ML26044A134
| ML26044A134 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 02/18/2026 |
| From: | Duke Energy |
| To: | |
| Shawn Williams | |
| References | |
| Download: ML26044A134 (0) | |
Text
Catawba Relief Request RA-26-0027 Pre-Submittal Meeting Impractical Inservice Testing (IST) for WL/WN Sump Pumps February 18, 2026
ASME Code Components Affected 2
Component ID Component Description 1WLPUANS 1A ND & NS SUMP PUMP 1WLPUAMS 1A CA SUMP PUMP 1WLPUATS TURBINE DRIVEN AUX FEEDWATER PUMP SUMP PUMP 1A 1WLPUBNS 1B ND & NS SUMP PUMP 1WLPUBMS 1B CA SUMP PUMP 1WLPUBTS TURBINE DRIVEN AUX FEEDWATER PUMP SUMP PUMP 1B 1WNPUA1 1A DIESEL GENERATOR ENG SUMP PUMP 1A1 1WNPUA2 1A DIESEL GENERATOR ENG SUMP PUMP 1A2 1WNPUB1 1B DIESEL GENERATOR ENG SUMP PUMP 1B1 1WNPUB2 1B DIESEL GENERATOR ENG SUMP PUMP 1B2 Component ID Component Description 2WLPUANS 2A ND & NS SUMP PUMP 2WLPUAMS 2A CA SUMP PUMP 2WLPUATS TURBINE DRIVEN AUX FEEDWATER PUMP SUMP PUMP 2A 2WLPUBNS 2B ND & NS SUMP PUMP 2WLPUBMS 2B CA SUMP PUMP 2WLPUBTS TURBINE DRIVEN AUX FEEDWATER PUMP SUMP PUMP 2B 2WNPUA1 2A DIESEL GENERATOR ENG SUMP PUMP 2A1 2WNPUA2 2A DIESEL GENERATOR ENG SUMP PUMP 2A2 2WNPUB1 2B DIESEL GENERATOR ENG SUMP PUMP 2B1 2WNPUB2 2B DIESEL GENERATOR ENG SUMP PUMP 2B2 CA - Auxiliary Feedwater System ND - Residual Heat Removal System NS - Containment Spray System WL - Liquid Waste Recycle System WN - Diesel Generator Room Sump Pump System
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Background===
Vertical line-shaft centrifugal pumps in open sump systems No recirculation path, which means sump level and suction pressure drop during the pump run No pumps have suction pressure gauge. Only the WN (Diesel Generator) sump pumps have a discharge pressure gauge.
Sump Pumps were brought into IST Program during the current (4th) Interval starting in 2016 when it was recognized that they have a safety support function.
WN sump pumps are installed to mitigate a postulated passive single failure Nuclear Service Water leak in the D/G rooms while in Single Supply Header Operation.
WL sump pumps are installed to prevent flooding in their respective pump pits for Auxiliary Feedwater (CA), Residual Heat Removal (ND), and Containment Spray (NS) pits.
Current (4th) IST Interval ASME Code is OM-2004/2006; ends August 19, 2026 Request will also apply to the upcoming Code of Record Interval (5th and 6th Intervals),
which will adhere to ASME OM-2020 approved in safety evaluation ML26005A084 (August 19, 2026 to August 19, 2049) 3
Applicable Requirements ISTB-3430 - Pumps Lacking Required Fluid Inventory: 2-year Comprehensive test ISTB-5200/5223 - Comprehensive test parameters: Flow, Vibration, and Differential Pressure (P)
Current Comprehensive test practice - flow and vibration are measured, P is not due to impracticality 4
Impracticality Open sump with no recirculation path Sump pump-down occurs within approximately two to four minutes Both suction and discharge pressure (i.e. P) change continuously during pump-down Options to achieve a constant sump level are not practical Dead-heading the pump causes equipment reliability issues Maintaining constant sump input to match pump output is not safe or repeatable (see the picture below for one example of the sumps where constant input is not feasible) 5
Impracticality (continued)
Differential pressure measurement not available WN pumps have discharge pressure gauges, but no suction gauges WL pumps have no suction or discharge pressure gauges The option to calculate suction pressure discussed in NUREG-1482 is not beneficial without a consistent sump level (i.e., hydraulic stability)
Plant modifications to install recirc lines / instrumentation across ~20 pumps would be extensive Relief requested under 10 CFR 50.55a(f)(5)(iii) as Code compliance is impractical LIC-102 and NUREG-1482 include plant modification as an example of impracticality 6
Proposed Alternative Pump flow is determined utilizing known sump volume and timing the sump pump-down time with calibrated stopwatch Consistent start/stop sump levels and inventory destination between tests Acceptance criteria established at the design flow (50 gpm for CA and D/G sump pumps; 100gpm for ND/NS sump pumps)
Flow rate must be greater than design requirements for sump pump functionality Pump vibration measured while pump removes sump inventory Baseline references established Alert and Required Action Limits per Table ISTB-5221-1 Vibration will be trended to detect pump degradation Differential pressure not measured 7
Basis for the Proposed Alternative Specified Sump Pumps are designed to operate on an as-needed basis rather than run continuously (i.e. lacking required inventory)
Design flow rate is verified each test and vibration monitoring trending is performed Alternate test method removes the sump inventory at design flow, thereby demonstrating adequate head Consistent start/stop sump levels and inventory destination establishes a reference between tests Proposed test with flow-rate verification and vibration monitoring is adequate to demonstrate the pump can meet safety support function Flow rate and vibration monitoring have been successful at detecting issues Two initial tests identified foreign material in sump; One early test resulted in motor replacement due to vibration 8
Precedent 9
Comanche Peak Safeguards Building Sump Pumps (SBSP)
Similar design issues - open sump lacking recirc and instrumentation Similar propose alternative - flow and vibration sufficient, no P 2006 - Relief granted as impractical for an interim period Safety Evaluation ML062510192 2009 - Alternative authorized under 50.55a(a)(3)(ii) (hardship)
Safety Evaluation ML091620548 2013 - Alternative authorized under 50.55a(a)(3)(ii) (hardship)
Safety Evaluation ML13148A437 2023 - Alternative authorized under 50.55a(z)(2) (hardship)
Safety Evaluation ML23121A220
Duration of Proposed Alternative & Schedule Current (4th) IST Interval (August 19, 2016 - August 19, 2026)
Next Code of Record Interval 5th and 6th IST Intervals (August 19, 2026 - August 19, 2049) 10 CFR 50.55a(f)(5)(iv) permits submission of Relief Request up to 12 months after Interval expiration Next scheduled test of current Interval is April 19, 2026 First scheduled test of next Interval is November 12, 2026 Submittal target - March 19, 2026 Approval requested on schedule consistent with NRC Graded Estimate Method (but within 9 months) 10