IR 05000261/1987009
| ML14175B462 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 05/18/1987 |
| From: | Jape F, Whitener H NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML14175B461 | List: |
| References | |
| 50-261-87-09, NUDOCS 8706020146 | |
| Download: ML14175B462 (10) | |
Text
REGqj UNITED STATES o
NUCLEAR REGULATORY COMMISSION
REGION II
101 MARIETTA STREET, ATLANTA, GEORGIA 30323 Report No.:
50-261/87-09 Licensee:
Carolina Power and Light Company P. 0. Box 1551 Raleigh, NC 27602 Docket No.:
50-261 License No.:
DPR-23 Facility Name:
H. B. Robinson Inspection Conducted:
April-10, 1987 sH.c L. Whitener a /
Date Signed Approved by:
-2({7
~
i4 F. Jape, bect on Chiet Date Signed Engineering Branch Division of Reactor Safety
)
SUMMARY Scope:
This routine, announced inspection was conducted in the areas of containment leak rate testing including examination of test conditions; observation of the periodic integrated leak rate test; review of test procedures; independent evaluation of test results; and followup inspection of outstanding item Results:
No violations and deviations were identifie PDR ADOCK 05000261 G
REPORT DETAILS 1. Persons Contacted Licensee Employees G. P. Beatty, Manager, Robinson Nuclear Project Department R. E. Morgan, Plant General Manager D. R. Quick, Manager, Maintenance
- A. R. Wallace, Manager, Technical Support
- S. W. Farmer, ILRT, Senior Engineer
- D. A. Sayre, Acting Director, Regulatory Compliance
- S. A. Griggs, Regulatory Compliance Other licensee employees contacted included integrated leak rate test personne Other Organizations Gilbert Associates R. E. Shirk, ILRT Engineering Consultant
.
J. J. Blessing, ILRT Engineering Specialist NRC Resident Inspectors H. E. P. Krug, Senior Resident Inspector
- R. M. Latta, Resident Inspector
- Attended exit interview 2. Exit Interview The inspection scope and findings were summarized on April 10, 1987, with those persons indicated in paragraph 1 above. The inspector described the areas inspected and discussed in detail the inspection finding No dissenting comments were received from the license Items discussed incldued:
Unresolved Item 50-261/87-09-01, The Supplemental test did not meet the acceptance criteria based on a Total Time analysis. The licensee will request an exemption to Appendix J to allow evaluation of the Supplemental test by the Mass Point analysis metho This item has the potential to impact plant start up (paragraph 5.c.(3)(b)).
Inspector Followup Item, IFI 50-261/84-39-01, which concerned a modification to the local leak rate test rig was closed (paragraph 7).
The licensee did not identify as proprietary any of the materials provided to or reviewed by the inspector during this inspectio. Licensee Action on Previous Enforcement Matters This subject was not addressed in the inspectio. Unresolved Items Unresolved items are matters about which more information is required to determine whether they are acceptable or may involve violations or deviation One unresolved item identified during this inspection is discussed in paragraph 5.c.(3)(b).
5. Containment Integrated Leak Rate Test (CILRT) - Unit 2 (70313) (70307)
The inspector reviewed and witnessed test activities to determine that the primary containment integrated leak rate test was performed in accordance with the requirements of Technical Specification 4.4, Appendix J to 10 CFR 50, ANSI-N45.4 and test procedure EST-085,
"Containment Integrated Leak Rate Test."
Selected sampling of the licensee's activities which were inspected included:
(1) review of the test procedure to verify that the procedure was properly approved and conformed with the regulatory requirements; (2) observation of test performance to determine that test prerequisites were completed, special equipment was installed, instrumentation was calibrated, and appropriate data were recorded; and (3) preliminary evaluation of leakage rate test results to verify that leak rate limits were me Pertinent aspects are discussed in the following paragraph a. General Observations The inspector witnessed and reviewed portions of the test preparation, containment pressurization, temperature stabilization and data processing during the period of April 5-10, 198 The following areas were inspected:
(1) The test was conducted in accordance with an approved procedur (2) Test prerequisites selected for review were found to be complete (3) Selected plant systems required to maintain test control were found to be operationa (4) Special test instrumentation was reviewed and found to be installed and calibrate (5)
Data required for the performance of the containment leak rate calculations were recorded at 15-minute interval (6) Problems encountered during the test were described in the test event lo (7) Pressurized gas sources were reviewed for proper isolation and venting to preclude in-leakage or interference of out-leakage through containment isolation valve (8) Temperature, pressure, dew point, and flow data were recorded at 15-minute intervals. Data were assembled and retained for final evaluation and analysis by the license A final ILRT report will be submitted to the Office of Nuclear Reactor Regulatio No deviations or violations were identified during this revie b. Procedure Review (70307)
Portions of EST-085,
"Containment Integrated Leak Rate Test," dated March 20, 1987, were reviewed to verify that test controls, valve alignments and acceptance criteria were specifie The inspector concluded that the test controls were detailed and adequate; the test acceptance criteria conformed to Appendix J of 10 CFR 50, including data analysis by the Total Time analysis method; and the valve alignments and valve restoration were specified in detail in attachments 8.2 and 8.8, respectivel The review of the valv alignment (Attachment 8.2) consisted of verifying that the vent and drain specifications for the systems were acceptabl A detailed valve by valve comparison of penetration alignment with plant design drawings was not performed at this tim c. Containment Integrated Leak Rate (CILRT) Performance (70313)
(1) Method A 24-hour containment integrated (Type A) leak rate test and an 11-hour supplemental leak rate test were performed on the Unit 2 primary containment at a reduced pressure of 21 psi Both Total Time and Mass Point linear regression analyses were used by the licensee to determine the leak rate and 95% upper confidence limit (UCL).
