ML102450688

EC 360234, Eval - Mech, Braidwood Station

ML102450688
Person / Time
Site:	Braidwood
Issue date:	09/01/2010
From:	- No Known Affiliation
To:	Office of Information Services
References
EC 360234, FOIA/PA-2010-0209
Download: ML102450688 (27)

Text

EC 360234 EVAL - MECH DRAFT FOR COMMENT Introduction In 1998 and 2000, leaks from Vacuum Breakers #3 and #2, respectively, on the Lake Blowdown line (0CW09C48) going to the Kankakee River resulting in water contaminated with radioactive tritium being released into the surrounding area and a local pond (referred to as the Exelon pond). Over time, the tritium entere~d the groundwater and due to the flow of the groundwater, the contamination has continued to spread. To remediate this problem, Exelon in conjunction with government agencies, has developed a plan to reduce the tritium concentration in the groundwater. The remediation plan involves lowering the level in the local pond to draw in turn the surrounding groundwater into the pond. The pond water level will be lowered via a pumping system that discharges into the Blowdown line where it will be discharged into the Kankakee River.

To accomplish this plan, the new pumping system must be installed, physical alterations must be performed on the Blowdown line and the operation of the plan must be procedurally controlled. All of these actions must be implemented while conforming to all Station design bases, licensing requirements, State permits and regulations and any new requirements imposed because of the spills and their remediation.

This EC 360234 evaluates the acceptability of discharging tritiated water from the Exelon pond, using the Interim Remedial Action Pumping System (IRAPS),

pumping the contaminated water into the Circulating Water System Blowdown Line (CW BDL) and discharging it to the Kankakee River. The EC provides a description of new and existing components, revisions to existing systems and components and their operation and control. Additionally, the EC provides the basis and the methods that will be employed to ensure the plan is acceptable with regards to licensing and regulatory requirements.

To accomplish this evaluation, numerous documents were reviewed and used as inputs for this EC and are referenced, as appropriate.

The document is comprised of six detailed sections. Each section addresses a specific portion of the plan.

Page I of 25

EC 360234 EVAL - MECH I DRAFT FOR COMMENT I Table of Contents Introduction 1 Executive Summary 3 Effect on Groundwater 4 Geology discussion 4 Remediation philosophy 4 Effects on neighboring residents 5 Communications with neighboring residents 6 Exelon Pond 7 General description 7 Tritium Concentration 7 Effect on pond fish 7 Pond level limits 8 Interim Remedial Action Pumping System 9 Flow path 9 Basic description of the IRAPS 9 Startup Testing 10 Procedural control of the IRAPS 10 IRAPS Interface with other Procedures 10 Basic description of IRAPS controls 11 Maintenance of IRAPS 11 Connection to Circulating Water System Blowdown Line 12 CW Blowdown Line configuration 12 Existing vacuum breaker configuration 12 Removal of Vacuum Breaker # 2 (0CW136) 13 Replacement piping/valve segment 13 Surge check valve removal from Vacuum Breaker # 2 14 Page 2 of 25

EC 360234 EVAL - MECH DRAFT FOR COMMENT Effect of Interim Remedial Action Pumping System on the Blowdown Line and Lake Blowdown 15 Actions to Prevent Leakage from the BDL Vacuum Breakers 15 Actions to Prevent Leakage from the Vacuum Breaker Enclosures 15 Remote monitoring of Blowdown Line Integrity 16 Local monitoring of. Blowdown Line Integrity 16 Concentration in Blowdown Line 17 Blowdown Line Integrity 17 IRAPS Pump to CW BDL Integrity 17 Vacuum Breaker surveillance 18 Transient Effects on the Blowdown Line 18 Failure Modes 18 Braidwood Station Cooling Lake Chemistry 18 Monitoring of Kankakee River 19 Offsite Dose Calculation Manual (ODCM) 19 Chemistry Procedure changes 19 Effect on Wilmington Pumping Station 20 NPDES 20 Approvals for Exelon Pond discharge 21 References 23 Executive Summary (Later by WGI)

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EVAL - MECH DRAFT FOR COMMENT Effect on Groundwater Geology discussion A comprehensive groundwater investigation program was conducted by Conestoga-Rovers & Associates (CRA) at Braidwood Station in 2005 and early 2006.

As a result of that investigation, an area was identified where tritium has been detected above the 35 IAC 620 (Illinois Administrative Code) groundwater standard (20,000. picocuries per liter (pCi/L)). This area, approximately 4.5 acres in size is located near Smiley Road, at the southeast corner of a pond owned by Exelon and just west of the Circulating Water Blowdown Line (CW BDL).

Data indicate that tritium at concentrations above the lower detection capability (approximately 200 pCi/L) has migrated into the Exelon pond, north of Smiley Road and, to a limited extent, past the pond. Maps included in the attached Interim Remedial Action Plan (IRAP) illustrate the location of the tritium plume in the groundwater. (Reference 1)

Remediation philosophy The Interim Remediation Action Plan (IRAP) has been developed to retard the movement of the tritium plume in the groundwater and reduce the tritium that have migrated into the downgradient of the Exelon pond.

The removal of tritium in the groundwater will be achieved by pumping water from the Exelon pond to lower the level in the pond and create a 'cone-of-depression' in the water table. Lowering of the pond will reverse groundwater flow from north of the Exelon pond and mitigate the concentrations of tritium over time. This will allow for the removal of tritium within the main plume area to prevent further tritium migration beyond the Exelon pond.

The IRAP involves the placement of a pump in the Exelon pond to transfer water from the pond into the Braidwood Station blowdown line. The pond water will be pumped via a forcemain (i.e., a discharge pipe to be installed from the pond to a connection point on the blowdown line).

