IR 05000260/1990013
| ML18033B479 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 07/25/1990 |
| From: | Garg H, Marinois E, Newberry S Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18033B478 | List: |
| References | |
| 50-260-90-13, NUDOCS 9008140178 | |
| Download: ML18033B479 (18) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION TVA PROJECTS DIVISION Report No.:
Licensee:
Docket No.:
Facility Name 50-260/90-13 Tennessee Valley Authority 6N 38A Lookout Place 1101 Market Street Chattanooga,.Tennessee 37402-2801 50-260 Browns Ferry, Unit 2 Inspector:
Evange os
.
arinos, earn Lea er
//6 Ha am C.
,
S
.
E ectrica Engineer Inspection Conducted:
April 23-27, 1990 7 /I/FD Da e 7-4-'Po Date Consultants:
J.
B. Gardner, W. A. Thue Approved by:
UZI o
co ew erry, ie a
e Instrumentation and Contr stems Branch 9008i40i78 9008i0 PDR ADOCK 05000260 O
0,
SPECIAL INSPECTION RELATED TO ELECTRICAL ISSUES l.
INTRODUCTION AND BACKGROUND The Browns Ferry Nuclear Plant, Unit 2 (BFN-2), Nuclear Performance Plan identified many electrical issues related to BFN-2 design and construction.
The NRC staff has been reviewing the programs which identified the corrective action taken by TYA to correct plant deficiencies.
This inspection was conducted from April 23-27, 1990, as a follow-up to previous inspection (IR 89-59) performed by the NRC during the week of December 4-8, 1989.
2.
PURPOSE AND SCOPE The purpose of this inspection was:
(I) to review the TVA's responses to eight open items which were identified in Inspection Report (IR) 89-59 and (2) to review the TVA analysis and perform plant walkdowns to verify the resolutions of the cable installation issues.
3.
SUMMARY The NRC team found that the implementation of the cable issues program meets the requirement.
The team has also agreed with the resolution of all the open items previously identified in IR 89-59.
4.
INSPECTION DETAILS The NRC team reviewed the corrective actions taken by TVA to resolve the open items identified in the previous inspection (IR 89-59).
The team also sampled several items for review for the cable installation issue.
The team inspection findings and conclusions for each item from that inspection are as follows:
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Open Item:
TVA in their ampacity calculations have not considered loading of cables in tray 2HO-ESII from motor heaters and plug receptacles.
TYA should either provide justification for this omission or the ampacity calculations for this tray should be done again with these loads energized.
TVA Res onse and Evaluation TVA in a letter dated April 9, 1990, stated that calculations have been reissued to address the loading of motor heaters and plug receptacles.
However, Rdvision I of the Cable Ampacity Calculation (RIM No. B22 900413 115)
dated March 31, 1990 indicated that only motor heaters were considered energized and no justification was provided for the omission of plug receptacles.
Additionally, TVA in their letter of April 9, 1990 has stated that revised calculations have not identified any additional safety-related cable failures, while the revised calculations lists safety related and non-safety related cable failures.
TVA agreed to revise the response with proper justification.
TYA in a letter dated May 21, 1990 has addressed the NRC concern and reissued the calculations to satisfactorily resolve this concer ~
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Open Item:
In order to ascertain proper cable separation the team planned to walkdown the signal tracing of a number of cables.
However, only one was walked down because of schedule constraints.
The team plans to walkdown the remaining cables at a later date.
TVA Res onse and Evaluation TVA in their response has stated that signal tracing has been completed and will provide the results by April 30, 1990.
TVA has provided a report with the results of the additional signal tracing (RIM No.
B22 90 0427 001) to the staff.
In accordance with this report, 13 additional cables were signal traced.
Five cables were routed as shown on the routing drawings.
The remaining eight cables were routed differently than as shown on the routing drawings.
TVA has analyzed these discrepancies and determined that none of these discrepancies violate cable separation or Appendix R requirements.
