ML041610286
| ML041610286 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 06/04/2004 |
| From: | Bezilla M FirstEnergy Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 3005, TAC MC0583 | |
| Download: ML041610286 (24) | |
Text
FENOC 5501 North State Route 2 FirstEnergy Nuclear Operating Company Oak Harbor, Ohio 43449 Mark B. Bezila 419-321-7676 Vice President - Nuclear Fax. 419321-7582 Docket Number 50-346 License Number NPF-3 Serial Number 3005 June 4, 2004 United States Nuclear Regulatory Commission Document Control Desk Washington, D. C. 20555-0001
Subject:
Supplemental Information Regarding License Amendment Application to Revise Technical Specifications Regarding Steam and Feedwater Rupture Control System Instrumentation Setpoints and Surveillance Intervals (License Amendment Request No. 03-0010; TAC No. MC0583)
Ladies and Gentlemen:
By letter dated August 25, 2003, the FirstEnergy Nuclear Operating Company (FENOC) submitted an application for an amendment to the Davis-Besse Nuclear Power Station (DBNPS),
Unit Number 1, Operating License Number NPF-3, Appendix A Technical Specifications, regarding a proposed modification to Technical Specification (TS) 3/4.3.2.2, "Instrumentation -
Steam and Feedwater Rupture Control System Instrumentation," including Table 3.3-11, "Steam and Feedwater Rupture Control System Instrumentation," Table 3.3-12, "Steam and Feedwater Rupture Control System Instrumentation Trip Setpoints," and Table 4.3-11, "Steam and Feedwater Rupture Control System Instrumentation Surveillance Requirements." The proposed amendment (DBNPS letter Serial Number 2960) would: revise the Steam and Feedwater Rupture Control System (SFRCS) Instrumentation Technical Specifications to clearly identify the appropriate actions to be taken if an SFRCS instrumentation channel's output logic becomes inoperable; relocate the SFRCS Instrumentation Trip Setpoints from the Technical Specifications; and decrease the Channel Functional Test frequency from monthly to quarterly for the SFRCS Instrument Channels and make the associated changes to the Trip Setpoint Allowable Values.
On November 24, 2003, FENOC received a request for additional information (DBNPS letter Log Number 6138, dated November 20, 2003) regarding the license amendment application.
Enclosure I provides the response to this request. This supplemental information does not affect
.aoA
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Page 2 the conclusion of the license amendment application that the proposed changes do not involve a significant hazards consideration and do not have an adverse effect on nuclear safety.
Should you have any questions or require additional information, please contact Mr. Gregory A. Dunn, Manager - Regulatory Affairs, at (419) 321-8450.
The statements contained in this submittal, including its associated enclosures and attachments, are true and correct to the best of my knowledge and belief. I am authorized by the FirstEnergy Nuclear Operating Company to make this submittal. I declare under penalty of perjury that the foregoing is true and correct.
Executed on
____C___
Very truly yours, MKL Enclosures cc:
Regional Administrator, NRC Region III J. B. Hopkins, NRC/NRR Senior Project Manager D. J. Shipley, Executive Director, Ohio Emergency Management Agency, State of Ohio (NRC Liaison)
C. S. Thomas, NRC Region m, DB-1 Senior Resident Inspector Utility Radiological Safety Board
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Page 1 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST (LAR) 03-0010 FOR DAVIS-BESSE NUCLEAR PONWER STATION UNIT NUMBER I (DBNPS)
Table 3.3-11 Question 1:
The new action statement, Action 18, that is proposed in the amendment reads as follows:
"With any component in the Output Logic inoperable, either declare the associated actuated component(s) inoperable, or place the associated actuated component(s) in the SFRCS-actuated position within one hour."
Provide the technical basis for declaring the associated actuated components inoperable as this will allow more time than allowed for placing the components in the SFRCS actuated position within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.
DBNPS Response to Table 3.3-1 1 Question 1:
These proposed changes have the desired effect of separating the Technical Specification (TS) requirements for the Steam and Feedwater Rupture Control System (SFRCS) instrumentation channels and output logic. This approach is consistent with the general approach found in NUREG-1430, "Standard Technical Specifications - Babcock and Wilcox Plants," Revision 3, wherein separate TS requirements are provided for instrumentation channels and output logic, reflecting the different impact each has on instrumentation system operability. The proposed Action 18 is consistent with the approach utilized in NUREG-1430 Specification 3.3.7, "Engineered Safety Feature Actuation System (ESFAS) Automatic Actuation Logic," which, in the event that one or more automatic actuation logic matrices are inoperable, allows one hour to either place the associated component(s) in the engineered safeguard configuration, or to declare the associated component(s) inoperable. The technical basis for the proposed Action 18 is consistent with the Bases for NUREG-1430 Specification 3.3.7, which states: "The Completion Time of 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> is based on operating experience and reflects the urgency associated with the inoperability of a safety system component." Under certain plant operating conditions, it may be undesirable from a technical standpoint to place an SFRCS-actuated component in its actuated position within one hour due to the effect this would have on the plant. For example, should the SFRCS output logic be unable to actuate a train of Auxiliary Feedwater (AFW), it would be
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Page 2 inappropriate to place the train in its actuated state, but appropriate to enter the 72-hour AFW TS Allowed Outage Time.
