Braidwood Station Alternate

Post Peroxide Cleanup Methodology

2

Refuel Outage Shutdown Chemistry

Proper shutdown chemistry is necessary in order to ensure:• Primary system dose rates and smearable

contamination levels are maintained ALARA to the extent that shutdown activities influence these parameters.

• The coolant is prepared for head lift (fully oxygenated and purified to within EPRI guideline endpoints).

• Plant effluents are minimized to the extent possible, and managed within station effluent limits.

• Water movement is managed to minimize liquid radwaste effluents and tritium releases.

3

Exelon Refueling Outage Shutdown Template

The Exelon Refueling Outage Shutdown Template is a tool to prepare for refueling outage shutdown. This “Alternate” template was developed for A1R13 to establish a different approach to shutdown that allows the LSIV’s to be closed prior to forced oxidation so that other outage work can be accommodated.

4

Exelon Shutdown ChemistryOutage Readiness

On-Line Chemistry - Maintained RCS at constant elevated pH

• U2 pH is maintained at 7.2 during fuel cycle. • U1 pH is maintained at 7.35 (first time) during fuel cycle.

RWST is placed on recirculation cleanup with an FC Demineralizer 3 months prior to the start of the outage to reduce soluble iron and radionuclides.

Prepare Both CV Demins and both FC Demins with fresh HOH resin underlay and macro-porous resin overlay.

• Plans for Orthoporous in one Letdown Demin use during A1R14.

5

Exelon Shutdown ChemistryOutage Readiness

Assess the condition (dose and differential pressure) of the reactor coolant filter approximately one week prior to shutdown to determine filter size / change out frequency.

• Normal use of 0.1 micron PAL filters U1 installing 0.05 micron filter – November 2008.

• Increase to 0.45 micron filters - if change out periodicity is less than 2 hours

• Increase to 1 micron filters - if change out periodicity is less than 1 hour

6

Exelon Shutdown Chemistry

Shutdown Chemistry – End of Cycle (EOC) Boron.• Determine the refueling boron concentration target

for the shutdown. • Exelon data shows that refueling outage dose

rates increase significantly when EOC boron is allowed to reach zero ppm.

• Since implementation of EOC Boron at 10 ppm, ~10% dose rate reduction on S/G tubesheets.

• Deboration is controlled through the Demins rather than through dilution to avoid oxygenated water.

7

Pre-Outage / Shutdown Dose Rates

U1 Pre-Outage Dose Rates

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22.00

24.00

26.00

28.00

30.00

12 w

eeks

11 w

eeks

10 w

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9 w

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8 w

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7 w

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6 w

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5 w

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4 w

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3 w

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2 w

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1 w

eek

Shu

tdow

n

mre

m/h

r

A1R13 A1R12 A1F34 A1R11 A1R10 A1R09 A1R08

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Alternate Post Peroxide Cleanup Methodology

Reduced volume of water for post peroxide clean up from 107,000 gallons to 62,000 gallons or 58% of original inventory.• Isolated Pressurizer • Isolated Steam Generators• Isolated some CV / Letdown areas

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Pre-Dissolution Activities

Chemical Degas• For the alternate template approach,

RCS Hydrogen must be reduced to < 5 cc/kg but maintained >1 cc/kg prior to the forced oxidation because the RCPs will be secured and LSIVs closed prior to the peroxide add.

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Pre-Dissolution Activities

Shutdown all 4 RCPs• Isolates Pressurizer and associated

piping from dissolution thus reducing pressurizer system dose rates.

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Pre-Dissolution Activities

Start-up Letdown Booster Pump• Cleanup flow at 160 gpm

Utilizing Two CV Demin Beds • Increased clean-up flow to 175 gpm

Letdown Relief Valve set point adjusted to adjusted to increase flow/pressure.• Engineering design change increased set

point from 205 psi to 230 psi.• Will increase flow to >180 gpm if using two

Letdown Demins

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Pre-Dissolution Activities

Isolation of Steam Generators via Loop Stop Isolation Valves (LSIVs).• Less opportunity for particulates to plate out

on S/G tube sheet or piping surfaces resulting with reduced dose rates on S/G platforms.

• Activity of water drained to RF sump is reduced. (less dose to clean sump)

• Activity of water transferred to RCDT reduced (and dose rates of components near tank).

