ML20080G188
| ML20080G188 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 02/06/1984 |
| From: | Zimmerman S CAROLINA POWER & LIGHT CO. |
| To: | Vassallo D Office of Nuclear Reactor Regulation |
| References | |
| NLS-84-051, NLS-84-51, NUDOCS 8402130294 | |
| Download: ML20080G188 (11) | |
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O-CD&L SERIAL: NLS-84-051 Carolina Power & tight Company FEB 061984 Director of Nuclear Reactor Regulation At tention:
Mr. D. B.'Vassallo, Chief Operating. Reactors Branch No. 2 Division of Licensing United States Nuclear Regulatory Commission Washington, DC 20555 BRUNSWICK STEAM ELECTRIC PLANT, UNIT NOS.1 AND 2 DOCKET NOS.' 50-325 & 50-324/LlCENSE NOS. DPR-71 & DPR-62
. ELECTRICAL DISTRIBUTION SYSTEM VOLTAGES
Dear Mr. Vassallo:
In a [[letter::05000324/LER-1983-094-03, /03L-0:on 831102,control Rod 38-23 Did Not Have RTGB Position Indication at 12 & Control Rod 30-39 Did Not Have RTGB Position Indication at 04.Caused by Problems on Indication Reed Switch of Each Rod|letter dated November 30, 1983]] Carolina Power & Light Company (CP&L) committed to answer three remaining questions from your request for additional information dated September 1, 1983.
1hese responses are included herein as.
-However, an error has been discovered in our previous submittal as discussed below.- As part of this letter, CP&L would like to advise your of fice ' of this situation, provide our preliminary analysis of the error, and our schedule for resubmitting a revised analysis.
Because of anticipated load additions, CP&L initiated an ?ngineering study to determine whether additional auxiliary capacity would require adding new transformers or.whether existing equipment'could handle the increased load.
-Preparation of data included a review of the transmission system characteristics..This review has uncovered an error in the data supplied to -
United Engineering & Constructors (UE&C) for the degraded grid voltage analysis. Specifically, it was determined that the worst case minimum grid voltage was actually. lower than that orginally supplied to UE&C.
An'assessme'nt of the_ impact of this error has been completed. Although the circuit. design will not meet the 2X LOCA scenario as defined in our original submittal, it has been concluded that the current plant design is capable of meeting worst case design scenarios required by current regulations.
-Attachment 2 provides a more detailed discussion of this matter including impacts on the results of our previously submitted analysis. Attachment 3
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-details our evaluation of the regulatory requirements as they pertain to worst
- case design scenarios for the degraded voltage study.
8402130294 840206 PDR ADOCK 05000324 P
PDR O
411 Fayettevine Street
- P. O. Box 1551
- Raleigh, N. C. 27602 s
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A new analyses to replace 'our earlier degraded voltage submittals will be
' transmitted to the NRC by August 31,-1984j] Should you have any questions
- concerning this letter please do not hesitate to contact a member of out.
Licensing Staff.
Yours.very'truly,
- ^^ ^
.S.
immerman nagee Nuclear Licensing Section
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Itc. D. O. Myers ' (NRO-BSEP).
Mr. J. P._O'Reilly (NRC-Ril)
Mr. M. Crotenhuis.(NRC) l M
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J, At tactinent 1 Letter NLS-84-051 February 1, 1984 Answers to Request for Additional Information Dated September 1, 1983 Question 7, 8, and 9 I
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IThe following items' are to clarify the referenced letter, enclosurs 3.
Question 7'
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Wh'at' was the grid voltage f or both the test measurements and test anlaysis?
Response
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,Eie grid voltage was measured by Gould Brush 260 recorder, and the value was
-constant at 230 Kv during-the site test. The same voltage was used as an 1
input data 'f or the test analysis.
Question 8-Account for the' difference between the " study voltage"' and the " test voltage" of Section 2.
In some cases the difference is greater than 4%.
Re sponse.
The summary off results of Section 2.0 shows that most of the testing voltages closely approach the study voltages obtained from UE&C " Volt Program." The deviations between test-and study-voltages 'are within the
- tolerance of the recording instrument, excepting the following two cases:
a)
EBus 2E and 2F' (Max:
-3.68%) - CWP Start -
The high % errors greater than instrument tolerance are mainly attributed to the f requent loading and unloading-of the station service air compressors..-These compressors fed from bus 2E and 2F caused the test voltage to vary and an accurate measuring was impractical.