Leakage analysis was based on data taken at 15-minute intervals for a minimum of 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Although both analyses were required by the test procedure the Total Time analysis is the method currently specified by Appendix Systems status during the test were as follows:
(a) RHR In shutdown cooling mode and operatin (b) Steam Generators In wet layu (c) SI Accumulators Depressurize (d) Primary System Vented at the high point ven (e) Fan Coolers Secured - no forced flo (2) Test Description After completion of the containment inspection, the containment was pressurized to the leakage rate test pressure, of 21 psi Significant test events extracted from the test log were as follows:
Date Time Event 4/6 0103 Pressurization of the containment was initiate Pressurization of the containment was secured at 36.77 psi Temperature stabilization was initiate Containment air temperature met the stabilization criteri The start time for the Type A test was declare Dew cell DPTE-5 was deleted and the weighting factor was assigned to DPTE-WD 1966, vent valve in hydrogen supply line to RCDT was incorrectly aligned and resulted in an excessive leakage (0.122 wt.%).
The valve was close /7 1700 Type A was terminate The leak rate was 0.0285 wt.% per day (Total Time Analysis).
1715 Supplemental test was starte An imposed leakage rate of 2.39 scfm (0.0727 wt.% day)
was establishe /8 0415 The supplemental test was terminated after 11 hours1.273148e-4 days <br />0.00306 hours <br />1.818783e-5 weeks <br />4.1855e-6 months <br /> with the composite leak rate outside of the +/-.25 Lt limit by Total Time analysis. Mass Point analysis was within the limit (3) Test Results (a) Type A Test The allowable reduced pressure test leakage (Lt)
for H. B. Robinson is a 0.0707 wt.%/da Therefore, the test acceptance limit of 0.75 Lt as required by Appendix J is 0.053 wt.%/day. Although the official test analysis method required by Appendix J is the Total Time analysis, the licensee processed the data by both the Total Time and the Mass Point analysis methods. Test results for the 24-hour test period of 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br />, April 6 to 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br /> April 7, 1987 are shown below in weight percent per day (wt.%/day).
Mass Point Total Time Leak Rate 0.039 0.0285 95% UCL 0.0408 0.0347 Based on these results, the Type A test is within the acceptance limit of 0.75 Lt (0.053 wt.%)
for both calculational method The inspector calculated weighted averages for containment temperature, pressure and vapor pressure using the weighting factors and individual sensor data for a sample of data sets to verify agreement with the weighted averages and mass calculations generated by the licensee's computer progra Subsequently, the mass points generated by the licensee's program were used by the inspector to calculate the leak rate, and the 95% upper confidence leak rate. The inspector's calculations agreed with the licensee's calculation (b) Supplemental Test Appendix J requires that a supplemental test be performed to verify the accuracy of the Type A test and ability of the CILRT instrumentation to measure *a change in leak rat An acceptable supplemental test method is described in Appendix C of ANSI-N45.4-1972, as follows:
A known leak rate (Lo)
is imposed on the containment and the measured composite leak rate (Lc)
must equal, within 0.25Lt, the sum of the measured Type A leak rate (Ltm) plus the known leak rate (Lo).
