ML15236A134
| ML15236A134 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 08/26/2015 |
| From: | Watford M Plant Licensing Branch IV |
| To: | Edington R Arizona Public Service Co |
| Watford M | |
| References | |
| TAC MC4702, TAC MC4703, TAC4704 | |
| Download: ML15236A134 (11) | |
Text
Palo Verde Nuclear Generating Station Generic Letter 2004-02 August 26th, 2015
Introductions
Tom Weber Department Leader Nuclear Regulatory Affairs
=
Background===
- 12/18/2013 - APS submitted Revision 2 to Supplemental Response to NRC Generic Letter 2004-02
- 4/15/2015 - PVAR 4644513 documents that APS failed to identify and evaluate Microtherm on the Reactor Vessel
- 6/10/2015 - Initial Public Meeting with NRC
- Beaver Valley Operating Experience with Microtherm
- Communication with the Industry
- Industry Testing of Microporous Insulation
- Extent of Condition 3
Microtherm Locations 4
Break Locations Limiting Break Location Steam Generator Hot Leg Nozzle Reactor Pressure Vessel (RPV) Nozzle break locations 5
Extent of Condition Red: Temp-Mat Impacting Existing Break Location (SG HL Nozzle) 6 Green: Temp-Mat Impacting New RPV Break Location LOCATION Unit 1 Unit 2 Unit 3 Cold Leg 1A, 1B, 2A, 2B RTD X
X X
Below RPV Nozzle X
X X
RPV Cavity X
X X
RPV ICIs X
X X
Crossover 1A, 1B, 2A, 2B RCP Nozzle X
Crossover 1A, 1B, 2A, 2B SG Nozzle X
Cold Leg 1A, 1B, 2A, 2B RPV Elbow X
Unit 3 Only
Analysis to date Debris Generation
- Primary success path is removal of Temp-Mat in the D-rings for current limiting break
- Microtherm ZOI (zone of influence) based on robustness of encapsulation
- Encapsulated Microtherm ZOI and restrained separation of pipe at RPV nozzle break limits Microtherm quantity to the local region of the break location Debris Transport
- RPV nozzle break - Temp-Mat generated to the Reactor Cavity will not transport to strainers based on very low flow velocity and upward vertical flow path of 18 to 23 feet
- Cold Leg RPV Elbow Temp-Mat is still being analyzed for impact (Unit 3 Only)
- Generated Microtherm assumed to transport to the strainers 7
Analysis to date (cont)
- Industry Testing / NPSH
- Salem U2 Test 6 Head Loss conditions (with Min-K) bound Palo Verde with Microtherm for post-LOCA flow scenarios
- Comparative analysis indicates Palo Verde NPSH and structural limits should be bounded by existing SG HL Break location 8
Actions to finalize
- Confirm Removal of Temp-Mat from D-ring
- Confirm Removal of Temp-Mat from Unit 3 RPV Cold Leg Elbows
- Confirm impact of identified Temp-Mat and Microtherm for RPV on chemical effects
Scenario
- Complete final review of assessment report 9
Summary
- A resolution path exists for D-ring and RPV nozzle break cases
- Confirmation of chemical effects and LPSI flow scenario items in process
- Open Strainer Area is expected to be comparable with original analysis
- Confirm removal of Temp-Mat in D-Ring
- Removal of RTD Temp-Mat (all 3 units)
- Removal of Crossover Piping Temp-Mat in Unit 3
- Confirm removal of Cold Leg RPV Elbows in Unit 3
- Supplement APS Response to GL 2004-02 10
11 We SAFELY and efficiently generate electricity for the long term