ML20114A799
| ML20114A799 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 08/14/1992 |
| From: | Creel G BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9208210204 | |
| Download: ML20114A799 (16) | |
Text
BALTIMORE GAS AND ELECTRIC i
L 1650 CALVERT CUFFS PARKWAY LUSBY, MARYLAND 20657-4702 GEoRoE C CREEL Vict PREsotNT NUCLE AR ENERGY (460)#60-4455 August 14,1992 U. S. Nuclear Regulatory Commission Washington,DC 20555 NITENTION:
Document Control Desk
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & 50-318 Electrical Distribution System Functional Inspection, Combined Inspection Report Nos. 50-317N2-80 and 50-31892-80
REFERENCES:
(a)
Letter from Mr. M. W. Ilodges (NRC) to Mr. G. C. Creel (BG&E),
dated June 5,1992, Electrical Distribution System Functional Inspection (EDSFI) of Calvert Cliffs Units 1 and 2, Combined Inspection Report Nos. 50-317/92-80 and 50-318/92-80 (b)
Letter from Mr. G. C. Creel (BG&E) to NRC Document Control Dess, dated July 8,1992, same subject Gentlemen:
Reference (a) transmitted three Notices of Violation telated to the Electrical Distribution System Functional Inspection (EDSFI) conducted at Cahert Cliffs from March 16, 1992, through forwards our response to the three April 30,1992. As discussed in Reference (b), This 1cto r violations. This letter is delayed beyond the intended date c! submittal discussed in Reference (b) in order to incoiporate changes necessary to ensure its clarity and accuracy. This delay has been discussed with Mr. Larry Nicholson of the Region I staff.
If, after consideration of the responses provided, the NRC wishes to discuss these issues further, we would be pleased to meet with members of your staff.
Very truly yours, 200083
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' August 14,1992 Page 2 i
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D. A.13 rune, Esquire J. E. Silberg, Esquire R. n. Capra, NRC -
D. G. Mcdonald, Jr., NRC T. T. Martin, NRC P. R. Wilson, NRC R. I. Mclean, DNR J. IL Walter, PSC
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7 REPLY TO A NOTICE OF VIOLATION -
[
_ INSPECTION REPORT NOS,50 317/92 80 AND 50 318/92-80 VIOLATION NO. I
- Both_ examples in this cited ~ violation are apparent violations of 10 CFR Pan 50, Appendix B,.
Criterion XI (Test Control) which require that all testing be performed in accordance with written test procedures which incerporate the recjuirements and acceptance ti:r.hs contained in applicable
- design documents. Criterion XI also requires that the test results be documented and eva uated to asrure that requirements have been satisfied. Each example is discussed separately below.
-(A)-
1.
~ DESCRIPTION OF VIOLATION The first example concerns the degraded bus relay settings at Calvert Cliffs. As opposed to the loss of voltage relays which protect the 4 kV busses from a sudden loss of voltage and have a lower setpoint and a shorter time delay, the degraded bus re:ays protect the 4 kV busses from prolonged reduced voltage conditions which v..uld impact the proper operation of safety-related equipment.
The degraded bus relays begin timing-upon a reduced voltage on the 4 kV safety busses. The voltage level that initiates timing of the relay, called the " dropout" setting, is stipulated by Technical Specification (TS) 3.3.2.1 to be 3628 volts +/-25 volts. If voltage does not recover above the " reset" level within 8.4 seconds, the relay initiates a trip causing the 4 kV busses to divorce from their normal offsite supply, the Emergency Diesel Generators (EDGs) to start, and the loading of the EDGs with the 4 kV busses.
Alth mgh 4 kV bus. voltage is the parameter of concern, the relays sense voltage on the low voltage side of a potential transformer and are set correspondingly. Thus a nominal _ dropout of 3628 volts on the bus corresponds to a relay setting of approximately 103.9 volts. This reflects the potential transformer voltage ratio (35:1) and the potential transformer (PT) error (-0.2% or a factor of 0.998). He PT error is constant for this transformer application and thus may be viewed as a correction factor rather than an error.
103.86 x 35 x 0.998 = 3628 The relay reset setting is determined by the relay deadband. The relay deadband is the difference between the dropout setting and the reset setting. Once the dropout setting is established the relay deadband is adjusted to yield the reset setting.