The acceptance criteria is expressed as follows:
Lo + Ltm -
0.25Lt < Lc < Lo + Ltm + 0.25Lt An eleven hour supplemental test starting at 1715 hours0.0198 days <br />0.476 hours <br />0.00284 weeks <br />6.525575e-4 months <br /> on April 7, was performed by the imposed leak rate method described in Appendix C to ANSI-N45.4-1972. The licensee's results calculated by both the Total Time and Mass Point analysis methods are shown below in wt.%/day:
Mass Point Total Time Ltm 0.039 0.0285 Lo 0.0727 0.0727
.25Lt 0.0177 0.0177 Lc 0.101 0.123 Using these values in the acceptance criteria yields the following:
Mass Point: 0.094 < Lc < 0.1294 Lc = 0.101 wt.%/day meets these acceptance limit Total Time: 0.0835 < Lc < 0.1189 Lc = 0.123 wt.%/day is not less than the upper boundary limit of 0.1189 wt.%/da Therefore, by the Total Time method, the composite leak rate (Lc)
does not meet the Supplemental test acceptance limit The test was terminated at 0415 hours0.0048 days <br />0.115 hours <br />6.861772e-4 weeks <br />1.579075e-4 months <br /> on April 8, with the above result The licensee concluded that there was sufficient technical justification on which to base a request for an exemption to the Appendix J requirement that the Total Time method be used in analysis of leak rate test
result Consequently, the licensee will request NRR's approval to use the Mass Point analysis which yields acceptable test result Paragraph III.A.3(b) of Appendix J to 10 CFR 50 requires that if the Supplemental test is not within the acceptance limits, the reason shall be determined, corrective action taken and a successful Supplemental test performe Some considerations involved in the licensee's decision to request an exemption rather than continue the test or rerun the test were as follows:
1) The reason the test was not successful was not an inability to measure the leak rate but rather was due to the weighted dependency of the test result on the initial data point, inherent in the Total Time method, coupled with the pattern of data scatter which occurred in the first hour and repeatedly through the tes Based on the assumption that the containment leakage is constant during a test, the Total Time analysis method consists of statistically averaging, by linear - regression techniques, a series of two point leak rates obtained by determining the slope between the initial mass data point and each of the succeeding mass data points. In this case, the first three data points following the initial data point indicated successively higher containment masses and consequently, negative leak rates of -0.14, -0.09 and-0.068 wt.%/day, respectively. As a result, the curve of the two-point leak rates on which the least square fit is performed, rose sharply, from -0.14 to 0.06 wt.%/day, in the first hour of the tes In the remaining ten hours, the curve trended slightly upward and flattened out at an average leak rate of about 0.092 wt.%/day over the last five hours of the tes A least square fit of a straight line to a curve such as described above will always yeild a calculated leak rate higher than the measured leak rat ) There were indications that the leak rate calculated by the Total Time analysis would eventually fall within the acceptance limit The calculated leak rate based on the least square fit of the two-pont total time leak rate data indicated a decrease of about 0.001 wt.%/day per hour over the last two hours of the tes The licensee estimated that to demonstrate a stabilized leak rate within the acceptance limits by the Total Time method could require an additional ten hours of critical path time while certain test data indicated the test was already meeting the acceptance limit Specifically, by the Mass Point analysis the leak rate, in the range of 0.095 to 0.1 wt.%/day, met the acceptance limits defined by the Mass Point method over the last eight hours of the tes Also, the two-point Total Time leak rates, which are not affected by previous data sets, indicate an average leak rate of about 0.092 wt.%/day over the last five hours of the test and is within the acceptance limits defined by the Total Time metho From the evaluation, the licensee concluded: 1) that there was no corrective action to be taken which could reduce the critical path waiting time and the associated economic impact using the Total Time method; 2) that to rerun the test using Total Time analysis would involve the same risk with no assurance that similar conditions would not result in a long test period; and 3) that there was sufficient information available to justify acceptability of the test results on a technical basis by Mass Point analysi The inspector reviewed the test results and concluded that convergence of the total time calculated least square fit leak rate to the test limits was delayed by the recurring large negative leak rates early in the tes Examination of the mass data showed that the scatter although somewhat cyclic in nature was not larg Overall, the mass data exhibited a linear trend which could be reasonably fitted by a straight line least square fit. The Mass Point leak rate was consistent during the Supplemental test at wt.%/day and satisfies the acceptance limits for the Mass Point analysi At the exit interview, the inspector informed the licensee that the Containment Leak Rate Test including the Supplemental test must be successfully performed prior to plant start u A successful Supplemental test was not performed by the Total Time analysis method as required by Appendix J. Acceptance of the Type A test and the Supplemental test on the basis of the Mass Point analysis requires an exemption to Appendix J. Failure to obtain the exemption or a delay in the exemption could result in retesting or could impact the plant start up schedule. The licensee acknowledged his understanding and stated that the exemption request was already in preparatio This matter was identified as an unresolved item as follows:
Unresolved Item 50-261/87-09-01:
verify that an exemption to Appendix J to allow acceptance of the 1987 Type A and Supplemental test on the basis of Mass Point analysis is obtained prior to final acceptance of the Containment Leak Rate Test and before plant start u. As Found Leak Rate The licensee performed the Type A test on the containment prior to making any repairs or adjustments to the containment boundary. Consequently, the Type A leak rate of 0.047 wt.%/day is the "as found" containment leakage and passes the Appendix J limit of 0.75 Lt of 0.053 wt.%/da. Review of Outstanding Item Closed - Inspector Followup Item 50-261/84-39-01 concerned the potential for make up air flow to bypass the flowmeter on the local leak rate test ri The inspector examined the test rig during this inspection and determined that the test rig has been modified to provide for isolation and venting of the bypass air supply. This item is closed.