ML20087E477
| ML20087E477 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 01/16/1992 |
| From: | Kovach T COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9201210257 | |
| Download: ML20087E477 (22) | |
Text
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- Chmm:n :calth Edistn t
r / 1400 Opus PIIce 1 Downsrs Grova, Illinois 60$15 January 16,1992 U.S. Nuclear R'egulatory Commission Attn: Document Control Desk-
_ Washington, DC 20555
Subject:
LaSalle County Nuclear Station UniS 1 ano 2 Response te Notice c1 Violation Inspection Report Nos. 5C1373/91019; 50-374/91019
- NRC Docket Nos. 50-373 and 50-374
Reference:
~ Brent Clayton letter to Cordell Reed dated 1
December 13,1991 transmitting NRO Inspection
. Report 50 373/91013; 50 374/91019
- Enclosed is Comneonwealth Edison Company's (CECO) rut,ponse to the subject Electrical Distribution Syc,!em Functionn! Inspection (EDSFl) Report svhich was transmitted with the referenced letter. The inspection Report cited two Level IV u.
-violations,4 deviations,2 unresolved items, and 2 opn items. CECO's response to these items is provided in Attachments A, B, C and 0 respectively, if your steff has any questions or comments concerning this letter, please refer them to Annette Denenberg, Compliance Engineer at (708) 515-7352.
l -
Very truly yours,
/;
e
<. Ko h
o Nuclear Lice' y g Manager Attachment cc:
A. Bert Davis, NRC Regional Administrator - Rill
- Bc Siegel,- Project Manager - NRR u
-T. Tongue, Senior Resident inspector Z. Falevits ' Rill-9201210257 920116 PDR ADOCK 05000373 Q-PDR s
- ZNLD/1406/1 :
/
y s
- 210028
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ATTACHMDIT A I
RESPONSE TO LEVEL IV VIOLATION INSPECTION REPORT 50-373/91019,50 374/91010 VIOLATION: IR 373/91019-01 A 10CFR50, Ap3endix B, Crherion XI, states that,"A test program shall be established to assure that al testing required to demonstrate that structures, systems, and components will perform satisfactorily in service is identified and performed in accordance with written test procedures which incorporate the requirements and acceptance limits contained in applicable design documents.... Test resuas shall be documented and evaluated to assure that test requirements have been satisflod."
Contrary to the above, prior to October 22,1991, the licensee 3erformed an instantaneous trip test on five 480Vac safety related air circuit areakers using a trip current of 20 to 40 times the normal current rating of the breaker trip coll, rather than the maximum 15 times specified by the vendor.
This is a Severity Level IV violation (Supplement 1).
REASON FOR THE VIOLATION:
CECO agrees that this is a violation. Originally, values of current were provided to LaSalle County Station which were designated as Test Currents. These values were typically four times the actual trip setting so that repeatability of trip times would be assured. These test currents sometimes exceeded the rating of the trip coil by greater than 20 times.
The largest test current used was 40 times the rating of the coll. The limit of 20 times the coil rating was not available to the Station via vendor published maintenance information. Th s value has since been given by the Manufacturer as an upper limit (not 15 as specified in the NOV),
CORRECTIVE S.EPS THAT HAVE BEEN TAKEN AND RESULTS ACHIEVED:
All in-service safety related breakers wnich had been tested with elevated currents were retested to assure that the breakers were not damaged by the elevated currents.
Testing of these breakers was completed on November 7,1991. None of the breakers had any signs of damage as a result of the elevated currevnt levels.
CORRECT 1VE STEPS THAT WILL BE TAKEN TO AVOID FURTHER VIOLATIONS:
Station procedures have been revised to ensure that the limit of 20 times the coil rating is not exceeded.
DATE WHEN FULL COMPLIANCE WILL BE ACHIEVED:
Full compilance was achieved on November 7,1991.
4 ZNLD/1436/2
ATTACHMENT A RESPONSE TO LEVEL IV VIOLATION INSPECTION REPORT 50-373/91019;50 374/91019 VIOLATION: IR 50-373/91019-01B 10CFR50, Ap aendix B, Criterion XI, states that, "A test program shall be established to assure that al testing required to demorstrate that structures, systemc, and components will perform satisfactorily in service is identified and performed in accordance with written test procedures which incorporate the requirements and acceptance limits centained in applicable design documents.... Test results shall be documented and evaluated to assure that test requirements have been satisfied."
