ML061150340
| ML061150340 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 04/19/2006 |
| From: | Cowan P AmerGen Energy Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 2130-06-20283 | |
| Download: ML061150340 (12) | |
Text
Amerl 0i7rn AmerGen Energy Company, LLC www.exeloncorp.com An Exelon Company 200 Exelol Way Kennett Square, PA 19348 2130-0)6-20283 April 19, 2006 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Oyster Creek Generating Station Facility Operating License No. DPR-1 6 NRC Docket No. 50-219
Subject:
Response to Request for Additional Information Concerning Technical Specification Change Request on Reactor Water Clean-up High Energy Line Break Detection and Isolation
References:
- 1)
USNRC email dated October 18, 2005, "Request for Additional Information (RAI) on Oyster Creek Generating Station Technical Specification Change Request - Reactor Water Clean-up High Energy Line Break Detection and Isolation (TAC No. MC6046).
- 2)
AmerGen letter 2130-05-20029 dated February 2, 2005, Technical Specification Change Request No. 280 - Reactor Water Clean-lup High Energy Line Break Detection and Isolation.
This letter provides additional information as requested by the NRC staff in Reference 1.
The request for information is in regard to AmerGen Energy Company's Technical Specification Change Request (TSCR) No. 280 (Reference 2) to include the setpoint for the Reactor Water Clean-up High Energy Line Break detection and isolation instrumentation in the Technical Specifications.
In Reference 1, the NRC staff requested additional information related to the methodology used at Oyster Creek in establishing the setpoint for the Reactor Water Clean-up High Energy Line Break instrumentation. A conference call was conducted on December 21, 2005 between AmerGen (D. Robillard, et al) and the NRC (G. Miller, ft al), to provide clarification on the proposed response. Prior to the submittal of the response to the RAI, the NRC requested another conference call on the RAI. On January 18, 2006, during a conference call between AmerGen (D. Robillard, et al) and the NFRC (G. Miller, et al), additional questions were proposed. An electronic mail from Ao01
U. S. Nuclear Regulatory Commission April 19', 2006 Page 2 G. Miller (NRC) to D. Robillard (AmerGen), dated January 25, 2006, clarified the additional questions proposed during the January 18, 2006 conference call. provides the AmerGen responses to the request for additional information.
NRC Requests 1 - 7 are the original RAI questions, while NRC Requests 8 - 14 are the additional questions clarified in the January 25, 2006 electronic mail. Enclosure 2 provid s the calculation for determining the nominal setpoint for the Reactor Water Cleanup High Energy Line Break temperature switches, and Engineering Standard ES-002, Instrument Error Calculation and Setpoint Determination, Revision 4, which was the revision in effect at the time of the calculation. No changes to the original license amendment request are required due to submittal of these responses to the NRC RAI.
If any additional information is needed, please contact Mr. Dave Robillard at (610) 765-5952.
I declare under penalty of perjury that the foregoing is true and correct.
Respectfully, Executed On Pamela B. Cowan Director - Licensing & Regulatory Affairs AmerGen Energy Company, LLC Enclosures cc:
S. J. Collins, Administrator, USNRC Region 1 G. E. Miller, USNRC Project Manager, Oyster Creek M. S. Ferdas, USNRC Senior Resident Inspector, Oyster Creek File No. 04036
ENCLOSURE 1 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION OYSTER CREEK GENERATING STATION TECHNICAL SPECIFICATION CHANGE REQUEST 280 REGARDING REACTOR WATER CLEAN-UP HIGH ENERGY LINE BREAK INSTRUMENTATION SETPOINT METHODOLGY Response to NRC Request for Additional Information 2130-06-20283 Page 1 of 9 NRC Request 1 Describe the instrumentation setpoint methodology used at Oyster Creek for establishing TS limits. This discussion should include acceptable as found band, acceptable as left band, setting tolerance, and reset criteria used to determine the acceptability of the instrumentation.
Respinse The Reactor Water Cleanup (RWCU) High Energy Line Break (HELB) Technical Specification (TS) limit was established by calculation C-1 302-215-E610-060. This calculation confirmed that with an isolation setpoint of 1800F, the RWCU system will isolate in approximately one minute, and room temperature will not exceed the Environmental Qualification value of 213 0F.
