IR 05000254/1987024
| ML20234C283 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 12/29/1987 |
| From: | Mendez R, Phillips M NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20234C261 | List: |
| References | |
| 50-254-87-24, 50-265-87-24, NUDOCS 8801060173 | |
| Download: ML20234C283 (11) | |
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U.S. NUCLEAR REGULATORY COMMISSION
REGION III
Report No. 50-254/87024(DRS); 50-265/87024(DRS)
Docket No. 50-254; 50-265 License No. DPR-29; DPR-30 Licensee:
Commonwealth Edison Company P. O. Box 767 Chicago, IL 60690 Facility Name:
Quad Cities Nuclear Power Station, Units 1 & 2 Inspection At:
Cordova, Illinois Inspection Conducted:
September 13 through December 8, 1987 Inspector:
R. Mendez
/,2/3 t/P7 Date N
Approved By:
M. P. Phillips, Chief nf M 't"7 Operational Programs Section Date Inspection Summary Inspection on September 13 through December 8, 1987 (Reports No. 50-254/87024(DRS);
No. 50-265/87024(DRS))
Areas Inspected:
Routine announced inspection by a Region based inspector of the Containment Integrated Leak Rate Test (CILRT) procedure, CILRT performance witnessing, CILRT results, local leak rate test results, action on a previous inspection finding, and licensee event report followup.
NRC modules utilized during this inspection included 61720, 70307, 70313, 70323 and 92701.
Results:
No violations or deviations were identified.
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DETAILS 1.
Persons Contacted Commonwealth Edison Company (CECO)
- R. L. Bax, Station Manager
- R. Robey, Services Superintendent
- S. Spedl, Technical Staff Supervisor
- J. Kopacz, Technical Staff Supervisor
~*E. Mendenhall, Technical Staff
- R.
Castro, Technical Staff
- M. Miller, Quality Assurance
- M. Kooi, Regulatory Assurance
- K.'Sturtecky, Technical Staff
- J. Dierbeck, Technical Staff J. Glover, Nuclear Services Technical K. Hill, Technical Staff E. Weinferter, Technical Staff J. Davis,. Technical Staff
- Denotes persons attending the exit meeting of December 8, 1987.
The inspector also contacted other personnel including members of the technical, operating and regulatory assurance staff.
2.
Licensee Action on a Previous Inspection Finding (Closed) Open Item (265-86016-01):
During the last Type A test, there were a number of systems that were not drained and vented outside the containment.
The results of local leak rate tests of unvented penetration must be added to the leakage rate measured during the ILRT (Lam) at the 95% upper confidence level.
The licensee tested 13 systems that had not been vented or drained during the CILRT and determ.'ned the leakage rate to be 0.113 wt.%/ day.
The penalties increase the Type A test result at the upper confidence level to 0.47 wt.%/ day (the licensee is limited to 0.75 wt.%/ day).
3.
Licensee Event Report followup (Closed) Licensee Event Report (265/87015-00):
Failure of Unit 2 CILRT due to leakage through the drywell head flange.
On October 12, 1986, before the start of the CILRT, a local leak rate test on the head flange indicated a high rate of leakage.
The licensee proceeded with the CILRT but during the test it became apparent that the leakage rate exceeded the allowable technical specification limit.
The licensee determined that the leakage was due to a deterioration of the sealing ability of drywell head seal material made by J-Bar Silicon Corporation.
The licensee replaced the gasket with one manufactured by Garlock and recommended by the flange designer (Chicago Bridge and Ircn).
A second
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CILRT-was successfully performed and the leakage rate was within the acceptable limit.
A local leak rate test (Type B) of the Garlock material gasket in the Unit I drywell head performed during the current refueling outage was determined to be within the acceptance criteria.
4.
Containment Integrated Leak Rate Test Procedure Review (Unit 1)
a.
Procedure Review The inspector reviewed the test Procedures QTS 150-1, Revision 15,
" Integrated Primary Containment Leak Rate Test (IPCLRT)" and related supplements relative to the requirements of 10 CFR Part 50, Appendix J, ANSI N45.4-1972 and the FSAR.
