ML102720160
| ML102720160 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 10/05/2010 |
| From: | Robert Pascarelli Plant Licensing Branch III |
| To: | Jennifer Davis Detroit Edison |
| Gibson, Lauren, NRR/DORL/LPL4, 415-1056 | |
| References | |
| TAC ME2555 | |
| Download: ML102720160 (11) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 October 5, 2010 Mr. Jack M. Davis Senior Vice President and Chief Nuclear Officer Detroit Edison Company Fermi 2 - 210 NOC 6400 North Dixie Highway Newport, MI 48166
SUBJECT:
FERMI 2 - RELIEF REQUEST NO. PRR-09, RELIEF FROM FIXED REFERENCE VALUE TESTING FOR THE THIRD 10-YEAR INSERVICE TESTING PROGRAM INTERVAL (TAC NO. ME2555)
Dear Mr. Davis:
By letter dated November 3, 2009 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML093140302), as supplemented by letters dated February 19 and August 20,2010 (ADAMS Accession Nos. ML100540147 and ML102320577, respectively),
Detroit Edison Company (DECo, the licensee) submitted 11 requests for relief from certain requirements of the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code) at Fermi, Unit 2 (Fermi-2) for the third 10-year inservice testing (1ST) program interval. The Fermi-2 third 10-year 1STprogram interval began on February 17, 2010, and ends on February 16, 2020.
This letter and the enclosed safety evaluation (SE) address Relief Request No. PRR-009 for relief from fixed reference value testing for the third 10-year 1STprogram interval. Specifically, pursuant to paragraph 50.55a(a)(3)(i) of Title 10 of the Code of Federal Regulations (10 CFR),
the licensee requested to use the proposed alternative described in PRR-009, on the basis that the alternative provides an acceptable level of quality and safety.
The NRC staff has reviewed the subject request and determined that the proposed alternative provides reasonable assurance that the Residual Heat Removal Service Water, Emergency Equipment Cooling Water Makeup, and Control Center Heating, Ventilation, and Air Conditioning chilled water pumps are operationally ready. Accordingly, the staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(3)(ii), and is in compliance with the ASME OM Code's requirements. Therefore, the NRC staff authorizes PRR-09 for the remainder of the third 10-year 1STprogram interval at Fermi-2.
All other ASME OM Code requirements for which relief was not specifically requested and approved in the subject request remain applicable.
J. Davis
- 2 If you have any questions, please contact the Project Manager, Mahesh Chawla, at (301) 415-8371.
Sincerely, Robert J. Pascarelli, Chief Plant Licensing Branch 111-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-341
Enclosure:
Safety Evaluation cc w/encl: Distribution via ListServ
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO RELIEF REQUEST NO. PRR-009 FOR FIXED REFERENCE VALUE TESTING THIRD 10-YEAR INSERVICE TESTING PROGRAM INTERVAL DETROIT EDISON COMPANY FERMI, UNIT 2 DOCKET NO. 50-341
1.0 INTRODUCTION
By letter dated November 3, 2009 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML093140302), Detroit Edison Company (DECo, the licensee) submitted 11 requests for relief from certain requirements of the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code) at Fermi, Unit 2 (Fermi-2) for the third 10-year inservice testing (1ST) program interval. The Fermi-2 third 10-year 1ST program interval began on February 17, 2010, and ends on February 16, 2020. This safety evaluation (SE) addresses Relief Request No. PRR-009 (PRR-09) for fixed reference value testing.
In its submittal, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(a)(3)(i), the licensee requested Nuclear Regulatory Commission (NRC) approval to use the proposed alternative described in PRR-009, on the basis that the alternative provides an acceptable level of quality and safety. Specifically, the licensee requested approval to use an instrument inaccuracy band for measuring certain Residual Heat Removal Service Water (RHRSW), Emergency Equipment Cooling Water (EECW) Makeup, and Control Center Heating, Ventilation, and Air Conditioning (CCHVAC) chilled water pump flow rates in lieu of using set reference values required by the ASME OM Code. By an e-mail dated January 7,2010 (ADAMS Accession No. ML101760333), the NRC staff requested the licensee to submit additional information to support request PRR-009, and by letter dated February 19, 2010 (ADAMS Accession No. ML100540147), the licensee submitted this additional information.
During a conference call on July 27, 2010, the NRC staff requested additional clarification from the licensee, which the licensee provided by letter dated August 20, 2010 (ADAMS Accession No. ML102320577).