Hence, this item has been satisfactorily resolved.
4.3 Instrument Sense Lines 4.3.1 Open Item:
The specification for installation of instrument sense lines, ER-BFN-EEB-001, does not require that the potential hazard posed by missiles caused by equipment failure be "considered when routing redundant instrument tubing.
TYA committed to revise the specification to require consideration of this hazard in the routing of these lines.
TVA Res onse and Evaluation TVA has committed to add, in the Revision 1 of the specification ER-BFN-EEB-001, the requirement that the potential hazard posed by missiles caused by equipment failure be considered when routing redundant instrument tubing.
Based on the commitment, this item is considered closed.
4.3.2 Open Item:
TVA review of as-built instrument line slope excluded pressure instruments that employ sealed capillary tubes for pressure transmission.
TVA justified this exclusion on the basis that slope is not critical in these devices because all gas is removed from the lines at manufacture.
While this is true, sometimes the sense element at the end of a capillary tube.connects to the process via an unsealed sense line.
The inspection identified two such instruments, both channels of Torus Wide Range Level.
At least one sense line for these sensors is oriented such that liquid could collect in the gas sense line.
During the inspection TYA confirmed that the two instruments in question are the only critical instruments that employ capi llary tubing and are connected to the process via an instrument tube.
Further, TYA committed to evaluate the impact of the incorrect slope on the torus level instruments and correct the installation if necessar '
-3-TYA Res onse and Evaluation TVA has reinspected the sense lines for the two instruments in question and based on this reinspection, has issued two maintenance requests to correct the installation.
TVA expects to complete the modification by August 7, 1990.
This satisfactorily resolves and closes the open item.
4.3.3 Open Item:
The inspection found some stainless steel instrument lines bearing ink marks that were made to track walkdown activities.
TVA could not confirm during the inspection whether the markings were made with chloride free pens.
They committed to determine if the marking material contains chloride and if so, clean the markings from the sense lines.
TVA Res onse and Evaluation TYA has tested the instrument sense line bearing the ink marks because the exact marker used is unknown.
The lines were tested in accordance with Technical Instruction 92 for detrimental halogans.
The results showed that the surfaces were acceptable.
TVA test results are documented in Revision 0 of MTB BFN 90018 (RIM No.
B22 90 0426 004)
and based on these results the open item is considered closed.
t 4.4
~F Open Item:
Th TVA Res onse and Evaluation e inspection for the Fuse Program found that the drawing revision and permanent labeling of the fuses will not be completed prior to start-up.
TVA should provide a commitment to complete this effort prior to start-up following the first refueling outage after the Unit 2 restart.
TYA has committed for each Class remove references to fuse rating that it can be referenced in the permanent labeling in accordance Both of these activities will be first refueling outage after the closes this open item.
4.5 Batteries 1E fuse to complete drawing revisions to and to provide a unique identification such fuse tabulation.
TVA will also install with Site Director Standard Practice 16.8.
completed prior to start-up following the Unit 2 restart.
This adequately resolves and Open Item:
The surveillance procedures for the battery test should be revised to reflect both electrolyte temperature and level correction.
TVA Res onse and Evaluation t
According to TYA, BFN's surveillance instructions (SIs) require that specific gravity measurement be obtained using a digital density meter (DMA-35).
This
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instrument automatically corrects specific gravity for electrolyte temperature.
TVA has also contacted the battery manufacturer (CED Power Systems, Inc.) who has informed TYA that the capacity of a fully charged cell will be the same, as long as electrolyte level is between high and low.marks.
Based on this, TVA has decided that it is not necessary to change the SI to include level correction.
The staff agrees with TVA's conclusion and considers this item closed.
4e6 Dr well Cable Tra s
Open Item:
TYA was unable to demonstrate by design drawing that the cable trays in the drywell are adequately grounded and has elected to demonstrate adequate grounding by test.
TVA Pes onse and Evaluation TVA has completed the test in accordance with the test plan previously accepted by the staff.