While the nominal dropout setting and the alto,vable time delay are specified in TR the reset setting is not. It must however, correspond to a 4 kV bus voltage lower thar..
Lthe worst case steady state voltage. Othenvise, a brief voltage transient could dip below the relay dropout setting, cause the relay to begin timing, and, with steady state
- voltage less than reset, the relay will initiate a trip because the reset setting is never reached. This relay trip will cause an unnecessary transient to the 4 kV busses and challenge to the EDGs.
During the EDSFI, the i_nspectors noted in STP results that a reset setting of 105.0 volts was recorded. This data was recorded for information only because the STP did not stipulate acceptance criteria for the reset setting.
The inspectors developed two concerns which are the basis for this violation example.
First, the inspectors were concerned that the STP did not contain acceptance criteria 3
- m..
1^
REPLYTO A NOTICE OF VIOLATION -
INSPECTION REPORT NOS,50 317/92 80 AND 50-318!92-80 VIDIATION NO,1 for the reset settings based on design document.<. Second, the inspectors perec;ved that the reset setting of 105.0 volts they observed was too high in that it corresponded to a 4 kV bus voltage greater than the worst case (lowest) steady state voltage. This created the potential for a short transient as described above to unnecessarily load the 4 kV busses onto the EDGs while oftsite power was still available. Thus a reset setting of 105.0 volts represented a potential challenge to safety systems. (See attached graph [1]) These two concerns are cited as an appaient violation of 10 CFR Part 50, Appendix B, Criterion XI (Test Control).
II.
REASON FOR VIOIATION Baltimore Gas and Electric Company (BG&E) does not agree that this example represents a violation of the referenced requirement. We believe some confusion exists regarding the requirements and acceptance limits for reset settings for the degraded grid relays.
h EDSFI inspection report states that Calculation E-90 31 determined the reset voltage to be 3668 volts. The report also indicates that this correlates to a reset setting of 104.8 volts. Therefore the report concludes that the recorded reset setting of 105.0 volts is unsatisfactory.
BG&E wishes to clarify these observations. First, the methodology used in the NRC inspection report to convert from reset setting to 4 kV bus voltage omits the use of PT error. This causes discrepancies between the NRC values and the values in use.
EDSFI inspection Report:
104.8 x 35 = 3668 105.0 x 35 = 3675 BG&E Calculation 105.0 x 35 x 0.998 =. 3668 By including PT crror, it becomes clear that 105.0 volts corresponds to 3668 volts on the 4 kV bus. It is an acceptable setting for the relay reset.
Second, Calculation E-90-31 did not determine 3668 volts to be the reset point or "the worst case 4160 bus running voltage" as stated in the report. Rather, the calculated reset setting of 105.0 volts discussed above was equated to a 4 kV bus voltage of 3668 volts. That number was then used as an input to calculate the minimum acceptable switchyard voltage necessary to clear the maximum reset setting following an Engineered Safety Features actuation (limiting case transient) under worst case conditions. This switchyard voltage was found to be 479 kV and would result in a final steady state 4 kV bus voltage of 3668.5 volts. (See attached graph (1])
' Operating Instruction (OI)-28 requires that switchyard voltage he maintained above -
485 kV 'Ihis value includes 5 kV margin for the maximum possible concurrent grid transient and an additional I kV for conservatism.
In summary, Calculation E-90-31 was done expressly to determine the minimum initial switchyard voliage required to clear the maximum reset setting for the limiting case transient. Switchyard voltage is controlled above that value with conservatism i
l 2
REPLY TO A NOTICE OF VIO1ATION INSPECTION REPORT NOS. 50-3!?/92-80 AND 50-31R!92-80 VIO1ATION NO. I and margin included. He observed reset setting of 105.0 volts is the maximum allowable reset setting.
Regarding the NRC concern that the STP did not contain the appropriate acceptance criteria, BG&E maintains that all applicable requitements have been met.
Because the reset setting is not a setooint stipulated in TS, it is not required to be tested under the STP Program. It is, however, controlled and tested by Functional Test Electrical (FTE) procedures using Relay Setting Sheets in accordance with the requirements of Criterion XI. This includes the fact that the acceptance criteria in the Relay Setting Sheets (no greater than 105.0 volts) is taken from design documentation (Calculation E-87-13).