The Bases for NUREG-1430 Specification 3.3.7 states:
The ESFAS LCOs in the BWOG Standard Technical Specifications (STS) are based on a system representative of the Crystal River Unit 3 design. As discussed earlier, this arrangement involves measurement channels shared among all actuation functions, with separate actuation logic channels for each actuated component. In this arrangement, multiple ESF components are affected by a measurement channel failure, but a single automatic actuation logic failure affects only one component. The organization of BWOG STS ESFAS LCOs reflect the described logic arrangement by linking actions for automatic actuation logic failures directly to the actions for the affected ESF component.
The overall philosophy is that if an automatic actuation logic fails, the affected component is put into its engineered safeguard configuration. This action eliminates the need for the automatic actuation logic. If the affected component cannot be placed in its engineered safeguard configuration, actions are taken to address the inoperability of the supported system component. This greatly simplifies delineation of ESFAS LCOs.
Furthermore, the LCO requirements on instrumentation channels, automatic actuation logics, and manual initiation are specified separately to reflect the different impact each has on ESFAS OPERABILITY.
The Bases for NUREG-1430 Specification 3.3.5, "Engineered Safety Feature Actuation System (ESFAS) Instrumentation," states:
The ESFAS consists of three protection channels. Each channel provides input to logics that initiate equipment with a two-out-of-three logic on each component. Each protection channel includes bistable inputs from one instrumentation channel of Low RB Pressure, Low Low RCS Pressure, High RB Pressure, and High High RB Pressure. Automatic actuation logics combine the three protection channel trips in each train to actuate the individual Engineered Safety Feature (ESF) components needed to initiate each ESF System.
The DBNPS SFRCS is comprised of two independent and redundant protection channels. Each channel has its own independent sensors, which are physically separated from the other channel's sensors and from non-safety system components. No communication exists between either protection channel.
For the purpose of testability and reliability, each SFRCS protection channel is further divided into two sensing channels and two trip logic channels. Each sensing channel provides all monitored digital plant status signals to either logic channel via signal buffer modules, thus making both sets of sensing and logic channels electrically independent. The corresponding
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Page 3 output signals of each logic channel are "AND-gated" to form the output logic (actuation) channel.
Signal processing is performed in the SFRCS logic cabinets. The status signal from each corresponding sensing channel monitoring the same plant variable is combined in a "2-out-of-2" logic before it is further processed by the SFRCS logic module. The SFRCS observes continuously two SFRCS sensing and logic channels for a simultaneous trip condition before actual SFRCS trip signals are sent to the SFRCS actuation channel. This makes the actual trip logic of each of the two redundant SFRCS protection channels a "2-out-of-2" logic.
In summary, it may be undesirable from a technical standpoint to place an SFRCS-actuated component in its actuated position due to the effect this would have on the plant during normal operation. Declaring the component inoperable and applying its associated TS action has the same result as if the component itself was inoperable and could not respond to an SFRCS actuation signal. Based on the above, the FirstEnergy Nuclear Operating Company (FENOC)
'believes that it is appropriate to use NUREG-1430 Specification 3.3.7 as a model for the proposed SFRCS Action statement.
Table 3.3-12 Question 1:
In Table 3.3-12, the allowable values for Functional Unit 1 (Steam Line Pressure-Low),
Functional Unit 2 (Steam Generator Level-Low), and Functional Unit 3 (Steam Generator Feedwater Differential Pressure-High) are all revised due to updated calculations and current setpoint methodology as stated in the amendment. Has the current setpoint methodology been approved by the NRC staff? If not, provide the setpoint methodology used to calculate the revised allowable values for the functional units mentioned above.
DBNPS Response to Table 3.3-12 Question 1:
As stated on page 12 of Enclosure 1 of the license amendment application, the updated instrumentation setpoint calculations have been prepared in accordance with Instrument Society of America (ISA) Standard S67.04, Part I, "Setpoints for Nuclear Safety-Related Instrumentation," September 1994, and ISA-RP67.04, Part II, "Methodologies for the Determination of Setpoints for Nuclear Safety-Related Instrumentation," September 1994. More specifically, the setpoint calculations utilize "Method 2" of the ISA Standard. ISA S67.04 Part I-1994 has been endorsed by the Nuclear Regulatory Commission (NRC) through Regulatory Guide (RG) 1.105, Revision 3, "Setpoints for Safety-Related Instrumentation," subject to four listed exceptions and clarifications. The Regulatory Guide does not address ISA-RP67.04, Part II-1994. The DBNPS-specific response to each of the four exceptions and clarifications was provided on pages 12 through 15 of Enclosure I of the license amendment application. This approach is consistent with a similar license amendment application, as described by letter dated July 14, 2000 (DBNPS letter Serial Number 2662), and as approved by License Amendment No. 243 dated September 14, 2000 (DBNPS Log Number 5704).
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Page 4 The SFRCS setpoint calculations which support the license amendment application are available for NRC review upon request.
Table 3.3-12 Question 2:
The amendment also states that the trip setpoints in the table are allowed to be removed since NUREG-1430 specifies only the allowable values for instrumentation functional units. To consistently reflect this specification, consider labeling the title of the table as:
"Steam and Feedwater Rupture Control System Instrumentation Allowable Values" DBNPS Response to Table 3.3-12 Question 2:
Although the trip setpoint nominal values listed in Table 3.3-12 are proposed to be removed from the table and relocated to the DBNPS Updated Safety Analysis Report (USAR), the Allowable Values listed in Table 3.3-12 are Allowable Values for the trip setpoints. The inter-relationship between the trip setpoints and the Allowable Values is described in the Bases. FENOC believes the current title to be adequate but would not object to the NRC incorporating this editorial change into the Safety Evaluation Report for the associated license amendment.
