ML050310436
| ML050310436 | |
| Person / Time | |
|---|---|
| Site: | Three Mile Island  |
| Issue date: | 01/28/2005 |
| From: | David Helker AmerGen Energy Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 5928-05-20045 | |
| Download: ML050310436 (7) | |
Text
10 CFR 50.55a January 28, 2005 5928-05-20045 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 Three Mile Island, Unit 1 Operating License No. DPR-50 NRC Docket No. 50-289
Subject:
Response to Request for Additional Information Concerning Relief Requests PR-01 and PR-02 for the Fourth Ten-Year Interval Inservice Testing Program
References:
- 1) Letter from M. P. Gallagher (AmerGen Energy Company, LLC) to U.S.
Nuclear Regulatory Commission, dated March 26, 2004
- 2) Letter from M. P. Gallagher (AmerGen Energy Company, LLC) to U.S.
Nuclear Regulatory Commission, dated July 19, 2004
- 3) Letter from T. G. Colburn (U. S. Nuclear Regulatory Commission) to C. M. Crane (AmerGen Energy Company, LLC), dated December 15,2004 In the Reference 1 letter, AmerGen Energy Company, LLC (AmerGen) submitted for your review and approval proposed relief requests in accordance with 10CFR 50.55a, associated with the fourth ten-year interval Inservice Testing (IST) program for Three Mile Island (TMI),
Unit 1. In the Reference 3 letter, the U. S. Nuclear Regulatory Commission requested additional information concerning our proposed relief requests PR-01 and PR-02. Attached is our response to that request.
If you have any questions or require additional information, please do not hesitate to contact us.
Very truly yours, David P. Helker Manager, Licensing and Regulatory Affairs AmerGen Energy Company, LLC
U.S. Nuclear Regulatory Commission January 28, 2005 Page 2
Attachment:
- 1) Response to Request for Additional Information For Relief Request PR-01 and PR-02 cc: S. J. Collins, Administrator, Region I, USNRC D. M. Kern, USNRC Senior Resident Inspector, TMI-1 T. G. Golburn, USNRC Senior Project Manager File No. 02078
ATTACHMENT 1 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION FOR RELIEF REQUEST PR-01 AND PR-02
Three Mile Island, Unit 1 Response to Request for Additional Information Relief Request PR-01 and PR-02 Page 1
References:
- 1) Letter from M. P. Gallagher (AmerGen Energy Company, LLC) to U.S.
Nuclear Regulatory Commission, dated March 26, 2004
- 2) Letter from Letter from M. P. Gallagher (AmerGen Energy Company, LLC) to U.S. Nuclear Regulatory Commission, dated July 19, 2004
- 3) Letter from T. G. Colburn (US. Nuclear Regulatory Commission) to C. M. Crane (AmerGen Energy Company, LLC), dated December 15,2004 Question:
On December 15, 2004, the Nuclear Regulatory Commission requested additional information (RAI) regarding the Three Mile Island Nuclear Station, Unit 1 lnservice Testing (IST) pump relief requests PR-01 and PR-02 (TAC No. MC2558). Specifically:
I . Provide the methodology or analyses of how the test results of the proposed alternative are used to monitor the hydraulic performance or to detect hydraulic degradation and failures.
- 2. Provide the acceptance criteria that will be used to ensure that the hydraulic performance of either pump has not degraded more than +/- lo%, or to demonstrate that the pump will continue to perform its intended safety function even though one or both of the pumps may have potentially degraded more than 10%.
Response
Relief Request PR Nuclear Services River Water Svstem Pumps In the Reference 1 letter, AmerGen Energy Company, LLC (AmerGen) provided Relief Request PR-01 for your review and approval. PR-01 requests relief from measuring individual pump flows for the Nuclear Services River Water Pumps (NSRW) during quarterly insewice testing.
As discussed in this relief request, due to the system design (i.e., no flow measuring device at the discharge of each pump), individual pump flow rates cannot be measured during Group A quarterly tests as required by ISTB-5221(b).
The proposed alternative will utilize quarterly qualitative pressure testing and continuous temperature monitoring to detect gross mechanical as well as hydraulic degradation or failures.
During the quarterly pump test, because of system requirements, two (2) pumps are normally in service and one (1) in standby. The discharge valve for one of the two pumps in service is throttled until the differential pressure reaches the reference pressure of 38 PSlD (88.2 feet TDH). Pump vibration is monitored during this evolution.
