IR 05000275/1997201
ML16342D789 | |
Person / Time | |
---|---|
Site: | Diablo Canyon |
Issue date: | 09/11/1997 |
From: | NRC (Affiliation Not Assigned) |
To: | |
Shared Package | |
ML16342D788 | List: |
References | |
50-275-97-201, 50-323-97-201, NUDOCS 9709180114 | |
Download: ML16342D789 (32) | |
Text
U.S.
NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION Docket Nos.:
50-275 '0-323 License Nos.:
50-275/97201 50-323/97201 Licensee:
Pacific Gas 8 Electric Company Facility:
Diablo Canyon Power Plant
~ Units 1 and
Location:
Avila Beach, Cali fornia Dates:
June 9-12, 1997 Inspectors:
Approved by:
Stephen D. Alexander.
Team Leader, NRR Billy H. Rogers.
Reactor Engineer, NRR Gregory C. Cwalina
~ Section Chief Vendor Inspect ion Secti on Special Inspection Branch Division of Inspection and Support Programs Office of Nuclear Reactor Regulation Enclosure
9709i80ii4 9'709'ii PDR
. ADOCK 05000275
EXECUTIVE SUMMARY During the period of June 9-12, 1997, representatives of the U.S. Nuclear Regulatory Commission's (NRC's) Special Inspection Branch conducted an inspection of Pacific Gas
& Electric Company's (PG8E's) activities related to the procurement, modification. testing and installation of replacement 4-kV circuit breakers at the Diablo Canyon Pc~sr Plant (DCPP), Units I and 2.
The inspectors reviewed engineering and quality assurance documentation.
interviewed cognizant staff and examined equipment in order to evaluate PG&E's dedication and modification of 4-kV Yaskawa circuit breakers for use in safety-related applications at DCPP.
In 1994, PG8E had d'.scovered that many of the existing 4-kV circuit breakers, both Class 1E (safety-related)
and non-safety-related at DCPP, did not have sufficient interrupting capacity (including'esired design margin) in order to assure successful clearance of the worst-ca.o (design) faults with the maximum available short-ci r uit current at their locations.
The existing switchgear used GE Type AH-4.16-250 Magne-Blast circe t breakers with 250 megavolt-amperes (HVA) interrupting capacity in the locations of concern where the licensee had determined that the next larger rating available of 350 MVA would be needed.
In order to fit a breaker rated for 350 HVA in the existing switchgear (breaker cubicles, buswork, etc..)
~
a more advanced and efficient fault arc interrupting technology would have to be employed.
Therefore, PG&E contracted National Technical Systems (NTS), Inc., of Acton, Massachusetts, in 1994 to undertake the project of acquiring replacement 4-kV circuit breakers using
.
sulfur-hexafluoride (SF,) gas interrupters to obtain 350-MVA interrupting capacity in a small volume.
NTS had the breakers modified and adapted to work in the existing switchgear by Power Distribution Systems (PDS), Inc., of West Chester.
Ohio).
NTS performed the engineering in consultation with the breaker manufacturer, Yaskawa Electric Co.. Ltd.. of Japan and with PDS.
All requisite design and production testing was conducted at PDS and at PSH Technologies.
Inc.
(PSH), of Pittsburgh.
a high-voltage, high-current test facility.
NTS provided the quality assurance coverage for the subcontractors required by 10 CFR Part 50, Appendix B.
The primary purpose of the inspect'.
n was to determine if prototype design verification testing of the modified Yaskawa breaker was accomplished in accordance with applicable NRC regulations and industry standards.
Although there is no regulatory guide endorsing the standards in question, PG8E had committed to them in the Final Safety Analysis Report (FSAR) for DCPP, and they are therefore relevant to the design and licensing basis of the plant.
A secondary purpose of the inspection was to examine several related issues involving production testing, modifications. post installation testing, and in-service failures.
The review included all documentation pertinent to the design, design verification (including prototype testing).
conversion/modi-fication
~ fabrication of adapting hardware, production testing, procurement and dedication done by PG8E, its principal contractor.
NTS, and PDS, the NTS subcontractor who actually performed the conversion The inspectors determined that PG&E's approach to design verification was generally consistent with the applicable NRC regulations.
primarily Criterion III, "Design Control," of 10 CFR Part 50. Appendix B, in that PG&E undertook to verify. by engineering analysis and a testing program. that DCPP's safety-related 4-kV electrical distribution system.
as converted and modified. would perform,its safety functions under al) de~ign basis conditions.
