EPRI Radiation Exposure
Management Program
Highlights
Sean Bushart
Dennis Hussey
Chris Wood
ISOE International Symposium
Lyon, France
March 24, 2004
Collective U.S. Dose Rate Compared to
Power Generated
100000
90000
0 .4 5
M W -yrs
P e rs o n -re m
P e rs o n -re m /M W -yr
80000
0 .4 0
0 .3 5
70000
0 .3 0
60000
0 .2 5
50000
0 .2 0
40000
0 .1 5
30000
0 .1 0
20000
10000
0 .0 5
0
0 .0 0
1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
2
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
Applied Technology
Radiation Exposure Management
Radiation Protection
Cobalt
Replacement
Radiation Field Control
Surface
PWR
Conditioning Chemistry
Co-free
SCr Process
pH control
hardfacings
Electropolishing
Zinc*
BWR
Activity
Chemistry
Removal
NMCA/Zinc*
UT Fuel Cleaning*
Guidelines
* These techniques may be applied for other reasons
– dual benefits: to be discussed later
3
2004 Manual
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
LOMI Decon
Chemistry Factors in Radiation Control
Materials BWR Internals - NMCA
PWR Primary - Zn
Degradation
Steam Generators
Balance of Plant
Water
Chemistry
guidelines
Chemistry
Interactions
Fuel Performance
Cladding Corrosion
Crud Deposition
4
Radiation Fields
Low Level Waste
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
5
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
6
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
Effect of Zinc on Corrosion Rates
Corrosion Rate at 3.5 Months for Various Alloys
4
20 ppb Zn
3.5
No Zinc
Corrrosion Rate, mdm
3
2.5
2
1.5
1
0.5
0
304 & 316
SS
Alloys 600
& 690
Inconel X750
Stellite 6
Materials
(from Esposito, et. al., Proceedings of the fifth Symposium on Environmental Degradation
of Materials in Nuclear Power Systems – Water Reactors, August 1991)
7
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
Post Zinc Dose Rate Trends:
Diablo Canyon 2
REM/Hr
Unit 2 S/G Bowl Ave. EPRI Survey Points
(Inside of Bowls Only)
14.0
12.0
10.0
8.0
6.0
4.0
2.0
0.0
13.0
10.1 10.5
8.1
11.0
13.3
10.5
8.5
7.8
5.5
2R1
2R2
2R3
2R4
2R5
2R6
2R7
2R8
2R9
2R10
Zinc Injection
8
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
Post Zinc Dose Rate Trends: Palisades
PALISADES CHANNEL HEAD DOSE RATES
14
Began zinc injection
cycle 14
12
A S/G
B S/G
10
S/Gs replaced
EOC-8
R/Hr
8
6
4
2
0
EOC-6
9
EOC-7
EOC-8
EOC-9
EOC-10
EOC-11
EOC-12
EOC-13
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
EOC-14
EOC-15
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
10
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
11
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
BWR Chemistry Effects On Dose Rates
Materials
Degradation
Requirements for an
effective NMCA program
and inspection relief
BWR
Chemistry
Interactions
Fuel Performance
Radiation Fields
Control of Cladding
Corrosion and
Crud Deposition
Zinc injection essential
to control dose rate increase
12
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
13
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
BWR Oxide Behavior Under Reducing
Conditions
Oxide stable
under normal
water chemistry
Fe2O3
(containing Co-60,
Co-58, Mn-54, etc.)