During the start-up of the system, the tritium concentration in the pumped water will be closely monitored and correlated with the flow rate. This will be done to ensure the tritium concentration entering the blowdown line will form a composite concentration in the blowdown line of less than 200 pCi/L.

The area will also be closely monitored during the start-up phase to ensure that lowering of the pond will not overdraw nearby shallow private wells. The operation is expected to last longer than one year, but pumping may not be continuous, once a steady state pond level is achieved.

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EC 360234 EVAL - MECH I DRAFT FOR COMMENT I The duration of the proposed interim remediation operation will be based on a review of the operating conditions at the impacted area and the effectiveness of the remedial action over time. This review will consider how the proposed pond pumping system could be modified to shorten the cleanup time and to increase tritium recovery. (Reference 1)

Effects on neighboring residents The influence on private wells of neighboring residents has been predicted by CRA and is documented in Reference 21.

The predicted drawdown, or drop in the level of the water table, at locations where private wells exist and are being used is shown on CRA drawing Reference 25. These drawdown values are based upon preliminary modeling performed to assist in the design of the pumping system. The estimated drawdown ranges are from 5.5 feet near the pond to 3.2 feet at locations farther north of the pond. This drawdown amount is valid only for the shallow sand aquifer and would not be experienced in the deeper bedrock private wells, which are installed at depths of 60, ft to over 600 ft, and are in different geological formations.

The predicted drawdown for the pond (7 ft) and the predicted drawdown in areas of the shallow private wells (3 to 5 ft) are based upon conservative modeling assumptions and simplified input parameters. As such, the drawdown required in the pond (and therefore the drawdown measured in the capture zone in the groundwater) may be less than predicted.

Planned monitoring of pond and groundwater levels at the start up of pumping will better establish the actual degree of drawdown or drop in the water table aquifer. Areas located out of the predicted capture zone, or approximately 1200 feet from the pond, would not be affected by the pumping according to the preliminary modeling evaluations.

It is not possible to predict, at this time, the specific affects on the shallow private wells because of unknown conditions such as:

• pumping level in the private wells

" average yield of the private wells

" average pumping rate of the private wells

• history of seasonal water table fluctuations around the pond.

Consequently, it is possible that the performance of some of the private wells may be affected by pond pumping. During the pumping operations, Exelon and CRA will monitor water levels in groundwater sampling wells and private wells and take actions to adjust pumping rates and/or provide water for any residential wells that show may be affected.

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EC 360234 EVAL - MECH DRAFT FOR COMMENT Audible noise impact to neighbors from the pumping site was considered and determined to be negligible, since the IRAPS pump/motor is submersible and will be below the surface of the pond, insulating the noise.

Communications with neighboring residents The communications plan for the interim remediation project consists of direct communication with the most affected stakeholders, outreach to local and county officials, media outreach and an information night to inform the general public (scheduled for April 6, 2006).

Door-to-door communications were made with the most affected stakeholders on March 29, 2006. This included residents whose groundwater is affected along with those who live in the vicinity of the plume or within 1000 feet of the blowdown line. These residents received an information packet that included a letter from the Braidwood Station Site Vice President and a copy of the news release that explained the interim remediation plan. They also received an invitation to the April 6, 2006 information night, and a page with frequently asked questions.

The information night event is intended to educate the public on the planned remediation efforts and to allow those interested to engage in one-on-one conversations with Exelon, State and NRC representatives.

Also on March 29, 2006, a news release was issued to inform the general public, and local and county officials were contacted by telephone and faxed pertinent information.

The news release and frequently asked questions documents were loaded onto the Braidwood Station tritium communications website (www.braidwoodtritium.info) and the information was included in a previously established hardcopy repository of tritium project documents at the Fossil Ridge Library in Braidwood, IL.

Prior to beginning the pumping, the remediation team will communicate with neighbors whose wells may potentially be affected to describe the monitoring process and contingency plans for any effect on private well performance.

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EC 360234 EVAL - MECH DRAFT FOR COMMENT Exelon Pond General description The Exelon owned pond at issue, is located north and east of the Smiley Road and Center Street intersection. This pond is generally square in shape, with the approximate dimensions of 1100 feet by 1150 feet and an average depth of 16 feet. Pond level is measured using a manual level reading gauge in the southeast corner of the pond. (Reference 2)

Tritium Concentration Tritium concentration in the pond is currently 2341 pCi/L, however, the concentration level will be assumed to be 3577 pCi/L based upon calculation of the maximum concentration the pond could reach, if all the plume was pulled into the pond. (Reference 17)

Effect on pond fish Tritium transport occurs rapidly through water and can accumulate in aquatic vegetation, fish and other animals. (Reference 9)

The pond contains several varieties of fish including large mouth bass, crappie, blue gill, catfish and grass carp (white amur). Estimated sizes for the bass are in the 6 to 10 pound range and the grass carp could weigh as much as 40 pounds. (Reference 9)

The Illinois Department of Natural Resources (IDNR) and Exelon's Environmental Department have determined the following: (Reference 9)

1. While the pond is expected to be pumped down an estimated 7 to 8 feet, leaving an approximate pond depth of 10 feet, moving the fish is expected to be more harmful than leaving them in the pond,

2. With IRAPS in operation, the lake should be monitored twice per week by conducting shoreline walk-downs to look for signs of stressed fish. A log of the shoreline inspections should be conducted including who conducted the inspection, time of day and general observations.

3. A contingency plan to move the fish from the pond will be established.

A fish sampling effort is tentatively planned for the end of April to collect representative species of fish. Collected fish will follow standard IDNR and/or IDPH contaminant sampling protocol and will be sent to a lab for tritium analysis. Completion of any such sampling, or the results, is not required prior to pumping of the pond.