The question of consistency of PG&E's approach to the conversion and its design verification process with applicable industry standards, in particular.
taking credit for certain design verification tests done by the manufacturer of the circuit breakers used in the conversion.
was referred to the Standards Board of the IEEE for consideration by the appropriate subcommittee.
In a letter to the NRC, dated August 21, 1997. the Chairman of the High-Voltage Circuit Breaker Subcommittee of the Switchgear Committee of the IEEE Power Engineerin'g Society (sponsor of the principal applicable standard, C37.59)
confirmed the licensee's understanding of the intent of the standard regarding required design ve~ification testing for conversions using modular assemblies.
The letter further stated that if the modular assembly is in no way altered with respect to the coupling of the interrupting chambers and the operating mechanism, then some of the original design tests performed by the manufacturer.
such as short circuit current interruption.
load switching and capacitance switching tests, need not be repeated.
Howevers the letter stated, to apply this waiver, it must be shown that the mechanical operating characteristics of the interrupting chamber, such as contact parting times and contact travel, are still within the range specified for the original module prior to the conversion.
With regard to the engineering evaluations necessary to support the PG&E approach, the inspectors could not, on the basis of documentation for review at DCPP, conclusively determine the adequacy of all the justifications for not reperforming certain design tests.
Therefore. this issue remains unresolved and the inspectors identified the need for further review at NTS
~ and possibly also at PDS.
Accordingly. this issue is designated Unresolved Item 50-275.323/97210-0 Re ort Details III.
En ineerin El Conduct of Engineering E.l 4-kV Swirch ear Conversion Desi n Verification a.
Ins ection Sco e
In order to verify that PG&E and its contractors.
NTS and PDS.
had properly verified the interrupting capacity of the 350-MVA Yaskawa SF6 interrupter breakers, adapted to fit into 250-MVA GE Magne-Blast switchgear, the inspectors reviewed engineering and quality assurance documentation, interviewhd cognizant staff.
examined equipment.
and evaluated PG&E's ded;cation and m~dification of 4-kV Yaskawa circuit breakers for use in safety related applications at DCPP.
The primary issues examined were:
e Whether the design verification testing conducted on the complete conversion (consisting of the Yaskawa
"modular assembly" plus the hardware to adapt it to the Magne-Blast cubicle) for PG&E (conducted for NTS at PSM) was consistent with ANSI/IEEE Std C37.59-1991, Paragraph 5. 1.4.2(2), for conversions using adapted modular assemblies.
o Whether taking 'credit for the Yaskawa ANSI testing of the modular assembly supplemented by technical evaluations was consistent with Section 5 of C37.59,
~
Whether the Yaskawa technical evaluations of its modifications made to the modular assembly after the original design verification tests were adequate to demonstrate that the original test results were still valid after those factory modifications, o
Whether the technical evaluations by NTS were adequate to demonstrate that its additional testing of the complete conversion as requi red by C37.59 was not invai.Jated by modificat;~ns made in response to installation, setup and operational problems made subsequent to the tests.
and
~
Whether PG&E adequately resolved the findings identified in its audits of NTS.
PDS, and Yaskawa.
Also examined were:
The material of the breaker secondary disconnect pins and The potential over travel situation involving the stationary auxiliary switch (SAS) in the cubicle possibly preventing full closure of the breakers and several other interface and operation issues
The inspectors reviewed the PG&E documentation related to the design tests of the 5GYB-1-1200 ANO SGYB-1-2000 circuit breakers performed by Yaskawa.
PDS.
'nd PSM: the evaluations performed by NTS which demonstrated the equivalency of the circuit breakers supplied to PG&E to the prototype circuit breakers tested by Yaskawa and the two circuit breakers tested by PDS and PSM; and the review gf the production m~Aificatio"~ ~~de by Yaskawa and PDS following the ANSI/IEEE testing.
T';e inspectors
. ~~iew was performed,to verify that the circuit breakers supplied to PG&E were equivalent to the circuit breakers tested by Yaskawa.
