ML20083M512

Forwards Second Rev to ECCS for Facility.Rev Incorporates Comments from Design Review Conducted by Anl

ML20083M512
Person / Time
Site:	Rhode Island Atomic Energy Commission
Issue date:	05/12/1995
From:	Tehan T RHODE ISLAND, STATE OF
To:	Mendonca M NRC (Affiliation Not Assigned)
References
NUDOCS 9505190288
Download: ML20083M512 (12)

Text

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TATE OF RHODE ISLAND AND PROVIDENCE PLANTATIONS Rhode Island Atomic Energy Commission NUCLEAR SCIENCE CENTER South Ferry Road Narragansett, R.I. 02882-1197 May 12, 1995 Docket No. 50-193 Mr. Marvin Mendonca, Senior Project Manager Non-Power Reactors, Decommissioning and Environmental Project Directorate Division of Reactor Projects - III/IV/V U. S. Nuclear Regulatory Commission Washington, D.C. 20555

Dear Mr. Mendonca:

Enclosed you will find a copy of the second revision to the Emergency Core Cooling System (ECCS) for Facility License No.

R-95. This revision incorporates comments from the design review conducted by Argonne National Laboratory. All previous comments from your organization have been answered.

The 1/2 orifices cited in the last correspondence on this matter have been installed. Mr. Tom Dragoun of NRC Region One recently viewed the partially installed system. He can provide third party comments regarding the installation. If there are any questions, please call me at 401-789-9391.

Sincerely, I h 1 yw',han\u  %

Terry b Direct TT:cd Enclosure l l

l cc: Dr. James Matos, Argonne National Laboratory JS0055 l 9505190289 950512 e I

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INTRODUCTION The_Rhode Island Nuclear Science Center research reactor has a design. capability of 5 MW (thermal) power level. The current licensed power level is 2 MW. The recent conversion to the LEU fuel necessitated a safety Analysis Review (SAR) which addressed a postulated loss of coolant accident (LOCA). The Nuclear Regulatory Commission approved the SAR and related information for the postulated loss of coolant for 2 MW operation.

This report. addresses the postulated loss of coolant for'5 MW operation and the proposed emergency core. cooling' system (ECCS) required. Since the original GE reactor design did not include provisions for emergency cooling, it was necessary to originate a design plan which would incorporate some of the positive features available at the. reactor site.

DESIGN CONSIDERATIONS The pool is specifically designed to preclude the probability of drainage. It is constructed of reinforced concrete with a heavy aluminum liner to resist the most severe earthquake that might be reasonably be expected in the area. There are no i penetrations below the top of the core that is open to pool water.

All nenetrations of the pool are provided with multiple barriers against the possiblilty of leakage of pool water.

Four 6 inch and two 8 inch beamports penetrate the liner at the core centerline. Each beam port is closed by a bolted cap at the pool end, by a heavy lead shutter located within the pool wall, and by a bolted shield plug at the outer end. Each beam port is equiped with a vent / drain line 1/2 inch diameter orifice and an isolation valve to limit pool leakage in the >

event the primary barrier of a beam port is breached.

Administrative controls are in place to limit potential leakage through any beam port experimental appratus, which takes the place of the outer bolted flange, to the equiva1.ent of a 1/2 inch diameter hole.

It is highly unlikely that the beam ports could be severely-damaged while the reactor core is in the high power section of the pool because of the restricted space and the protection afforded by both the reactor and the bridge'which cover a major part of the area.

Additionally, severe damage to a penetration in the pool could be prevented from uncovering the core by:

1. Opening the bypass valve on the automatic pool filling system;

2. Closing the beam port vent / drain isolation valves; 1

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'3. Moving the bridge / core to.the adjacent pool and a closing the gate between the two pools;-

Operations that can be completed in a matter of a few minutes.

DESIGN BASIS' ACCIDENT In view of the inherent integrity.of the-design features, a loss of pool water to.the point of. uncovering some portion of the core and damaging the aluminum cladding is unlikely.