• 377’ IMB General Area dose rates also reduced.

13

Pressurizer Isolation

Top of Pressurizer normally 25 - 35 mrem/hr general area with 350 – 450 mrem/hr contact dose rate on RY Spray line (post dissolution & flush)

A1R13 (isolation & flush) was 15 – 20 mrem/hr general area with 150 – 170 mrem contact on RY Spray line.

14

Pressurizer Isolation

Bottom of Pressurizer normally 100 – 150 general area with 700 – 900 mrem/hr contact dose rate on RY Surge line (post dissolution & flush)

A1R13 (isolation & flush) was 50 mrem/hr general area with 180 mrem/hr contact on RY Spray line.

A2R13 (second cycle zinc) saw increased dose rates due to increased RCS activity and low flow area.

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Pressurizer Isolation

Pressurizer Weld Overlay Project • Project estimate 20.963 Rem• Project challenge 16.940 Rem• Actual Project total – 13.641 Rem• 7% TLD bias – 12.686 Rem• Lowest Dose industry PWOL using PCI

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Pressurizer Isolation

RY Platform • RY Platform general area dose rates

are normally 150 – 500 mrem/hr.• A1R13 general area dose rates were 50

– 200 mrem/hr.

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CV / Letdown Isolation

CV / Letdown Isolation • Only in Containment after depressurization• CV / Letdown general area dose rate

normally 50 – 350 mrem/hr.• CV / Letdown contact dose rate normally 300

– 600 mrem/hr.• A1R13 general area dose rate were 20 – 150

mrem/hr.• A1R13 contact dose rate were 100 –150

mrem/hr.

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Standard Measurement Radiation Points

Unit 1 SMRP

0.0

1.0

2.0

3.0

4.0

5.0

A1R

01

A1R

02

A1R

03

A1R

04

A1R

05

A1P

02

A1R

06

A1R

08

A1R

10

A1R

11

A1R

12

A1R

13

Outage

Rem

/hr

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Steam Generator Maintenance

Lowest dose U1 Steam Generator Maintenance in station history.• A1R13 = 19.379 person-rem• A1R12 = 27.951 person-rem• A1R11 = 23.213 person-rem• A1R10 = 39.080 person-rem• A1R08 = 24.960 person-rem• A1R06 = 44.413 person-rem• A1R05 = 34.600 person-rem• A1R04 = 33.920 person-rem• A1R03 = 47.600 person-rem• A1R02 = 63.990 person-rem

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Base Point SurveysU1 377' IMB Base Point Survey

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70

A1R

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A1M

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A1R

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A1R

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A1R

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A1R

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A1R

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A1R

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A1R

13

Outage

mre

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r

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Outage Maintenance

A1R13 was second largest scope in station history (SGRP was largest)

Included PWOL, ECCS Strainer, and S/G Insulation replacement, Split Pin, Core Barrel, Ex-Core Dosimetry and Barton Transmitters.

Major Modifications accounted for 30 Rem109 Rem goal - 92 Rem actual

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Historical Outage Exposure

A1R13 = 92 person-remA1R12 = 98 person-remA1R11 = 81.8 person-remA1R10 = 134.8 person-remA1R09 = 79.7 person-remA1R08 = 96.8 person-remA1R07 = 221 person-rem (SGRP)

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Alternate Post Peroxide Cleanup Methodology

Peak Dissolution Activity• 12.8 Ci/ml

Flood Up• EPRI Guidelines suggests clean-up to less than

0.05 Ci/ml.• Actual cleanup prior to flood up was 0.028 Ci/ml.• Final cleanup was 0.015 Ci/ml.

Clean up window is 40 hours.

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Alternate Post Peroxide Cleanup Methodology

Both FC Demins put into service.• Outage unit provides cavity – cavity cleanup

capabilities.• Operating unit provides spent fuel pool –

cavity cleanup.

Use of 1 micron PAL filters in both Tri-Nukes (600 & 240)

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Alternative Post Peroxide Cleanup Methodology

U1 Pre-Outage / Disolution / Start-Up Rad Monitor Dose Rates

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60.00

70.00

80.00

mre

m/h

r

A1F34 A1R11 A1R10 A1R09 A1R08 A1R12 A1R13