PDS.
and PSM and that any modifications made to the circuit breakers by Yaskawa or PDS did not invalidate the original design testing.
b. Observations b.1 Validity of Design Verification Approach During the initial stages of the original circuit breaker production, Yaskawa had performed the ANSI/IEEE design testing on prototype breakers as represen-tatives of the circuit breaker which Yaskawa would subsequently sell as commercial grade products (non safety-related).
This circuit breaker was the Yaskawa SF, gas
"Fluopac" Series, medium-voltage (4.76-kV-rated), rotary-arc circuit breaker of 350-MVA interrupting capacity.
PG&E contracted with NTS to provide the Yaskawa circuit breakers as Class 1E (safety-related)
equipment.
NTS purchased breakers from Yaskawa and subsequently subcontracted their modification and additional testing to PDS and PSM, to be performed under the quality assurance (QA) coverage of NTS.
The particular models of these breakers that underwent design verification
.
testing were Yaskawa Models 5GYB-1-1200 and 5GYB-1-2000NTS.
The conversions performed by POS used the interrupting chambers and their attached operating mechanisms and chassis (frame) from the circuit breakers.
According to the applicable industry standard.
ANSI/IEEE Standard C37.59-1991.
these components constitute a "modular assembly."
PDS adapted the modular assemblies for retrofit into the existing GE Magne-Blast cubicles at OCPP by mounting each assembly in a custom-fabricated enclosure and truck unit containing the necessary hardware with which to make the primary and secondary electrical connections in the cubicles to the 4-kV busses and 125-Vdc control power respectively, as..ell as the..>echanical interfaces with the cubicle vertical lift apparatus, statioiiary auxiliary switch. truck-operated cubicle switch, and cubicle inter lock devices.
The applicable NRC regulations were Appendix A, "General Design Criteria for Nuclear Power Plants," to Part 50 of Title 10 of the Code of Federal Regulations (10 CFR Part 50. Appendix A); 10 CFR Part 50. Appendix B, "Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants;"
CFR 50.59, "Changes'ests'nd Experiments;"
and
CFR Part 21,
"Reporting of Defects and Noncompliance."
The 10 CFR Part 50, Appendix B.
criteria that are especially applicable to this project are Criterion III,
"Design Control," and Criterion VII, "Control of Purchased Material, Equipment and Services."
The principal industry standards applicable to switchgear conversions are ANSI/IEEE Standards C37.59-1991.
"IEEE Standard Requirements for Conversion of Power Switchgear Equipment:" C37.09-1979.
"IEEE Standard Test Procedure for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis'
" and C37.04-1979.
"IEEE Standard Rating Structure for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis."
Although there is no regulatory guide endorsing the standard.
- n question, the inspectors determined that PG&E had committed to them in the Final Safety Analysis Report (FSAR) for DCPP, and they are therefore relevant to the design and licensing basis of the plant.
Paragraph 5. 1.4.2(2) of C37.59.
which deals vith conversions using modular assemblies'equires that the modular assembly undergo the entire series of design tests in accordance with C37.09.
PG&E and NTS interpreted this to mean that it m'ust be verified that the complete series'f design tests per C37.09 has been performed on a prototype(s) of +he modular assembly, e.g.
by the manufacturer as part o original testing, with satisfactory results.
However.
on the basis of
- e general guidance in the beginning of Section 5 of C37.59.
PG&E further interpreted the standard to provide that if engineering evalua-tions of all subsequent modifications can demonstrate that functions or characteristics (e.g.. interrupting capacity) of the converted breaker are not adversely affected by the modifications such that the original tests would be invalidated, then the C37.09 design tests of those functions or characteris-tics need not be repeated on the complete conversion.
According to the documentation provided to PG&E by NTS (and reviewed by the inspectors),
the original circuit breaker design tests had been performed by Yaskawa in accordance with ANSI/IEEE C37.09-1979.
C37.20.2-1987.
C37.59-1-1991 and PG&E Specification 1001-E-NPG Section 12.1.
The purpose of the tests was to determine the adequacy of the design of this particular type and model and its component parts to meet its assigned ratings and operate satisfactorily under normal service conditions/special conditions defined by the PG&E specification.
NTS Report No. 60431-95N-C.
"'quivalency Evaluation of ANSI Type Tests and ANSI C37 Test Reports," Revision
~ dated June
~
1997.
documented the required ANSI/IEEE tests performed.
specifying a description of each test.
which company had performed the test, and including the applicable test report.