2.0 REGULATORY EVALUATION
The regulations in 10 CFR 50.55a(f), "Inservice testing requirements," require, in part, that 1ST of certain ASME Code Class 1, 2, and 3 pumps and valves be performed at 120-month (10-year) program intervals in accordance with the specified ASME Code and applicable Enclosure
- 2 addenda incorporated by reference in the regulations. Exceptions are allowed where alternatives have been authorized or relief has been requested by the licensee and granted by the NRC pursuant to paragraphs (a)(3)(i), (a)(3)(ii), or (f)(6)(i) of 10 CFR 50.55a. In proposing alternatives or requesting relief, the licensee must demonstrate that: (1) the proposed alternatives provide an acceptable level of quality and safety (10 CFR 50.55a(a)(3)(i));
(2) compliance would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety (10 CFR 50.55a(a)(3)(ii)); or (3) conformance is impractical for the facility (10 CFR 50.55a(f)(6)(i)). Section 50.55a allows the NRC to authorize alternatives and to grant relief from ASME OM Code requirements upon making necessary findings.
In accordance with 10 CFR 50.55a(f)(4)(ii), licensees are required to comply with the requirements of the latest edition and addenda of the ASME Code incorporated by reference in the regulations 12 months prior to the start of each 120-month 1ST program interval. The regulations in 10 CFR 50.55a(f)(4)(iv), state that 1ST of pumps and valves may meet the requirements set forth in subsequent editions and addenda that are incorporated by reference in 10 CFR 50.55a(b), subject to NRC approval. Portions of editions or addenda may be used provided that all related requirements of the respective editions and addenda are met. The guidance contained in NRC Generic Letter (GL) 89-04, "Guidance on Developing Acceptable Inservice Testing Programs," dated April 3, 1989, provides alternatives to ASME Code requirements which are acceptable. Further guidance is given in NRC GL 89-04, Supplement 1, dated April 4, 1995, and NUREG-1482, Revision 1, "Guidelines for Inservice Testing at Nuclear Power Plants," dated January 2005. ASME OM Code cases that are approved for use by the NRC are listed in NRC Regulatory Guide 1.192, "Operation and Maintenance Code Case Acceptability, ASME OM Code," dated June 2003. The Code of record for the Fermi-2 third 10-year 1ST program interval is the ASME OM Code, 2004 Edition and No Addenda, as required by 10 CFR 50.55a(f)(4)(ii).
The NRC's findings with respect to approving alternatives associated with Fermi-2 relief request PRR-009 are given below
3.0 TECHNICAL EVALUATION
3.1 Alternative Request PRR-009 The requirements in ISTB-5121(b), ISTB-5123(b), ISTB-5221 (b) and ISTB-5223(b) of the ASME OM Code state that, The resistance of the system shall be varied until the flow rate equals the reference point. The differential pressure shall then be determined and compared to its reference value. Alternatively, the flow rate shall be varied until the differential pressure equals the reference point and the flow rate determined and compared to the reference flow rate value.
The ASME OM Code requires that for subsequent 1ST, after the establishment of reference values, the flow rate or differential pressure (DP) shall be set to the exact reference value. The Code does not acknowledge the possibility that there may be limitations in the ability to set to an
- 3 exact reference value. This issue is discussed in NUREG-1482, Revision 1, Section 5.3, "Allowable Variance from Reference Points and Fixed-Resistance Systems."
The licensee has evaluated the ability to test the pumps in the 1ST program and determined that several cases exist where compliance with the ASME OM Code and NUREG-1482, Revision 1 recommendations cannot be achieved. The characteristics of the affected piping system designs do not allow flow to be adjusted to an exact value.
The licensee noted that the RHRSW pumps are tested at a flow rate of 5,400 gallons per minute (gpm) and are throttled to reference flow using a 24-inch motor-operated globe valve (MOV).
These globe valves are in high-radiation areas which preclude manual operation. Experience with throttling these valves has shown that the most rapid operation of the MOV controls yields changes in flow rate from 30-60 gpm. The ECCW Makeup pumps are tested at a flow rate of 15 gpm and are throttled to reference flow using 1-inch manual globe valves. These globe valves provide some throttling capability but small changes in valve position result in relatively significant changes in flow. Finally, the CCHVAC chilled water pumps are tested at a flow rate of 233 gpm and are throttled to reference flow using a 4-inch manual gate valve. Because gate valves are not designed for throttling purposes, a flow tolerance of.:t.3 gpm, or 1.3 percent, has been determined by the licensee to be the best achievable. The licensee has also stated that precision flow measurement instruments cannot be used in these tests due to accessibility issues.
