1. Ultrasonic Fuel Cleaning at STP William T. Bullard- CHP STP Health Physics Dominion Engineering, Inc. NATC International ALARA Symposium Orlando, FL January 14, 2003 CENTEC XXI

2. Agenda  Drivers and Benefits of Fuel Cleaning  Overview Cleaning System  Review of Plant Experience  Callaway Radiological Data  Questions & Answers

3. Benefits of Cleaning Reload Fuel  Reduce risk of Axial Offset Anomaly (AOA) on feed fuel by eliminating redistribution of crud from low to high power assemblies  Eliminate AOA on high duty, second cycle fuel  Lower fuel costs  Lower risk to fuel rod integrity as threatened by crud induced corrosion  Improve fuel cladding inspection  Lower crud inventory to minimize personnel radiation exposure during operation and refueling outages

4. Axial Offset Anomaly (AOA)  Unexpected depression in fissions in upper core  Caused by crud and lithium borate deposits on fuel in upper core  Exacerbated in high duty core  Impedes economic fuel performance  STP fuel duty has been limited by concern for AOA susceptibility.

5. Fuel Cost  STP fuel cycles can be designed for four less feed assemblies than would otherwise be used (typically reducing from 76 to 72 assembly feed batches).  Increases average discharge burnup by about 5%,  Fuel cost reduced by about $1 M per cycle.  Savings for future spent fuel storage and handling.

6. Equipment Overview

7.  Seismically qualified to support fuel, freeing the spent fuel handling hoist  Double-chamber configuration for maximum throughput  Crud traps are minimized by seal welding joints, sleeving cables and polishing exposed parts.  Independent transducer assemblies may be easily inserted and removed for storage or repair Cleaning Chamber

8. Equipment Overview  Redundant pumps and sets of 4 filter housings  Filters changed while other bank is isolated  Capture of the crud removed from the fuel assemblies  Process monitoring via various instruments Pump/Filter Assembly

9. Equipment Overview Independent transducer assemblies may be easily inserted and removed for storage or repair

10. Equipment Overview Lowering dual cleaning chamber into spent fuel pool - August 2002

11. Cleaning Fuel --- Fall 2002  120 reload assemblies cleaned  5 assemblies per hour (fuel handler dependent rate).  Inspection is done with cameras at the cleaner.  Monitor filter radiation level and pump discharge process radioactivity

12. Cleaning Fuel Fall 2002 400 Cleaning Time (sec) Inline Gamma Detector (mR/hr)  Initial cleaning time set at 6 minutes  4-minute cleaning time was more than adequate.

13. Cleaning Fuel Fall 2002  Initial Filter Change criterion set @ 1.3 Gy h -1 based on ALARA consideration and conservatism for waste classification  Radiation level increase per fuel element - 80 to 120 mGv h -1  Increaed Filter change criterion to 2.6 Gy h -1  Side stream surrogate sample using 0.45 micron glass filter media for off-site analysis

14. STP Results Before After

15. Radiation Field (ALARA) Benefit  Although reducing plant radiation fields was not a specific objective of the fuel cleaning, preliminary results are promising  Callaway reports overall decontamination factor in primary plant was about 50% (DF=2)  Local radiation fields reduced by up to 80%  Long-term use expected to have significant worker exposure benefit

16. Radiation Field (ALARA) Benefit Cycle 12 CYCLE 12

17. Conclusions  The fuel ultrasonic cleaning system met all of STP’s expectations.  We will be monitoring the performance of the upcoming fuel cycle regarding the effects of the fuel cleaning on RCS activities and on fuel performance.  STP is installing a fuel cleaning system in our twin unit in January. Some design improvements were identified during the initial system installation, and they have been incorporated.

18. Questions???