Paragraph 5.1.4.2(2) of C37.59 then requires specific additional testing of the complete conversion, which includes dielectric, momentary (C37.20.3-1987),
continuous current, interlock and auxiliary functions, and mechanical endurance testing (C37.06-1987).
The inspectors confirmed by review of the test documentation that these tests were performed on two representative complete conversions with satisfactory results.
In reviewing the design verification of the breaker conversion.
the inspectors learned that PG&E had consulted with several industry exper ts to confirm that its approach was consistent with the requirements of the applicable strandards.
However, PG&E had not requested confirmation or interpretation of the standard from the appropriate subcommittee of the IEEE.
The experts PG&E consulted included Dr. Ward Laubach who was employed as a consultant to NTS.
Dr. Laubach was a member of the IEEE Switchgear Committee of the IEEE Power
Engineering Society, sponsor of ANSI/IEEE Standard C37.59-1991.
However, the inspectors noted that Or. Laubach.
who asserted that PG8E's approach was consistent with the provisions of the standard.
was not a member of the High-Voltage Circuit Breaker Subcommittee, but rather'e was on the Low-Voltage Switchgear Devices Subcommittee.
In additions the inspectors noted that two other pyrties consulted by PG8E, who also confirmed the validity of PG8E's approach.
were (I) one of the other bidde, s on the project.
an employee of Pacific Breaker Systems, Inc.
(who had used the same approach in a project involving French Merlin-Gerin breakers for the Quad Cities and Oresden Nuclear Stations).
and (2) an employee of Square 0 Company, the U.S. representative for Merlin-Gerin (both of which companies are owned by the Schneider Electric conglomerate).
The inspectors determined that the industry experts consulted by PG8E were not totally disinterested parties because they were directly or indirectly involved in this or other similar projects'.
Therefore.
by NRC letter dated July 24, 1997 (Attachment 1 to this report).
the question of consistency of the approach with applicable standards, in particular, taking credit for certain design verification tests done by the manufacturer of the circuit breakers used in the conversion, was referred to the Standards Board of the IEEE for consideration by the appropriate subcommittee.
In a letter to the NRC, dated August 21.
199?
(Attachment 2 to this report)
~ the Chairman of the High-Voltage Circuit Breaker Subcommittee of the Switchgear Committee of the IEEE Power Engineering Society (sponsor of the principal applicable standard, C37.59) confirmed the licensee's and the inspectors'nderstanding of the intent of the standard regarding required design verification testing for conversions using modular assemblies.
The IEEE letter stated that while it was intended that all design tests be performed on the converted equipment.
in the case of a conversion using a
modular assembly, in addition to the specific tests explicitly required to be performed on the complete conversion by Paragraph 5. 1.4.2(2) of C37.59-1991.
only those design tests that cover an area of performance affected by the modifications associated with the conversion must be repeated on the complete conversion.
The letter further stated that if the modular assembly is in no way altered with respect to the coupling of the interrupting chambers and the operating mechanism, then some of'he original design tests performed by the manufacturer, such as short circuit current interruption, load switching and capacitance switching tests'eed not be repeated.
However, the letter stated.
to apply this waiver, it must be shown that the mechanical operating characteristics of the interrupting chamber.
such as contact parting times and contact travel, are still within the range specified for the original module prior to the conversion.
b.2 Equivalency Evaluation The inspectors found that the original Yaskawa breaker required extensive and substantial modification in order to successfully adapt it for use in the Hagne-Blast switchgear; modification for which neither Yaskawa, nor PG8E's contractors or subcontractors had originally or promptly provided to PG&E comprehensive engineering evaluation(s)
(at least in english) to establish that the modifications would not adversely impact the tested interrupting capacity.
and would not invalidate the original design tests by Yaskaw According to the certifications provided to PG&E, NTS had established that several areas were critical to determining that the circuit breakers supplied to PGSE were equivalent to the circuit breakers tested by Yaskawa.
PDS and PSM.
The documentation further certified that NTS had maintained the design control of materials, dimensions, and processes, verified that all ANSI/IEEE testing,was performed by approved vendors (or s<<rveilled)
and performed in a calibrated test facility. and materials si the supplied circuit breakers were appropriately dedicated.
In addition, NTS reviewed all design changes made by Yaskawa and PDS and certified that the modification did not invalidate the ANSI/IEEE testing performed by Yaskawa and PDS (and for NTS/PDS at PSH).