The maximum resistance measured was 3.3 ohms which meets acceptance criteria of 25 ohms or less set by the National Electrical code Article 250-84.
The test results are documented by TVA internal memorandum identified as RIM No.
B22 90 0201 003.
Based on the test results this item is considered closed.
4.7 Cable Installation The purpose of this inspection was to review TYA resolutions of cable installation concerns.
Pullby damage similar to that identifed at Watts Bar was of primary concern for the team.
The inspection focused on - (1) review of backup documentation to TVA 's submittal of June 19, 1989, (2) review of test data from Hi-pot testing and (3) walkdowns to identify other potential problems with cable installation.
4.7.1
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The following areas related to cable installation concerns were reviewed during this inspection:
a cable lubrication b
location of pull points and length of cable pulls c
method for cable pullbys d
cable jamming e
cable bend radius (f vertical support (g)
cable damage at WBN The NRC team identified conduit runs for inspection prior to arrival at the site, so that necessary paperwork and actions could be completed to help expedite the inspection.
TVA removed covers from the pull boxes and condulets for the team inspection.
The team inspected the open boxes requested to be opened and saw additional boxes that happened to be open for some other wor E I
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4.7.2.1 Cable Lubrication The inspection team observed that while few boxes had generous quantities of the yellow material known as yellow 77 still visible on the cable bundles and conduit hub, other boxes had only minimal yellow material that was still visible.
The team determined that about ten percent of the pull boxes had evidence of abundant lubricant but could not definitely determine whether lubricants had not been used during the cable pulling.
This is based on the following reasons:
(a)
Large quantities of cement dust was seen inside some of the boxes which could have masked the presence of lubricant.
(b)
The later pulls were made with Polywater J Lubricant which leaves no visible residue.
(c)
According to site electricians and engineers the normal practice was to clean up excessive lubricant from the cables and conduits before placing seals in conduit ends.
These seals were present in the majority of the boxes inspected.
4.7.2.2 Location of Pull Points and Len th of Cable Pulls TYA has provided isometric drawings for all conduit runs that were inspected by the team.
However, these drawings were not to scale and dimensions were not shown.
Also, the nature of bends was not accurately reflected in these drawings.
TVA explained that these drawings were not used for calculations and were only provided for the convenience of the team.
Walkdown packages which showed the actual length of the run and bend angles of the conduit run were provided by TVA.
TYA has claimed that excessive lubricant at the boxes and condulet demonstrates that all available pull points were used.
However, since the inspection team independently could not determine that excessive lubricant was present at all pull points, it was decided that slack in cables at pull points will be a more reliable indicator of pull point use.
Based on this, the inspection team performed another walkdouwn to observe slack in cables at the pull points.
During this walkdown it was observed that reasonable slack was available in most cases.
There were some instances where some cables were rather tightly run across a junction box which could have been created by the forces of later pullby or could also have been the result of pulling out'lack of some others from a nearby pullbox.
Also, the team did not observe any evidence of cable'amage that may have resulted from pulling through LB condulets.
The team agreed, with the TVA conclusion that in general all available pull points were used during cable pullin '0 4.7.2.3 Method for Cable Pullb s
During the plant walkdown the inspection team noted that almost all pull boxes and condulets had one or more single conductor No.
10 insulated pull wire that was apparently used f'r pulling cable.
Calculated pull tension values, however, for some conduits indicated that some other means such as pull ropes or parachute cords have been used for pullby activities instead of just insulated wires.
The wet dc high potential testing should demonstrate whether damage has been caused by pull ropes or pull cords.
.7.2.4
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The staff asked TVA to provide a list of all conduits within the jam ratio of 2.8 and 3.1 (Jam ratio is defined as D/d, where D is the diameter of conduit and d is the diameter of cable).
The staff reviewed the list and determined that most of the conduits with cable sizes of less than 300 MCM, within the prescribed jam ratio, had a very short run and jamming even if it occurred, would not have caused any cable damage.
