air or gas filled systems The approach - visual inspection during maintenance activities with alternate inspections if the minimum representative sample size is not achieved Alternative inspections may include (a) visual inspection for discoloration when leakage from inside the piping system would discolor the external surfaces of the component (b) monitoring and trending of pressure decay when the bolted connection is located within an isolated boundary (c) soap bubble testing on the external mating surface of the bolted component (d) thermography, when the temperature of the process fluid is higher than ambient conditions around the component 7
RAI B2.1.9-2 Response to Request 1 (Water, Steam, or Oil filled Systems )
Closure bolting in water, steam, or oil filled systems that are not normally pressurized will be managed consistent with the approach used for closure bolting on normally pressurized water, steam, or oil filled systems The approach - periodic and routine visual inspections of bolted joints to detect signs of leakage Standby systems that are not normally pressurized are typically maintained filled with fluid such that degradation of bolted joints would result in detectable leakage.
All ASME Code Class 1, 2, or 3 systems, including safety-related systems that are normally maintained depressurized in standby, are subject to periodic VT-2 testing with the system pressurized such that leakage from bolted joints would be detected Certain systems may not (be) normally pressurized, system pressurization occurs during testing and surveillance, infrequent plant operations such as startup and shutdown, and system makeup activities such that adequate opportunities exist to detect leakage from bolted joints during these activities Periodic inspections required by this program include inspection for signs of past leakage (including discoloration/staining and damaged insulation) and loose or missing bolting and provide reasonable assurance that leakage from water, steam, or oil filled systems that are not normally pressurized will be detected 8
Conclusion The existing scope of SLRA Enhancement #4 is appropriate because inspection of closure bolting for components that are not normally pressurized is adequately addressed:
Closure bolting in air or gas filled systems that are not normally pressurized (e.g., exhaust lines) will be managed via the same method (approach) used for closure bolting on normally pressurized air or gas filled systems The approach - visual inspection during maintenance activities with alternate inspections if the minimum representative sample size is not achieved Closure bolting in air or gas filled systems that are not normally pressurized is in the same sample population as bolting in air or gas filled systems that are normally pressurized Closure bolting in water, steam, or oil filled systems that are not normally pressurized will be managed via the same method (approach) used for closure bolting on normally pressurized water, steam, or oil filled systems The approach - periodic and routine visual inspections of bolted joints to detect signs of leakage Sample based inspections are not applicable to bolting subject to periodic and routine visual inspections Ultimately, closure bolting in systems that are not normally pressurized (regardless of process fluid) undergoes visual inspection during maintenance activities 9
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