Yaskawa had provided NTS information on all design.
parts, or material changes made to the circuit breaker since Hay of 1993 'hen the type tests had been performed.
up to the time of the NTS purchase.
The Yaskawa changes were described'in Yaskawa Document No. GA9400864.
"Statement of Design Change."
Re~ision 2. dated July 31, 1955: which was included in Section 5.0 of NTS Report No. 60431-95N-C.
Yaskawa had made numerous changes to the :perating mechanism, the interrupter and the general assembly.
including items such as material changes.
dimensional changes, and drawing changes.
Yaskawa stated that none of the indicated changes would impact the results of the ANSI/IEEE type tests which had been performed by Yaskawa in 1993 'nd provided certification to that effect with the circuit breakers shipped to NTS.
In addition. the documents stated that NTS had reviewed the changes and performed an evaluation of those which NTS determined to have the potential to affect the critical characteristics of the as-tested design.
The documents also concluded that the Yaskawa changes had not affected the results of the type tests originally performed by Yaskawa.
In addition to Yaskawa's modifications of the modular assemblies.
PDS, under NTS controls, had also made modifications to the circuit breakers to facilitate the modular conversion and allow them to operate in the installed DCPP Magne-Blast switchgear.
The PDS engineering change notice (ECN) table for Job f1466. included in NTS Report No. 60431-95N-C, described all of the changes that NTS considered relevant to the conversion design.
The PDS modifications were primarily mechanical changes to the ci rcuit breaker frame.
wheels, and hardware.
Each ECN was accompanied by an evaluation for impact on the validity of ANSI/IEEE testing which had been performed by Yaskawa, PDS or PSM.
NTS Repcrt No.
5043 95N-C concluded that none of the PDS modifications invalidated the circuit breaker testing performed by Yaskawa.
PDS or PSH.
b.3 Low-Voltage Fault Current Test The inspectors found that although PGSE did not conduct a rated-voltage, rated-fault current interrupting capacity test on the complete conversion. it ordered a special fault current test at PSH (in addition to the additional testing on'he complete conversion required by C37.59).
which was conducted at 480 volts instead of 4760 volts.
PGSE explained that there might be adverse effects of fault-current magnetic fields on the components added to the complete conversion to adapt it to the auxiliary switches and mechanical interlocks of the Magne-Blast cubicle.
These effects might cause the added hardware to impede breaker tripping on a fault: effects that may not have been covered by the testing required by the standards.
Therefore, PG8E decided to
conduct an interrupting capacity test of a prototype of the complete conversion unit that was already undergoing the testing required by Paragraph 5. 1.4.2(2) of ANSI/IEEE Std C37.59 in July 1996 at PSH.
However.
due to some problem with or unavailability of PSN's main high-current test facility generator.
the test was done at 480 Vac (although presumably at the requi red current, level) instead of t~e 4760 Vv- "o~o"tedly required for 4-kV breakers by C37.09
- Referenced i C37.59).
reer. argued, that even though the test was at low voltage, the fault current would produce magnetic fields to adequately simulate the fault interrupting conditions that might conceivably affect the operation components in question irrespective of the voltage at which the 41,000-amp test was conducted.
as only the current.
not the voltage gives rise to the magnetic fields.
c.
Conclusion I
The inspectors concluded that PG&E's approach to design verification was generally consistent with the applicable NRC regulations.
primarily Criterion III. "Design Control." of 10 CFR Part 50, Appendix B. in that PG8E undertook to verify by engineering analysis and a testing program that DCPP's safety-related 4-kV electrical distribution system as converted and modified would perform its safety functions under all design basis conditions.
On the basis of the IEEE interpretation of the intent of C37.59.
the inspectors further concluded 'that the PG8E approach was consistent with applicable industry standards, provided the required supporting engineering evaluations were adequate.
On the basis of the review of the supporting documentation supplied by Yaskawa, NTS, and PG8E. the inspectors further concluded that the applicable ANSI/IEEE tests had been performed with satisfactory results.
However. although PG&E had certifications from NTS that equivalency had been established between the tested ci rcuit breakers and those supplied to PG8E.
the inspectors could not conclude on the basis of documentation available for review at DCPP that the technical evaluations performed primarily by NTS demonstrated that the modification made by Yaskawa and PDS had not impacted the validity of the ANSI/IEEE tests performed on the circuit breakers:
therefore, the inspectors could not conclusively determine the adequacy of all the justifications for not reperforming certain design tests.