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EC 360234 I EVAL - MECH DRAFT FOR COMMENT Pond level limits The pump will be operated at a sufficient flow rate to drop the pond level by approximately 7 feet. The actual level that will be maintained by the pump will be dependent upon the groundwater level responses in monitoring wells surrounding the pond to ensure that private shallow wells in the area are not lowered to a level that may limit residences water intake. (Reference 1 and 25)

Although preliminary modeling was performed to develop the initial design criteria, the system will be closely monitored and modified during the start-up phase. That is, the steady state pond level and the pump flow rate can and will be varied depending on groundwater response, if design conditions change. (Reference 1)

CRA will provide the aforementioned monitoring and advise Exelon of any recommended changes to monitoring or pumping operation.

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EC 360234 EVAL - MECH I DRAFT FOR COMMENT I Interim Remedial Action Pumping System Flow path The IRAPS is designed to transfer water from the Exelon Pond into the Circulating Water System Blowdown Line (CW BDL) through a connection in the Vacuum Breaker #2 vault. Once injected into the Blowdown Line (0CW09C48), the pond water will be diluted with the blowdown water from the Braidwood Cooling Lake and ultimately discharged to the Kankakee River.

Basic description of the IRAPS The ]RAPS pump is attached to an 8-inch flexible hose that flanges under the water level to an 8-inch carbon steel line resting on the walls of the pond.

The 8-inch carbon steel line rises above the surface of the pond to a 20-foot horizontal run of above ground piping. This 20-foot section of piping includes the locally mounted instrumentation required to operate the system.

Instrumentation and valves include a 1-inch vent line, pressure indicator, flow meter, including totalizer, 2-inch line for compositor feed, an 8-inch wafer check valve, and an 8" globe valve. All instrumentation and controls will physically be located on a concrete pad near the point where the IRAPS pump discharge exits the pond surface. (Reference 2)

The carbon steel line then is flanged to a 10 inch High Density Polyethylene (HDPE) line. This HDPE line, SDR 11 rated for 160 psig, is routed underground, approximately 4 feet below the surface for freeze protection, and enters the Vacuum Breaker # 2 vault through a penetration in the side of the vault.

Within the vault, the 10-inch HDPE is connected, via an 8" reducing flange, to the temporary piping/valve segment that replaces Vacuum Breaker # 2.

HDPE pipe sections are heat fusion welded' together. When fusion pressure is applied at the designated temperature and prescribed force, with special fusion welding equipment, the molecules from each pipe surface end mix.

As the joint cools, the molecules return to their crystalline form, the original interfaces have been removed, and the two pipes have become one continuous length. The result is a fusion joint that is as strong, or stronger, than the pipe itself, creating a leak-free joint.

There are no underground flanged connections within the HDPE piping.

The iRAPS pump has a shut off head of 75 psig, below the design pressures of the HDPE and the CW BDL of 160 psig and 110 psig, respectively. This pump is capable of 1000 gpm, however, flow will be throttled, based upon the dilution calculation included in Operating Procedure BwOP CW-28, Rev 0, described further in this document.

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EC 360234 EVAL - MECH I DRAFT FOR COMMENT Startup Testing Upon completion of IRAPS piping construction, before connecting to the IRAPS pump and CW BDL and prior to any pumping operation, hydrostatic testing of the new piping will verify its integrity at a pressure of 150 psig, twice the shut-off head pressure of the pump.

In addition to hydrostatic pressure testing, standard construction testing, electrical 'dead circuit' testing and instrument calibrations will also be performed.

Testing conducted by the piping contractor will be directed by Exelon.

Specific test descriptions and results will be documented in the final version of this EC.

Procedural control of the IRAPS Initial startup operation of the IRAPS will be performed by a new procedure, Braidwood Station Operating Procedure, BwOP CW-28, Rev 0, 'Operation of the Exelon Pond Pump'.

BwOP CW-28 will incorporate the following topics:

1. Implementation/installation of the temporary piping/valve segment replacing Vacuum Breaker # 2.

2. Verification of the valve lineup.

3. C(alculation of IRAPS pump flow rate, based upon tritium sample results.

4. Starting of the IRAPS pump and throttling flow to the calculated dilution flow rate.

5. Daily monitoring of IRAPS and CW systems for proper operation.

6. Direction to shutdown the IRAPS prior to any planed change in CW Blowdown flow, or after any transient causing Blowdown flow to change.

7. Direction to shutdown IRAPS pump immediately, after being notified of leak detection in any of the CW Blowdown Line vacuum breaker vaults by means of the remote monitoring system.

,-8. Removal of the temporary piping/valve segment, when no longer required, and replacing Vacuum Breaker # 2.

IRAPS Interface with other Procedures BwOP CW-28 will provide direction for continued operation of the IRAPS, including limitations of pump flow, based upon evaluations of tritium concentrations in the pond. SPP 06-003, 'CW BD Flow Throttled at Discharge Structure Test' determined the CW BDL pressure at which all installed CW BDL Page 10 of 25

EC 360234 I EVAL - MECH DRAFT FOR COMMENT Vacuum Breakers are fully seated. The CW BD flow at this pressure will be incorporated into a procedure revision to BwOP CW-12, 'Circulating Water Blowdown System Fill, Startup, Operation and Shutdown'. An Excel spreadsheet, attached as part of this EC, will be used in procedure BwOP CW-28 in order to determine maximum IRAP pump flow to keep tritium concentration in Blowdown line below 200pCi/L.

BwOP CW-28 will address any changes in CW Blowdown flowrate, by securing IRAPS until further evaluation of an acceptable discharge rate from IRAPS can be completed. Furthermore, BwOP CW-1 2, 'Circulating Water Blowdown System Fill, Startup, Operation and Shutdown' will require cross reference to BwOP CW-28.

Basic description of IRAPS controls IRAPS has a Hand/Off/Auto switch mounted in the panel board, which is the main control of the pump. When in the Hand mode, the pump will remain in operation until it is placed in the Off mode or it is turned off by the Internet remote shutoff.