• Corrosion Films
• Vessel crud
• Fuel crud
14
Restructuring under
HWC conditions
Fe3O4
Form of oxide
Small insoluble
particles containing
Co-60, Mn-54, etc
Soluble Co-60, etc
released during
restructure
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
Mitigating impact of NMCA on shutdown radiation fields First recommendation: control hydrogen, increase zinc
10
9
8
March 2001
Interim guidance
7
Dose Rates (mSv/hr)
Pre NMCA Dose Rate mSv/hr
Post NMCA Dose Rate mSv/hr
6
5
4
3
2
1
15
B
h
ac
Pe
D
ua
ne
Ar
no
ld
ot
to
m
-2
Fi
tz
Pa
tri
ck
H
at
ch
Q
ua
-1
d
N
C
in
iti
e
es
M
-1
ile
P
Pe
oi
ac
nt
-1
h
B
ot
to
m
-3
H
at
ch
-2
D
re
sd
en
-2
La
Sa
Q
lle
ua
-1
d
N
C
in
iti
e
es
M
-2
ile
Po
in
t-2
0
Plant
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
Radiation History 1
Hatch 1
400
HWC
30
22 scfm
45
50
45
5-6
8
350
Pleated Filters
Dose Rate (mR/hr)
300
NZO
DZO
250
O2 Inj
200
NMCA
150
100
50
0
Oct-86
16
Jun-89
Mar-92
Dec-94
Sep-97
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
Jun-00
Mar-03
Radiation History 2
Nine Mile Point 1
1250
Two hrs after
shut down
Dose Rate (mR/hr)
1000
Two days
after shut
down
750
HWC 8
scfm
500
NMCA
250
Small source of natural zinc from condenser
0
1/1/81
17
9/28/83
6/24/86
3/20/89
12/15/91
9/10/94
6/6/97
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
3/2/00
11/27/02
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)
18
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
First Post NMCA Cycle Shut Down Dose Rate
vs. RW Median Co-60(s) to Zn(s) Ratio w/o NMP1
300
Average Values of Ratio
R2 = 0.6964
KKM
Post NMCA BRAC Dose Rates, mR/hr
Dresden 3
250
Linear (Average Values of Ratio)
200
150
100
50
0
0.0E+00
1.0E-05
2.0E-05
3.0E-05
4.0E-05
5.0E-05
Cycle Median Co-60(s) to Zn(s) Ratio
19
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
6.0E-05
7.0E-05
Summary Timeline of Draft Recommendations
Prior to NMCA
Noble Metal
on fuel:
First Application
NM<30ug/cm2
Post Application
Reapplication
NM<30ug/cm2
(not apply to same batch)
Hydrogen addition:
Inject HWC
for >6 months
Target Hydrogen availability > 95%
Zinc injection:
Maintain RW ratio Co-60/Zn(s)<2x10-5
RW Zn 5-10ppb
FW Zn<0.4ppb
for 3 months
before NMCA
Be prepared to
increase FW Zn
Target cycle average FW Zn 0.4ppb
or less
Fuel considerations:
Consider baseline
fuel exam
Consult fuel vendor on Zn limit & consider
fuel exam if Fe>1.5ppb or Cu>0.05ppb
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
21
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
22
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
PWR: Schematic of Fuel Cleaning System
23
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
Fuel Cleaning and AOA Mitigation - Callaway
6
Cycle 11 – 16 Assemblies Cleaned
4
2
AO (%)
0
-2
-4
-6
-8
-10
0
2
4
6
8
10
12
14
16
18
20
22
Bur nup (GWD/M TU)
Cycle 12 – All Reload Assemblies Cleaned
24
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
Callaway Dose Rate Trend
CVCS Heat Exchanger
CVCS Letdown Heat Exchanger Inlet Dose Rate Trend
1600
C8 Inlet
C9 Inlet
C11 Inlet
C12 Inlet
C10 Inlet
1400
1200
Trip on
3/9/01
800
600
400
200
100
80
60
40
20
Days to Shutdow n
25
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
0
0
-20
mR/hr
1000
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
26
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
Ultrasonic Fuel Cleaning for BWRs
27
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
([email protected])
28
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
Radiation Field Control Manual
Radiation Exposure Management
Radiation Protection
Cobalt
Replacement
29
Radiation Field Control
Surface
PWR
Conditioning Chemistry
Co-free
SCr Process
pH control
hardfacings
Electropolishing
Zinc*
2004 Manual
BWR
Activity
Chemistry
Removal
NMCA/Zinc*
UT Fuel Cleaning*
Guidelines
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
LOMI Decon
Questions?
30
Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.