Accordingly, the inspectors identified the need for further review at NTS.
and possibly also at PDS and designated th-;s issue as Unresolved Item 50-275,323/97201-01.
E.2 4-kV Production Breaker Installation and Performance Concerns a.
Ins ection Sco e
The inspectors identified three areas of concern regarding 4-kV breaker installation and performance:
(1) 4-kV breaker secondary disconnect contact pin material, (2) breaker operation interference due to stationary auxiliary switch (SAS) overtravel, and (3)
SAS adjustment/performance.
To address these issues.,
the inspectors reviewed the associated DCPP Action Requests (ARs) and thei r dispositions, interviewed cognizant engineering and operations personnel, and examined some representative component b. Observations b.1 Secondary Disconnect Pin Haterial In the case of the secondary contact pin material.
the pins on the breakers for DCPP. Unit 1. which had not yet been sh~oped were replaced with pins of a stiffer. rrore tempered material.
The pir.s on the breakers in Unit 2 were not replaced en masse.
but rather inspected and replaced if permanently deformed or otherwise damaged or degraded.
In additions PG8E had discovered that the reason the pins (of more malleable material than those of the original GE.
secondary contact blocks) were becoming deformed.
in some cases enough to degrade electrical contact.
was the manner in which mainte~ance electricians had become used to removing the secondary contact test position adapter cable and plug assembly, i.e..
by yanking it off partially sideways.
Accordingly.
PG&E changed procedures and conducted training to ensure that the test cable plugs would b~ pulled off carefully and only with vertical force to prevent any future pin deformation.
In addition, procedures were changed to require the use of a GE s~.ondary contact pin spreading or gapping tool after each test cable removal to ensure that the four segments of each pin were properly spread for adequate electrical contact when the breaker was fully racked up into its operate position.
The inspectors determined that DCPP Operations and Engineering were satisfied that the corrective action was adequate.
PG&E stated that there were sufficient replacement pins of the improved'tiffer, more tempered material on site to replace any pins that should become irreparably deformed despite improved handling procedures.
b.2 Stationary Auxiliary Switch (SAS) Overtravel With respect to the potential for an overtravel condition in the SASs potentially preventing the converted Yaskawa breakers from closing fully (which never occurred in service, only during off-line experimentation).
the inspectors determined that PG&E's minimum required gap (0.040") between the stationary auxiliary switch operating rod and the breaker's mechanism-operated cubicle plunger (set by adjusting shims in the plunger and thereafter by manually adjusting open breaker elevation in its cubicle), in conjunction with the procedures that required checking and establishing this gap each time a breaker was racked in. would prever" the overtravel condition from occurring.
b.3 SAS Adjustment and Performance Having suffered several equipment failures since the installation of the converted Yaskawa breakers attributable to problems with the SASs (i.e., not all sets of contacts consistently changing state with breaker operation),
PG&E had determined (through testing) the worst case stroke requirement (they are somewhat variable)
among all the SASs (i.e., stroke of the operating rod required to ensure that all contacts in the SAS.
a GE SB-12 switch, will fully change state).
Some older switches that had actually caused failures or were found through testing to be unreliable or out of tolerance were replaced.
PG8E then determined the maximum allowable breaker-open, plunger-SAS operating rod gap that would ensure that all SAS contacts would change state when the breaker closed given the worst case (largest)
required stroke of all the SB-12 switche Ouring this period, another related problem presented itself.
Upon investigating the failure of a pump to start, PGSE found that another instance of 4-kY breaker-SAS adjustment to be the cause.
Inspection revealed that even though the gap had been set by procedure when the affected breaker was last racked in. the as-found gap was too wide.
Thus when this breaker was closed, not all-.of the contacts in its SAS had changed state.
Through further testing and investigation, PG8E discovered that wh.n the adjustment screw at the top of the breaker's SAS plunger is retorqued after replacing adjustment shims.
the linkages that operate the SAS plunger become slightly cocked as joints in the linkages expand to their maximum end float.
This condition raises the SAS plunger up as much as 0.050 or 0.060 inch above its normal, breaker-open.
rest gosition.
During the first subsequent closing operation after the gap has een set with the plunger in the slightly raised position, the end float or looseness in the various linkage connections is closed up which effectively shortens the plunger stroke and thereafter not all of the SAS contacts may change state.