The inspector's comments were discussed with the licensee during the course of the inspection.
All inspector comments were satisfactorily resolved.
b.
Clarification of Appendix J Requirements To ensure the licensee's understanding of Appendix J requirements, the inspector conducted numerous discussions with licensee personnel during the course of the inspection.
The following is a summary of the clarifications discussed with the licensee.
(1) The only methods of data reduction acceptable to the NRC are total time or point-to point as described in ANSI N45.4-1972 including a statistically calculated instrument error analysis.
The following options are available to the licensee.
(a) Total time (<24 hour duration test) in accordance with Bechtel Corp. Topical Report BN-TOP-1, Revision 1.
Whenever BN-TOP-1 is used it must be followed in its entirety except for any section which conflicts with Appendix J requirements.
(b) Total time (>24 hour duration test using single sided 95% UCL).
(c) Proposed Regulatory Guide MS 021-5, Regulatory Position No. 13.
If this method is utilized, the licensee must submit an exemption request to NRC and receive approval for its use prior to the expiration of the Type A test frequency requirements stated in the Technical Specifications.
(2) Periodic Type A, B, and C tests must include as-found results as well as the as-left.
If Type B ard C tests are conducted prior to a Type A, the as-found condition of the containment must be calculated by adding any improvements in leakage rates, which are the results of Repairs and Adjustments (R&A),
to the Type A test results using the " minimum pathway leakage" methodology.
This method requires that:
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(a) In the case where individual leak rates are assigned to two valves in. series (both before and after the R&A), the penetration through-leakage would simply be the smaller of the two valves' leak rates.
(b) In the case where a leak rate is obtained by pressurizing between two isolation valves and the individual valve's leak rate is not quantified, the as-found and as-left penetration through-leakage for each valve would be 50 percent of the measured leak rate if both valves are repaired.
(c) In the case whr a a leak rate is obtained by pressurizing between two isolation valves and only one valve is repaired, the as-found penetration leak rate would g
conservatively be the final measured leak rate, and the
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as-left penetration through leak rate would be zero (this assumes the repaired valve leaks zero).
(3) Penetrations which are required to be Type C tests, as
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described in the FSAR and SER, must be vented inside and outside the containment during the CILRT.
All vented penetrations must be drained of water inside the containment and between the penetration valves to assure exposure of the containment isolation valves to containment air test pressure.
The degree of draining of vented penetrations outside of containment is controlled by the requirement that the valves be subjected to the post-accident differential pressure, or proof that the system was built to stringent quality assurance standards comparable to those required for a seismic system.
(4) Whenever penetration configurations during a CILRT deviate from the ideal, the results of LLRTs for such penetrations must be added as a penalty to the CILRT results at the 95% confidence level.
The penetration leakage penalty is determined using the
" minimum pathway leakage" methodology.
This methodology is defined as the minimum leakage value that can be quantified through a penetration leakage path (e.g., the smallest leakage of two valves in series).
This assumes no single active failure of redundant leakage barriers.
Any increase in containment sump, fuel pool, reactor water, or suppression pool level during the course of the CILRT must also be taken as a penalty to the CILRT results.
If penalties exist, they must be added (subtraction is never permitted) to the upper confidence level of the CILRT results.
l (5) The start of a CILRT must be noted in the test log at the time the licensee determines that the containment stabilization has been satisfactorily completed.
Reinitializing a test in progress must be " forward looking," that is, the new start time
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must be the time at which the decision to restart is made.
This also implies that the licensee has determined that the test has failed and has enough data to quantify the leakage rate.
Any deviation from these positions should be discussed, and documented, with the NRC inspector as they occur to avoid later invalidations of the test results.
Examples of acceptable deviations of reinitializing the start time of the test in the past are:
time at which a leaking penetration which has an obvious effect on the test data was secured, accidental opening and later closing of a valve which has an obvious effect on the test data, the time at which an airlock outer door was closed and the inner door was open.