'The basic assumptions used were:

1. An 8 inch diameter beam tube is ruptured following an-infinite period of operation at a 5 Megawatt power-level.

2. The reactor scrams concurrent with the beam tube rupture.

3. Emergency cooling System fill starts.

Initial pool level remains at 23 feet above the datum (appendix-C) for 44 hours5.092593e-4 days <br />0.0122 hours <br />7.275132e-5 weeks <br />1.6742e-5 months <br /> while the campus water supply tank is drawn down. Emptying of the reactor pool to the datum will require an addit.ional 31 hours3.587963e-4 days <br />0.00861 hours <br />5.125661e-5 weeks <br />1.17955e-5 months <br /> due to the flow restrictions of the 1/2 inch diameter orifice and the 1/2 inch maximum opening in the outer end of the beam port. The total time required to empty the pool is 75 hours8.680556e-4 days <br />0.0208 hours <br />1.240079e-4 weeks <br />2.85375e-5 months <br />, The lower active portion of a fuel plate-will then be standing in slightly more than 8 inches of water (Appendix C; SAR,Section X, Loss of Cooland Accident) s FACILITY WATER SUPPLY The Wakefield Water Supply Company provides water to the University of Rhode Island Bay Campus. The Rhode Island Nuclear Science Center reactor facility is located on the Bay Campus.

Water at 40 psi is supplied from the Wakefield Water Supply Company to a 300,000 gallon tank located adjacent to the Bay Campus. The tank booster pump delivers water at 75 psi to the Bay Campus distribution system. If pressure drops or more flow is needed a standby fire pump energizes maintaining system flow rate and pressure. The 3 fire pumps in the system have emergency generator backup. The Bny Campus demand (1992 records) is about 83 gpm. The ECCS flow rate will be set at 30 gpm. The total Campus demand will be 113 gpm (83 gpm + 30 gpm). This provides a reserve supply in the 300,000 gallon tank to maintain both the Bay Campus demand and the pool filling requirements for 44 hours5.092593e-4 days <br />0.0122 hours <br />7.275132e-5 weeks <br />1.6742e-5 months <br />.

A copy of the fire pump test results conducted for the system by Kelly Associates, the design firm, is enclosed.

The reliability of the system was discussed in the SAR dated December 1992 in Section B, IX.

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4 The URI 300,000 gallon tank

• can be cross. connected to the Wakefield Water Company which also has a 300,000 gallon tank about 1 mile away providing additional reserve capacity.

• See Appendix D - Administrative Controls PRESENT POOL FILL SYSTEM OPERATION '

The existing pool is filled through the make-up demineralizer system. The pool fill system has an automatic electrically operated valve which opens when the pool level float switch

is activated for a nominal one inch drop in pool water level.

.The pool fill system has a manual by-pass valve should the automatic valve fail. Measurements reflect that the make-up system can provide 25 gpm to the pool. This is sufficient to-

-maintain pool water level at 17 feet above the datum with the i postulated maximum pool. leak (ref. TABLE A).

PROPOSED EMERGENCY CORE COOLING SYSTEM OPERATION Refer to the Emergency Core Cooling System (ECCS) Schematics in Appendix A and B.

The ECCS will operate under AC power with emergency power backup from the emergency generator. This assures operation of electrical components with loss of AC power.

At present the RINSC emergency generator has 1600 watts of excess capacity. The solenoid valve and flow measuring ,

instrument would require less than 100 watts and would be a minimal load.

The reactor control system will be provided with two alarm circuits to be used for 5 MW' operation. The first is an ECCS water line pressure sensor located between the pressure regulator and the automatic valve (AV) which monitors the-water supply line pressure. The second alarm function would indicate that the ECCS automatic valve is opened. The alarms will sound at the front desk and in the Control Room.

The line also contains a flow meter indicating ECCS water flow during testing (Appendix D) or during a pool fill event.

This unit will read out locally in the Demineralizer Room.