To prevent this situation and ensure that the correct (and otherwise consistent)
SAS plunger stroke is always obtained.
PGEE changed procedures and conducted training to ensure that the plunger is tapped down into its fully withdrawn, breaker-open rest position before setting'the lunger-to-SAS operating rod gap.
This ensures that all the end float in the inkage is closed up so that a stable gap can then be reliably set by manually adjusting the breaker elevation in the cubicle.
c.
Conclusion With respect to the 4-kY breaker installation. interface.
and performance concerns discussed above, the inspectors determined that PG8E's corrective actions were appropriate and adequat Licensee PARTIAL LIST OF PERSONS CONTACTED Shawn LaForce Stan Ketelsen Bill Bayne Bob Whitgell Charlie Nichols Michael Jacobson Chuck Lewis Bill Colry Tom Bennett Dave Taggart I
Tho-.,as W. Packy Klemme Herman Ed Kahler Tom Fetterman Pat Colbert Eric Nelson David Oatley Jim Holden Terry Grebel RS NSAL-RS Procurement Systems Nuclear Quality Systems (NQS)
Materials NQS NQS Regulatory Services Operations NQS-Engineering Dir.
8 Procurement NQS-PA Nuclear Technical Services NTS NTS NTS(4-kV Conversion Project)
Mechanical Maintenance Maintenance Services Operations Regulatory Services Engineer Supervisor
~upervisor Supervisor Director Sr.
Engineer Engineer Engineer Director Director Lead Auditor Electrical Supervi sr Project Hanager Director Electrical Supervisor General Foreman Manager Manager Director USNRC Brad Olson, Don Allen Region IV, Walnut Creek Field Office (WCFO)
Region IV, WCFO Project Engineer DCPP Resident Inspector Open Items Th s report categorizes the inspection findings as unresolved items and inspection follow-up items in accordance with the NRC Inspection Manual, Manual Chapter 0610.
An ~
esolved item (UR.i is a matter about which more information is required to determine whether the issue in question is an acceptable item, a deviation.
a nonconformance, or a violation.
The NRC Office of Nuclear Reactor Regulation wi 11 issue any enforcement action resulting from their review of the identified unresolved items.
An inspection follow-up item ( IFI) is a matter that requires further inspection because of a otentia1 problem, because specific licensee or NRC action is 'pending.
or ecause additional information is needed that was not available at the time of the inspection.
Item Number Finding Title 50-275;50-323/97201-01 URI Meeting ANSI/IEEE C37.59-1991 (Section 5)
qI ~ Rtcu (,4 C~'o
~'W op lf**44 REPORT 550-275/97201 ATI'ACHNENT 1 UNITED STATES NUCLEAR REGULATORY COIVIIVIISSION WASHINGTON, O.C. 20555400I July 24, 1997 The Secretary IEEE Standards Board 445 Hoes Lane P,O.
Box 1331 Piscataway, NJ 08555-1331 Gentlemen:
I The Nuclear Regulatory Commission is reviewing a 4.16-kV switchgear conversion by one of our utility licensees using Yaskawa 350-HVA SF gas-rotary-a<'c circuit breakers (as modular assemblies)
to replace GE 230-HVA Hagne-Blast circuit breakers in Class 1E (and non-Class 1E) applications.
The modular assemblies, consisting principally of the interrupters, mechanism and frame of the Yaskawa breaker, were adapted for retrofit into the unaltered Hagne-Blast cubicles by mounting each modular assembly in a custom-fabricated enclosure and truck unit which contains the necessary hardware with which to make the primary and secondary electrical connections as well as the mechanical interfaces with the cubicle vertical lift apparatus, auxiliary switches and cubicle interlock devices.
To accomplish design verification, the licensee elected to follow the guidance of ANSI/IEEE Standard C37.59-1991.
Our licensee holds that C37.59 provides in the beginning of Section 5 for taking credit for certain design verification tests, done by the original equipment manufacturer in accordance with ANSI/IEEE Standard C37.09.
However, there must be engineering evaluations that demonstrate that modifications made to the modular assembly itself, and/or by the additional hardware added to form the complete conversion, will not have an adverse effect on the performance of the modified breaker in such a way as to, invalidate the tests for which credit is being taken.