(6) The supplemental or verification test should start within one hour after the completion of the CILRT.
If problems are encountered in the start of the supplemental test, data recording must continue and be considered part of the CILRT
until the problems are corrected and the supplemental test can begin.
(7) For the supplemental test, the size of the superimposed leak rate must be between 0.75 and 1.25 times the maximum allowable leak rate LA.
The higher the value, the better.
The supplemental test must be of sufficient duration to demonstrate the accuracy of the test.
The NRC locks for the results to stabilize within the acceptance criteria, rather than the results being within the acceptance criteria.
Whenever the BN-TOP-1 methodology is being used, the length of the supplemental test cannot be less than approximately one-half of the CILRT.
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(8) During a CILRT, it may become necessary to reject or delete specific sensors or data points due to drifting or erroneous sensors, or data outliers.
Data rejection criteria should be developed and used so that there is a consistent, technical basis for data rejection.
One example of an acceptable method for data outliers is described in an appendix to ANSI /ANS 56.8-1981.
Sensor data rejection criteria should be plant specific and based upon a sensor's trend relative to the average scatter, slope, and/or absolute output of the sensor.
(9) An acceptable method for determining if the sum of Type B and C test exceeds the 0.60 La Appendix J limit is to utilize the
" maximum pathway leakage" method.
This methodology is defined as the maximum leakage value that can be quantified though a penetration leakage path (e.g., the larger, not total, leakage of two valves in series).
This assumes a single active failure to the better of two leakage barriers in series when performing Type B or C tests.
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(10) Test connections must be administrative 1y controlled to ensure their leak tightness or be subject to Type C testing.
One way I
to ensure their leak tightness is to cap, with a good seal, the test connection after its use.
Proper administrative controls should ensure valve closure and cap reinstallation within the l
local leak rate testing procedure, and with a checklist prior to unit restart.
(11) Whenever a valve is replaced, repaired, or replaced during an
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outage for which Type A, B, and/or C surveillance testing was scheduled, local leak rate testing for the as-found as well as i
the as-left condition must be performed on that penetration.
In the case of a replaced valve, the as-found test can be waived if no other containment isolation valve of similar design exists at the site.
No violations or deviations were identified.
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Containment Integrated Leak Rate Test Witnessing (Unit 1)
a.
Instrumentation The inspector reviewed the calibration data and determined that all the instruments used in the CILRT had been properly calibrated and that the correct weighting factors had been placed in the computer program as required.
The following instrumentation was used throughout the test:
Type Quantity RTD's
Dewcells
Pressure Gauges
Flowmeter
One dewcell and two RTD's were deleted before the start of the as-left CILRT.
Dewcell No. 39 in subvolume No. 10 was deleted from the data scan due to reading above the dew point temperature.
RTD No. 8 was deleted from the data scan since it could not be placed in the same position as in the previous CILRT.
RTD No. 23 was deleted due to lack of output readings.
No other sensors or data sets were rejected during the second test.
(b) Witness of Test The licensee attempted to perform an as-found Type A test at the start of the Unit 1 outage.
The inspector witnessed two CILRT's, an as-found test on September 13 and the as-left test on December 5, 1987, and noted that test prerequisites were met and that the appropriate revision to the test procedure was followed by test personnel.
Valve lineups for the following systems were verified to ensure that no fluid could enter the containment atmosphere and that adequate venting and draining was provided:
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System Penetration Drywell Pneumatic x-320 Service Air to Drywell x-21 Instrument Air to Drywell x-22 HPCI x-11 Core Spray to Reactor x-23 RHR Containment Spray x-39 6.
Test Results Evaluation a.
CILRT Data Evaluation (As-Found Test)
On September 13, 1987, at 4:15 p.m., the licensee started the pressurization phase of the CILRT.
An as-found short duration BN-TOP-1 CILRT was attempted at 63.5 PSIA with data collected and reduced by the licensee every 10 minutes.