The automatic valve has a manual bypass valve in case of the failure of the electrical activator. The manual valves are used for a system by-pass flow testing.

A manual valve is used to isolate the system. It will be locked open. The four inch supply gate valve to the fire main and the ECCS system will be locked in the open position.

Activation of the automatic valve is from a low level pool switch. The unit will have a low pool level limit of 24 .

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inches below the suspension frame base plate. The.ECCS system will cycle (on and off) to' maintain the pool water level at the 24 inch limit. This level corresponses - with an actual pool level of 23 feet above the datum.

The reactor is scrammed on a low pool water level limit of 16 inches below the suspension frame base plate from a separate low water level sensor. (Tech. Spec. Table 3.1).

ECCS WATER SUPPLY ANALYSIS An analysis of the 4 inch sprinkler supply connection point of the ECCS with a proposed 1 1/4 inch line supply to the pool indicates sufficient flow capacity to maintain the reactor pool full with the postulated maximum leak rate.

The pressure (supply) at the 4 inch pipe entering the building is based on the accompanying fire test report. Due to high pump pressure available, the proposed 1 1/4 inch line (ECCS) will have a pressure reducing value. A 55 psi setting is more than adequate for expected demand. The valve would prevent excessive ECCS line pressures when the Bay Campus fire pumps are in use.

The analysis was performed with a 55 psi supply pressure.

Assumptions:

Flow through a 1.25 in smooth pipe; Friction loss 1.25 in, 50 psi = 21 psi /100ft of pipe *;

Equivalent loss (pipe lengths) for fittings:

1 Press reducing valve lft 3 valves 0 1 ft/ valve 3ft 7 tees 0 3 ft/ tee 21ft 7 elbows 0 4 ft/ elbow 2&f.A Total 53ft Actual pipe length 68ft Equivalent loss 121ft Friction head loss = 121ft/100ft

• 21 psi = 25.4 psi Elevation head loss = 32ft

• 0.43 psi /ft = 13.8 psi Total head losses = 25.4 psi + 13.8 psi = 39.2 psi Demand Flow = Supply - Head losses

= 50gpm 0 55 psi - 39.2 psi = 50gpm 0 15.8 psi 4 .' '

r TABLE A CALCULATED MAXIMUM HEAD ABOVE DATUM FLOW RATE (GPM) FRQM BEAM PORT 25.29 30.13 24.29 29.53 23.29 28.91 22.29 28.28 21.19 27.64 20.29 26.98 19.29 26.31 18.29 25.62 17.29 24.91 16.29 24.18 15.29 23.42 14.29 22.65 13.29 21.84 12.29 21.00 11.29 20.13 10.29 19.22 9.29 18.26 8.29 17.25 7.29 16.17 6.29 15.02 5.29 13.78 4.29 12.40 3.29 10.86 2.29 9.06 1.29 6.80 0.79 5.31 0.00 0.00 It is assumed that (1) the diaphragm valve to the beamport vent line is fully OPEN; (2) The beamport " shutter" is in the full OPEN position.

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CONCLUSIONS A postulated " Loss of Coolant" accident for power levels above the existing 2 MW licensed power level could lead to possible reactor core damage due to decay heat generation. An Emergency Core Cooling System has been installed which will ensure that pool remains full for at least 44 hours5.092593e-4 days <br />0.0122 hours <br />7.275132e-5 weeks <br />1.6742e-5 months <br /> after a design basis accident occurs. An additional 31 hours3.587963e-4 days <br />0.00861 hours <br />5.125661e-5 weeks <br />1.17955e-5 months <br /> are required to drain the pool. The resulting 75 hour8.680556e-4 days <br />0.0208 hours <br />1.240079e-4 weeks <br />2.85375e-5 months <br /> time period is sufficient to carry out emergency procedures to resolve the situation.