When the position switch is in the Off mode, the pump cannot be turned on remotely.

A level switch, mounted with the pump, is functional when the switch is placed in the Auto mode. This level switch sends a signal to the pump controller, turning the pump on or off based upon the 4 to 20ma control signal.

The remote monitoring device receives a 4 to 20 ma signal, which allows an operator to determine the level in the pond at any time. The pond level is monitored by a website providing notification to the operators, through a telephone call, if the pond level is high or low.

If the pump is in any mode other than Off, the remote monitoring device has the ability to Trip and Restart the pump, at any time.

The main operating panel is equipped with a main disconnect switch and transformer disconnect. The transformer powers the breaker panel that powers the internal outlets, the pump controller and the remote monitoring device.

Power for the IRAPS is supplied from the Commonwealth Edison off-site power, not an on-site Braidwood Station power supply.

Maintenance of IRAPS Maintenance of the IRAPS system will be done by a service contract that is created by the station to include any preventive maintenance on the system and for repair of any equipment if it malfunctions or fails.

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EC 360234 EVAL - MECH DRAFT FOR COMMENT Connection to Circulating Water System Blowdown Line CW Blowdown Line configuration The CW BDL is constructed of pre-stressed concrete 'Embedded Cylinder Pipe' (ECP) manufactured by Interpace Corporation, Design Class D with an internal working pressure of 110 psig. The pipe has been evaluated for full internal vacuum and has been found acceptable. (Reference 26)

ECP is a steel cylinder, fully encased in a concrete core, which is subsequently wire-wrapped and externally coated with a cement-rich mortar.

Existing vacuum breaker configuration CW Blowdown Line, 0CW09C48, has eleven air/vacuum valves strategically placed along the length of the Blowdown line. (Reference M-44 Sheet 3A and M-900 series of Braidwood P&IDs).

These valves, referred to as vacuum breakers in this discussion, act to introduce air into the line under conditions where a section, or sections, of the pipe are no longer water solid, thus helping prevent a vacuum condition, or to release air from the line when filling the system or during operation.

Referred to as a 'vacuum breaker', the device is actually a combination of an air/vacuum valve and an air release valve, both mounted on top of a surge check valve.

The air/vacuum valve operates to allow air to escape freely at any velocity (maximum discharge velocity is approximately 300 feet per second at 6.7 PSI)

The surge check valve operates on the interphase between the kinetic energy in the relative velocity flows of air and water. This surge check is a normally open valve, spring loaded, so that air passes through unrestricted.

When water rushes into the surge check unit, the disc begins to close against the spring tension and reduces the rate of water flow into the air valve by means of throttling holes in the disc.

This action ensures normal gentle closing of the Air/Vacuum Valve regardless of the initial velocity flows involved and minimizes pressure surges when the valve closes.

As soon as the air/vacuum valve is closed, the pressure on both sides of the surge valve disc equalizes and the disc automatically returns to its open position. This means the air/vacuum valve does not need an incipient vacuum to open, but can open at any time the water level drops and line pressure approaches atmospheric and immediately have full re-entry flow of air into the pipeline before a vacuum can form.

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EC 360234 EVAL - MECH I DRAFT FOR COMMENT The slow closing feature protects the air/vacuum valve itself and at the same time prevents the air/vacuum valve from creating a surge in the pipeline by slamming shut.

Removal of Vacuum Breaker # 2 (OCW136)

Vacuum Breaker # 2, 0CW 136, will be removed from the CW System Blowdown Line. Replacing the vacuum breaker, within the concrete vault, will be a combination of new 8" carbon steel line, flange connected to the existing butterfly isolation valve, 0CW]135, and surge check valve and two 8" check valves. The piping/valve segment will be connected to the previously installed 10, to 8" reducer, part of the Interim Remedial Action Pumping System.

EC 360112 will provide an opening for the High Density Polyethylene (HDPE) pipe of the IRAPS to enter Vacuum Breaker # 2 vault. The vault will be appropriately sealed after the HDPE pipe entry into the vault is completed.

Replacement piping/valve segment The new piping/valve segment will consist of new 8 inch piping, fittings, two check valves and support. This configuration was designed to be installed in place of Vacuum Breaker # 2 and attached to the Vacuum Breaker surge valve.

Piping and components shall conform to the requirements of Piping Design Table 100BB.

,Any welding shall be performed in accordance with applicable Exelon procedures.

A support capable of supporting 500 lbs is required between the pipe and the new floor of the vault. Wood cribbing, a jack stand or other suitable configurations that can support the weight of the piping is acceptable. The additional support is required to prevent placing an eccentric load on the CW blowdown pipe. Since the new concrete floor is on grade, it is capable of supporting the additional load.

Configuration details are provided on sketch, Reference 30.

A hydrostatic test will be performed for the piping/valve segment. Test pressure shall be equal to the test pressure for the pond piping. If shop tested, pressure shall be 150 psig.

Verification of check valve flow orientation will be verified.

All components of this new piping/valve segment are designed for a working pressure greater than either the IRAPS or CW Blowdown Line Page 13 of 25

EC 360234 EVAL - MECH I DRAFT FOR COMMENT I Surge check valve removal from Vacuum Breaker # 2 The surge check valve portion of OCW136, Vacuum Breaker # 2, is not designed to pass 1000 gpm flow, per the vendor. Removal can be accomplished using two methods:

1. Removing only the surge check valve internals, which can be accomplished without disconnecting isolation butterfly valve, OCW1 35.

Following removal of the air/vacuum valve portion of 0CW136, the internals of the surge check valve can be removed through the top of its body.