The 1800 F maximum setpoint, considered as the TS limit, was then used to determine an Actual Trip Setpoint (ATSP) of 1600 F in calculation C-1302-215-E320-063. A copy of this calculation is being provided to NRC at their request.
The acceptable As-Left band is same as the setting tolerance. It is calculated by statistically combining the 2 sigma values of all of the module's accuracies that comprise the surveillance test loop and the accuracies of the test equipment used during calibration. The As-Left band is +/- 40F and is provided in the applicable site surveillance procedure.
The acceptable As-Found band is defined as the algebraic sum of the As-Left band and Total Loop Uncertainty (TLU). The TLU is calculated by the square root of the sum of the squares (SRSS) of the 2 sigma values of the instrument accuracies, test gauge accuracies, drift, temperature effect, and power supply effect. The TLU in this application is 80F. Therefore, the As-Found band is 120F and is included in the applicable site surveillance procedure.
The reset criteria means that instruments require adjustment to bring the value within As-Left band when As-Found value exceeds As-Left band.
NRC Request 2 For the setpoint to be added, clarify whether it is a Limiting Safety System Setting (LSSS) as discussed in 10 CFR 50.36(c)(ii)(A). If you determined that it is not, explain why not.
The staff will generally use the following criteria to determine whether the instrument:
setpoint being changed falls within the scope of this LSSS issue or not:
(a) Instrument setpoints for TS functions in the Reactor Protection (Trip) System.
2130-06-20283 Page 2 of 9 (b) Instrument setpoints for TS functions that protect a safety limit (whether or not the Bases designates the function as an LSSS).
(c) Setpoints that are not in Instrumentation LCOs but whose function protects a safety limit (whether or not the Bases designate the function as an LSSS).
Response
Per 1 CI CFR 50.36, an LSSS is a setting required to protect a Safety Limit. OC TS, Section 2, identifies the plant Safety Limits, which are tied to protection of the reactor fuel arid reactor pressure vessel. These LSSS are Reactor Pressure, Reactor Level, and Neutron Flux. The OC RWCU High Area Temperature trip setpoint's function is to isolate the Reactor Pressure Vessel due to a high energy line break. This is a primary containment isolation function, and by definition is not an LSSS.
NRC Request 3 10 CFR 50.36(c)(ii)(A) requires that if it is determined that the automatic safety system does riot function as required, the licensee shall take appropriate action. Describe how the surveillance test results and the associated TS limits as determined by the plant setpoint methodology are used to establish the operability of the safety system. Include a discussion of plant processes for evaluating channels identified to be operable but degraded. If the requirements for determining operability of the instrumentation being tested are located in a document other than the TS (e.g., plant test procedure), discuss how the requirements of 10 CFR 50.36 are met.
Response
Not applicable. The RWCU HELB instrumentation is not a LSSS.
NRC Request 4 10 CFR 50.36(c)(ii)(A) requires that an LSSS be so chosen that automatic protective action will correct the abnormal situation before a SL is exceeded. Discuss how TS limits established by the plant setpoint methodology will ensure that the SL will not be exceeded. Include in your discussion information on the controls you employ to ensure that the as left trip setting after completing periodic surveillances is consistent with your setpoint methodology. If the controls are located in a document other than the TS (e.g.,
plant test procedure), discuss how those controls satisfy the requirements of 10 CFR 50.36.
Response
Not applicable. The RWCU HELB instrumentation is not a LSSS.
21 30-0'3-20283 Page 3 of 9 NRC Request 5 For setlpoints that are not defined as LSSS in response to Question 2, discuss what measures have been taken to ensure that it is capable of performing its specified safety functions. Include in your discussion information on the controls you employ to ensure that the as left trip setting after completing periodic surveillances is consistent with your setpoint methodology. If the controls are located in a document other than the TS (e.g.,
plant test procedure), discuss how those controls satisfy operability requirements.