In the event that the casualty occurs during normal operating hours, personnel will be available to stop the leak or move the core from the high power section and install the dam. In the worst case situation, the core could be unloaded to the fuel racks which would provide significant additional cooling. In the event that the casualty occurs when the facility is unmanned, a low pool level alarm will be actuated when the pool level decreases by 1 inch. This alarm will be transmitted to the command center of the company which monitors reactor systems on a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> / day basis and RINSC staff will be notified. An individual will be called in to check the reactor status and necessary corrective action will be taken. The 44 hour5.092593e-4 days <br />0.0122 hours <br />7.275132e-5 weeks <br />1.6742e-5 months <br /> time period provided by the ECCS before the pool level begins to decrease is more than sufficient to allow corrective action prior to the pool draining to a point where the water level would not provide adequate shielding to personnel working above the core.

Operating procedures have been developed to ensure that the system remains in a high state of readiness. These procedures specify the steps to be taken in the event of a serious Loss of Coolant Accident.

The above analysis is conservative in a number of areas. The facility operating cycle is much less than the postulated case which would result in lower initial decay heat. The maximum LOCA is assumed with no operator action to close the beam port shutter and the vent and drain lines. The time allowed to move the core or unload the core is very conservative. Also, e sumptions regarding the available water supply are very conservative.

The conclusion of this report is that the proposed ECCS and its operating procedures provide a very high degree of assurance that the design basis accident will not result in situation where the fuel elements are not adequately cooled.

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APPENDIX A EMERGENCY CORE COOUNG SYSTEM DIAGRAM

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ECCS TO FIRE REACTOR ROOM FLOOR ECCS CONNECTION TO EXISTING 4 INCH WATER UNE m

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3 I i TO SUMP i V LVE I, i 1 - MANUAL SHUT-OFF VALVE 2 - MANUAL BYPASS VALVE

, 3 - MANUAL DRAINffEST VALVE

[ gg 4 - MANUAL SUPPLY / TEST VALVE I!

VALVE PR-PRESSURE REGULATOR  :

i _J PG-PRESSSUREGAGE AV - AUTO (ELECTRIC) VALVE FROM 4 INCH FM- FLOW METER SENSOR SUPPLYTO PS-PRESSURE SWITCH FACILIT(

INSTRUMENTATION BLOCK DIAGA/iM Appendix B AV Automatic Fill 110 v AC Valve Emergency Generator 12 volt DC i Alarm l Pool Level switch i

Supply Pressure switches Flow Indicator System l 1

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Appendix C CALCULATIONS LEAK RATE (MAX)

Datum is el. 114.1 feet (invert of bottom of 8" beam tube) el. 139.4 feet (water level of pool) head = 139.4 feet - 114.1 feet = 25.3 feet area of leak = two 1/2 inch diameter holes a = 2nr2 = 2n ( 0. 5/24 ) 2 a = 2.727 x 10-3 feet 2 0.61 - void coefficient /see attached (Mechanical Engineering Handbook)

Flow through the standard orifice:

V = 0.61a Y2 gh

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V = 0.61 x 2.727 x 10 Y 2 x 32.2 x 25.287 V = 0.0G7 ft /sec V = 0.067 ft /sec x MR4x .48 gal min g 3

V = 30.127 9al min Drain time of pool with two 1/2 inch diameter holes:

Discharge under falling head 2a(K - 1K)

Ca12g h1 = 139.417 feet - 114.13 feet = 25.287 feet h2 =0

A is the area of surface of pool = .50 feet 2 C is the orifice coeficient = 0.61 a is cross sesction area of t wo 1/2 .i.nch diameter holes = 2.727 x 10-3 feet 2 t= 2 Kl@ U2b 287 <

0.61 x 2.727 x 10' x Y2 x 32.2 1 = lMM- = 113.010 seconds 0.01335 t = 31.39 hours4.513889e-4 days <br />0.0108 hours <br />6.448413e-5 weeks <br />1.48395e-5 months <br /> l

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Administrative Controls Appendix D j

1. Bay Campus 300,000 gallon Tank Water Level:

The Bay Campus 300,000 gallon tank has an altitude valve ,

that automatically maintains the water level at 128.1 j feet using Wakefield Water Company's water supply at 40  ;

psi. The automatic valve is monitored by a remote q recorder at URI's maintenance office with malfunction d alarms at the water station, maintenance and security offices.