2. Removing the entire surge check valve assembly would require securing the CW Blowdown Line, since the manual isolation butterfly valve, OCW135, cannot provide isolation from the Blowdown Line during removal. This is due to the integrated assembly (shared flange bolting) of the manual isolation butterfly valve and the surge check valve.

OBwOS CW-Al, 'Circulating Water System Blowdown and Makeup Vacuum Breaker Valve Inspection', an annual inspection, was last performed on 11/11/2005 to verify proper operation of OCW135. However, should method number 1 above be used, the possibility still exists that the CW Blowdown may need to be secured if 0CW135 does not properly seal.

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EC 360234 EVAL- MECH I DRAFT FOR COMMENT I Effect of Interim Remedial Action Pumping System on the Blowdown Line and Lake Blowdown Actions to Prevent Leakage from the BDL Vacuum Breakers The following actions are being taken to provide a high level of confidence that the vacuum breaker valves will not leak while executing the [RAP.

1. Each vacuum breaker valve that will be in service was inspected prior to initially commencing the interim remediation operation, and in particular:

" float integrity and seating surface components within each vacuum breaker valve were inspected to ensure the proper sealing of those components to prevent leakage.

" replacement of any vacuum breaker release valves found faulty.

2. A review was performed to evaluate if vacuum breaker PMs require revision or addition due to the higher operating pressure of the CW BDL. (SPP 06-003 will adjust CW BDL pressure as discussed below).

It was concluded that the PM frequency for the vacuum breakers was adequate, and that the PM frequency for the air release valves would need to be updated for replacement every 2 years for all 11 of the vacuum breakers.

3. During the interim remediation pumping operation, the blowdown line will be operated 'pressurized' (pipe water solid) along the full length of the pipeline to ensure the vacuum breaker valves that are in service will remain seated (i.e., closed). 'Pressurization' will be accomplished by throttling a new 18 inch valve installed per EC 360114, "Add an Additional Valve to CW Blowdown Line 0CWC2CA18", at the end of the Blowdown line near the discharge point into the Kankakee River.

4. SPP 06-003, 'CW BD Flow Throttled at Discharge Structure Test', will determine the CW BDL flow at the desired pipe pressure to fully seat the vacuum breakers. The CW BD flow at this pressure will be incorporated into a procedurerevision to BwOP CW-12, 'Circulating Water Blowdown System Fill, Startup, Operation and Shutdown'.

Actions to Prevent Leakage from the Vacuum Breaker Enclosures The vacuum breaker vaults were modified to be watertight. Watertight manhole frames and gasketed bolted covers are anchored to the concrete vault roof slab. A watertight gasket will be installed between the frame and the concrete roof slab to prevent water intrusion.

New concrete floors for the vaults are reinforced with welded wire fabric mesh and doweled into the manhole walls to prevent cracking and differential movement of the slab. A bentonite water-stop is installed at all Page 15 of 25

EC 360234 EVAL - MECH I DRAFT FOR COMMENT joints and slab penetrations (floor slab to manhole wall, floor slab to drain pipe, floor slab to flange outlet) and a twelve inch wide strip of joint wrap will be applied around the vault wall at the wall to floor slab interface to preclude water movement into or out of the vault. The inside of the vaults were covered with suitable waterproof coatings at the base of each vacuum breaker pit were installed per EC 3601.12 to contain any leakage within the vault. (Reference EC 360112)

Remote monitoring of Blowdown Line Integrity Since all eleven vacuum breaker vaults were sealed, as described in the previous discussion, the source of any water within the vault will be from the CW BDL and not from groundwater. A continuously monitored leakage detection system will be installed in all eleven of the vacuum breaker enclosures to promptly detect any such leakage.

This leakage detection system will consist of sensors placed at the bottom of the vacuum breaker enclosure that will be wired to a transmitting device installed next to the vacuum breaker. If the sensors detect water, the transmitter will send a signal via a cellular telephone network to Operators in the Braidwood Main Control Room. Upon receipt of notification from the system, operators will promptly take action, remotely or manually, to turn off the pump at the pond to secure the interim remediation operation.

The transmitting device is powered by a solar panel mounted outside of each vacuum breaker vault. A 6-day battery provides backup power and is charged by the solar panel.

Upon receipt of an alarm from the leak detection system, operators have two options.

1. connect via a web site (alarmagent.com) and remotely shut down the IRAPS pump at the pond

2. dispatch an equipment operator to turn off the pump at the pond to secure the interim remediation operation.

Operation of the remote leak detection system is controlled by BwOP CW-28.

Local monitoring of Blowdown Line Integrity On a daily basis the BDL right-of-way will be inspected for signs of leaks.

Personnel performing the inspection will notify the Braidwood Station Main Control Room (MCR) to secure the IRAPS pumping if signs of leakage are found. Specific details of the daily inspection will be included in the

'Operator Rounds' package.

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EC 360234 EVAL - MECH I DRAFT FOR COMMENT I Concentration in Blowdown Line Chemistry and Operations procedures include sampling and flow rate limitations to ensure that the composite concentration of tritiated water remains less than 200 pCi/I at all times. This limitation is governed by a table in BwOP CW-28, which lists maximum flow rates from the pond pump based on CW BDL flow. The maximum flow rates were determined by a dilution calculation assuming a Cooling Lake tritium concentration of 35 pCi/I, which was obtained via enhanced LLD sampling of the Cooling Lake) and an assumed maximum pond concentration of 3577 pCi/I. Weekly chemistry sampling of the pond will verify that the pond concentration remains below 80% of the assumed maximum concentration.

Blowdown Line Integrity On December 20-22 and 27-30, 2005, and January 4-6, 2006, the Pressure Pipe Inspection Company inspected part of the 48" Concrete Blowdown Line using its patented Sahara Leak Detection Technology.