In PRR-009, the licensee proposed an alternative to perform the quarterly Group A pump testing for the centrifugal pumps listed in Table 1, using the following "set parameter" reference value bands:
For RHRSW pumps, a total tolerance inclusive of instrument inaccuracy of
.:t.2.78 percent For EECW Makeup pumps, a total tolerance inclusive of instrument inaccuracy of
.:t.3.0 percent For CCHVAC chilled water pumps, a total tolerance inclusive of instrument inaccuracy of.:t.3.5 percent Table 1 Pump Description Code Class OM Group E1151C001A RHRSW Pump A 3
A E1151C001 B RHRSW Pump B 3
A E1151C001C RHRSW Pump C 3
A E1151C001D RHRSW Pump D 3
A P4400C002A EECW Makeup Pump A 3
B*
P4400C002B EECW Makeup Pump B 3
B*
T4100C040 South CCHVAC Chilled Water Pump 3
A T4100C041 North CCHVAC Chilled Water Pump 3
A
- Per alternative request PRR-007, these pumps are to be reclassified and tested as Group A pumps.
- 4 Additionally, for the CCHVAC chilled water pumps, the licensee will utilize a more conservative DP acceptance criteria range of -8.0 percent to 6 percent for the quarterly Group A test in lieu of the,:t1 0 percent required by the ASME OM Code.
On January 7, 2010, the NRC staff requested that the licensee provide justification for the tolerance of the reference value bands being greater than,:t2.0 percent for each group of pumps listed in Table 1. In its letter dated February 19, 2010, the licensee stated that the additional tolerance would still allow for pump performance to be accurately monitored. The larger flow test band results in increased scatter in the DP data.
The licensee routinely uses a flow normalization method to analyze short-term trends in pump performance. In its letter dated February 19, 2010, the licensee provided the following excerpts from the Fermi-21ST Program Technical Position, TP-12, which describes this method:
DATA NORMALIZATION:
For pump testing where a reference band is allowed, there will be some scatter associated with the measured variable data. This guidance will allow the evaluator to normalize the variable data in order to properly assess trends. An example is a centrifugal pump where flow is set to an established reference value but allowance is given within the procedure for test flow to be plus or minus a given range around the reference value. Discharge and suction pressures are then measured at some measured flow value within the allowed test flow range.
The evaluator needs to establish a known linear pressure-flow relationship, either from baseline data or from an assessment of a large quantity of pressure to flow data accumulated over several years. Using MS Excel, this linear relationship will need to be expressed as a table with at least 4 rows of data relating pressure to flow. One set of values will be at or below the minimum end of the allowable test flow band, another set at or above the maximum end and the remaining data at or very close to the middle (reference flow). The evaluator shall then use the Excel Forecast function to input an actual measured test flow and derive what the DP should be. The numerical difference between the derived DP and the DP at the center of the flow range shall then be subtracted from or added to (as applicable) the actual measured DP for that test flow. This should done for all measured data to be used in the trend analysis.
Following this excerpt, the licensee continued in the supplement by stating:
DP analysis performed in this manner is accurate regardless of the degree of scatter caused by variation in test flow. In addition, long term pump performance analysis is done using a moving average technique that eliminates the effects of scatter in DP data. The [recorded flow values for the RHRSW pumps demonstrate] that there is no discernible bias in the historic flow variance for these pumps. The number and amplitude of points with test flow below reference flow is roughly equal to those above reference flow. Averaging of the DP within the data scatter produces an accurate plot for pump performance.
- 5 On July 27, 2010, during a conference call with the licensee, the NRC staff requested the licensee to submit additional information to support request PRR-009. Specifically, the NRC staff requested additional clarification of the operating margin for the pumps affected by the request, and an explanation of how the data normalization technique will be used by the licensee. By letter dated August 20,2010, the licensee submitted this additional information.
The licensee stated that Table 2 (provided below) shows the available margin between the average of the last three test values and the 1ST Required Action Low criteria, except for RHRSW Pump C. Because this pump has been recently replaced, the available margin is based on the average of only two available test values.
Table 2 i'
Pump
- i******.******
/.....
- i.