Contrary to the above, prior to October 24,1991, the licenese failed to include safety related relays K-32, K-33, and K-39 in the Station's calibration program.
This is a Severity Level IV violation (supplement 1)
REASON FOR THE VIOLATION:
CECO agrees that this is a violation. Presently, LaSalle County Station does not check timing relays to verify settings. The station does however utilize both logic test and functional tests on safety-related systems to ensure that the system and its associated components (including time delay relays)iming relays are calibrated to ensure tha perform their intended function. When required by the Technical Specification, t specified time delay will occur in a predetermined interval. These tests are pe, formed per planned surveillance rec ulrements on a periodic basis and documentation is cbtained to show that the re ays and other components functioned as designed in their respected circuits.
CORRECTIVE STEPS THAT HAVE BEEN TAKEN AND RESULTS ACHIEVED:
The identified relays have not had the time delays verified; 'nowever, they have been and are being tested under the existing surveillance program. This testing is comprised of monthly, semi-annual, and refueling tests. While rat Individually timed during these tests, the relays are functionally tested to assure compliance with the Technica Specifications. Thus, although the time delays have not been verified, the overaillogic requirements have been met, and future testing will be incorporated in the calibration program described below. Therefore, the safety significance is minimal.
CORRECTIVE STEPS THAT WILL BE TAKEN TO AVOID FURTHER VIOLATIONS:
LaSalle Station will review Station electrical desig-
.mngs to identify timing relays for which the time delay performs a function that is important to the safety of the plant.
After this review is completed, a calibration program will be designed and imalemented to further ensure the proper performance of the relays. It is expected that th s program will be developed by March 31,1993 and start implementation at the first refueling outage thereaf ter.
DATE WHEN FULL COMPLIANCE WILL BE ACHIEVED:
Full comp! lance will be achieved prior to startup following the completion of the second lefueling outage, for each unit, after March 31,1993.
ZNLD/1436/3
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ATTACHMENT A RESPONSE TO LEVEL IV VIOLATION INSPECTION REPORT 50 373/91019;50-374/91019 VIOLATION: IR 50-373/91019-07 LaSalle Technical Specification 4.8.1.1.2.d.4 (applicable to both Unit 1 and Unit 2) requires verifying the de energization of the emergency busses in response to a
' simulated loss of offsite power.
i Contrary to the above, from initial operation through November 8,1991, the licensee falled to demonstrate the capability of the loss of offsite power undervoltage relay logic circuitry to automatically de energize the emergency busses for both units.
This is a Severity Level IV violation (Supplement I).
REASON FOR THE VIOLATION:
' CECO agrees that this is a violation. During the EDSFI, the NRC team members discovered that two contacts in the undervoltage trip logic (which automatically -
de-energize the emergency busses for both units) had not been tested during or since the first refueling outage on Unit 1 and Unit 2 at LaSalle County Station. These contacts had been tested during the initial preoperational testing and th'.,refore compliance was maintained through the first cycle of operation on each unit. In each case, the contacts are required to close in order to initiate the trip logic. Although the operation of these contacts had not been tested, the relay itself, including other contacts on the relay, was testec; every 18 months. Subsequent testing of the identified contacts determined they all function properly, therefore the safety significance was minimal.
The reason for falling to perform the surveillance is that the contact test steps were not included in the original writing of the surveillance due to an oversight.
CORRECTIVE STEPS THAT HAVE BEEN TAKEN AND RESULTS ACHIEVED:
On November 7,1991 at 3:00 pm, upon confirraation that the contacts had not been tested by existing station procedures, a procedure was generated to assure that these E
contacts still performed their intended functions. This test was completed satisfactorily at 10:30 am on November 8,1991.
. CORRECTIVE STEPS THAT WILL BE TAKEN TO AVOID FURTHER VIOLATIONS:
All of the procedures needing this correction have been identified and will be revised by their next required use or 9/9/92, whichever comes first.
Prior to this discovery, LaSalle County Station had been in the process of reviewing bids for a Safety Related contact testing assurance program. This program is being developed to ensure that all relays / contacts which are assumed to be tested to comply with Technical Specifications, are in fact tested by station procedures. This program will be utilized to assure that no further violations occur due to untested contacts. This effort is expected to be completed by May 31,1994, DATE WHEN FULL COMPLIANCE WILL BE ACHIEVED:
Full compliance was achieved November 8,1991.