Table 4.3-11 Question 1:
The methodology described in Electric Power Research Institute (EPRI) TR-103335-R1 is representative of extending calibration intervals based upon instrument drift analysis. The NRC staff has not accepted the ERPI TR and has issued a status report dated December 1, 1997, which documents the staff's issues with the report. The amendment requests surveillance interval extensions for channel functional tests from monthly to quarterly for the four Functional Unit 1 instrument channels on Table 4.3-11. The staff has previously accepted surveillance test interval extension requests based on a probability analysis result for core damage frequency and large early release frequency showing significantly lower increments together with a failure mode and effect analysis. Provide the technical basis for your request based on analysis that the staff has previously accepted.
DBNPS Response to Table 4.3-1I Question 1:
The issues identified in the December 1, 1997 NRC letter are addressed in the attachment. It is noted that other licensees have successfully utilized the EPRI TR approach after having addressed the issues identified in the December 1, 1997 letter, for example, Perry Nuclear Power Plant, Unit 1, Amendment No. 115 to Facility Operating License No. NPF-58 dated August 29, 2000.
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Page 5 No new failure modes are introduced as a result of the extension of surveillance from one-month to three-months. The equipment will be subjected to the same environment during that period.
An evaluation of the risk significance of increasing the functional testing interval for the SFRCS from monthly to quarterly was performed using the DBNPS internal events Probabilistic Safety Analysis (PSA). For conservatism, the evaluation neglected any potential benefit resulting from a decreased risk of initiating events resulting from test performance. The results of this evaluation determined that the risk increase associated with the proposed functional testing interval change is very small. The Core Damage Frequency (CDF) increase was less than I E-08/yr. The increase in Large Early Release Frequency (LERF) was also evaluated. There is a very small increase in LERF for the proposed functional testing interval change of approximately 6.OE-1 1/yr.
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Attachment Page 1 ISSUES ASSOCIATED WITH NRC STATUS REPORT DATED DECEMBER 1,1997 The following are excerpts or paraphrases from the December 1, 1997 NRC letter to EPRI, "Status Report on the Staff review of EPRI Technical Report TR-103335, 'Guidelines for Instrument Calibration Extension/Reduction Programs,' dated March, 1994". These excerpts are followed by the DBNPS staffs' evaluation of each issue identified in the status report.
STATUS REPORT Item 4.1, Section 1, "Introduction", Second Paragraph:
"The staff has issued guidance on the second objective [evaluating extended surveillance intervals in support of longer fuel cycles] only for 18-month to 24-month refueling cycle extensions (GL 91-04). Significant unresolved issues remain concerning the applicability of 18 month (or less) historical calibration data to extended intervals longer than 24 months (maximum 30 months), and instrument failure modes or conditions that may be present in instruments that are unattended for periods longer than 24 months."
DBNPS EVALUATION The requested extension is from a one-month surveillance frequency to a three-month surveillance frequency for channel functional testing. The setpoint is verified as part of the channel functional test. The setpoint data used in the drift study was for three consecutive months when no adjustment was made to the instrument. As a result of this, extrapolation of data was not required as would be required to extend the surveillance frequency for channel calibration from an 18-month surveillance to a 24-month surveillance period.
STATUS REPORT Item 4.2, Section 2, "Principles of Calibration Data Analysis", First Paragraph:
"This section describes the general relation between as-found and as-left calibration values, and instrument drift. The term 'time dependent drift' is used. This should be clarified to mean time dependence of drift uncertainty, or in other words, time dependence of the standard deviation of drift of a sample or a population of instruments."
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Attachment Page 2 DBNPS EVALUATION As stated above, the requested surveillance extension is from a one-month surveillance frequency to a three-month surveillance frequency. The calculation used data for three-month periods in which there was no adjustment of the instrument setpoint. Therefore, the calculations developed for this surveillance extension request do establish a time dependence of the standard deviation of drift for a sample of instruments.
STATUS REPORT Item 4.2, Section 2, "Principles of Calibration Data Analysis", Second Paragraph:
"Drift is defined as as-found - as-left... As mentioned in the TR, this quantity unavoidably contains uncertainty contributions from sources other than drift. These uncertainties account for variability in calibration equipment and personnel, instrument accuracy, and environmental effects. It may be difficult to separate these influences from drift uncertainty when attempting to estimate drift uncertainty, but this is not sufficient reason to group these allowances with a drift allowance. Their purpose is to provide sufficient margin to account for differences between the instrument calibration environment and its operating environment. See Section 4.7 of this report for a discussion of combining other uncertainties into a 'drift' term."
DBNPS EVALUATION The drift determined by analysis does include other uncertainties, such as Measurement and Test Equipment (M&TE) error, Setting Tolerance error, etc., as stated in the letter.
This is considered to increase the calculated drift value, and is therefore conservative.
The M&TE, Setting Tolerance, etc., uncertainties were included separately in the final calculated value in addition to the calculated drift value. This is considered to increase the total uncertainty in the conservative direction.