E1151C001A RHRSW Pump A 8.43%
E1151C001 B RHRSW Pump B 7.89%
E1151C001C RHRSW Pump C 8.29%
E1151C001D RHRSW Pump D 6.09%
P4400C002A EECW Makeup Pump A 4.23%
P4400C002B EECW Makeup Pump B 5.00%
T4100C040 South CCHVAC Chilled Water Pump 8.41%
T4100C041 North CCHVAC Chilled Water Pump 8.3%
For all pumps listed in Table 2, the initial acceptance criteria for minimum and maximum DP are calculated per ASME 2004 OM Code, Section ISTB, as a function of the existing single-point reference DP values. The criteria are then conservatively truncated. A pump is declared inoperable if any test falls outside the minimum and the minimum and maximum DP acceptance criteria, which are contained in the pump surveillance test procedures.
The 1ST program manager uses the data normalization technique for long-term and short-term trend analysis. Data normalization is completed separately from surveillance testing, after testing is performed.
3.2
NRC Staff Evaluation
As stated above, Section ISTB of the ASME OM Code does not allow for variance from a fixed reference value for pump testing. However, NUREG-1482, Revision 1, Section 5.3, acknowledges that certain pump system designs do not allow for the licensee to set the flow at an exact value because of limitations in the instruments and controls for maintaining steady flow. The licensee has presented a case that each of the pumps listed in Table 1 falls into this category.
I\\lUREG-1482, Revision 1, Section 5.3 states that "[t]he allowed tolerance for setting the fixed parameter must be established for each case individually, including the accuracy of the instrument and the precision of its display." It also states that for a flow measurement, a total tolerance of +/-2 percent of the reference value is allowed without prior NRC approval. This
- 6 agrees with Table ISTB-351 0-1, which states that the required instrument accuracy for flow rate is.:t2 percent. NUREG-1482, Revision 1 also states that "[f]or a tolerance greater than the allowed percent (which may be necessary depending on the precision of the instrument), the licensee may make a corresponding adjustment to acceptance criteria to compensate for the uncertainty, or may perform and document an evaluation to justify a greater tolerance."
The RHRSW pumps are throttled to reference flow using a 24-inch motor-operated globe valve (MOV). These globe valves are in high radiation areas which preclude manual operation. The most rapid operation of the MOV controls yields changes in flow rate from 30-60 gpm. Based on this information and the analysis of previous pump tests, an optimum flow tolerance of
+/-100 gpm or 1.85 percent is achievable. Combining this tolerance with an instrument accuracy tolerance of 0.8 percent and rounding up for readability yields a reference value tolerance of 2.78 percent. Also, per NRC-authorized request PRR-007 dated July 6,2010 (ADAMS Accession No. ML101670372), the Acceptable Range for the Group A tests for these pumps will be 0.95 to 1.068Pr. The Required Action High will be >1.068Pr.
The EECW Makeup pumps, per the NRC-authorized request PRR-007, will be reclassified and tested as Group A pumps. The pumps are throttled to reference flow using 1-inch manual globe valves. The valves provide some throttling capability, but small changes in valve position result in relatively significant changes in flow. Experience with throttling these globe valves shows that the optimum flow tolerance achievable is +/-0.3 gpm or 2.0 percent of the reference value.
Combining this tolerance with the stated instrument accuracy tolerance of 0.8 percent and rounding up for readability yields a reference value tolerance of 3.0 percent. Also, per NRC authorized request PRR-007, the Acceptable Range for the Group A tests for these pumps will be 0.90 to 1.068Pr. The Required Action High will be >1.068Pr.
The NRC staff concludes that this slight increase in reference value tolerance from +/-2 to
+/-2.78 percent for the RHRSW pumps and from +/-2 to +/-3 percent for the EECW Makeup pumps is acceptable for the following reasons. The intent of this ASME OM Code testing is to assess the hydraulic and mechanical condition of a pump and monitor for degradation. The licensee continues to perform ASME OM Code Group A pump tests using the reference point acceptance criteria given in ASME OM Code, 2004 Edition, Tables ISTB-5121-1 and ISTB-5221-1. The larger flow tolerance will yield increased scatter in the differential pressure data. However, the licensee performs analysis of the results using a data normalization methodology to minimize the effect of the scatter in assessing pump degradation. In addition, any small increases in undetected degradation will not affect pump operability as the RHRSW pumps are tested at a 6.09 to 8.43 percent margin above the 1ST Required Action Low criteria and the EECW pumps are tested at a 4.23 to 5.0 percent margin above the 1ST Required Action Low criteria. Furthermore, the licensee has observed that the RHRSW pumps degrade uniformly over a 12-to 15-year period, and the EECW Makeup pumps show no hydraulic degradation, which gives adequate time to detect and correct degrading trends in performance.