Response
Any TS or TS supported instrument As-Found setpoint found outside of the As-Left limit must be reset to within the As-Left calibration tolerance before returning the instrument to service. The As-Left Tolerance (ALT) is usually a much tighter band than the As-Found limit band around the required setpoint. An Issue Report (IR) is generated in accordance with procedure LS-AA-120 (Issue Identification) for instruments that do not satisfy the As-Found criteria established in the instrument calibration surveillance procedures. Operations is procedurally required to review IRs associated with plant equipment operability. The normal routing process of the IR will notify the associated System Manager of the instrument out of tolerance (OOT). Exelon procedure ER-AA-2002 for System Health reporting requires that repeat instrument OOT's be identified as a "chronic problem," and action plans be developed to address the problem.
Based on this process, a TS instrument not performing within the expected band, established by the setpoint calculation, would be identified, and an IR would be initiated.
If the issue is a repeat issue, the chronic problem action plan will identify corrective actions (e.g., instrument replacement, setpoint re-calculation, etc.). If the As-Found value of the instrument exceeds the established value in the TS, the instrument would be declared inoperable, and actions would be taken to restore operability.
NRC Request 6 Provide commitment to assess applicability of the TSTF's TS changes pertinent to instrument setpoints, when approved by the NRC, to determine whether changes to Oyster Creek's licensing basis are necessary.
Response
AmerGen has not yet determined if Oyster Creek will submit a license amendment request following approval of the TSTF change traveler by the NRC. After NRC approval of the TSTF, AmerGen will evaluate the TSTF for application to Oyster Creek.
If AmerGen chooses to submit a license amendment request for Oyster Creek, the requirements of the TSTF model application and safety evaluation will be addressed in that submittal.
2130-06-20283 Page 4 of 9 NRC Request 7 By letter dated June 8,1992, to John J. Barton, the NRC concluded that the methodology the licensee used to calculate pressure sensor setpoints in LAR dated May 29, 1990, did not show conclusively adherence to Regulatory Guide 1.105, Revision 2, "Instrument Setpoints for Safety-related Systems," Instrument Society of America (ISA) standard, ISA-S67.04-1982, "Setpoints for Nuclear Safety-related Instrumentation Used in Nuclear Plants" or licensee's Engineering Standard, ES-002, "Instrument Error Calculation and Setpoint Determination." Furthermore, the NRC terminated review of the LAR, and recommended appropriate modifications to ES-00)2 and recalculation of the setpoints. Describe the measures taken to address the NRC's comments in the letter dated June 8,1992.
Response
The current revision of Engineering Standard ES-002 is essentially the same as the revision of ES-002 that was provided to the NRC in a letter to the NRC dated May 9, 1990. In response to a request for additional information from the NRC staff, dated May 1, 1991, Oyster Creek stated that ES-002 is based on the requirements of ISA-S67.04 (1982), the approved setpoint methodology document at that time. No documentation that Oyster Creek responded to the June 8,1992 NRC letter could be recovered.
Calculations performed during 1988 -1989 time frame did not consider calibration tolerance. Calculations considered that Total Loop Error = Calibration Tolerance - As-Found limit. The calculations were revised to account for calibration tolerance as required by ES-002. The As-Found limit was then established by algebraically adding the Calibration Tolerance and the Total Loop Error. It should be noted that Oyster Creek has no known docketed commitment to the requirements of Regulatory Guide 1.105. Also, per Section D of RG 1.105, Revision 2, dated February 1986, Oyster Creek was excluded from the requirements of the RG, because the Oyster Creek Operating License was issued prior to February 1986. This exclusion is stated in Section 7.2.2.3 of the Oyster Creek UFSAR.
NRC Request 8 The license amendment request (LAR) specifies in TS Table 3.1.1, for Function P, RWCLJ HELB Isolation, a "Trip Setting" of < 180 degrees F. Explain the meaning of the terms, 'Trip Setting," "Check" and "Test" used in TS Tables 3.1.1 and TS 4.1.1.
Response
The "Trip Setting" is the point at which the instrument will initiate automatic protective action, as described in TS 3.1.A.3. "Check" and 'Test" are defined in TS 1.19, INSTRUMENTATION SURVEILLANCE DEFINITIONS, as follows:
2130-06-20283 Page 5 of 9 Channel Check - A qualitative determination of acceptable operability by observation of channel behavior during operation. This determination shall include, where possible, comparison of the channel with other independent channels measuring the same variable.