STATUS REPORT Item 4.2, Section 2, "Principles of Calibration Data Analysis", Third Paragraph:
"The guidance of Section 2 is acceptable provided that time dependency of drift for a sample or population is understood to be time dependency of the uncertainty statistic describing the sample or population; e.g., the standard deviation of drift. A combination of other uncertainties with drift uncertainty may obscure any existing time dependency of drift uncertainty, and should not be done before time-dependency analysis is done."
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Attachment Page 3 DBNPS EVALUATION As stated above, the requested surveillance extension is from a one-month surveillance frequency to a three-month surveillance frequency. The calculation used data for three-month periods in which there was no adjustment of the instrument setpoint. Therefore, the calculations developed for this surveillance extension request do establish a time dependence of the standard deviation of drift for a sample of instruments.
STATUS REPORT Item 4.3, Section 3, "Calibration Data Collection", Second Paragraph:
"When grouping instruments, as well as manufacturer make and model, care should be taken to group only instruments that experience similar environments and process effects.
Also, changes in manufacturing method, sensor element design, or the quality assurance program under which the instrument was manufactured should be considered as reasons for separating instruments into different groups. Instrument groups may be divided into subgroups on the basis of instrument age, for the purpose of investigating whether instrument age is a factor in drift uncertainty."
DBNPS EVALUATION Four groups were established based on service application. No additional subgroups were necessary as described below. The instruments in each group are nearly all of the same manufacturer model number and manufacture date. The instruments in each group are located in similar environments and experience similar process effects. A review of the devices follows:
SFRCS Low Pressure instruments - All were replaced in 1990. Three have been replaced since that time, two in 1993 and one in December 1999. A review of the As-found - As-left data for the switches that were replaced revealed data similar to the remaining switches.
SFRCS Feedwater Differential Pressure instruments - Two switches have been replaced, one in 1996 and one in 2000. A review of the data for switches that were replaced revealed As-found - As-left data that was similar to the remaining switches.
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Enclosure I Attachment Page 4 SFRCS Low Level instruments - These instruments were installed in 1988. Two have been replaced since that time, one in 1990 and one in 1996. A review of the As-found - As-left data revealed the data to be similar to the remaining bistables.
SFRCS Reactor Coolant Pump Monitor instruments - All instruments are the same age. There are no replacement impacts on the drift data.
STATUS REPORT Item 4.3, Section 3, "Calibration Data Collection", Second Paragraph (continued):
"Instrument groups should also be evaluated for historical instrument anomalies or failure modes that may not be evident in a simple compilation of calibration data. This evaluation should confirm that almost all instruments in a group performed reliably and almost all required only calibration attendance."
DBNPS EVALUATION As stated above, the instruments were reviewed from initial installation to the present.
There have been very few replacements of equipment and no failure pattern is present.
As discussed in the license amendment application, Enclosure 1, pages 9 and 1 0, the component failures appear to be random in nature.
STATUS REPORT Item 4.3, Section 3, "Calibration Data Collection", Third Paragraph:
"Instruments within a group should be investigated for factors that may cause correlations between calibrations. Common factors may cause data to be correlated, including common calibration equipment, same personnel performing calibrations, and calibrations occurring in the same conditions. The group, not individual instruments within the group, should be tested for trends."
DBNPS EVALUATION Because Measurement and Test Equipment (M&TE) is calibrated on a regular basis and different calibration devices are frequently used during testing, the effect of test equipment between calibrations is considered to be negligible and random. A review for a sample of calibrations for each of the instrument types revealed several instances of a single M&TE device being used two or more months in a row. The calibration data was
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Attachment Page 5 reviewed and there is no indication that repeated use of a single M&TE device had an impact on calibration of the installed instruments. Based on the frequent calibration of M&TE and the frequent use of different M&TE to accomplish the testing, effects due to M&TE is not considered a correlation factor in the result of the drift analysis.
A review for a sample of data was accomplished to determine if there could be effects caused by technicians. There were several instances where the same technician was involved in the instrument calibration two or more months in a row. In all but a few cases, there were either three or four technicians involved in the testing. A review of the data when different technicians were performing the test resulted in no indication that there was any effect by any one technician. Due to the testing being accomplished by procedures, and additional trained and qualified technicians being involved in the testing, the effect due to technicians is not considered a correlation factor in the result of the drift analysis.
All equipment in each equipment group experienced similar environments. The equipment would experience temperature variations that would impact the calibration data. Based on this, the variations in data would include temperature effects and would result in larger standard deviations when analyzing the data. This is considered conservative and would not have a negative impact on the drift analysis.
STATUS REPORT Item 4.3, Section 3, "Calibration Data Collection", Fourth Paragraph:
"TR-103335, Section 3.3, advises that older data maybe excluded from analysis. It should be emphasized that when selecting data for drift uncertainty time dependency analysis, it is unacceptable to exclude data simply because it is old data. When selecting data for drift uncertainty time dependency analysis, the objective should be to include data for time spans at least as long as the proposed extended calibration interval, and preferably several times as long, including calibration intervals as long as the proposed interval. For limited extensions (e.g., a GL 91-04 extension), acceptable ways to obtain this longer-interval data include obtaining data from other nuclear plants or from other industries for identical or close-to-identical instruments, or combining intervals between
,which the instrument was not reset or adjusted. If data from other sources is used, the source should be analyzed for similarity to the target plant in procedures, process, environment, methodology, test equipment, maintenance schedules and personnel training. An appropriate conclusion of the data collection process may be that there is insufficient data of appropriate time span for a sufficient number of instruments to support statistical analysis of drift uncertainty time dependency."