BG&E does not believe that this example constitutes a violatica of Appendix B Test Control requirements. Although the reset setting is not controlled by an STP, it is not required to be, and it is controlled by an appropriate test program. The as-found value of 105.0 volts was not inconsistent with design and as described above does not represent a potential challenge to safety systems. Therefore, BG&E requests that the NRC reconsider this example as a violation of Appendix B requirements.
(11) 1.
DESCRIPTION OF VIOLATION The second example in this cited violation involves the documentation and evaluation of EDG test results.
Verification of the CCNPP emergency diesel generator (EDG) operating parameters is accomplished by surveillance testing. Attachment 10 to STP O-4 requires, in part, that the maximum frequency (Ilz) obtained during sequencing of load steps be recorded based on data from the visicorder trace. The STP acceptance criterion for the maximum frequency recorded was 66 IIz.
Upon review of the visicorder traces associated with STP O-4, conducted on EDG 11, the NRC team noted that the maximum frequency appears to be 66.2 Ilz (based on timing of voltage peaks) at 0.23 seconds into step zero (0) of the loading sequence, llowever, the maximum recorded frequency in STP O-4 was 61 Ilz, evidently incorrect. The inspection report indicated that BG&E: (i) failed to properly record the maximum frequency observed during EDG loading sequencing, and (ii) failed to properly evaluate the impact of frequency exceeding the maximum acceptable value during the STP. Section 4.2.2 of the inspection report concluded that these apparent problems constituted a violation of 10 Cl'R Part 50, Appendix B, Criterion XI (Test Control).
11.
REASON FOR VIOLATION BG&E disagrees that this example is a violation of NRC requirements. As detailed below, the frequency transient and subsequent recovery at step 0 of the surveillance test is not caused by a step load increase but rather is the result of normal engine start. As such, it is not subject to the frequency criteria described in the UFSAR and contained in the STP. Therefore its oraission from the test frequency data is not incorrect and its inclusion is not necessary to properly evaluate the test results.
3
REPLY TO A NOTICE OF VIOLATION JESPECTION REPORT NOS. 50-317/92 80 AND 50-318/92 80 VIOLATION NO.1 During the inspection, some disagreement existed over interpretation of the test criteria. BG&E wishes to clarify the basis for our position.
Th-NRC team apparently concluded that STP O-4 evaluated the maximum frequency observed during all EDG sequence steps --including step zero. However, based on the UFSAR, BG&E believes that step zero is not considered a " load sequence step" for the purposes of evaluating transient frequency performance. As a result, the maximum frequency for steps I th:ough 7 was recorded (61 liz); the frequency for step zero (66.2 IIz) was not. Accordingly, the 66 Hz maximum frequency requirement only applied to steps 1 through 7.
UFSAR Section 8.4.1.2 states, "During recovery from transients caused by step load increases or resulting from the disconnect of the largest single load, the speed of the diesel generator will not exceed nominal speed plus 75% of the difference between j
nominal speed (900 rpm and 115%) of nominal speed
- This indicates that the EDG speed is limited to 1001 rpm (900 + 0.75 x[1.15 x 900 -
900] = 1001.25 rpm), which corresponds to 66.7 Hz. Although maximum EDG frequency'was less than 66.7 IIz in all steps, this requirement applies only to steps I through 7.
The transient during step 0 is a starting transient due to the acceleration and subsequent overshoot of the engine from rest to approximately 900 rpm in less than 10 seconds. This overshoot is normal and necessary to allow the governor to take 1
control and esteblish 60 Hz frequency. Although a small amount of electrical loads are placed on the EDG at step 0, these loads represent less than 15% of the engine rating and have minimal impact on the transient when compared to the energy required to accelerate the engine from rest to rated speed in less than 10 seconds. In addition, observed frequency response during testing supports this explanation since frequency continues to increase for a short period after the output breaker closes rather than decrease due to the addition of loads. As such, this transient is not :s transient caused by a load step increase and therefore the transient frequency criteria in the UFSAR does not apply.