The Sahara inspection was conducted on a 5.06 mile long section of the 48" Concrete Blowdown Line, between Vacuum Breaker (VB) #1 (0CW058), and the 48" x 30" reducer that is located 890ft past VB # 11 (0CW078). Nine insertions were required at the vacuum breakers to complete the inspection.

Analysis of the data obtained during the inspection revealed no leaks within the inspection area.

RAPS Pump to CW BDL Integrity The HDPE piping connecting the IRAPS to the piping/valve segment replacing Vacuum Breaker # 2 was hydrostatically tested at 150 psig prior to burial, per the construction testing. (The piping was buried for freeze protection, thus eliminating the need for heat tracing). The HDPE pipe is rated for 160 psig (design pressure).

The span of approximately seven hundred feet of HDPE piping, from the pumping system to the connection at Vacuum Breaker # 2, will not be observed by a daily walkdown, since the piping is new with a recent hydrostatic test.

HDPE pipe is made from high-density polyethylene, which is known for its flexibility, toughness and chemical resistance. Since HDPE pressure pipe is fusion welded together, the weld is as strong as the original pipe, it becomes a monolithic or one piece pressure piping.

Refer also to section 'Basic description of the IRAPS' for a description of

'fusion welding'.

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EC 360234 EVAL - MECH I DRAFT FOR COMMENT I Vacuum Breaker surveillance OBwOS CW-Al, 'Circulating Water System Blowdown and Makeup Vacuum Breaker Valve Inspection', an annual inspection, was last performed on 11/11/2005 to verify the integrity of the CW BDL vacuum breakers and their manual isolation valves.

Transient Effects on the Blowdown Line Dynamic analysis and conclusions reached (later).

Failure Modes IRAPS pipihg (HDPE) failure is improbable, as explained in section 'IRAPS Pump to CW BDL Integrity' above.

Failure of a check valve, in the piping/check valve segment which replaced Vacuum Breaker # 2, is improbable since the valve s are new and were tested prior to installation. However, should one check valve fail, the second check valve provides redundancy.

Since the shutoff head of the IRAPS pump is less than the design pressure of the HDPE pipe, there is no concern of over pressurization.

Braidwood Station Cooling Lake Chemistry Water chemistry of the cooling lake is controlled by the blowdown and make-up process by means of the Kankakee River.

Operation of the IRAPS may require a reduced lake blowdown flowrate from current values, due to measures taken to ensure the Blowdown Line is maintained 'water solid'. Any potential reduction in flowrate is expected to be small, however, flowrate is projected to be 17,800 gpm or greater.

(Chemistry evaluation later)

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EC 360234 EVAL - MECH DRAFT FOR COMMENT Monitoring of Kankakee River Offsite Dose Calculation Manual (ODCM)

The following ODCM changes will be made:

• Sections 10.2.1.2 "Liquid Release" has been added to the liquid release section in Chapter 10 to define the flow path, monitoring, and controls for the Exelon Pond Remediation process.

• Section 10.2.3.1.2.2 "Release Limits" was added to describe the Administrative Limit (200 pCi/L) for the remediation.

• Figure 10.3 was changed to include the Exelon pond and the flow path into the CW BD.

• Table 12.3-1 to document the continuous monitoring, frequency (weekly, monthly, quarterly) and type of sampling (gamma, tritium, I-131 etc.)

C hemistry Procedure changes New Chemistry Department procedures were created for the IRAPS process:

• BwCP 1003-14, 'Exelon Pond Weekly Discharge'.

" BwCP 1003-15, 'Exelon Pond Monthly Discharge'.

• BwCP 1003-16, 'Exelon Pond Quarterly Discharge'.

These new procedures describe the weekly, monthly, and quarterly composite and grab sample requirements, frequencies. etc.

BwCP 1003-14 also includes steps for comparing weekly grab sample tritium concentrations from the Exelon Pond to the calculated maximum concentration that the Exelon Pond is expected to reach to ensure that we do not exceed the 200 pCi/L CW BD outfall limit.

The weekly, monthly and quarterly OBwCSR 12.3.1 .b.1-1, OBwCSR 12.3.1 .b.1-2, OBwCSR 12.3.1.b.1-3, were revised to ensure that the composite samples are pulled, tabulated and quantified.

An inline monitor is not required for the Exelon Pond remediation based on environmental groundwater gamma analysis results from the plume characterization project of less than the lower limit of detection and that gamma- analysis will be performed for the Exelon Pond samples. required by the procedures above.

Page 19 of 25

EC 360234 EVAL - MECH DRAFT FOR COMMENT Effect on Wilmington Pumping Station The CRA evaluation considered the effect of introducing tritium into the CW BDL on the Kankakee River, particularly the effect on the Wilmington public water intake. Tritium releases to the Kankakee River are allowed in concentrations up to the limits specified in the Offsite Dose Calculation Manual (ODCM) i.e., 1 E6 pCi/I. The concentration of tritium discharged to the Kankakee River under this interim remediation plan will be less than 200 pCi/I. Even without considering any further dilution from river flow, this concentration would not have any adverse effect on the Wilmington public water supply or any private wells close to the river. (Reference 21 and 25)

NPDES The IRAP will utilize the existing NDPES permit allowing discharge of the water to the Kankakee River through the Blowdown Line, therefore eliminating the need for additional agency permitting.

Without specific guidance from IEPA for monitoring the offsite pond discharge to the Blowdown Line, Braidwood Chemistry believes this. discharge would be considered a sub-waste stream of the Blowdown Line and therefore no specific reportable NPDES monitoring of the discharge would be required.

Should the IEPA propose sampling requirements, the requirement would be incorporated into the existing NPDES sampling procedure, BwCP 323-18, NPDES Surveillance Procedure Page 20 of 25

EC 360234 EVAL - MECH I DRAFT FOR COMMENT I Approvals for Exelon Pond discharge Illinois Attorney General permission to implement the pumping plan is anticipated after P.O.R.C review of this EC evaluation and approval will subsequently be documented in this EC.