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- b)
MCC 2PB-(Max: +3.51%) - SWP. Start
. Starting of SWPfmotor'is represented by an estimated admittance as
'shown on study model Figure 4, Site Test Voltage Study Report, revision 2.
The study voltage (442 V) at MCC 2PB was calculated based on the
= estimated input-data - motor admittance.
The site test-v'ltage varied at the transient state when motor started, o
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i.e., it' dipped to 427.V and recovered to 473 V with no time delay (instantaneously).
The'.high' % difference (+3.51%) concerned was calculated using the conservative input data (427 V - min); however, it will be improved to
-1.7% when taking mean value (450 V = 427 + 473 -- 427).
2
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- Total' instrument loop error (%)
'.(PT' error).x (RMS error) x -(recorder error)
=
'= 1.006:x 1.01~x-1/0035 = + 2%.
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Question 9 Demonstrate that the test measurements and test analysis were for identical station electrical loading.
Response
- The BOP and emergency bus loads were fed from the startup transformer No. 2.
At the time of the test, the power generator was 40% of the rated capacity of
.each unit and the following major loads were running:
1.
Bus 2B - Reactor Recirculating Water Pumps 2A and 2B 2.
Bus 2C - Circulating Water Pump 2C, Condensate Booster Pump 2A, Heater Drain-Pump 2B, Condensate Pump 2A 3.
Bus 2D - Circulating Water Pump 2D, Condensate Booster Pump 2C, Heater Drain Pump 2C, Condensate Pumps 2C, Chillers 2A 4.
Bus E3 - Control Rod Drive Hydraulic Pump 2A, Nuclear Service Water Pump 2A, Conventional Service Water Pump 2A 5.
Bus E4 - Nuclear Service Water Pumps 2B, Conventional Service Water Pumps 2B-6.-
Bue Common B - Turbine Building Cooling Tower Pumps 2A and 2B 7.
Bus E7 -Reactor Building Closed Cooling Water Pumps 2A and 2C, Reactor Building Supply Fans 2A and 2C, Reactor Building Exhaust Fans 2A and 2C 8.
. Bus E8 - Reactor Building Exhaust Fans 2B 9.
xBus 2E - Turbine Building Closed Cooling Water Pump 2A, Turbine Building Supply Fans 2C, Turbine Building Exhaust Fans 2A and 2C 10.
Bus 2F - Turbine Building Closed Cooling Water Pumps 2C, Turbine Building Supply Fans 2B and 2D, Turbine Building Exhaust Fans 2B The above station loads were measured at the same time (15:48 p.m.,
December 12, 1980) at various locations as shown on Sketch 1.
For test analysis, megawatts were taken directly from site test data and megavars were computed (see Appendix A of the study report) from megawatt, voltage, and current data with the exception of motor starting loads noted in Response 8.
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f Attachnent II Letter NLS-84-051 1
February 1,19h4 Description of Problem 2
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t Description of Problem As a result of. a study conducted by CP&L's corporate engineering group (NELD) it has been determined th'at UE6C's voltage drop study was based on information
' provided by CP&L which showed that for a proposed 2X LOCA, the switchyard voltage would drop to no less than 0.96 pu.
Using this 0.96 pu for the worst
-case.for source voltage, UE&C's computer model and study concluded that BSEP was adequately designed to handle the 2X LOCA. However, the NELD study's l preliminary results (based on existing current available transmission system data):showed that the switchyard voltage at BSEP could actually drop lower than the 0.96 pu in the 2X LOCA scenario.
Further review revealed that BSEP has no regulatory commitments for degraded
- grid voltage to meet the 2X LOCA accident scenario effects for off-site
.' power. The evaluation of applicable regulatory requirements (see attachment 3) revealed that'BSEP is actually required to demonstrate adequate
- grid voltage in the case of LOCA on one unit with a controlled shutdown of the other unit.
In fact, however, the situation where one-unit is already shutdown and a LOCA occurs on the operating unit is a more limiting case with respect to degraded voltage at BSEP. As such, NELD's preliminary study was based on this more conservative scenario. Results of this preliminary study indicate that BSEP is currently able to handle this more conservative scenario satisfactorily.
- The ' comparison between the preliminary NELD valtage drop study and the UE&C voltage drop study also identified two less significant items.
First, since the UE&C study, larger Circulating Water Intake Pump (CWIP)
~ induction motors.have beenLinstalled.. As such, the running loads and starting : currents were not a part of the UE6C study.