ZNLD/1436/4
a n
A3TAQMENT B RESPONSE TO DEVIATION (373/91019-05 A(DRS);374/91019_ 05 A (DRS))
I STARTING VOLTAGES AT SAFETY RELATED MOTORS' Descrintion of Condition The team noted that the design documentation for the majority of 4 kV and 480 VAC
' safety related motors specified that the motor starting voltage must be at least 80% of nominal voltage. This is contrary to UFSAR Section 8.2.3.2.2 which states that all safety related motors are upable of startiiig with voltage at their terminals equal to 75% of the
- nominal values. Inadequate motor starting voltages could prevent the motors from -
J performing their safety functions. The licensee acknowledged this concern and indicated
- that this issue would be addwssed ri part of the ongoing degraded voltage reviews being conducted at Commonwealth Edison facilities
The team considered the'80% motor starting voltage requirement for safety related motors to be.a deviation (373/91019-05A(DRS); 374/91019-05A(DRS)) from the commitment
- made in UFSAR Section 8.2.3.2,2.
c Brotis As acknowledged during the EDSF1 audit, insuffic ent documentation exists to demonstrate nat most safety related moten are capable of starting at_a terminal voltage of 75%'of rr ted voltage. In addition, our investigation of this issue concluded that the safety relaicd moters at LaSalle were not required to meet this specification. The 4 kV and 460 VAC ESF motors for LaSalle were originally specified in accordance with Sargent and
~ Lundy (S&L) Standard Specifications for Alternating Current Motors Constant Speed, Squirrel-Cage Type, Form.1800 - This specification contained the following requirements on motor terminal voltage:s
'1.
Motors shall deliver their rated horsepower continuously without damage, when the -
voltage at the :nninals is 10% above or below rated voltage, with rated frequency.
- 2.. - Mo' ors shall deliver their rated full load torque without damage when the voltage at t
thi terminals drops t'o 75 % of rated voltage for infrequent one-minute intervals.
Them regiremer,ts were in accordance with the industry standards (i.e., NEMA MG-1) that existed during the design of LaSalle. Furthermore, no industry standards existed
+
L--L.'---~-- - - --
o, ATTACHMENT B during the design of LaSalle that provided additional guidelines ca motor starting voltages other than those requirements already included in S&L Fcrm 1800. Thus, we believe that the 75% starting voltage requirement contained in UFSAR Section 8.2.3.2.2 was incorrectly derived from the second Form 1800 requirement noted above. This deviation from the UFSAR commitment does not represent a safety issue because the LaSalle auxiliary power system was not designed assuming that any safety related continuous duty motors were able to start with 75% rated voltage applied to their terminals. The LaSalle auxiliary power system was designed to provide adequate starting and running
- voltages to all safety related loads at the minimum expected switchyard voltage. At the minimum expected switchyard voltage, S&L Calculation 4266/19AZ13 indicates that the starting voltage available at the terminals of the continuous duty, safety related motors will be greater than 80% of metor rated voltage.
In addition, the preliminary calculations that were performed to verify the adequacy of the original degraded voltage setpoint (3814 +/- 76 volts) conservatively used 85% of motor
. rated voltage as the minimum acceptable starting voltage for all 4 kV and 460 VAC safety related continuous duty motors (see S&L Calculation 4266/19AZ13). Based on these calculations we implemented compensatory measures to ensure that all safety related motors would have adequate starting voltages (see CECO letter dated October 2,1991).
An acceptance criteria of 85% of motor rated voltage for the starting voltage is conservative for the following reasons:
1.-
ANSI Standard C50.41-1982, Polyphase It Juction Motors for Power Generating Stations, requires that medium voltage (4 kV) motors rated 250 hp and above be
- capable of starting at a terminal voltage of at least 85% of motor rated voltage.
Although this standard was not issued until after the design for LaSalle was
, completed, the design documentation indicates that the 4 kV motors at LaSalle can start with 80% rated voltage at their terminals.
2.
Although there are still no industry standards that provide starting voltage guidelines for low voltage (460 V) motors, the 460 V motors at LaSalle will be able to start at a terminal voltage equal to 65 % of rated. These motors were specified as NEMA Design B motors and, depending on the size of the load, have a breakaway (starting) torque requirement that varies from_35% to 85% of fullload torque. In fact, most of the mechanical loads have a breakaway (starting) torque that is less than 35% of fullload torque, Per NEMA Tables MGl-12.37 and MGi-12.38 which provide starting and breakdown torque requirements for low voltage motors, an induction motor which can produce at rated voltage a starting torque equal to 100% of running torque will produce at 80% rated voltage a starting torque equal to 64% of running torque.
