TMI-11-158, Submittal of Relief Request PR-05 Associated with the Fourth Inservice Testing (IST) Interval
| ML113010335 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 10/28/2011 |
| From: | Jesse M Exelon Generation Co, Exelon Nuclear, Exelon Corp |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| PR-05, TMI-11-158 | |
| Download: ML113010335 (8) | |
Text
10 CFR 50.55a TMI*11*158 October 28, 2011 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555*0001 Three Mile Island Nuclear Station, Unit 1 Renewed Facility Operating License No. DPR*50 NRC Docket No. 50*289
Subject:
Submittal of Relief Request PR*05 Associated with the Fourth Inservice Testing (1ST) Interval Attached for your review is a relief request associated with the fourth Inservice Testing (1ST) ten*year interval for Three Mile Island Nuclear Station (TMI), Unit 1. TMI, Unit 1 is requesting relief to perform alternative testing of the Reactor Building Emergency Cooling River Water pumps. Based on a start date of September 23, 2004, the fourth ten-year TMI, Unit 1 1ST Program complies with the requirements of the ASME Code for Operation and Maintenance of Nuclear Power Plants, 1998 Edition through 2000 Addenda. The need for this relief request was identified during a self assessment that identified the system could not be treated as a fixed resistance system in accordance with the ASME Code.
There are no regulatory commitments in this letter.
If you have any questions concerning this letter, please contact Tom Loomis at (610) 765-5510.
Respectfully,
Attachment:
Relief Request PR*05 cc:
Regional Administrator, Region I, USNRC USNRC Senior Resident Inspector, TMI USNRC Project Manager, [TMI] USNRC
Attachment Relief Request PR-05
Relief Request PR*05 to Implement an Alternative Concerning Reactor Building Emergency Cooling River Water Pump Testing in Accordance with 10 CFR 50.55a(a)(3)(ii) 1 of 1.
ASME Code Component's) Affected:
Component ID RR~P~1A RR~P~1 B Class 3
3 Group B
B Description Reactor Building Emergency Cooling River Water Pump "A" Reactor Building Emergency Cooling River Water Pump "B" Component/System Function:
The Reactor Building Emergency Cooling Water System is comprised of two 100 percent capacity trains. Each river water pump is capable of providing greater than 1450 gpm through each emergency cooling pump coil. Following an engineered safeguards signal, the two 100 percent capacity Reactor Building Emergency Cooling River Water Pumps deliver water from the river directly to the emergency cooling coils at a pressure in excess of the containment design pressure, which is maintained by a pressure control valve on the discharge. These redundant river pumps may also be used to provide the Emergency Feedwater Pumps with a source of water if the condensate inventories are ever depleted.
Receipt of the Reactor Building isolation signal (4 psig Reactor Building ambient pressure or a low reactor pressure of either less than 1600 psig or less than 500 psig backup signal) automatically switches the Reactor Building emergency cooling system to the emergency mode and starts the Reactor Building Emergency Cooling River Water pumps.
===2.
Applicable Code Edition and Addenda===
ASME OM Code~1998 Edition and Addenda through OMb-2000
===3.
Applicable Code Requirement===
ISTB~3550, "Flow Rate", states in part "when measuring flow rate, a rate or quantity meter shall be installed in the pump test circuit. If a meter does not indicate the flow rate directly, the record shall include the method used to reduce the data." Additionally, "external recirculated flow is not required to be measured if it is not practical to isolate, has a fixed resistance, and has been evaluated by the Owner to not have a substantial effect on the results of the test."
For Group B vertical line shaft pumps, ISTB-5222, "Group B Test Procedure", states "Group B tests shall be conducted with the pump operating at a specified reference point.
The test parameter value identified in Table ISTB~3000~1 shall be determined and recorded as required by this paragraph."
Paragraph ISTB-5222 and Table ISTB-3000-1 require flow rate or differential pressure to be measured or determined.
===4.
Reason for Request===
The Reactor Building Emergency Cooling River Water pumps each have a minimum flow line in parallel with a test line that can be utilized for the Group B pump test. With the associated solenoid valve (RR-V10AlB) open, the minimum flow line provides a fixed
Relief Request PR-05 to Implement an Alternative Concerning Reactor Building Emergency Cooling River Water Pump Testing in Accordance with 10 CFR 50.55a(a)(3)(ii) 2 of resistance flow path from the pump discharge to the test line and then to the suction basin.
The isolation valve (RR-VlOAlB) in this line opens on a pump start and closes when the main discharge line isolation valve (RR-V1A1B) is fully open. The minimum flow path is not provided with throttling capability. The test line provides a parallel flow path from the pump discharge to the suction basin. The configuration is depicted on a drawing attached to this request. The test line flow path does have throttling capability. However, neither the minimum flow lines nor the test lines are provided with flow instrumentation. Physical configuration of the minimum flow lines and test lines do not allow for installation of temporary flow measurement equipment that would yield flow readings suitable for Code-compliant pump testing because there is not adequate straight piping that will be water-solid in these lines.
An instrumented full flow path is available for pump testing; however, use of this flow path is only practical at an extended (refuel) frequency as discussed below. Performance of this full flow test requires the pumps to introduce river water into the Reactor Building Emergency Cooling (RBEC) coils. Since river water contains silt and microorganisms, the system must be drained to the Reactor Building sump and refilled with Nuclear Services Closed Cooling Water following the testing. Approximately 5,000 gallons of water must be processed through the Liquid Waste Disposal System after each test. Processing this much water every quarter to comply with Code-required pump testing is costly from both a manpower and monetary standpoint and represents an undue hardship as compared to the proposed alternative testing.