The containment of Quad Cities Unit 1 is limited to leakage rate of 0.75 wt.%/ day (0.75 La).
The following results were obtained by the licensee (units are in weight per day).
Measurement Licensee Leakage rate measured during CILRT (Lam)
1.576 Lam at upper 95%
Confidence level 2.130 Prior to the start of the CILRT, the licensee performed a local leak rate test on the main steam line drain valves MO 1-220-1 and MO 1-220-2.
The test was unsuccessful due to an inability to pressurize the volume between the valves.
The test was inconclusive since it did not indicate whether one or both of the valves were leaking excessively.
The licensee decided to prepare for the CILRT.
On September 13, 1987 at approximately 9:30 p.m., the licensee started the stabilization phase of the CILRT.
During stabilization, the licensee monitored the test instrumentation for information only and determined that the drywell was leaking in excess of 0.75 wt.%/ day.
A temporary valve lineup change was generated to close additional valves and drains on the Drywell Pneumatic System receiver and moisture separator and main steam line drain system.
Additionally, the purge and vent valves, Drywell Purge Inlet and the reactor building to suppression chamber vacuum breakers were investigated.
Closing of the additional valves on the main steam line drains and the other systems mentioned above did not significantly reduce the leakage rate.
On September 14, 1987 at about 8:00 a.m., the licensee decided to terminate the CILRT, although, the excessive leakage had not been quantified, the unofficial results were more than twice the allowable leakage.
Since the Type A test exceeded The allowable leak rate of 0.75 wt.%/ day, the test was considered an as-found failure by the licensee and NRC inspector.
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On September 29, 1987, the licensee issued Licensee Event Report (LER) 254-87019 to document failure of the as-found CILRT.
During the refueling outage, the licensee performed the scheduled local leak rate tests on valves and penetrations but were not able to determine the root cause or causes for failing the as-found test.
The licensee had originally suspected main steam line drain valves Mo 1-220-1 and MO 1-220-2 but the total leakage detected using minimum pathway leakage was only 30 SCFH (during the outage the licensee replaced the main steam line drain valves).
The total leakage for all valves and penetrations tested during the outage amounted to 390 SCFH.
The total leakage rate was expected to be in the range of 600 SCFH.
In order to prevent recurrence of the as-found failure the licensee developed a temporary procedure during the outage to describe I
methods to identify excessive leak paths from the primary containment.
Temporary Procedure 5096, "IPCLRT Containment Leak Detection," also included instructions in the method used to inject Argon gas into containment during the pressurization phase of the CILRT.
The licensee planned to inject two bottles of approximately 660 SCF of Argon and measure the leakage at several sample points with an Argon leak detector.
If the calculated leakage was found to be excessive during the CILRT, a general survey of containment using the leak detector would be performed.
(b) CILRT Data Evaluation (As-Left Test)
On December 5, 1987, at approximately 2:50 a.m., the licensee started to pressurize the drywell.
During the pressurization phase the contents of two Argon bottles were injected into the drywell.
The licensee checked selected containment boundaries to determine possible leak paths.
Additionally, several vent valves were opened to determine whether the Argon leak detector could measure the Argon in the drywell, Samples of the drywell air-Argon mixture pegged the meter on the leak detector.
However, no excessive leakage paths were detected during the containment survey.
Test pressure for the CILRT was achieved approximately six hours later but during the stabilization phase, the licensee experienced a leakage rate above La.
The licensee found that the torus level was dropping and water was being lost through the core spray system.
The licensee closed valves 1-1402-12A, 15A, 17A and 18A which stopped a further drop in torus level.
These valves were not part of the normal CILRT valve lineup and were not containment isolation valves.
According to the licensee the valves had been opened due to maintenance activities during the outage.
The test director recommended that these valves be added to the CILRT valve checklist.
Closing of the valves also reduced the leakage rate.
Upon satisfactory completion of the required stabilization period an as-left short duration BN-TOP-1 CILRT was performed at 64.9 psia.