If the Bay Campus tank fails, the pipe line supplying the Bay Campus can be cross connected to the Wakefield Water Company's 300,000 gallon tank that is about 1 mile away.

This cross connection can provide 200 gpm at 40 psi.

The Bay Campus and the Wakefield Water Company tanks do not provide for gravity feed.

2. Use and testing of the ECCS:

The normal position of the valves are:

Valve #1 - Locked open Valve #2 - Locked closed Valve #3 - Locked closed Valve #4 - Locked open Gate Valve (4 inch) - Locked open Mannual operation:

a. Open valve #2.

b. Check for proper water flow rate on local indication.(minimum 30 gpm).

c. Return all valves to normal positions and locked.

Testing:

a. To test the ECCS for proper operation, depress float switch to simulate a low water level in pool.

b. Check for proper water flow rate on local indication. (minimum 30 gpm).

Procedures:

a. Section 3.7 of the RINSC Emergency Plan ,

Implementing Procedures ( Appendix E) provides the l procedure for isolation of the pool in the event of l a pool leak.

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.- Appendix E l e 1 3.7 POOL LEAKAGE l 3.7.1 Isolation Of High Power 3.7.2 Isolation Of The Low Section Of The Pool Power Section Of The  !

I Pool If the pool leak is determined to be in the west end (high If the pool leak is determined to power section of the pool, the he in the east end (Iow power reactor grid box containing fuel section) of the pool, any stored must be moved eastward to the fuel must be moved westward to low power section followed by the mid section of the pool isolation of the west side of the followed by isolation of the east pool by the following side of the pool by the following procedure: procedure:

1) Shut all (6) beam port vent / drain 1) Using cables attached to the portable isolation valves. .

storage racks, move each rack to the fuel

2) Using a remote hook, uncouple the storage section of the pool. Be sure that cooling system piping from the reactor rack is balanced when lifted and do not suspension frame, lift rack more than necessary to clear floor

3) Clear track rails of cables, lines, surfaces. Move racks slowly and tubing, etc. carefully.

4) Release the bridge brake by turning 2) Arrange racks in the fuel storage the lock device on the tram column section with greatest possible space counterclockwise. between them. Allow room for

5) Hand tram the bridge east until it movement of the gate.

reaches the rail stops. 3) Place cable attached to the gate into the

6) Place the cable attached to the gate crane hook. Center crane hock over the into the crane hook. Center the crane gate by moving crane.

hook by moving crane over the gate. 4) Lift gate until it is clear of hangers &

7) Lift gate until it is clear of hangers & fuel storage racks.

any devices in the bottom of the pool. 5) Slowly move gate south & begin gate

8) Slowly move gate south & begin rotation so that gate gasket will be on gate rotation so that gate gasket will be east side of the gate, on west side of gate. 6) With gate elevated, move crane east

9) With gate elevated, move crane west until gate contacts pool wall. Be sure until gate contacts pool wall. Be sure gate hangs parallel to and is centered with gate hangs parallel to and is centered the pool wall protmsion, with the pool wall protrusion. 7) With gasket gently contacting

10) With gasket gently contacting protruding walls, lower gate slowly into protruding walls, lower gate slowly its hangers.

mto its hangers. 8) If necessary, inflate gate gasket to

11) If necessary inflate gate gasket to provide seal.

provide seal. 9) Turn off clean-up demineralizer pump.

1 j Turn off clean-up demineralizer Attach hose to water fill line and divert pump. automatic fill to cast end.

13) Refer to Operating Procedures 10) Arrange for temporary and permanent Section 5, and move fuel elements to repairs for damage to east end.

the fuel storage racks.

14) Arrange for temporary and permanent repairs for damage m west end.

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