Therefore, the Code-required testing would necessitate either: 1) a major system piping modification to allow installing either temporary or permanent flow instrumentation, or; 2) the processing of significant amounts of water through the Liquid Waste Disposal System to facilitate full flow testing through the RBEC coils quarterly. The associated cost of either option results in a hardship and unusual difficulty without a compensating increase in the level of quality or safety.
===5.
Proposed Alternative and Basis for Use===
With both the minimum flow line and test line available, it is more desirable to perform the Group B testing of the Reactor Building Emergency Cooling River Water pumps at substantial flow using both lines rather than testing solely on the non-instrumented minimum flow line. Three Mile Island Nuclear Station (TMI), Unit 1 proposes to perform quarterly testing of the Group B Reactor Building Emergency Cooling River Water pumps (RR-P-1 A, RR-P-1 B) using a combination of the minimum flow line and test line to establish the equivalent of a "fixed resistance" system.
This equivalent "fixed resistance" system flow path will be created by throttling the 12" butterfly valve RR-V2A1B in the test line to a predetermined fixed number of hand wheel open tums in combination with the 2" minimum flow line isolation valve RR-V10AlB which opens fUlly on a pump start.
Relief Request PR-05 to Implement an Alternative Concerning Reactor Building Emergency Cooling River Water Pump Testing in Accordance with 10 CFR 50.55a(a)(3)(ii)
.....aloe 3 of The testing will be performed as follows: 1) the pump will be started with RR-V10AlB opening automatically to provide a minimum recirculation flow path; 2) RR-V2A1B will then be throttled open the predetermined fixed number of hand wheel turns to establish system resistance at a repeatable fixed value; 3) the system will be allowed to stabilize, and; 4) after allowing time for system stabilization, pump differential pressure will be determined and recorded.
RR-V2A1B are 12-inch butterfly valves with large hand wheels that are capable of being precisely positioned. The accuracy of the throttle point for RR-V2A1B will be +/- 1/8 of a hand wheel turn from the predetermined value of 12.5 hand wheel turns open. This tolerance has been evaluated and limited to ensure the maximum hydraulic variance for the valve position is within the lnservice Testing acceptance criterion for Group B pump testing and confirms that the test method meets the definition of a "fixed resistance system" as long as the RR-V2A1B operator is functioning normally.
The accident required flow rate for these pumps is 4350 gpm. Based on differential pressure test data and comparison to the manufacturer's pump curve, quarterly Group B testing using the proposed test method establishes a flow rate on the sloped portion of the pump curve (attached to this relief request) at a value of approximately 5000 gpm. The slope of the pump curve between 4000 gpm and 6000 gpm is approximately -0.035 feet of head/gpm. The slope of the pump curve at flows below 3000 gpm (where the pump would be if operating solely on the minimum flow line) is almost zero (-0.005 ft of head/gpm).
Establishing a reference point at the higher flow rate (corresponding to the "fixed" throttle valve position) allows the pumps to be operated at a point on the curve that is effective for monitoring and detecting hydraulic degradation. The slope of the curve does increase slightly at flows greater than 5000 gpm, but not significantly to enhance the ability to detect hydraulic degradation.
During the performance of this proposed quarterly Group B pump testing, pump differential pressure will be determined and recorded. This provides a reference value for differential pressure that can be duplicated during subsequent tests. This methodology provides for the acquisition and trending of differential pressure at a repeatable hydraulic condition, thus providing adequate means of monitoring for pump degradation.
Additionally, while not required for Group B pump testing, TMI, Unit 1 will monitor and trend pump vibration for the Reactor Building Emergency Cooling River Water pump against the limits specified in Table ISTB-5200-1. This provides an additional means of monitoring for pump degradation on a quarterly basis.
A comprehensive test will also be performed on each pump in accordance with ISTB-5223.
This proposed alternative testing in accordance with 10 CFR 50.55a(a)(3)(ii) provides reasonable assurance that the Reactor Building Emergency Cooling River Water pumps will be operationally ready.
Relief Request PR-05 to Implement an Alternative Concerning Reactor BUilding Emergency Cooling River Water Pump Testing in Accordance with 10 CFR 50.55a(a)(3)(ii)
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===6.
Duration of Proposed Alternative===
The fourth ten-year interval for TMI, Unit 1 began on September 23,2004, and will conclude on September 22,2014. TMI, Unit 1 proposes to utilize this relief for the remainder of the interval.
===7.
Precedents===
None
Relief Request PR-05 to Implement an Alternative Concerning Reactor Building Emergency Cooling River Water Pump Testing in Accordance with 10 CFR 50.55a(a)(3)(ii)
(Page 5 of 6)
Drawing excerpt showing the installed bypass flow paths for routine testing of RR-P-1AlB:
RR- /128 12 1
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RR-V2G Full Flow Path
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.J t RR-V12/4, Minimum Flow Line To Suction Basin
Relief Request PR-05 to Implement an Alternative Concerning Reactor Building Emergency Cooling River Water Pump Testing in Accordance with 10 CFR 50.55a(a)(3)(ii)
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