Prior to beginning the interim remediation pumping, approval will be required by the parties involved in the Complaint filed March 6, 2006, against Exelon.

These parties include Illinois Attorney general (representing Illinois Environmental Protection Agency) and the Will County State's Attorney. This approval will be in the form of an "Agreed Preliminary Injunction Order,"

signed by Exelon and the parties involved in the complaint.

The content of the Order is currently being negotiated. It is expected that the following requirements related to interim remediation will be included explicitly in the Order. (Reference xx)

Interim Remediation Action - Vacuum Breakers Nos. 2 and 3

1. Within fourteen (14) days of entry of this Preliminary Injunction Order, in order to halt the further migration of the tritium plume emanating from vacuum breakers No. 2 and No. 3 into groundwater on and offsite, Exelon Generation shall initiate pumping of the Exelon pond. Such pumping activity shall be conducted in accordance with the work plan titled, "Interim Remedial Action Plan," which is attached hereto as Exhibit A and incorporated by reference herein.

2. Prior to the commencement of the pumping activity required by Paragraph 12 above, Exelon Generation shall convene a community information night to inform area residents of the planned pumping activity. This community information night was held on April 6, 2006.

3. Exelon Generation may discharge the water recovered from the pumping required by Paragraph 12 above, by means of the blowdown line. At all times when discharging such water through the blowdown line, Exelon Generation shall:

L conduct a daily visual inspection of the pipeline corridor to check for signs of pipe failure and document its findings. This documentation shall be available for inspection by the Plaintiff; ii. employ a continuous monitoring system in each vacuum breaker vault to warn Exelon Generation of any water discharges from the vacuum breakers. Exelon Generation shall immediately cease pumping water from Exelon Pond into the blowdown line if such discharge(s) are identified; iii. install and maintain impermeable barriers at the base of each vacuum breaker pit; iv. operate the blowdown line in a pressurized condition; and Page 21 of 25

EC 360234 EVAL - MECH I DRAFT FOR COMMENT

v. take all other necessary steps to ensure that water from the Exelon Pond, and any other wastewaters, are not discharged at any point other than the permitted outfall to the Kankakee River.

vi. Upon entry of all parties into the Order, and prior to pumping, the tritium team will verify that the specific conditions of the Order have been met.

In addition, the NRC has asked to review our plan for interim remediation, although no formal approval is required. A letter to the NRC, dated April 4, 2006, describes the plan. (Reference 23) Prior to beginning of pumping, the Braidwood tritium team will verify the NRC has no unresolved concerns with the plan.

Page 22 of 25

EC 360234 EVAL - MECH DRAFT FOR COMMENT References

1. 'Interim Remedial Action Plan', Exelon Generation Company LLC -

Conestoga-Rovers & Associates (CRA), dated March 2006

2. 'Interim Remedial Action Pumping System' Project 45065-01, Conestoga-Rovers & Associates, Drawings:

" CS-01

" EF-01, 'Engineering Flow Diagram Legend'

• EF-0, "Engineering Flow Sheet 1'

• ST-01, 'Site Plan'

" ST-02, 'Valve Station Pad'

• ME-01, 'Piping @ Valve Station'

" E-01, 'Electrical Panel'

• E-02, 'Panel Schematic Wiring Diagram'

3. 'Conceptual Design and Operation of an Interim Remediation System for Tritium in Groundwater near Smiley Road at the Braidwood Site', Conestoga-Rovers & Associates, Memorandum dated February 3, 2006

4. SPP 06-003, 'CW BD Flow Throttled at Discharge Structure Test'

5. BwOP CW-28, Rev 0, 'Operation of the Exelon Pond Pump'

6. BwOP CW-1 2, 'Circulating Water Blowdown System Fill, Startup, Operation and Shutdown'.

7. Offsite Dose Calculation Manual

8. NPDES

9. 'Braidwood Pond Fish Management', Braidwood Station memo, e-mail from A. Haeger /J. Petro (Braidwood Station) to B. Acas (WGI),

dated March 27, 2006

10. 'Preliminary Review of NPDES Issues', Braidwood Station memo, J.

Tidmore (Braidwood Chemistry) to A.Haeger (Exelon), dated March 28, 2006.

11. 'Interim Remedial Action Pumping System Dilution Calculation', Excel spreadsheet attachment to EC 360234.

12. Reference documents/drawings for vault monitoring system.

13. Reference documents/drawings for remote IRAPS control system.

14. EC 360112, 'Waterseal of Vacuum Breaker Vaults' Page 23 of 25

EC 360234 EVAL - MECH I DRAFT FOR COMMENT I

15. EC 360114, 'Add an Additional Valve to CW Blowdown Line OCWC2CA-18.'

16. Reportability of low-level tritium release document from Exelon.

17. 'Tritium Concentration in Pond', e-mail from N. Smith/P. Harvey (CRA) to A. Haeger (Exelon) dated February 28, 2006.

18. 'Violation Notice: Exelon Generation - Braidwood Station, Violation Notice No.: W-2005-00537', M. Garretson (Illinois EPA) to J. Petrio (Braidwood Station), dated December 16, 2005.

19. 'Braidwood Station Response to Violation Notice W-2005-00537', K.J.

Poison (Braidwood Station) to B. Booker (Illinois EPA), dated February 2, 2006.

20. '48" ECP Circulating Water Blowdown Line; Interpace Corporation Project No. SB-77-27" e-mail from R. Deremiah (Price Brothers) to E.

Stukas (WGI), dated April 4, 2006.

21. 'Estimate of Groundwater Level Drawdown in the Shallow Sand Aquifer in the Vicinity of the Exelon Pond During Interim Remediation', Memorandum from P. Harvey (CRA) to A. Haeger (Exelon) dated April 4, 2006.