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Enclosure I Attachment Page 6 DBNPS EVALUATION Over three years of calibration data for each of the instrument types was collected and analyzed. As this is a factor of 12 times the requested surveillance interval of three months, it is considered an acceptable analysis of drift data for the instruments.
STATUS REPORT Item 4.3, Section 3, "Calibration Data Collection", Fifth Paragraph:
"TR-103335. Section 3.3 provides guidance on the amount of data to collect. As a general rule, it is unacceptable to reject applicable data, because biases in the data selection process may introduce biases in the calculated statistics. There are only two acceptable reasons for reducing the amount of data selected: enormity, and statistical dependence. When the number of data points is so enormous that the data acquisition task would be prohibitively expensive, a randomized selection process, not dependent upon engineering judgment, should be used. This selection process should have three steps. In the first step, all data is screened for applicability, meaning that all data for the chosen instrument grouping is selected, regardless of the age of the data. In the second step, a proportion of the applicable data is chosen by automated random selection, ensuring that the data records for single instruments are complete, and enough individual instruments are included to constitute a statistically diverse sample. In the third step, the first two steps are documented. Data points should be combined when there is indication that they are statistically dependent on each other, although alternate approaches may be acceptable. See Section 4.5, below, on 'combined point' data selection and Section 4.4.1 on '0%, 25%, 50%, 75%, and 100% calibration span points'."
DBNPS EVALUATION As stated above, over three years of calibration data for each of the instrument types was collected and analyzed. All data for all instruments from this time period was included in the analysis. Since the amount of data analyzed includes the equivalent of a factor of 12 times the requested surveillance interval of three months, it is considered an acceptable analysis of drift data for the instruments.
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Attachment Page 7 STATUS REPORT Item 4.4, Section 4, "Analysis of Calibration Data":
Sub-item, 4.4.1, Sections 4.3 and 4.4, "Data Setup and Spreadsheet Statistics", First Paragraph:
"The use of spreadsheets, databases, or other commercial software is acceptable for data analysis provided that the software, and the operating system used on the analysis computer, is under effective configuration control. Care should be exercised in the use of Windows or similar operating systems because of the dependence on shared libraries.
Installation of other application software on the analysis machine can overwrite shared libraries with older versions or versions that are inconsistent with the software being used for analysis."
DBNPS EVALUATION During creation of the calculation, one function required is review/checking of the calculation by at least a second individual. As part of that checking process, the calculations, including software generated calculations, are verified to be correct. This may include a sample or complete recalculation of the formulas used in the spreadsheet.
As most of the formulas in generating the analysis are simple addition, subtraction, multiplication, and division, these values are easily verified. The one exception to this is the standard deviation. The formula identified in the license amendment application was used and compared against the results of the Excel-generated standard deviation with identical results. Based on the calculations, including Standard Deviation, being confirmed using alternate software or hand calculations, shared libraries is not considered to be a concern.
STATUS REPORT Item 4.4, Section 4, "Analysis of Calibration Data":
Sub-item, 4.4.1, Sections 4.3 and 4.4, "Data Setup and Spreadsheet Statistics", Second Paragraph:
"Using either engineering units or per-unit (percent of span) quantities is acceptable. The simple statistic calculations (mean, sample standard deviation, sample size) are acceptable. Data should be examined for correlation or dependence to eliminate over-optimistic tolerance interval estimates. For example, if the standard deviation of drift can be fitted with a regression line through the 0%, 25%, 50%,75%, and 100% calibration
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Enclosure I Attachment Page 8 span points, there is reason to believe that drift uncertainty is correlated over the five (or nine, if the data includes a repeatability sweep) calibration data points. An example is shown in TR-103335, Figure 5.4, and a related discussion is given in TR-103335 Section 5.1.3. Confidence/tolerance estimates are based on (a) an assumption of normality (b) the number of points in the data set, and (c) the standard deviation of the sample. Increasing the number of points (utilizing each calibration span point) when data is statistically dependent decreases the tolerance factor k which may falsely enhance the confidence in the predicted tolerance interval. To retain the information, but achieve a reasonable point count for confidence/tolerance estimates, the statistically dependent data points should be combined into a composite data point. This retains the information but cuts the point count. For drift uncertainty estimates with data similar to that in the TR example, an acceptable method requires that the number of independent data points should be one-fifth (or one ninth) of the total number of data points in the example, and a combined data point for each set of five span points should be selected that is representative of instrument performance at or near the span point most important to the purpose of the analysis (i.e., trip or normal operation point)."
DBNPS EVALUATION None of the SFRCS drift values are based upon a 5 or 9 point calibration. The installed devices for which this license amendment application applies are either switches or bistables. Therefore, the discussion above is not applicable to the DBNPS submittal.
STATUS REPORT Item 4.4, Section 4, "Analysis of Calibration Data":
Sub-item 4.4.2, Section 4.5, "Outlier Analysis":
"Rejection of outliers is acceptable only if a specific, direct reason can be documented for each outlier rejected. For example, a documented tester failure would be cause for rejecting a calibration point taken with the tester when it had failed. It is not acceptable to reject outliers on the basis of statistical tests alone. Multiple passes of outlier statistical criterion are not acceptable. An outlier test should only be used to direct attention to data points, which are then investigated for cause. Five acceptable reasons for outlier rejection, provided that they can be demonstrated, are given in the TR: data transcription; errors, calibration errors, calibration equipment errors, failed instruments, and design deficiencies. Scaling or setpoint changes that are not annotated in the data record indicate unreliable data, and detection of unreliable data is not cause for outlier rejection, but may be cause for rejection of the entire data set and the filing of a licensee event report. The usual engineering technique of annotating the raw data record with the reason for
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Attachment Page 9 rejecting it, but not obliterating the value, should be followed. The rejection of outliers typically has cosmetic effects; if sufficient data exists, it makes the results look slightly better; if insufficient data exists, it may mask a real trend. Consequently, rejection of outliers should be done with extreme caution and should be viewed with considerable suspicion by a reviewer."