Channel Test - Injection of a simulated signal into the channel to verify its proper response, including, where applicable, alarm and/or trip initiating action.
NRC Request 9 The GPU Nuclear Calculation, C-1302-215-E320-063, RWCU HELB High Temperature Setpoint Error Calculation, has stated 1800F as the process Safety Limit, 1600F as the "Setpcint" and 172cF as the "As-Found" values. Explain the meaning of the terms, "Process Safety Limit," "Setpoint" and "As-Found" used in the calculation.
Response
The "Process Safety Limit" used in the calculation is equivalent to the term "Allowable Value' and is the maximum setpoint as-found value for an instrument for which it can still be considered operable. The meanings of "Setpoint" and "As-Found" are discussed in the response to NRC Request 10.
NRC Request 10 The AmerGen Engineering Division Standard ES-002, Instrument Error Calculation and Setpoint Determination, refers to ISA-S67.04 (1982). Explain how the various tolerances, including Total Loop Uncertainty, specified in ISA-S67.04 for calculating Nominal Trip Setpoint, Acceptable As-Left, Acceptable As-Found and Allowable Values have been accounted for in the calculation of the Oyster Creek RWCU HELB Isolation tolerances and setpoints.
Response
The Allowable Value (AV) is the maximum setpoint as-found value for an instrument for which it can still be considered operable. In industry standard methodology (i.e., ISA RP67.04), the AV is calculated from the Analytical Limit (AL) or from the Limiting Trip Setpoint (LTSP). The AL is a value representative of the Safety Limit (SL) used in site safety analyses.
Oyster Creek's setpoint methodology is as follows:
ATSP(Actual Trip Setpoint) = AV - (TLU + Cal Tolerance + Margin)
TLU = Total Loop Uncertainty.
AV = Allowable Value= Tech Spec Limit 2130-0)6-20283 Page 6( of 9 ATSP = Actual Trip Setpoint= Nominal Trip Setpoint (NTSP)
Cal Tolerance = As-Left Tolerance The As-Left tolerance is calculated by statistically combining the 2 sigma values of all of the module's accuracies that comprise the surveillance test loop and the accuracies of the test equipment used during calibration.
TLU is calculated by the square root of the sum of the squares (SRSS) of the 2 sigma values of instrument accuracies, test equipment accuracy, drift, temperature effect, and power supply effect.
The R'WCU HELB instrumentation's safety function is to isolate the RWCU line in the event of a line break. This isolation function is not associated with any Technical Specification Safety Limit, therefore, there is no associated AL in the safety analysis.
When the RWCU high temperature isolation function was added in 1998, calculation C-1302-21 5-E610-060 was completed for a room heat-up analysis. This analysis confirmed that with an isolation setpoint of 1800 F, the RWCU system will isolate in approximately one minute, and room temperatures will not exceed the Environmental Qualification value of 2130 F.
The 1800 F maximum setpoint, i.e., AV, was then used to calculate an actual trip setpoint: (ATSP) in calculation C1302-215-E320-063. Instrument channel uncertainties (i.e., drift, instrument accuracy, and test equipment uncertainty) are tested periodically and are included in the allowance between the allowable value and the trip setpoint.
Since there are no instrument channel uncertainties (such as radiation, high temperatures due to the HELB, humidity, and seismic events) that are not tested during the surveillance test, the allowable value is equal to the analytical limit.
The graphic below shows the relationship between the various temperature values:
213 -F (Safety Limit)
180 OF (AV = Tech Spec Limit/Analytical Limit)
Margin = 8 OF
172 OF (As-Found Limit/Acceptable As-Found)
TLU = 8 OF
164 OF (Upper As-Left Limit/Acceptable As-Left)
Cal Tolerance = + 4 OF
160 OF (ATSP/NTSP)
Cal Tolerance = - 4 OF
*156 OF (Lower As-Left Limit/Acceptable As-L.eft) 2130-06-20283 Page 7 of 9 NRC lequest 11 Calculation No. C1302-215-E320-063 states in clause 4.2, that all manufacturer's data is assumed to have 3 sigma confidence level. Provide an explanation for this assumption.
