1. 1 BWR Fuel Cleaning: Ultrasonic Fuel Cleaning Pilot Campaign A Collaboration of Exelon – Quad Cities, EPRI, Centec, AREVA, Dominion Engineering Presented by Kenneth Ohr (Radiation Protection Manager, Quad Cities NPP, USA) 2005 ISOE / EPRI International ALARA Symposium 12 January 2005

2. 2 Quad Cities Nuclear Generating Station Two Unit GE-BWR III Cordova, Illinois United States On-line: 1973 Unit 1: 824 MWe Unit 2: 824 MWe (912 MWe power uprate installed)

3. 3 Where is Quad Cities? Quad Cities Station Cordova, Illinois United States 170 miles (275 km) West of Chicago, Illinois on the Mississippi River Two (2) units of a total of eleven (11) operating in Illinois

4. 4 History  2000 - Very high dose rates developed in the drywells at Quad Cities 1 & 2 due to chemistry excursion associated with the implementation of Noble Metals Chemical Addition (NMCA) and its interaction with Depleted Zinc Injection (DZO)  Several OE and GE SIL 631 subsequently issued (and twice revised) to capture issue, consequences and method to prevent occurrence in other BWR units  The principle radiation source was Co-60 in the Reactor Recirc piping  Crud normally formed on the fuel held a significant amount of cobalt which was redistributed by the long duration chemistry “transient”  Redistributed further aggravated by high moisture carry-over impact the secondary side systems as well

5. 5  A six-team, senior management-led charter was developed to address both the immediate dose concerns and the long term, underlying source term drivers of the high collective exposure at Quad Cities:  Cobalt Reduction  Chemistry Optimization  RWCU Capacity Maximization  Exposure Reduction  Cobalt Transport  Fuel Cleaning  Strong leadership and a diverse set of approaches resulted in successes across all six teams  Today’s focus will be on the BWR Ultrasonic Fuel Cleaning Pilot Exposure Reduction Charter

6. 6 BWR Fuel Cleaning  BWR Fuel Cleaning was explored in response to the published successes seen at the Callaway and South Texas Project NPPs  The Charter drove the evaluation of fuel cleaning as a viable method for reducing source term for BWR-type reactors  Through review of the initial results seen at Callaway and STP, estimated dose saving of 99-111 rem (0.99 to 1.11 Sv) per cycle were identified based on the current Quad Cities elevated dose rates.

7. 7  Chemical decontamination  Utilized at Paks NPP plant in Hungary but failed due to thermal shock after cleaning (human performance issue).  Ice Crystal Slurry  European approach (Icedec) had only been tested on three bundles with insufficient data to consider  Ultrasonic cleaning  Performed at 2 U.S. PWR facilities successfully  Calloway NPP and South Texas Project NPP  Decision made after comparison of risks and unknowns to apply PWR Ultrasonic technology building off of the successes of Callaway and South Texas Project. Fuel Cleaning Techniques Considered

8. 8 UFC Equipment  Fuel cleaning equipment  Pumping loop system  Ultrasonic transducers and cleaning chamber  Fuel sipping equipment  Centec crud scraping equipment  Visual inspection equipment  0.45 micron filters  Differences between the successful PWR application and the BWR pilot included expansion of the ultrasonic transducers to the entire length of the fuel assemble and considerations for the expected magnitude of activity to be collected

9. 9 Fuel Cleaning System Schematic PWR Schematic

10. 10 Pilot Program - Phase #1  Four thrice-burned (discharge) fuel bundles were selected and cleaned  Bundles selected based on power history and presence in core during critical plant chemistry parameter changed  Implementation of DZO (Zinc Injection) – 2 cycles  Application of NMCA (Noble Metals) – final cycle  A battery of four (4) 0.45 micron filters were used to collect crud  Pre and post cleaning visual inspections completed on all 4 bundles  Crud scraping samples taken on two bundles prior to ultrasonic cleaning for baselining of data  Goal was to verify qualification conclusions  Crud removal efficiency and cleaning time  Effects on fuel, spacers and nozzles  Vibration  Oxide layer  Flow blockage  Filter fouling

11. 11 Phase #1 Actions and Results  Project Theme: “Make history, not OPEX”  Fuel assemblies were cleaned, on average, for 6-8 minutes each  The process removed a total of 661 curies of which Co-60 contributed 210 curies of activities  Final dose rates on 4 filter assembly 450 to 600 rem/hr (4.5 to 6.0 Sv/hr)  Each bundle was sipped to ensure no fuel failures  All bundles were returned to U2 spent fuel pool  Success, but with questions to be answered…