The CCHVAC chilled water pumps are throttled to reference flow using a 4-inch manual gate valve. Because gate valves are not designed for throttling purposes, a flow tolerance of +/-3 gpm or 1.3 percent is the best achievable flow tolerance. Also, precision flow measurement instruments cannot be used in these tests due to accessibility issues. The installed analog instrumentation used for testing these pumps has an accuracy of 2.0 percent. Combining this
- 7 tolerance with the flow tolerance of 1.3 percent and rounding up for readability yields a reference value tolerance of 3.5 percent. Because of the increased reference value tolerance, the licensee has proposed a corresponding adjustment to the acceptance criteria to compensate for the uncertainty as presented in NUREG-1482, Revision 1, Section 5.3.
Specifically, the allowable DP acceptance range will be reduced for Group A tests from the ASME OM Code Table ISTB-5121-1 required range of 0.90 to 1.10llPrto 0.92 to 1.06llPr (NRC-authorized request PRR-007 changed the upper end of the Acceptable Range from 1.1OllPr to 1.06llPr). The Required Action Low will be <0.92llPr and the Required Action High will be >1.06llPr.
The NRC staff concludes that this increase in reference value tolerance from ~2 to +/-3.5 percent for the CCHVAC chilled water pumps with a corresponding adjustment to the acceptance criteria, as stated, acceptable for the following reasons. As stated by the licensee, the 2 percent change in the minimum DP acceptance criteria would increase the test criteria DP by 0.5 pounds per square inch differential (psid), based on a reference value of 24.55 psid. The 3.5 percent test flow tolerance is equivalent to 8 gpm (233 gpm x 0.035 = 8 gpm). In the range of the test flow on the pump curves, the relationship between flow and discharge pressure is approximately 2.2 pounds per square inch (psi) per 40 gpm. Therefore, an 8-gpm flow uncertainty yields a 0.44 psi DP uncertainty. Increasing the minimum DP acceptance criteria by 2 percent (or 0.5 psid) is greater than the 0.44 psid expected uncertainty and is, therefore, conservative. In addition, any small increases in undetected degradation will not affect pump operability since the pumps are tested at an 8.3-8.41 percent margin above the 1ST Required Action Low criteria.
The licensee also stated that the data normalization technique is used by the 1ST program manager for long term and short term trend analysis. Data normalization is completed separately from surveillance testing, after testing is complete. For all pumps listed in Table 1, the initial acceptance criteria for minimum and maximum DP are calculated per ISTB, as a function of the existing single point reference DP values. The criteria are then conservatively truncated. A pump is declared inoperable if any test falls outside the minimum and the minimum and maximum DP acceptance criteria, which are contained in the pump surveillance test procedures.
Based on the above information, the NRC staff concludes that requiring the licensee to perform Group A tests for the pumps listed in Table 1, at a flow rate reference point, as required by the OM Code, and within +/-2 percent of the test flow tolerance would cause hardship or unusual difficulty without a compensating increase in the level of quality and safety. The inability to perform the testing, as required, is due to the poor throttling capabilities of the valves in the discharge lines of the pumps. The licensee's ability to accurately trend performance of these pumps using flow reference value bands, in lieu of fixed reference points, and flow normalization methodology, despite increased data scatter during testing, due to higher flow tolerance bands around the flow rate reference points, is an acceptable alternative to the ASME OM Code requirements. This alternative provides reasonable assurance that the pumps listed in Table 1 are operationally ready.
- 8
4.0 CONCLUSION
As set forth above, the NRC staff determines that the proposed alternative as specified in request PRR-009 provides reasonable assurance that the RHRSW, EECW Makeup and CCHVAC chilled water pumps listed in Table 1 are operationally ready. Accordingly, the staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(3)(ii), and is in compliance with the ASME OM Code's requirements.
Therefore, the NRC staff authorizes the alternative noted above, at Fermi 2, for the remainder of the third 1a-year 1ST program interval, which began on February 17, 2010, and ends on February 16, 2020.
All other ASME OM Code requirements for which relief was not specifically requested and approved in the subject request remain applicable.
Principal Contributors: Russell Lake Robert Wolfgang Date: October 5, 2010
J. Davis
- 2 If you have any questions, please contact the Project Manager, Mahesh Chawla, at (301) 415-8371.
Sincerely, IRAJ Robert J. Pascarelli, Chief Plant Licensing Branch 111-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-341
Enclosure:
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RPascarelli DATE 09/29/10 09/30/10 09/29/10 09/21/10 10/05/10 OFFICIAL RECORD COpy