DBNPS EVALUATION Only one set of data met the criteria for outliers as identified above. There were 88 three month calibration periods that were available for analysis after exclusion of this data.
This is considered an adequate sample of data to establish representative drift values.
STATUS REPORT Item 4.4, Section 4, "Analysis of Calibration Data":
Sub-item 4.4.3, Section 4.6, "Verifying the Assumption of Normality":
"The methods described are acceptable in that they are used to demonstrate that calibration data or results are calculated as if the calibration data were a sample of a normally distributed random variable. For example, a tolerance interval which states that there is a 95% probability that 95% of a sample drawn from a population will fall within tolerance bounds is based on an assumption of normality, or that the population distribution is a normal distribution. Because the unwarranted removal of outliers can have a significant effect on the normality test, removal of significant numbers of, or sometimes any (in small populations), outliers may invalidate this test."
DBNPS EVALUATION As stated above, there was one set of data determined to be outliers. All other data indicated that the devices performed consistent with or better than a normally distributed population, i.e., data had higher peaks in the middle, making a higher percentage within the first standard deviation.
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Attachment Page 10 STATUS REPORT Item 4.4, Section 4, "Analysis of Calibration Data":
Sub-item 4.4.4, Section 4.7, "Time-Dependent Drift Considerations":
"This section of the TR discusses a number of methods for detecting a time dependency in drift data, and one method of evaluating drift uncertainty time dependency. None of the methods uses a formal statistical model for instrument drift uncertainty, and all but one of them focus on drift rather than drift uncertainty.... There are acceptable methods depending upon other bases than mathematical statistics. In particular, a physical model for a specific instrument type that is validated and can predict the effect of long-term operation without calibration would be an acceptable substitute. If it is to be used with the setpoint calculation method of TR-103335, Section 7, it should still provide an estimate of drift standard deviation over the intended calibration interval."
DBNPS EVALUATION The analysis accomplished for the extension of the surveillance from a one-month interval to a three-month interval used data for devices where no adjustment to the instrument was done for a three-month period, the same interval requested in the license amendment application. Therefore, the statistical analysis results in a standard deviation of the three-month drift of the instruments.
STATUS REPORT Item 4.4, Section 4, "Analysis of Calibration Data":
Sub-item 4.4.5, Section 4.8, "Shelf Life of Analysis Results":
"The TR gives guidance on how long analysis results remain valid. The guidance given is acceptable with the addition that once adequate analysis and documentation is presented and the calibration interval extended, a strong feedback loop must be put into place to ensure drift, tolerance and operability of affected components are not negatively impacted. An analysis should be re-performed if its predictions turn out to exceed predetermined limits set during the calibration interval extension study. A goal during re-performance should be to discover why the analysis results were incorrect. The establishment of a review and monitoring program, as indicated in GL 91-04,, Item 7, is crucial to determining that the assumptions made during the calibration interval extension study were true. The methodology for obtaining reasonable and timely feedback must be documented."
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Attachment Page 1 1 DBNPS EVALUATION The current applicable SFRCS surveillance procedures for the Steam Generator Low Pressure and the Feedwater Reverse Differential Pressure switches have acceptance criteria that are more restrictive than the calculated drift values. The surveillance procedures for the Steam Generator Low Level and Reactor Coolant Pump Monitoring bistables do not have acceptance criteria that are more restrictive than the calculated drift values. The acceptance criteria for those instruments will be revised to be consistent with the other surveillance procedures. With this change, compliance with the acceptance criteria during the proposed quarterly testing will validate the calculated drift values for all of the SFRCS instruments. In addition, the applicable SFRCS surveillance procedures will be revised to require that any calibration that is outside of the acceptance criteria requires generation of a Condition Report under the DBNPS 10 CFR 50 Appendix B Corrective Action Program for trending and analysis purposes.
STATUS REPORT Item 4.5, Section 5, "Alternative Methods of Data Collection and Analysis":
"Section 5 discusses two alternatives to as-found/as-left (AFAL) analysis, combining the 0%, 25%, 50%, 75% and 100% span calibration points, and the EPRI Instrument Calibration Reduction Program (ICRP). Two alternatives to AFAL are mentioned: as-found/setpoint (AFSP) analysis and worse case as-found/as-left (WCAFAL). Both AFSP and WCAFAL are more conservative than the AFAL method because they produce higher estimates of drift. Therefore, they are acceptable alternatives to AFAL drift estimation. The combined-point method is acceptable, and in some cases preferable, if the combined value of interest is taken at the point important to the purpose of the analysis. That is, if the instrument being evaluated is used to control the plant in an operating range, the instrument should be evaluated near its operating point. If the instrument being evaluated is employed to trip the reactor, the instrument should be evaluated near the trip point. The combined-point method should be used if the statistic of interest shows a correlation between calibration span points, thus inflating the apparent number of data points and causing an overstatement of confidence in the results. The method by which the points are combined (e.g., nearest point, interpolation, averaging) should be justified and documented."
