Very Low Exposure Rates: The
Culmination of a Series of Source
Term Reduction Efforts
Richard L. Doty
PPL Susquehanna, LLC
1
But Really, A Story Of
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2
Challenges
Management Commitment
Strategic Dose Reduction Planning
Execution of the Plan
Results
Challenges in the 1990s
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3
High insoluble iron levels in feedwater
Plan to implement hydrogen injection to
reduce susceptibility to stress corrosion
cracking of reactor vessel internals
Recognition that while Susquehanna was
improving dose-control performance, other
plants appeared to be improving faster
Management Expectation
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4
Develop a plan to meet the strategic goals
for the station (top quartile or better)
Base that plan on industry experience and
good forecasting
Address both outage and operational periods
Implement that plan, recognizing that full
implementation may take several years
Expected Dose Reduction with CFS
and One Chem Decon per Reactor Unit
(PERSON-SV)
8.00
7.00
6.00
5.00
4.00
3.00
2.00
Pre-HWC
Post-HWC
1.00
5
Actual
With HWC
With HWC & CFS
Chem Decon
2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
0.00
Susquehanna Unit 2 Milestones
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6
Condensate Filtration
FW Iron Injection
HWC
Chemical Decon
GEZIP (DZO)
Chemical Decon
6/99
7/99
8/99
3/01
12/02
3/03
SSES U2 Average BRAC
Sus quehanna 2
600
Crud Resins
HWC
500
P leat ed Filt ers
DZO
0
Jan-86
Jan-88
Dec-89
Dec-91
Dec-93
BRAC
7
Dec-95
M ilestones
Dec-97
Co-60 Dose
Dec-99
DZO
Chem Decon
Chem Decon
100
Iron Inj
40% extraction steam piping replaced 1994
Start replacing pins/rollers 1991
200
Power Uprate 1994
300
Start replacing extraction steam piping 1993
Dose Rate (mR/hr)
400
Dec-01
Dec-03
Dec-05
Unit 2 Cycle 12 Chemistry and
Operational Data 3/03-3/05
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8
Pre-Decon BRAC 3/03
Post-Decon BRAC 3/03
Median FW Zn(S)
Median FW Fe(I)
Median RCS Zn(S)
Median RCS Co-60(S)
Median RCS Co-60(I)
3.9 mSv/hr
0.1 mSv/hr
0.43 ppb
0.66 ppb
6.49 ppb
0.67 Bq/ml
0.61 Bq/ml
Unit 2 Cycle 12 Chemistry and
Operational Data 3/03-3/05
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9
Median Co-60(S)/Zn(S)
HWC
Estimated DZO kg
9.5E-02 Bq/ml-ppb
1.8-2.0 ppm
4 cycle 11
66 cycle 12
Cycle Run
677 days
End of Cycle Coast-down with semi-soft
shutdown
2005 BRAC
0.32 mSv/hr
EPRI PROPRIETARY MATERIAL - JUNE 2005
MOST RECENTLY REPORTED BRAC RESULTS FOR 39 BWRs
DIFFERENTIATED BY CHEMISTRY REGIME AT TIME OF MEASUREMENT
900
800
BRAC Dose Rate (mR/hr)
700
600
500
400
300
Median Value = 132.5
200
100
Plant BRAC Order
HWC
NWC/NMCA
10
HWC/NMCA
Pre Decon
NWC
Median
39
37
35
33
31
29
27
25
23
21
19
17
15
13
11
9
7
5
3
SUS1
0
Other Susquehanna Unit 2 Project
Milestones
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Permanent Drywell Shielding
3/05
Feedwater Heater Bay Shielding 3/05
Equipment Reliability Enhancements
–
11
Example: redesign of MSIVs
Examples of Other Source-Term
Reduction Program Elements
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12
Hydrolazing
Hot Spot Flushes
Stellite Reduction
- Enhanced “Clean-up” Post-maintenance
- Design Changes for Components to
eliminate stellite
Examples of Time/Distance/Shielding
Program Elements
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Remote audio, video, and dosimetric
monitoring
Virtual tours
Robotics
HWC flow reduction modeling
Risk-based ISI
Work management improvements
–
13
Example: 360-degree reactor cavity work platform
Health Physics Technician Drywell Dose
Compared to Prior Outages
Cumulative DW HPT Outage Dose vs. Outage Day
16000
14000
12000
Person-mrem
10000
2003
2002
8000
2004
2005
6000
4000
2000
0
1
3
5
7
9
11
13
15
17
19
21
23
25 27
Outage Day
14
29
31
33
35
37
39
41 43
45
47
49
Susquehanna vs. U.S. BWRs
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WANO/INPO PI data through 3Q05
BWR Single Fuel Cycle CRE
–
–
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BWR 12-Month Collective Dose
–
–
15
Best Quartile 1.19 person-Sv
SSES
1.14 person-Sv
Best Quartile 0.88 person-Sv
SSES
0.85 person-Sv
Susquehanna vs. BWRs Worldwide
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16
Average collective dose per reactor (personSv), using available data for 2004
European BWRs 0.81
Japanese BWRs 1.58
SSES – 2005
0.86
Historical Susquehanna SES Cumulative SRD Dose
1000
920
900
795
800
person-rem
743
694
700
627
600
474
500
529
466
440
396
400
353
383
333
300
255
265.2
285
304
222.9
245
200
170.6
100
Year
17
20
05
20
04
20
03
20
02
20
01
20
00
19
99
19
98
19
97
19
96
19
95
19
94
19
93
19
92
19
91
19
90
19
89
19
88
19
87
19
86
19
85
0
Summary from Chemistry Control
Perspective
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18
Implementation of chemistry modifications
along with excellent chemical
decontaminations has been a success
Condensate filtration system with iron addition
has been run effectively.
Pre-conditioning the fuel and FW piping to
DZO prior to the refueling outage and an
excellent chemical decontamination reduced
impact of recontamination rates.
Summary from Chemistry Control
Perspective, continued
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The SSES U2 Co-60(s)/RCS Zn(s) ratio is
about a factor of 6-10 less than the current
EPRI recommendation for NMCA plants.
The Co-60(s)/RCS Zn(s) ratio appears to work
for moderate HWC plants
Minimizing this ratio is important. Maintaining
FW and RCS Zn (s) at desired levels is also
important.
Summary from Dose Control
Perspective
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20
Results: Top quartile plant - collective dose
Result: INPO strengths – management
commitment and dose modeling techniques
Recognition: Techniques Susquehanna used
were not especially unusual, except perhaps
in their timing
Recognition: You’re only as good as your
latest results
Summary, continued
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Recognition: Continuing improvements are
required – higher standards, better results
Recognition: Importance of planning the work
and working the plan
Recognition: One team, one commitment –
there is success only by that approach