TVA has walked down, analyzed all the cables of 300 MCM or larger, and determined that jamming had not occurred.
The inspection team did not observe any visible indication of jamming during the plant walkdown.
Hence, we conclude that cable jamming has not caused cable damage at BFN.
4.7.2.5 Cable Bend Radius TVA has performed plant walkdowns for medium voltage cables and has identified conduits with bend radius violations.
For some conduits that did not meet the bend radius requirements a technical justification has been provided and some cables have been replaced.
TVA's justification for retaining some cables is that low voltage power, control and instrumentation cables can only experience random fai lures, since they generally operate below their design temperature and voltage ratings.
Also Hi-pot testing will identify damage with cables that may have exceeded their bend radius.
The NRC team determined that pullboxes were generally quite large so that sharp bends were not observed.
In two cases of congested cables, because of complexity of looping and training, it was difficult for bending to occur inside the boxes.
Hence, some multi-conductor cables may have been at or below the standard bend radius limits.
However, the amount of bending was minimal and no more than commonly observed in any other nuclear plant.
TVA will submit the corrective actions taken, based on their walkdowns and Hi-pot testing, to the staff at a
later date.
The staff will evaluate TVA's submittal and will document this evaluation in a forthcoming safety evaluation report.
4.7.2.6 ~Ti
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TVA has performed walkdowns for all medium voltage cables and for those conduits that exceed the vertical drop requirements dc high-pot testing has been performed.
Low voltage cables will be walked down after restart; this schedule has been previously accepted by the staff.
During the plant walkdowns
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the NRC inspection team could not observe the support points of cable runs containing long vertical runs because of difficult access.
However, conduit seals were noted at junction boxes located somewhere in the middle of the vertical run which provided support to the downward portion of the run relieving
, some of the tension that would otherwise have been passed to the top end of the run.
TVA will submit their corrective action taken, based on walkdowns and Hi-pot testing, at a later date.
The staff will evaluate TVA's submittal and will document this evaluation in a forthcoming safety evaluation report.
4.7.2.7 Cable Dama e at HBN As a result of discovery of pullby damage at MBN, TYA agreed to wet Hi-pot test ten worst case conduits at BFN.
During this inspection the team reviewe the walkdown packages and calculations performed to determine the ranking o
conduits.
Since the difference between pull tension and sidewall pressure for number 1 and number 2 ranked conduits was extremely high, the team asked TVA to perform new calculations at the reduced coefficient of friction and weight ction factor The new calculations for pull tension and side-wall pressure produced values for the number 1 conduit much closer to ac tual d'O'
However it should be noted that these numbers may still be too
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sed.
Also the conservative if generous quantities of pulling lubricants were use
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of friction has no significant impact in a straight pull while successive bends in the conduit will cause 'the tension at each ben o g p
y an exponential factor.
The team determined that the coefficient of friction and weight factor did not have a significant impact on the ranking of conduits because these factors were applied to all conduits equally.
The inspection team also reviewed the test procedures used for Hi-pot testing and based on this review, it was determined that flooding of the conduit was adequately controlled to ensure that water was retained throughout the test.
Leakage currents were recorded at the appropriate times so that polarization levels could be determined.
Therefore, it is the team's opinion that successful completion of Hi-pot testing will adequately resolve this concern.
4.7.3 Conclusion The team has not identified any significant disagreements between the documentation and the installed conduits, and concludes that the cable installation program was being properly implemented.
Successful completion of the Hi-pot,tests should demonstrate the integrity of the cable installation at BF ~
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'ISTRIBUTION (w/enclosure)
'~ll.50-26M PDR LPDR PDI I-4 R/F FHebdon SBlack BWilson, RII AThadani SNewberry Et1arinos HGarg TRoss EJordan, AEOD OGC ACRS (10)
PKellogg RBorchardt, EDO tlCallahan, CA/GPA SICB R/F Central File
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