DBNPS EVALUATION The applicable devices are switches and bistables, thus the combination of 0%, 25%,
50%, 75%, and 100% calibration points does not apply. The AFAL method was used for
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Enclosure I Attachment Page 12 calculating the values for the switches and bistables. Based on using the AFAL method, the remaining discussion of AFSP and WCAFAL does not apply to the requested extension from one-month surveillance to a three-month surveillance.
STATUS REPORT Item 4.6, Section 6, "Guidelines for Calibration and Surveillance Interval Extension Programs":
"This section presents an example analysis in support of extending the surveillance interval of reactor trip bistables from monthly to quarterly. Because these bistables exhibit little or no bias, and very small drift, the analysis example does not challenge the methodology presented in TR-103335 Section 4, and thus raises no acceptability issues related to the drift analysis that have not already been covered.... The binomial pass/fail methodology of Section 6.3 is acceptable as a method of complying with GL 91-04,, item 1 for bistables, 'Confirm that acceptable limiting values of drift have not been exceeded except in rare instances.' This method provides guidance... "
DBNPS EVALUATION A review of the devices results in the following evaluation for instruments being outside of the calculated drift value:
SFRCS Low Pressure switches - 88 three-month calibrations during the evaluation period, 0 instances or 0.0% outside of the calculated drift value.
SFRCS Reverse Differential Pressure switches - 99 three-month calibrations during the evaluation period, 2 instances or 2.0% outside of the calculated drift value.
SFRCS Low Level bistables - 191 three-month calibrations during the evaluation period, I instance or 0.5% outside of calculated drift.
SFRCS Reactor Coolant Pump Monitor bistables - 400 three-month calibrations during the evaluation period, 4 instances or 1.0% outside of calculated drift value.
The worst case value of 2.0% is better than the 5% expected value based on a 95/95 criterion. Therefore, it is considered that the drift value is not exceeded except in rare instances.
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Enclosure I Attachment Page 13 STATUS REPORT Item 4.7, Section 7, "Application to Instrument Setpoint Programs":
"Section 7 is a short tutorial on combining uncertainties in instrument setpoint calculations. Figure 7-1 of this section is inconsistent with ANSIIISA-S67.04-1994, Part I, Figure 1. Rack uncertainty is not combined with sensor uncertainty in the computation of the allowable value in the standard. The purpose of the allowable value is to set a limit beyond which there is reasonable probability that the assumptions used in the setpoint calculation were in error. For channel functional tests, these assumptions nonnally do not include an allowance for sensor uncertainty (quarterly interval, sensor normally excluded). If a few instruments exceed the allowable value, this is probably due to instrument malfunction. If it happens frequently, the assumptions in the setpoint analysis may be wrong. Since the terminology used in Figure 7-1 is inconsistent with ANSIISA-S67.04-1994, Part I, Figure 1, the following correspondences are suggested:
the 'Nominal Trip Setpoint' is the ANS/ISA trip setpoint; ANSI/ISA value 'A' is the difference between TR 'Analytical Limit' and 'Nominal Trip Setpoint'; 'Sensor Uncertainty' is generally not included in the 'Allowable Value Uncertainty' and would require justification, the difference between 'Allowable Value' and 'Nominal Trip Setpoint' is ANSMISA value 'B'; the 'Leave-As-Is-Zone' is equivalent to the ANSI/ISA value 'E' and the difference between 'System Shutdown' and 'Nominal Trip Setpoint' is the ANSI/ISA value 'D'. Equation 7-5 (page 7-7 of the TR) combines a number of uncertainties into a drift term, D. If this is done, the reasons and the method of combination should be justified and documented. Thejustification should include an analysis of the differences between operational and calibration environments, including accident environments in which the instrument is expected to perform."
DBNPS EVALUATION Application of the drift values to plant setpoints was performed in accordance with ISA S64.07 and the associated Recommended Practice ISA-RP64.07. No information from the EPRI document was used in establishing the Allowable Value and the Trip Setpoints.
Therefore, the above correlations need not be addressed.
STATUS REPORT Item 4.8, Section 8, "Guidelines for Fuel Cycle Extensions":
"The TR repeats the provisions of Enclosure 2, GL 91-04, and provides direct guidance, by reference to preceding sections of the TR, on some of them."
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Attachment Page 14 DBNPS EVALUATION The following are excerpts from Enclosure 2, "Guidance for Addressing the Effect of Increased Surveillance Intervals on Instrument Drift and Safety Analysis Assumptions,"
of GL 91-04. These excerpts are followed by the DBNPS staffs' evaluation of each issue identified.
- 1. "Confirin that instnrment drift as determined by as-found and as-left calibration data from surveillance and maintenance records has not, except on rare occasions, exceeded acceptable limits for a calibration interval."
Calibration data was reviewed for those surveillances proposed for revision to a three month interval. As-found and as-left data has not exceeded acceptable limits except on rare occasions. These were discussed above in response to Item 4.6, Section 6.
- 2. "Confirm that the values of driftfor each instrument type (make, model, and range) and application have been determined with a high probability and a high degree of confidence. Provide a summary of the methodology and assumptions used to determine the rate of instrument drift ivith time based upon historical plant calibration data.