Response
The RWCU HELB setpoint calculation was prepared and approved in accordance with OC ES-002, Revision 4. Section 6.1 of ES-002, Revision 4, stated that it was acceptable to assume vendor accuracy data at a 3 sigma confidence level. Section 6.1 also required that all calculations provide loop accuracy and setpoint values at a 2 sigma probability, to assure conformance with the NRC accepted 2 sigma limit for instrument setpoint accuracy. ES-002, Revision 4, also provided guidance for converting the 3 sigma vendor baseline data to 2 sigma data. Therefore, unless specified otherwise, vendor accuracy was assumed to be 3 sigma. This was changed in Revision 5 of ES-002 as vendor accuracy, unless specified otherwise, was assumed to be 2 sigma. Considering vendor accuracy at 2 sigma will result in a larger TLU, a smaller allowance for margin, and the same actual trip setpoint.
NRC request 12 Calculation No. C-1 302-215-E320-063 states in clause 4.5, that since control logic has seal-in feature and since switch will actuate within one minute following RWCU HELI3, error due to radiation and pressure is not considered in the calculation. Provide an explanation for this conclusion.
Response
Since the instrument performs its safety function prior to the development of severe environmental conditions, factors such as high radiation, humidity, temperature, and pressure were not included. Normal radiation is considered mild and has no effect on the switch performance. There is no power supply effect on the process temperature switches. The seal-in feature of the logic needs to be reset manually from the Control Room after initiating signals are cleared.
NRC Flequest 13 Calculation No. C-1 302-215-E320-063 indicates in clause 7.6 that Test Equipment Error and Temperature Switch Error have been used twice to calculate Upper As-Found Limit.
Provide an explanation why they have been used twice to calculate the Upper As-Found Limit.
2130-06-20283 Page 13 of 9
Response
In a letter from the NRC to GPU Nuclear Corporation, dated November 16,1988, "Safety Systems Outage Modifications Inspection Findings (SSOMI)", the NRC identified the following:
"The team identified a second concern during review of setpoint calculations for modifications. Current calibration practices include allowance for instrument drift and loop inaccuracies, but do not account for inaccuracies resulting from the calibration setpoint being left at the upper limit of the calibration tolerance, which, in turn, was determined arbitrarily. When added to instrument drift and loop inaccuracies, it is possible for the value of the process variable to exceed Technical Specification limits.
You are requested to ensure setpoints are established and maintained in a manner such that the sum of all inaccuracies does not cause the Technical Specification limit to be exceeded."
In response to the above NRC concern and subsequent discussions with the NRC SSOMI team members, GPUN had agreed to perform the instrument setpoint calculations such that the instrument inaccuracies and the test equipment inaccuracies will be considered in establishing the calibration tolerance (As-Left) values for the instrument loop. Also, while establishing the total loop uncertainty (TLU), the Accuracy rating of the Instrument tested, Temperature Error Effect, Power Supply Effect, the Drift of the Instrument tested, and the Test Equipment Inaccuracies will be considered.
Thus the As-Found Limit is defined as the algebraic sum of the As-Left limit and the TLU.
Our current Standard, ES-002, "Instrument Error Calculation and Setpoint Determination", complies with this requirement.
NRC Request 14 Calculation No. C-1 302-215-E320-063, indicates that drift has been positive between 05/21/91 and 01/02/93, low between 01/02/93 and 10/11/94, and mostly negative between 10/11/94 and 10/14/96. Provide an explanation for using all of the values except one outlier in the drift evaluation of the RWCU HELB High Temperature Setpoint Error Calculation, and what investigation has been done on the time dependency of this drift.
Response
The R'NCU HELB temperature switches are identical to the Main Steam Line High Temperature switches. The historical drift data used in the calculation is from the surveillance data for the Main Steam Line High Temperature switches. The Note on Page 10 of the calculation provides an explanation of this issue. The Note states that 2130-06-20283 Page 9 of 9 the "as-found data for TS-IB1 OD recorded on 10/14/96 is excluded from this calculation because this switch deviates from the mean by 6.07 times the standard deviation, arid thus would be a rare random event, and is assumed to be an outlier." No time dependency drift investigation has been done because the RWCU HELB instrumentation setpoint is not a LSSS, and drift history of the switch, since installation in 1993, does not warrant such an investigation.