Three Mile Island, Unit 1 Response to Request for Additional Information Relief Request PR-01 and PR-02 Page 2 The process is then repeated until all three pumps have been tested. The required action range for the test is 35.3 PSID (82 feet TDH). The differential pressure achieved for each pump is documented and will indicate a mechanical degradation prior to reaching the required action range specified in the test. The accident required pressure is 29.4 PSID (68.3 feet TDH). The difference between the test pressure and the accident required pressure demonstrates that there is significant margin for these pumps and that TMI will be able to identify hydraulic degradation.
In addition to the quarterly differential pressure test, high temperature alarms are provided on the outlet of the Nuclear Services Heat Exchangers (see Nuclear Services River Water System Diagram, contained in the Reference 1 letter). These components are supplied water from the NSRW pumps. Gross hydraulic degradation of the NSRW pumps would be detected through the high temperature alarms.
These two (2) indications (i.e., the quarterly pressure test and the continuous temperature monitoring), in addition to the quarterly vibration measurements, will be capable of detecting gross mechanical failures or significant hydraulic degradation which would threaten the accident-required functions of the NSRW pumps.
In addition to the quarterly pressure test and temperature monitoring discussed above, the refueling outage testing of individual pumps has been effective in determining pump degradation. The NSRW pumps were rebuilt in 1987 (NR-P-lA), 1992 (NR-P-18) and 1996 (NR-P-1C). The refueling interval testing in 2001 identified that the hydraulic performance of NR-P-1A was approaching its accident-design limit. Based on this, these pumps were replaced in 2002 (NR-P-1A and NR-P-16) and 2003 (NR-P-1C). The replacement pumps (Johnson pumps) are designed with stainless steel impellers (vs. the bronze impellers for the previous pumps) and a cast steel bowl assembly (vs. cast iron for the previous pumps). These design features will reduce the potential for hydraulic degradation of these pumps.
As shown in the table below, each NSRW pump had undergone at least one single-pump test during the refueling outage testing, in addition to the presewice testing following pump replacement. The observed degradation is minimal over time and shows significant margin between observed TDH and accident-required TDH requirements.
NR-P-1A NR-P-1 B NR-P-1 C ACCIDENT MEASURED MEASURED MEASURED REQUIRED MARGIN TDH (FT) TDH (FT) TDH (FT) TDH (FT) (FT) 2/15/02 85.7 68.3 17.4 2/28/02 82.4 68.3 14.2 3/9/03 84.5 68.3 16.3 10/23/03 82.2 68.3 13.9 10/23/03 81 .O 68.3 12.7 10/23/03 84.5 68.3 16.2 2/6/04 82.2 68.3 13.9 2/13/04 82.9 68.3 14.6 4/8/04 84.5 68.3 16.5
Three Mile Island, Unit 1 Response to Request for Additional Information Relief Request PR-01 and PR-02 Page 3 As an enhancement to the existing refueling interval (comprehensive pump testing) requirements, we propose to add a requirement to extrapolate the measured pump performance to the next scheduled refueling test to ensure that the pump will be able to provide adequate hydraulic performance during the intervening period.
During normal operations, two (2) NSRW pumps are normally in service to provide adequate cooling for various components. One (1) pump is in standby. As discussed in Section 9.6 (Cooling Water Systems) of the TMI, Unit 1 Final Safety Analysis Report, in the event of a LOCA, 100% redundancy of all nuclear services equipment is obtained by isolating nonessential items so that flow requirements are reduced to approximately half that of normal operation.
Therefore, only one (1) of the three (3) pumps is necessary for operation in a post-LOCA condition.
As additional precedence for approval of this testing methodology, as stated in the previously approved relief request (TAC No. M93777, October 11, 1996) for these pumps;
. .. The licensee has proposed to measure the flow rates of each pump individually every refueling outage. During power operation, pump vibration and differential pressure would be taken on a quarterly frequency. This is similar to guidance provided in GL 89-04, Position 9, which allows the measurement of pump flow rate to be deferred to refueling outages for pumps which can be tested only on recirculation flow quarterly but can be tested at substantial flow during refueling outages. The licensee stated in the August 22, 1996, phone conversation that the quarterly pump test for all three pumps would be performed at a substantial flow rate. The licensees proposal provides reasonable assurance of operational readiness because the pumps would be operated at a substantial flow quarterly, vibration and differential pressure measurements would continue to be collected quarterly, and the Code hydraulic testing would be petformed on all three pumps, albeit on a refueling outage frequency...