Regarding the observation that BG&E failed to properly evaluate the impact of l
frequency exceeding the maximum allowable value during the STP, we deduce from l
the logic outlined above that the STP load step frequency criteria did not apply to j
step 0. The evaluation of test results therefore was consistent with the requirements and intent of the UFSAR. In addition, the 66 Hz STP requirement was a self-imposed value chosen for conservatism and convenience. As discussed above, the actual maximum allowed frequency in steps I through 7 is 66.7 Hz. It can be logically assumed, however, that the observed frequency of 66 2 Hz for step 0 is technically acceptable since this is below 66.7 Hz.
In summary, BG&E considers that the procedure was adequate and served its function. The results and acceptance criteria were properly documented and evaluated by test personnel and EDG performance regarding frequency meets all applicable requirements. BG&E believes that no violation exists and we request i
reconsideration of this exampi.: as a violation of 10 CFR Part 50, Appendix B, Criterion XI.
4
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~ ~
REPLY TO A NOTICE OF VIOLATION
~ INSPECTION REPORT NOS. 50-317/92 80 AND 50-318/92 80 VIOLATION NO 1 J
l 111. - ~ CORRECI'IVE STEPS TAKEN AND RESULTS ACIllEVED No corrective action is necessary.
IV.
- CORRECI'IVE ACTIONS WillCll WILL HE TAKEN TO AVOID - FURTilER -
VIOLATIONS No corrective action is necessary.
.1 V.
' DAT6 WIIEN FULL COMPI,IANCE WILL HE ACillEVED
- Full compliance with NRC requirements has been maintained.
p --
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DEGRADED BUS RELAY PROTECTION AT CALVERT CLIFFS 4 kV BUS VOLTAGE
- 3770c, 3760 BUS-.V OLTAG E...W/_ YARD. AT_4 85 AV 3750 3740 3730 3720,1NITI AL BUS VOLTAGE W/ VARD AT 479 kV 3710~
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3 7 0 0 3690
- - - - - - - - - - - - - - - - - ~ -
3 6 8 0g- ----- -
--NRC CALCULATED RESET (iO5 35I 675g
~
3 AGTtJKL RESET (iOS*35 0.998 3668) i 3660 3650 VOLTAGE T 3ANSIENT DURING ESF START 3630 I- -
RE. Ay eROiOUT POINT (3628Y 3620
---/
3610 3600 0:00 0:08 graphlil 4
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n REFLY TO A NOTICE OF VIOLATION--
iiNSPECTION REPORT NOS. 50-317/92 80 AND 50418/92-80 VIOLATION NO. 2 -
' I.
DESCRIPTION OF VIDIATION-Baltimore Gas and Electric Company Technical Specification (TS), Section 6.8.1, states that
-written procedures shall be established and implemented covering the applicable procedures recommended in Appendix A of Regulatory Guide 1.33, Revision 2.
. Regulatory Guide 1.33, Revision 2, Append:x A, parrgraphs 8.a and b, state that procedures appropriate to the circumstances should be provided to ensure that instruments and controls are properly controlled and calibrated to maintain accuracy and specific surveillance test procedures written to cover these activities.
- During the EDSFI, the inspectors noted that su'veillance procedures such as STP O-4 for the Emergency Diesel Generator and STP M-522-2 for degraded bus protection did not include instrument inaccuracies and calibration errors fer instruments such as voltage relays, voltmeter, wattmeter,- ammeter,-.visicorder frequency meter, ' current transformer and
- potential transformer.to ensure that the EDO and the degraded bus protective relays operated within the design values. This was perceived by the inspectors to be an apparent -
violation of the Regulatory Guide 1.33 requirements committed to in TS 6.8.1.
11.
RFASON FOR_JIIE VIOLATION BG&E has reviewed the cited violation and believes that no violation of NRC requirements -
exists. As stated in Technical Specification 6.8.1, BG&E is committed to the requirements set ferthLin Regulatory Guide (RG) t.33, Revision 2.'
The Notice of Violation (NOV) indicates that this RG requires that surveillance procedures, to be adequately implemented.
must include instrument accuracies and calibration errors. However, after a detailed review
- of paragraphs 8.a and b of this RG, BG&E has concluded that no such requirement exists.
Regulatory Guide 1.33, Revision 2, Paragraphs 8.a and b are as follows:
- a.
Procedures of a type appmpriate to the circumstances should be provided to ensure that
. tools, gauges, insuuments, controls, and other measuring and testing devices are properly controlled, calibrated, 'and adjusted at :pecifiedperiods to maintain accuracy.