22. 'Simulated Groundwater Drawdown in the Shallow Sand Aquifer at Private Well Locations When Pumping from the Pond', CRA Drawing 45065-01 (PRES001)GN-WA001, dated March 31, 2006.

23. 'Groundwater Tritium Interim Remediation', letter to US Nuclear Regulatory Commission from K. Poison (Exelon) dated April 4, 2006.

24. Dynamic calculations (later).

25. M-900 series of Braidwood Station Piping and Instrument Drawings

• Sheet 13, REV 1 Blowdown piping to outfall structure Braidwood Station units 1 & 2

• Sheet 3, Rev C, Outdoor Piping Arrangement Braidwood Station Units 1 & 2

• Sheet 4, Rev B, Outdoor Piping Arrangement Braidwood Station Units 1 & 2

" Sheet 5, Rev B, Outdoor Piping Arrangement Braidwood Station Units 1 & 2

" Sheet 6, Rev A, Outdoor Piping Arrangement Braidwood Station Units 1 & 2 Page 24 of 25

EC 360234 I EVAL - MECH DRAFT FOR COMMENT

26. Conestoga-Rovers & Associates, Project 45065-01 Drawing #

(PRES001)GN-WA001 MAR 31/2006

27. 'Full Vacuum Condition Design For Prestressed Concrete Steel Cylinder Pipe', Interpace Project No. SB-77-27 dated April 4, 2006

28. M-44 Sheet 3A, Braidwood Station Piping and Instrument Drawings

29. 'Remediation Preps - ODCM and Chemistry Changes', e-mail from A.Haeger/J.Eggart (Braidwood) to B.Acas/J.Damron (WGI), dated April 5, 2006.

30. Sketch of piping/check valve segment, WGI supplied, (reference date later)

Page 25 of 25

Action Items for Interim Remediation Action Plan

1. After 3 months of operation of the IRAPS, review the effectiveness of the operation. This review will consider how the proposed pond pumping system could be modified to shorten the cleanup time and to increase tritium recovery.

2. During the pumping operations, Exelon and CRA will monitor water levels in groundwater sampling wells and private wells and take actions to adjust pumping rates and/or provide water for any residential wells that show they may be affected.

3. Prior to beginning the pumping, the remediation team will communicate with neighbors whose wells may potentially be affected to describe the monitoring process and contingency plans for any effect on private well performance.

4. A contingency plan to move the fish from the pond will be established. A fish sampling effort is tentatively planned for the end of April to collect representative species of fish. Collected fish will follow standard IDNR and/or IDPH contaminant sampling protocol and will be sent to a lab for tritium analysis.

Completion of any such sampling, or the results, is not required prior to pumping of the pond.

5. Startup Testing Upon completion of IRAPS piping construction, before connecting to the IRAPS pump and CW BDL and prior to any pumping operation, hydrostatic testing of the new piping will verify its integrity at a pressure of 150 psig, twice the shut-off head pressure of the pump.

In addition to hydrostatic pressure testing, standard construction testing, electrical 'dead circuit' testing and instrument calibrations will also be performed.

Testing conducted by the piping contractor will be directed by Exelon. Specific test descriptions and results will be documented in the final version of this EC.

6. It was concluded that the PM frequency for the vacuum breakers was adequate, and that the PM frequency for the air release valves would need to be updated for replacement every 2 years for all 11 of the vacuum breakers.

7. On a daily basis the BDL right-of-way will be inspected for signs of leaks.

Personnel performing the inspection will notify the Braidwood Station Main Control Room (MCR) to secure the IRAPS pumping if signs of leakage are found.

Specific details of the daily inspection will be included in the 'Operator Rounds' package.

8. Prior to IRAPS startup, complete dynamic analysis of blowdown line with VB-2 removed.

9. Prior to or during installation of the tie in to VB-2, a hydrostatic test will be performed for the piping/valve segment. Test pressure shall be equal to the test pressure for the pond piping. If shop tested, pressure shall be 150 psig.

Additionally, verification of check valve flow orientation will be verified.

Page 1 of 2

Action Items for Interim Remediation Action Plan

10. Complete evaluation of lake chemistry effect of blowdown flow reduction following completion SPP 06-003.

11. A continuously monitored leakage detection system will be installed in all eleven of the vacuum breaker enclosures to promptly detect any such leakage.

12. Ensure ODCM changes are implemented for the IRAPS system:

Sections 10.2.1.2 "Liquid Release" has been added to the liquid release section in Chapter 10 to define the flow path, monitoring, and controls for the Exelon Pond Remediation process.

Section 10.2.3.1.2.2 "Release Limits" was added to describe the Administrative Limit (200 pCi/L) for the remediation.

Figure 10.3 was changed to include the Exelon pond and the flow path into the CW BD.

Table 12.3-1 to document the continuous monitoring, frequency (weekly, monthly, quarterly) and type of sampling (gamma, tritium, 1-131 etc.)

13. Ensure new and revised Chemistry Department procedures are implemented for the IRAPS process:

BwCP 1003-14, 'Exelon Pond Weekly Discharge'.

BwCP 1003-15, 'Exelon Pond Monthly Discharge'.

BwCP 1003-16, 'Exelon Pond Quarterly Discharge'.

Weekly, monthly and quarterly OBwCSR 12.3.1.b.1-1, OBwCSR 12.3.1.b.1-2, OBwCSR 12.3.1.b.1-3

14. Prior to beginning of pumping, the Braidwood tritium team will verify the NRC has no unresolved concerns with the plan.

15. Ensure preliminary injection order is completed and signed by all parties prior to initiating interim remediation. Verify contents of order to ensure all order commitments are covered in EC 360234.and related documents.

Page 2 of 2