Relief Request PR Nuclear Services Closed Coolina Water Pumps In the Reference 1 letter, AmerGen Energy Company, LLC (AmerGen) provided Relief Request PR-02 for your review and approval. PR-02 requests relief from measuring individual pump flows for the Nuclear Services Closed Cooling Water (NSCCW) pumps during quarterly inservice testing. Due to system design, individual pump flow rate cannot be measured during the Group A test as required by ISTB-5121(b).
The proposed test would test NSCCW pumps in pump pairs. As stated previously, individual pump flow cannot be measured during normal quarterly operations since individual flow instrumentation does not exist. Also, two (2) pumps are normally required to be inservice to provide adequate cooling for system components. The NSCCW pumps are centrifugal pumps (not vertical line shaft) and have a design flowrate of 2,800 GPM at a design TDH of 136 feet.
The accident-required hydraulic criteria are a minimum indicated flow of 1,972 GPM at a TDH of 17.3 PSlD (40.2 feet). The current quarterly inservice test tests all combinations of paired-pumps (A-B, B-C, A-C). During these tests, pump dP is set at 58 PSlD and combined pump flowrate is measured. Current reference values for flow range from 5,500 GPM to 5,900 GPM, with required action levels ranging from 4,950 GPM to 5,310 GPM. These levels are significantly above the accident required hydraulic requirements.
Three Mile Island, Unit I Response to Request for Additional Information Relief Request PR-01 and PR-02 Page 4 To better assess the individual pump hydraulic performance, the quarterly testing procedure will be revised to calculate individual pump flowrates.
As an enhancement to the existing test methodology, individual flow rates will be calculated during quarterly tests and acceptance criteria will be set at greater than 110% of accident-required flow rate for each pump. Corrective actions will be taken in accordance with ISTB-6200 in the event that this criteria is not met. Additionally, the pumps will continue to be tested individually in accordance with ISTB-5123, Comprehensive Test Procedure, during refueling outages.
As requested in question 1, these tests will be capable of detecting gross mechanical failures or significant hydraulic degradation, which would threaten the accident-required functions of the NSCCW pumps.
In response to question 2, acceptance criteria for calculated individual pump flowrate during quarterly testing will be set to greater than 110% of accident-required flow. In addition, the acceptance criteria for Group A, paired-pump testing will continue to be established as required by Table ISTB-5100-1.
As additional precedence for approval of this testing methodology, as stated in the previously approved relief request (TAC No. MC0856, July 2, 2004) for these pumps;
"..,The NSCCW pumps are operated in pairs by design to satisfy system heat load requirements while operating at power. The flow instrumentation for the NSCCW pumps is a single flow indicator located in the common piping for all three pumps.
Consequently, flow for any given pump can only be measured when a single pump is in operation. The current piping configuration does not allow installation of individual pump flow instrumentation due to insufficient straight runs of pipe in the pump discharge lines. Installation of individual flow instrumentation would require system redesign and modification, which would be costly and burdensome to the licensee. Each pump has an individual suction pressure gauge and an individual discharge pressure gauge. The pressure and flow instruments meet the accuracy requirements specified by the ASME Code.
The licensee has proposed to use paired pump testing on a quarterly basis in order to meet the ASME Code requirements. Hydraulic and mechanical acceptance criteria will be established for test parameters per OMa- 1988, Part 6, Table 3. If acceptance criteria are not met, an analysis will be made to demonstrate that pump operability is not impaired and the pump will still fulfill its safety function. If the analysis cannot support the operability of the pump, the pump will be repaired or replaced. In addition to paired pump testing on a quarterly basis, the licensee will perform individual pump testing during refueling outages.
With respect to granting relief to perform paired pump testing on a quarterly basis in order to meet the ASME Code requirements, the NSCCW system is not currently designed to either operate or be tested with only one pump operating during power operation. In order to test the pumps individually at power, significant modifications to the system would be required. Therefore, the licensee has demonstrated that it is impractical to test these pumps individually while operating at power.. ."