Data was collected and reduced by the licensee every 15 minutes.
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The inspector monitored and evaluated leak rate data to verify the licensee's calculations of the leak rate and instrument performance.
The results were as follows:
(Units are in weight percent per day).
Measurement Licensee Inspector Leakage rate measured during ILRT (Lam)
0.319 0.320 Lam at upper 95%
confidence level 0.351 0.352 Appendix J acceptance criteria at 95% UCL <0.75 wt.%/ day A review of the as-found and as-left CILRT results indicate a difference of about 1.25 wt.%/ day or approximately 600 SCFH.
As mentioned in Paragraph 6.a the total leakage from local leak rate tests amounted to about 390 SCFH.
The licensee is continuing its efforts to account for the remainder of the leakage.
c.
Supplemental Test Data Evaluation After satisfactory completion of the CILRT, a known leakage (based on the inspector's independent readings and calculations) of 8.9 SCFH, equivalent to 1.077 weight percent per day was induced.
Data was collected and analyzed by the licensee every 15 minutes.
After five hours, the supplemental test was terminated with satisfactory results as indicated by the following summary (units are in weight percent per day).
Measurement Licensee Inspector Measured leakage rate during supplemental, Lc 1.349 1.351 Induced leakage rate, Lo 1.077 1.077 Lc - (Lo + Lam)
-0.047-0.046 Appendix J acceptance criteria:
-0.250 $ [Lc - (Lo + Lam)] 5 + 0.250 as indicated above, the licensee's test results were satisfactory.
d.
CILRT Valve Lineup Penalties Due to penetration configurations which deviated from the
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penetration requirements for the CILRT, the results of local leak rate tests for each penetration must be added to Lam at the 95 percent UCL.
At the conclusion of the CILRT, the licensee had not tested all penetrations that had not been vented and drained.
The licensee has committed to quantify the minimum pathway leakage for the following penetrations or leak paths.
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Penetration RCIC Steam Exhaust and Drain
. Cleanup Demineralized HPCI Steam and Drain Drywell Floor Drain SRM/IRM Purge Drywell. Equipment Drain 0 Analyzer
TIP Purge Check Valve ECAD RHR Feedwater All Electrical Penetrations CAM While the penalties for the above penetrations have not been determined to date, it is not anticipated that the total'will exceed 0.40 wt.%/ day.
However, it is the licensee's responsibility to ensure that the results of local leak rate tests on the above penetrations do not cause the containment to leak in excess of the allowable limit at the time containment integrity is required.
No violations or deviations were identified.
c.
As-Found Condition of CILRT Results The as-found condition is the condition of the containment at the
.beginning of the outage prior to any repairs or adjustments to the containment boundary.
Since the licensee performed the first CILRT prior to repairs of containment isolation valves and penetrations, the only adjustment would have been due to valve lineup penalties that deviated from the ideal.
The licensee is limited to a total as-found leakage of 0.75 wt.%/ day at the 95% upper confidence level.
As mentioned in Paragraph 6.a of this inspection report, the licensee obtained a leak rate of approximately 2.13 wt.%/ day and therefore, exceeded their allowable leak rate.
As indicated above, the as-found condition exceeded the allowable limit of Appendix J (0.75 wt.%/ day).
The two previous CILRT's, performed in 1986 and 1984, also exceeded the as-found Appendix J limit due to excessive leakage from containment isolation valves.
As more than two consecutive as-found CILRT's have failed to meet the acceptance criteria in 10 CFR 50, Appendix J, Section III.A.6(b),
the next Type A test shall be performed at the next plant outage for refueling unless exempted by the NRC.
No violations or deviations were identified in the review of this area.
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7.
, Exit Interview
The inspector met with licensee representatives denoted in Paragraph 1 l
during and at the conclusion of.the inspection on December 8, 1987.
The inspector summarized the scope and results of the inspection and discussed the likely content of this report.
The licensee. acknowledged the information and did not indicate that any of the information disclosed during the inspection could be considered proprietary in nature.
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