In addition, the starting 'of a fourth CWIP with three already running was not analyzed in the NELD study. The NELD study did not include the starting of a fourth pump since our National Pollutant Discharge Elimination System (NPDES) permit normally limits circulating water flow to two pumps in the winter and three pumps in,the-summer. There are, however, provisions in the permit which do permit occasional starting of a fourth pump under certain conditions.
Since definite operator action is required to start the fourth pump, CP&L believes the potential.for a fourth pump start during a LOCA is extremely remote.
Addit.onally, the NELD study assumes the existance of the large loads of the radwaste crystallizer heaters which have not been installed. With these conservatisms, NELD's study shows that the starting of a third CWIP (with two already running) is acceptable from a degraded voltage standpoint.
In summary, the low probability of an operator taking action to start a fourth CWIP.during a LOCA, the margin added by the assumption of additional electrical loads that do not exist, and the satisfactory results of the
. starting of a third CWIP provide reasonable assurance that BSEP will satisfactorily meet. the 'NRC's published guidelines for degraded grid voltage.
Second, an updated 208/120 voltage study was not included in the NELD's
. preliminary study. A review of the UE&C study showed that there were no problems with the 208/120 systems under their 2X LOCA scenario. The 480 VAC bus f voltages were compared between the UE&C and NELD studies. The NELD study 480 'VAC results were higher than the UE&C 480 VAC results. Consequently, F-(1)
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the 208/120 VAC bus degraded voltage ' effects are judged to be acceptable.
Additionally, the 208/120 VAC analysis will be included in tha final NELD voltage drop-study.
The.necessary modification to the NELD computer model to address the identified discrepancies are in progress.
Final revisions to and reviews of the BSEP degraded voltage studies are currently scheduled for July 1984 with
. final submittal to NRC scheduled for August 31, 1984.
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I At tachment III Letter NLS-84-051 February 1, 1984 Regulatory Requirements e
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iWith regard to the" regulatory' design ~ requirement for 2X LOCA or 1X LOCA plus
' shutdown of - the other unit, the f ollowing. comments are pertinent.
. General' Design Criteria 5, in Appendix A of _10 CFR 50, states -in-part i
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.that systems important to. safety shall'not be shared unless such sharing "will notfsignificantly impair their ability to perform their safety functions, including, in the event of an accident in one unit, an' orderly-shutdown and cooldown of the remaining unit".
(Emphasis added) y
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Regulatory - Guide 1.81,.Re' vision 1, January 1975, Shared Emergency and Shutdown Electric Systems for Multi-Unit Nuclear Power Plants, states E'
in part:- "The staff has_ determined that, because of the low probability of a major reactor accident, a suitable design basis for multi-unit nuclear power plants ie~the assumption that an accident occurs in only one of the units at a time, with all other remaining units proceeding to-an orderly shutdown and a maintained cooldown condition".
(Emphasis added) 13)'
IEEE Standasd 308-1971,' paragraph 8.1.1, states in part, "A multi-unit In station may', share' preferred power supply capacity between units..
such a case ' as a minimum' the total preferred capacity be sufficient to
. operate the engineering safety-features for a design basis accident on g
one unit -and those' systems required for concurrent safe shutdown on the l
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' remaining units." (Emphasis Added)
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Section' 8 'of the BSEP FSAR, (original) Electrical Power System, states that the " plant electrical distribution system has been designed in accordance with the guidelines'as outlined in IEEE Standard 308-1971 5)
Section 8.7.5 of the original BSEP FSAR, states that the switchyard is designed to supply power for "a unit in a' design-basis accident
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- condition.while supplying the' auxiliary power _ requirements f or shutdown
.of:the.other unit".
This' basis requirement is restated for.other
- portions of the electrical ~ system 'in paragraph 8.10.5.2.
qUs'ing generslly accepted terms, controlled orderly shutdown ~ implies time is
[permitteduto}take necessary' compensating actions on the transmission grid
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prior to unloading;the generation and rod insertion, etc.-
Additionally, unanticipated tripping of ~ generators and plant scrams are generally referred to as'" trips" and " scrams".
Based on-the above, it may be concluded that
_1) there is no. design.or ' regulatory requirement f or the 2X LOCA, or LOCA on one. unit with a simultaneously uncontrolled loss of output for the second unit fand that 2) the regulatory design basis.of the plant is a design basis accident _(LOCA) on_one plant-with a controlled, orderly shutdown of the remaining unit.
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