Paragraph 5. 1.4.2(2) of C37.59, specifically addressing the modular assembly type of conversion states that the full series of design tests in accordance with C37.09 is to be done on the modular assembly, and the additional tests specified in the paragraph are to be done on the complete conversion.
The licensee's interpretation, taken in context with the general provisions at the beginning of Section 5, is that performing the full series of design tests on the modular assembly means that it must be verified that all the required tests were conducted (e.g.,
by the manufacturer)
in accordance with the applicable ANSI/IEEE standards, with satisfactory results.
Further, those tests that are part of the full design series, but that are not explicitly required as additional tests by 5. 1.4.2(2),
in particular, a full-rated-voltage interrupting capacity test, need not be repeated, provided it can be demonstrated by engineering evaluation that none of the subsequent modifications would adversely affect breaker performance in a manner that would invalidate the original test(s).
The Secretary The NRC requests that the appropriate subcommittee or working group respons1bl.
for the portions of C3I,59 i
- uestion indicate whether the interpretation stated above is consistent, with the provisions and the intent of the standard.
We appreciate greatly your assistance in this matter.
Sincerely, Stuart A.
Richards, Chief Special Inspection Branch Division of Inspection Support Programs Office of Nuclear Reactor Regulation
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/OE 804.r r 5 O327 HioH VOLTAos SAITcHes A. Monroe LISC0 P 0 BOA 10023 Birmingham. AL 35202 VoA 205-592-724 i Loh'o'Aos SwircNSLAR DSTAcfs R. J. Puckett DOPOnt ErgineCrIng Beach Street Engineenng Certer 16/2817 101 BeaChSt
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~ 302.695-0" 66 Re L05ERs ANO SecTloNALQSRs J. G. Wood Pacific Gas 8, Elec!nc, Distrihution Dept i23 Mission St. T(12A P 0 Box 770000 San Francisco, CA 94177 Vox 4 I5-973-3355 Sn T HSEAR AssfL'SLi(S T. A. Bursa PAS-C-A E:AN K. I. Gray AuL'uSI I
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(.)I'tice OI'Xucie;Ir Re;Ict>>r Re ut ltion Re,.
( '7 54 Standard Interpretation
't sll(luld be noted tilllttile Sc(II)e I section I, I I of the ret'erencc(i Standard C.T7.5'I specifically eicludes equipment that is labeled or listed bi'a third parti. or involved in I'uclear Regulatory C'ommission required conformance.
As specitically requested. and in ret'erence to Clause 5 of'37.5 Il the intent ot the standard is to specif'y i( hat desiiln tests haie to be perforlned on the conlpleted coni ersion. depending upon the extent of'such conversion.
It is intended to require that all ot'the desiiin tests specified in C37.09 have been pertormed on the converte(f equipment. A dt ttercntiation is m lde betiieen those conversions ivhlch use individual components such as: interrupting chambers which are not a part nt a complete assembly and the ones where a complete circuit breaker module. where the operating mechanism is an integral part of'the assembly.
is used.
fn the first case all design tests are required. but in the later case only those tests that take into consideration modifications made to the module and which directly may affect a certain pert'ormance characteristic of the circuit breaker: then. the design test covering such area ot performance must be repeated.
ivfore specifically. it the circuit breaker inndule. ivhich consist ot an interrupter chamber coupled with a stored energy operating mechanism.
is used and if'the assembly of'the THE INSTITUTE OF ELECTRICALAND ELECTRONICS ENGINEERS, Hr, ItEE
module is in no iiai <<ltered w ith respect to the couplinu ot'he interruptinu chan>hers aiid the operatine mechanism then
~ mme ol'the le i~~~ rests. such as: Short Circuit Current lnferrtiptlon..0<<d SN Il'llllnuand Cap<<cit.uv ' '.cnln" tests need not to be repeated.
ln this case the test certification provided hy the manulacturer ot'th>> module would sul'lice.
Howeer in order to apply this waiier it inust he sllown that the mechanical operating characteristics ot the interruptin chamber. such as contact partinu times and contact travel are still within the ran ~e specified lor the ori<~inal inodule prior to the coni'ersion.
Those tests which are explicitly listed in subclause 5. I,4.2 t2> must be pertormed on the completed coni ersion.
l hope that the ahorse willanswer your questions.
Ruhen D. Garzon fEFE Switchuear Coinmittee HVCB Chairman