Drift values were determined for each instrument string. Basic statistics calculated for each drift value included a 95/95% tolerance factor and a 95/95% tolerance interval.
Normality of the drift data was verified by histogram and/or the W test. All data was either normal or more centrally located, indicating better overall performance.
As stated above, time dependency is not a factor due to the method of using data for three consecutive months in which the instrument setpoints were not adjusted as the input for calculated drift.
- 3. "Con rm that the magnitude of instrumnent drift has beei determined iithl a high probability and a high degree of confidence for a bounding calibration interval of 30 months for each instnument type (make, model number, and range) and application that performs a safetyfitnction. Provide a list of channels by TS section that identifies these instnrment applications. "
The requested three month surveillance interval was calculated using a 95195% tolerance interval. The channels affected by this calculation method are as described in the license amendment application.
- 4. "Confirmn that a comparison of the projected instnrment drift errors has been made with the values of drift Used in the setpoint analysis. If this results in revised setpoints to accommodate larger drift errors, provide proposed TS changes to update trip setpoints.
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Attachment Page 15 If the drift errors result in a revised safety analysis to support existing setpoints, provide a summary of the Updated analysis conclusions to confirm that the safety limits and safety analysis assumptions are not exceeded. "
The instrument drift errors were determined in the calculation for establishing the trip setpoint and Allowable Value. Revised setpoints and Allowable Values are as described in the license amendment application. The Analytical Limits are not affected by the established drift values.
- 5. "Conzfirm that the projected instnrmenit errors caused by drift are acceptable for control ofplant parameters to effect a safe shutdown with the associated instntmentation. "
As discussed in the response to question 4, the Analytical Limits were not affected by the established drift values. The calculated trip setpoint for the Steam Generator Level and Reverse Differential Pressure were more conservative and have been revised in the plant.
The Reactor Coolant Pump Monitors low current setpoint calculation calculated a lower trip setpoint value, thus the plant setpoint remains at the existing, conservative setpoint value. The calculated trip setpoints will ensure actuation of equipment prior to reaching the Analytical Limit.
- 6. "Confirn that all conditions and assumptions of the setpoint and safety analyses have been checked and are appropriately reflected in the acceptance criteria ofplant surveillance procedures for channel checks, channelfiunctional tests, and channel calibrations. "
The applicable surveillance and periodic test procedures were reviewed to verify that they appropriately reflect all applicable conditions and assumptions of the setpoint and safety analysis. As stated above, the plant has already instituted the revised setpoints, if they are more conservative, and has revised surveillance procedures and the associated acceptance criteria to reflect these changes.
- 7. "Provide a summary description of the program for monitoring and assessing the effects of increased calibration surveillance intervals on instrument drift and its effect on safety."
The current applicable SFRCS surveillance procedures for the Steam Generator Low Pressure and the Feedwater Reverse Differential Pressure switches have acceptance criteria that are more restrictive than the calculated drift values. The surveillance procedures for the Steam Generator Low Level and Reactor Coolant Pump Monitoring bistables do not have acceptance criteria that are more restrictive than the calculated drift values. The acceptance criteria for those instruments will be revised to be consistent with
Docket Number 50-346 License Number NPF-3 Serial Number 3005 Attachment Page 16 the other surveillance procedures. With this change, compliance with the acceptance criteria during the proposed quarterly testing will validate the calculated drift values for all of the SFRCS instruments. In addition, the applicable SFRCS surveillance procedures will be revised to require that any calibration that is outside of the acceptance criteria requires generation of a Condition Report under the DBNPS 10 CFR 50 Appendix B Corrective Action Program for trending and analysis purposes.
Docket Number 50-346 License Number NPF-3 Serial Number 3005 COMMITMENT LIST THE FOLLOWING LIST IDENTIFIES THOSE ACTIONS COMMITTED TO BY THE DAVIS-BESSE NUCLEAR POWER STATION (DBNPS) IN THIS DOCUMENT. ANY OTHER ACTIONS DISCUSSED IN THE SUBMITTAL REPRESENT INTENDED OR PLANNED ACTIONS BY THE DBNPS. THEY ARE DESCRIBED ONLY FOR INFORMATION AND ARE NOT REGULATORY COMMITMENTS. PLEASE NOTIFY THE MANAGER - REGULATORY AFFAIRS (419-321-8450) AT THE DBNPS OF ANY QUESTIONS REGARDING THIS DOCUMENT OR ANY ASSOCIATED REGULATORY COMMITMENTS.
COMMITMENTS DUE DATE The current applicable SFRCS surveillance Concurrent with or prior to procedures for the Steam Generator Low implementation of the associated Pressure and the Feedwater Reverse Differential license amendment.
Pressure switches have acceptance criteria that are more restrictive than the calculated drift values. The surveillance procedures for the Steam Generator Low Level and Reactor Coolant Pump Monitoring bistables do not have acceptance criteria that are more restrictive than the calculated drift values. The acceptance criteria for those instruments will be revised to be consistent with the other surveillance procedures. With this change, compliance with the acceptance criteria during the proposed quarterly testing will validate the calculated drift values for all of the SFRCS instruments.
The applicable SFRCS surveillance procedures Concurrent with or prior to will be revised to require that any calibration implementation of the associated that is outside of the acceptance criteria requires license amendment.
generation of a Condition Report under the DBNPS 10 CFR 50 Appendix B Corrective Action Program for trending and analysis purposes.