Specific - examples of such equipment to 'be calibrated and = tested 'sre readout
-instmments, interlock permissise and prohibit circuits, alarm devices, sensors. signal '
conditioners, controls, protective circuits, and laboratory equipmern.
- b.
Specific procedures for surveillance tests, inspectiorn, and calibrations shocid be written (implementing procedures are required for each surveillance test," inspection, or
. calibration listed in the technicalspecifications)...."
BO&E complies with the~ requirements contained in each paragraph ofl Regulatory
- Guide 1.33 cited above. At CCNPP:'(i) procedures exist to properly control, calibrate and -
adjust tools, gauges, instruments, controls, and othe. measuring equipment to maintain x
'. accuracy, and (ii) procedures exist for surveillance tests, inspections and calibrations. BG&E
. does not interpret the above requirements to mean that surveillance procedures must include instrument accuracies and calibration tolerances in all cases to ensure that equipment operates within design values.
r L
1
- REPIN TO A NOTICE OF VIOLATION INSPECTION REPORT NOS,50-317/92 80 AND 53 318/92 80
-l
--VIOLATION NO. 2 In addition, based on an industry survey conducted at the time of the inspection and further discussions with other utilities, we have found that our procedures are consistent with general
- industry practice regarding instrument inaccuracies and calibration tolerance.
4-
~
In light of the discussion outlined above, BG&E requests that thc NRC reconsider its position on this issue or address it as a generic industry concern.
III.
CORRECTIVE STEPS TAKEN AND RESULTS AClllEVED i
No corrective action is necessary.-
IV.
CORRECrlVE - ACTIONS WillCII WILL llE TAKEN TO AVOID FURTilER VIOLATIONS No corrective action is necessary.
V,-
DATE WIIEN FULL COMPLIANCE WILL llE ACIllEVED Full compliance with NRC requirements has been maintained.
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L 2
j REPIN TO A NOTICE OF VIOLATION INSPECTION REPORT NOS. 50-317/92-80 AND 50-318/92-80 VIOLATION NO. 3 The two examples in this citation are apparent violations of 10 CFR Part 50. Appendir B, Criterion Ill (Design Control) and the corresponding Balticaore Gas and Electric Company (BG&E) Quality Assurance Policy. 'Itese documents require that design methods provide for verifying or checking the adequacy of design.
BG&E has reviewed the cited violation and concurs that,in the Grst exampic, a failure to properly check the adequacy of design occurred as the result of a failure to follow established pu>cedures.
Regarding the second example, however, we contend that a violation of regulatory requirements did not occu. Each example is discussed separately below.
(A) 1.
DESCRIPTION OF VIOL ATION The first examph concerns the apparent failure to verify er check the adequacy of assumptions utilized in design calculations. Five assumptions are identiGed to illustrate the violation. These are: (i) conductor temperature of 75 C, (ii) motor starting capabilities at 75% of nameplate rating for 460V load center loads and 4 kV loads and 70% of nameplate rating for MCC loads, (iii) computer modeling without considering all power cables, (iv) starting and running values of motor torque are the same, and (v) 460V runningvoltages were less than the required 90% of rated nameplate rating.
11.
REASON FOR TIIE VIOL ATION The violation cites that BG&E used these assumptions without adequate verification or checking. BG&E agrees that two of the noted assumptions repret,ent otors in inputs to calculation, namely starting and running values of motor torque are the same, and 460V running voltages were less than the required 90% of rated nameplate rating. However, we contend that the remaining assumptions are vcl;d. They are categorized under unresolved item #2 (9240-06), Reference (b) and in our view are not illustrative of the cited violation. We request they be withdrawn as exampics.
BG&E requests consideration of the following:
Conductor temperature nf 75"C BG&E calculation E-90-24 develops cable impedances for use in load Gow calculations. The cable impedance are based on a conducto operating temperature -f 75 C. This assumption was based on the everage conductor temperature wr the postulated scenarios of all cables in the load flows not exceeding 75 C. The approach of basing cable impedances with all cables operating at 75 C is considered conservative by BG&E..
Use of 90 C, when the cable rating is 90 C, as the average conductor operating temperature will yield more conservative results, but not more accurate ones. The value of 90 C is the maximum continuous operating temperature of the cable without sustaining damage for 90 C rated cables.
