1. EPRI Radiation Exposure Management Program Highlights
Sean Bushart
Dennis Hussey
Chris Wood
ISOE International Symposium
Lyon, France
March 24, 2004

2. Collective U.S. Dose Rate Compared to Power Generated

3. Radiation Exposure Management
Applied Technology
Radiation Exposure Management
Radiation Protection Radiation Field Control Manual
Cobalt
Replacement
Surface
Conditioning
PWR
Chemistry
BWR
Chemistry
Activity
Removal
Co-free SCr Process pH control NMCA/Zinc* UT Fuel Cleaning*
hardfacings Electropolishing Zinc* Guidelines LOMI Decon
* These techniques may be applied for other reasons – dual benefits: to be discussed later

4. Chemistry Factors in Radiation Control
Materials
Degradation
BWR Internals - NMCA
PWR Primary - Zn
Steam Generators
Balance of Plant
Water Chemistry
guidelines
Chemistry
Interactions
Fuel Performance
Cladding Corrosion
Crud Deposition
Radiation Fields
Low Level Waste

5. EPRI Experiences In Field Control
Experience shows that the easiest way to get radiation control technology implemented is to identify another high profile benefit of the technique
i.e. mitigation of materials or fuels issues
Examples:
Zinc for PWRs
Zinc for BWRs using noble metals
Ultrasonic fuel cleaning
Each of these examples will be discussed in this paper
Win-win situations
Implementation may still be an uphill task, but perhaps not quite such a steep hill for the RP Manager

6. PWR Zinc Addition Program
Zinc injection used at most BWRs to control radiation fields
The objective of the PWR program was:
To evaluate the long term effect of zinc addition in mitigating Alloy 600 PWSCC and radiation fields
To ensure that zinc does not have an adverse effect on fuel performance and other components
Zinc addition demonstrations were conducted at Farley-2 and Diablo Canyon-1
Palisades and European plants use depleted zinc to reduce radiation fields

7. Effect of Zinc on Corrosion Rates
(from Esposito, et. al., Proceedings of the fifth Symposium on Environmental Degradation
of Materials in Nuclear Power Systems – Water Reactors, August 1991)

8. Post Zinc Dose Rate Trends: Diablo Canyon 2
Zinc Injection

9. Post Zinc Dose Rate Trends: Palisades
Increase after SG replacement, caused by oxidation? Why was it constant before, chemistry changes?

10. Conclusions on Zinc
Farley, Diablo Canyon and Palisades show significant reductions in PWR shutdown radiation fields with Zn additions
No adverse effects of Zn additions observed on Zircaloy or ZIRLO fuel cladding corrosion
Need to resolve potential issues associated with Zn injection on fuel performance in high duty plants
Latest Chemistry Guidelines (September 2003) recommend PWRs should consider implementing 5-10 ppb Zinc
Reduce radiation buildup

11. BWR Radiation Field Control: Hydrogen Water Chemistry, Zinc Injection, Noble Metal Addition
BWR Chemistry Topics:
Purpose of Noble Metal Chemical Addition (NMCA)
U.S. plant experiences with NMCA applications
Restructuring of Corrosion Products
Radiation fields

12. BWR Chemistry Effects On Dose Rates
Materials
Degradation
Requirements for an
effective NMCA program
and inspection relief
BWR
Chemistry
Interactions
Fuel Performance
Control of Cladding Corrosion and
Crud Deposition
Radiation Fields
Zinc injection essential
to control dose rate increase

13. Effect of NMCA on Out-of-Core Radiation Fields
Noble metals reduce the ECP:
Crud on fuel restructures, releasing Co-60
Insoluble and Soluble Co-60 increases in reactor water
Transient effect – slow return towards original levels
Deposition on out-of-core surfaces increases
Biggest effects at high cobalt plants
Mitigated by zinc
High FW iron increases effects
More crud on fuel
Reduces effectiveness of zinc
All the above becomes more complicated for plants that add hydrogen and/or zinc after NMCA

14. BWR Oxide Behavior Under Reducing Conditions
Restructuring of

15. March 2001 Interim guidance
Mitigating impact of NMCA on shutdown radiation fields - First recommendation: control hydrogen, increase zinc
March 2001
Interim guidance