12. 12 In-Line Dose Rate Monitoring 6 minutes

13. 13 Filter Dose Rate Monitoring  Dose rate meter located in a fixed geometry to filters, but not at contact or at point of highest dose rates later measured

14. 14 Visual Inspection Results  All four fuel assemblies were de-channeled and inspected both prior to and following ultrasonic cleaning  Results:  50-60% of the “fluffy” crud was removed  <5-10% of the “tenacious” crud was removed  Somewhat less “fluffy” layer removal performance than anticipated (target of 80%)  Retaining the “tenacious” layer considered beneficial by Fuel Services due to potential delamination / uneven burn issues should large, but inconsistent section of the tenacious layer be disturbed

15. 15  The First fuel assembly (YJA-197) was cleaned and seemed to be slow in moving through the expected radiation peak. At T+9 minutes of cleaning, a crud plume was observed emitting from the top of the fuel assembly  Issue: the fuel cleaning chamber did not allow the fuel bundle to fully seat at the bottom of the chamber (a design error by the system supplier)  This was remedied by replacing the flow diverter valve with a 6 inch extension.  Cause: The cleaner design did not account for the Quad Cities fuel assemblies being 5 inches shorter than the drawings used for the cleaner design.  The drawings used were on BWR 4+ fuel. Phase #1 Issues and Lessons Learned

16. 16  Upon dechanneling, on spaced plate noted as dislodged with apparent weld failure  Issue: Ultrasonic cleaning approved as a non-destructive technique  Any concern of physical damage to components of the fuel assembly would abort project  Cause: During the pre-cleaning visual inspection, while re- channeling one fuel bundle, YJA-172, a spacer was damaged. The channel apparently contacted two spacers and caused the spacer positioning support piece on each spacer to break (Fuel Handling human performance issue)  Ultimately, self-critical support of Fuel Handler was key to ensure confidence in process prior to station senior management approval of Phase #2 Phase #1 Issues (continued)

17. 17 Station Approval  The results of Pilot Program-Phase #1 were assessed in “Fuel Cleaning Using Ultrasonics on 16 GE Bundles Design Review Report”. The report recommended specific process controls for cleaning and concluded that the process was acceptable for the fuel.  The Quad Cities Station PORC committee reviewed the report and approved the cleaning of 16 fuel assemblies during Q2R17  Used the Operational Decision Making process to document justification for cleaning additional fuel assemblies and reinserting them into the Q2C18 core

18. 18 Pilot Phase #2(Reload Fuel)  16 Fuel Assemblies selected for cleaning  Each was ultrasonically cleaned for 5 minutes  All 16 once burned fuel assemblies  Following cleaning all 16 were sipped for fuel failure  3 Assemblies selected for dechanneling and performed post cleaning inspections on three  Four filters were used to collect crud  Contact filter dose rates ranged from 436-837 rem/hr (4.4-8.4 Sv/hr)  605 rem/hr (6.05 Sv/hr) average  Approximately 300 Curies total activity (~100 Curies Co-60) removed  All 16 fuel assemblies reinserted into core as proof-of-principle bundles

19. 19 Pre and Post Images Pre: Post:

20. 20 Future Fuel Assembly Inspections  One Cycle Inspections:  3 bundles were de-channeled and inspected both pre and post cleaning. These were the 1 st, 8 th, and 16 th bundles cleaned.  Inspection included examination of lower tie plates, each spacer and each face of the assembly  Examinations will be performed during Q2R18 to assess the effects of cleaning and then “burning” fuel and to determine the viability of additional fuel cleaning  Current Fuel Performance:  No indications of fuel failure at 300 days on-line

21. 21 Conclusions  Visual observations of the fuel confirmed that much of the soft crud was removed and that most of the tenacious crud remained on the fuel  Proof-in-concept of ability to clean BWR fuel positively demonstrated  Impact of 16 bundles cleaned on overall dose rates in the Drywell after one cycle expected to be negligible based on small percentage of reload core cleaned  Extrapolated full core cleaning benefit of 25% reduction following a 2 year cycle remains consistent with hypothesis that cleaned fuel will provide a vastly preferential crud deposition site versus primary (Recirc) piping and will effectively eliminate additional Recirc piping Co-60 loading  This results in dose field reduction consistent with the decay rate of Co- 60 (~5.27 year half-life)

22. 22 Future Actions  Cleaned fuel will be burned for one cycle prior to re- examination to assess the effects of fuel cleaning on the fuel reloaded into Q2C18  Unit Two full reload scope of cleaning to be determined after inspections during Q2R18 (2006)  Unit One Fuel Cleaning will have first opportunity in 2007 following Unit Two fuel analysis and fuel vendor / Exelon Fuel Services concurrence of results  More to follow in 2006…

23. Thank you. Questions? Comments?