Typical continuous cable temperature ratings are 60 C, 75 C, and 90 C.
Power cables generally have overload and emergency temperature ratings as well as continuous temperature ratings. For example, a 90 'C rated cable will typically have a one hour overload rating of 135"C and an cmergency rating (fault conditions) of 250 C. There is no industry requirement to use one 1
o.
- REPLYTO A NOTICE OF VIOLATION INSPECI' ION REPORT NOS. 50-317/92-80 AND 50 318/92-80 VIOLATION NO.3 conductor temperature versus another when perforraing load flow calculations. IEEE 1411986, Section 3,11.1, indicates use of a conductor temperature of 75"C for average loading and 90 C for maximum loading.
m Subsequent to the EDSFI, BG&E developed new load flows at the anti.j ated cable operating temperatures and compared the results to the p
existing loads flows based on an average conductor operating temperature of 75 C (reference our letter of July 8,1992). 'Ihe existing load floe based on U
an average conductor temperature of 75 C yielded more conservative results.
Calculpion E-90 24 postulated an average conductor operating temperature for use in determ ning cable impedmces to be used in load fiavi calculations that is in accordance with industry guidance and yicids conservative results.
This assumption was reviewed and verified as adequate as part of the calculation review and approval process in accordance with BG&E Ouality Assurance Program requirements. BG&E concludes that the verification and review were adequate and not in violation of regulatory requirements.
Motor starting capabilities of 75% of name plate rating for 460 volts load center loads and 4 kV loads and 70% of nameplate rating for MCC loads BG&E calculations E-90 28 and E-90-41 develop the minimum voltage -
requirements at 480V load centers and MCCs respectively. Motor loads supplied directly from load centers are assumed to have the capability to start with 75% of rated nameplate voltage at their terminals. MCC supplied motor f
loads are assumed to have the capability to start with 70% of rated nameplate voltage at their terminals.
In_BG&E's view: (i) A/E documentation attached to calculation E-90-28 verifies that safety related motors supplied direct!v from the load centers will start : with 75%. of - motor rated voltage at their tetminals and (ii) calculation E-90-41 develops an adequate ba.iis to provide reasorable assurance that MCC supplied motor loads have the capability to start with 70% of rated nameplate voltage at_ tlicir terminals.
Computer modeling without etmsidcring all power cables i;
j The computer model used to develop the load Gow calculation E-90 5 i aas a F
limit on the number of nodes allowed for use in the calculation. As a result of j,
the software limitation, BG&E could not include all the motor power cables
- in the model.- The appraach taken by BG&E was to identify tue worst case condition with regard to motor loads. This was considered to be the longest cable runs to a number of motors.- It was recognized at the time of the review L
- of the calculation by the design review engineer, that the terminalvoltage of all safety related motors was r.ut modeled. However, given the limitations of the software, the approach taken was considered adequate.
BG&E concurs that the-originator and the design review engineer of the calculation did not consider the effects of increased currents resulting from decreased motor terminalvoltages. BG&E plans to develop new load flow E
studies as part of a master calculation concept to model the Calvert Cliffs t
E 2-
REPLYTO A NOTICE OF VIOLATION DSPECTION REPORT NOS. 50-317/92 R0 AND 50 318/92-80 VIOLATION NO.3 Nuclear Power Plant electrical auxiliary system. The master calculation will employ the CYME software The new load ilow calculations will model the safety related electrical system including the power cables to the associated motors.
In the view of BG&E, calculations E-90 24, E-90 28, E-90-31, and E-90-41 received an adequate resiew and verification. Each of these c;lcu!ations were independently reviewed in accordance with BG&E procedute DESP-6, Paragraph 6.1, C. of DESP-6, in part, requires tha" "The resiewer shall verify the accuracy of the calculation using either critical review of the calculatian including reasonableness of input, assumptions and results; alternate calculations; or qualification testing of design... The reviewer shall documen the calculation rcview, including any specific comments, using the Calculation Review Record (Attachment D).. "
Each of these calculations contained an executed Calculation Review Rcrord and the calculation cover sheet was signed in the appropriate place by t!e Riga review engineer. BG&E's review of these calculations subsequent to the ins, ction supports the validity of the original assumptions and has been discussed in our lew :tated July 8,1992. We therefore request that NRC reconsiders these illustrations as examples of the cited violation.