16. Radiation History 1

17. Radiation History 2

18. Why did plants behave differently after NMCA?
Increase due to:
High cobalt inventory (e.g. QC, NMP)
Recent change to HWC or poor HWC control
Lack of zinc (e.g. NMP1)
Decreases resulted from:
Good hydrogen control (stable chemistry) (e.g. Hatch)
5-10 ppb zinc present before change (e.g. Hatch)
For plants on HWC, dose rates increase with RW Co-60 to zinc ratio (see next slides)

19. First Post NMCA Cycle Shut Down Dose Rate
vs. RW Median Co-60(s) to Zn(s) Ratio w/o NMP1
Credit Dan Malaskus (check spelling…)

20. Summary Timeline of Draft Recommendations
Prior to NMCA First Application Post Application Reapplication
NM<30ug/cm NM<30ug/cm2
(not apply to same batch)
Inject HWC Target Hydrogen availability > 95% for >6 months
RW Zn 5-10ppb Maintain RW ratio Co-60/Zn(s)<2x10-5
FW Zn<0.4ppb Be prepared to Target cycle average FW Zn 0.4ppb for 3 months increase FW Zn or less before NMCA
Consider baseline fuel exam
Consult fuel vendor on Zn limit & consider fuel exam if Fe>1.5ppb or Cu>0.05ppb
Noble Metal
on fuel:
Hydrogen addition:
Zinc injection:
Fuel considerations:

21. Current Status of NMCA Noble Metal Effectiveness
Good but need high hydrogen availability
Reapplication: limit on amount of NM deposited on fuel
Fuel Concerns
More adherent crud, potential spallation issues
Limits on FW zinc injection rates
Radiation Dose Rates
Control using RW Co-60/zinc ratio
Reduce FW iron input to mitigate fuel/radiation issues
Future Developments
UT fuel cleaning

22. Ultrasonic Fuel Cleaning: Status and Recent Developments
Ultrasonic fuel cleaning is a new technique designed to remove crud from fuel cladding surfaces
Fuel assemblies are cleaned one at a time in the fuel pool during refueling outages
Process takes only a few minutes
Little or no impact on critical path time
Crud is collected on filters in containers in fuel pool
Already used on 4 PWRs, first BWR application planned for 2004
Original objective was to reduce local flux depression (AOA) in PWRs, but significant dose rate benefits also observed
BWR application will mitigate dose rate increase following noble metal application

23. PWR: Schematic of Fuel Cleaning System
Note radial configuration is reason why it works (previous had planar UT waves)

24. Fuel Cleaning and AOA Mitigation - Callaway
Cycle 11 – 16 Assemblies Cleaned
Cycle 12 – All Reload Assemblies Cleaned

25. Callaway Dose Rate Trend CVCS Heat Exchanger

26. Ultrasonic Fuel Cleaning for BWRs
Feasibility studies completed with Exelon, NMP and TVA
Qualified for BWR Use
Applied on 16 fuel assemblies at Quad Cities BWR, March 4-7, 2004
Corrosion products collected on 4 filter cartridges (~800R/hour)
Potential benefits:
Reduced radiation buildup on out-of-core surfaces
Mitigating fuel concerns by removal of crud
Reduce loading of noble metals on fuel, increasing the relative proportion of NM on the internals

27. Ultrasonic Fuel Cleaning for BWRs

28. Radiation Field Control Manual: Goals of the 2004 Revision
A comprehensive, unbiased review of the methodologies and technologies available for field reduction, prevention and control
The manual will provide a comprehensive compilation of radiation field control techniques that can be used as
A learning tool for new RP, Radwaste and chemistry managers, engineers, and technicians
A reference for experienced managers and engineers
Industry review is a priority requirement
The manual is intended to serve the industry needs
Industry input about the content is desired greatly
If interested in being a reviewer or participate in the workshop, please contact Dennis Hussey

29. Radiation Field Control Manual
Radiation Exposure Management
Radiation Protection Radiation Field Control Manual
Cobalt
Replacement
Surface
Conditioning
PWR
Chemistry
BWR
Chemistry
Activity
Removal
Co-free SCr Process pH control NMCA/Zinc* UT Fuel Cleaning*
hardfacings Electropolishing Zinc* Guidelines LOMI Decon

30. Questions?