With regard to the balance of the assumptions: starting and running values of motor torque are the same, and 460V running mitages were less than the required 90re of rated nameplate _ rating; both of these assumpticas are contained in calculation E-9216. An adequate review of this calculation was not performed by BG&E. Sufficient documentation supporting the assumptions contained within this calculation were not provided. The reason for the inadequate review is personnel error and not suffi:icntly following established BG&E procedures.
Starting and running values of motor torque are ti same Generally it is a conservative assumption to consider starting torque equal to running torque, where the value of running torque is greater than starting torque. The BG&E reviewer knew Charging Pump 13 was a__ positive displacement pump but did not realize that the pump n6ator had a gear box.
The assumption that starting torque equaled runmng torque with a motor with a gear box was, therefore, non-conservative.
460V running voltages were less than the required 90% of rated nameplate ruting The reviewer assessed the reasonableness of this assumption after a number of discussions with the external responsible design organization that developed the calculation.
Although - this assumption appears to be a reasonable conclusion of NEMA-MGl (i.e., that a sersice factor of 1.15 increases the current rating of the motor winding by 15%), the resiewer did not require that sufficient documentation be dc eloped in the form of references or development of equations as a proof to support the methodology employed.
3
REPLY TO A NOTICE OF VIOLATION INSPECrl'sN MEPOll NOS. 50-317/92 80 AND 50 318/92-80 VIOLATION NO,3 The two assumptions in Calculation E-9216 discussed above did result in erroneous inputs to calculations. However, they were not caused by a lack of means to verify or check the adequacy of design. Rather they resulted from a failure to properly follow procedures: the first case involved the failure to verify the reasonableness of input and assumptions; the second case involved the failure to document the justification for assuniptions.
Nonetheless, as part of our design basis recompilation program, most of the original plant electrical calculations have been redone in much greater detail. However, given the content of the original calculations and plant design which serve as the starting noint for our effort, all of the information required to make a calculation may not be availev.,. rd usumptions must be made. 'These assumptions are clearly identiGed and supported by the best information available at the.ime of the calculation. As the design basis process progresses and additional information is discovered, these assumptions will be refined or eliminated.
(11) 1.
DESCillirrlON OF VIDIATION The second example regards the translation of design requirements into test acceptance criteria and the apparent failure to include instrument uncertainties into these critcria.
Criterion III states that, *The design control measures shall provide for venfying or checking the adequacy of design, such as by the performance of design revicws,.. or by the performance of a suitable testing program.
Design control measures shall be applied to items such as the following:
.. delineation of acceptance criteria for irapections and tests." Specifically, the Notice of Violation states that, "the design documents E-90-31 and E-6713 for degraded bus protection and E-88-15 and E-90 39 for diesel generator loading calculation were nct verified or checked properly to ensure that test criteria are developed correctly with instrument inaccuracies, tolerances and errors. Furthermore, the licensee's ' master calibration data sheets' record the various meter tolerances. This has not been factored into any engineering calculations includmg the above."
11.
ItEASON FOlt V101ATION BG&E has reviewed the cited violation and the requirements of 10 CFR Part 50 Appendix B, Criterion III, and we contend that no violation exists.
Criterion 111 addresses tests in two contexts. First,in specifying the acceptable means of verifying the adequacy of design, performance of a suitable testing program is one alternative listed.
The-design of diesel generator loading and degraded bus protection cited in the violation do not fit into this category, as the method used for verifying their design adequacy was performance of design reviews. another of Criterion Ill's listed alternatives.
The final sentence of Criterion lit specifies that " design contrch measures shall be applied to items such as.. delineation of criteria for inspections and tests." BG&E does accomplish applicod of design control measures to specify test acceptance t
4 l
REPIN TO A NOTICE OF VIO1ATION jfMPECTION REIM)l!T NOS,50-317/92-80.A.N6 50-318/92-80 VIOLATION NO,3 criteria through its test procedure control process. Design enginecting input is obtained in developing equipment tests, and changes to test pmcedures are reviewed by the Responsible Design Organization under the criteria of 10 CFR 50.59. No j
instances were identified where design control measures were not applied.
)
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The substance of the alleged violation, then, is that the inspectors disagreed with the specific design values used in BG&E's tests. Their contention is that tests must j
accomm(xiate the full range of conservatisms used in the design assumptions and must in addition provide further margin to compensate for the instrument accuracy used in the test. BG&E disagrees with this contention.
In considering whether to apply instrument accuracy to electrical test acceptance criteria, BG&E has considered the existing regulatory guidance. No regulatory guidance specific to the treatment of instrument accuracies is cited in the Notice of Violation, and we are aware of none which relates to the issues cited in the violation.
J l
Regulatory guidance regarding instrument uncertainties does exist for Limiting Safety j
System Settings (LSSS) as defined in 10 CFR 50.36(c)(1)(ii)(A). This is appropriate considering the elevated safety significance of these parameters and the degree of i
precision associatcd with this instrumentation.
In these instances, instrument inaccuracy can be a substantial portion of the total design uncertainty, and it is prudent to consider it. The LSSSs for Calvert Cliffs are contained in Technical Specification Table 2.21, This table does not include electrical system parameters and specifically docs not include the par:* meters associated with the systems and components cited in the violation.
Our approach in using nominal values as test setpoints is prudent for the types of major electrical equipment discussed in this violation. Large electrical eqdpment such as breakers, motors, and diesel generators are built with considerable margin to allow for the inherent deviation in bus conductivity, dimensional tolerances, spring tension, etc.
The degree of precision is substentially less than that of the LSSS-related equipment. Industry experience with electrical equipment supports this, as observed moderate beyond specification occurrences have not caused l
equipment failure and detailed calculations, when feasible, have shown substantial L
conservatisms.
We acknowledge that the design margins of our EDG capacity and degraded grid voltage protection do not afford the degree of conservatism typical of our design. We have committed substantial efforts to mad;fymr plant equipment to improve these margins. As described in Reference (b), we are enmmit ed to installing two new 5000 kW Class lE EDGs to complement our existing onsiw rapability. In addition, pursuant to the future addition of an additional 500 kV connection to the sim we are l
evaluating the addition of voltage regulating equipment which will improve our l
protection against potential degraded grid voltage conditions. We' ;cvc these l-efforts will effectively improve the safety of the systems addressed in this alleged violation. Those actions, not revised design standards for equipment test setpoints, are the correct focus of the technical concern.
In summary, BG&E finds no specific regulatory guidance which supports the purported requirement to include instrument tolerance in the testing of EDG loading or degraded grid valtage protection. We believe our existing practice is adequately 5
REPIN TO A NOTICE OF VIOLATION INSPECTION REPORT NOS. 50-317/92 80 AND 50-318/92 80 VIOLATION NO.3 controlled and technically prudent. We have verified that our approach is consistent with -industry practice.
We consider that imposition of the interpretation of CriterionIII contained in this alleged violation would constitute a new regulatory requirement on BG&E and other utilities. Finally, we believe that the physical modifications already planned substantiaPy improve the design margins which caused
- this issue to be raised.
III.
CORRECTIVE STEPS TAKEN AND RESULTS AClllEVED A.
- Corrective actions to resolve the assumptions contained within E-9216 as well as
- other questions raised by the inspection team c<mccrning this calculation are contained within the BG&E response to the four issues requiring expedited review and resolution, dated July 8,1992. Tnere actions include enhancements to the offsite supply improving the reliability of the preferred supply to the safety related system, a number of new studies and analyses, and performance of tests on MCC contactor coils to verify their withstand capabilities. Calculation E-9216 will be reassessed and corrected appropriately.
In addition, new analyses are being developed employing a Master Calculation concept using CYME software. The new analyses will include new load flow
. calculations which will model the safety related electrical system including the power cables to the asociated motors.
.B.
No corrective action is necessary.
IV.
CORRECTIVE -- ACTIONS WillCil M1LL llE TAKEN TO AVOID FURTIIER
- VIDIATIONS :
A.:
Training _will be provided to.the appropriate BG&E oiganizations regarding the
- responsibilities of-a design originator and a design review engineer and the lessons
~
- learned from this issue.
B.
No corrective action is necessary.
- V. --
DATE WIIEN FULL COMPLIANCE WILL llE ACillEVED -
A.
Training of appropriate BG&E organizations will be completc October 15,1992.
B.:
Full compliance with NRC requirements has been maintained.
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