This UFS AR deviation will be resolved when the study for the long term solutions for
- r. _
a.,-
' ATTACHMENT B degraded voltage is completed per the schedule provided in our response to unresolved item (373/91019-06(DRS); 374/91019-06(DRS). This study will identify the actual minimum acceptable starting voltage for all safety related motors, and if this value is different from the starting voltage requirement specified in UFSAR Section 8.2.3 2.2, a revision to the UFSAR will be initiated.
4 1
A e
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ATTAC!: MENT B
--Description of Condition The team noted that the loading calculation for EDG 2A identified a continuous loading value of 2727kW. This is contrary to UFSAR Table 8.3-1 which states that the continuous loading on EDG 2A is 2627 kW.
The team pointed out that the actual EDG 2A loading may be higher than 2727 kW since the existing loading calcuhtion did not account for all EDG losses such as eatle losses. The team considered the identified 2727 kW loading of-EDG 2A to be a deviation from the commitment made in UFSAR Table 8.3-1.
Response
The problem identified by the team is one of document update. The UFSAR Table revision for EDG 2A loading was submitted on September 23,1991 to BWR Systems Engineering by Sargent and Lundy, as a result of a review performed as an SSFI commitment. When subrequently sent to the Station for comment, several changes were requested, which resulted.in additional revision to calculation 4266/19AKl9. These revisions are new in progress. Upon completion, these revisions will be incorporated into the annual UFSAR update, i-L a(
p
m ATTACHMENT B
- RESPONSE TO DEVIATION (373/91019-05D(DRS);374/91019-05D(DRS))
' DEGRADED VOLTAGE SETPOINT METIlODOLOGY l
(
Dncription of Condition The team determined that the setpoints for the degraded voltage protection relays contained in Table 3.3.3-2 of the Technical Specifications were not based on a setpoint methodology that addrersed all known errors associated with this instrument. The licensee, in response to FSAR Question Q31.159, committed to address instrument-accuracy, calibration,' and drift allowance.
Technical Specification Table 3.3.3 2, Trip Function D.2.a requi es 3814 +/- 76_ volts.-- The team's review of historical as-left and as-found data indicated that these relays had drifted -
- as much as -94.5 volts over a 4 month period which exceeded the +/- 76 volt T~:hnical -
Specification allowance. ;Sargent and Lundy Calculation'4266/19AN15 also indicated an :
accuracy of +42 volts is typical for the potential tran? formers associated with the degraded voltage protection. Additionally, the relay manufactmer and Sargent and Lundy.
g identified other relay tolerances'that could add another +/- 38.5 volts to the actual setpoint..
- Since the maximum deviation of +/- 76 volts allowed by the Technical Specifications is not large enough to account for these errors and the licensee lacks a setpoint methodology to establish a setpoint with all known errors included, the relays'may not detect degraded
- voltage conditions and transfer safety loads to the emergency diesel gamerators at a -
voltage level adequate to ensure proper safety equipment performance or to prevent -
safety equipment damage; The team considered this to be an example of a deviation (373/91019-05D(DRS); 374/91019-_0$D(DRS)) from the commitment made in response to -
lFSAR Question Q31.159.-
lResoense _
- The original analysis for the degraded voltage setpoint determined that the minimum
' allowkble voltage on the 4 kV busses was approximately 3740 volts.- The trip setpoint was
- set about 2% above this value at 3814 volts to account for instrument errors. Howev::r, a
~ formal setpoint calculation ;was~ not performed to establish the trip setpoint because we did
- not believe that the commitment made in response to FSAR Question Q31.159 applied to j
auxiliary power system relays. We believed that the commitment to r/idress all known i
i ATTAC"'iENT B 4
instrument errots such as instrument accuracy, calibratien, and drift allowance, in
)
determining the setpoint applied only to mstrumer.ts in the reactor protection, isolation j
actuation, ECCS, and control rod block systems.
Based on the preliminary calculations thht were performed to verify the adequacy of the l
original degraded voltage setpoint (3814 +/- 76 velts), Engineering recommended in a letter dated October 2,1991, (ref.1) that the trip setpoint for the ESF Division 1 and 2 j
degraded voltage relays be increased to 3885 +/- 5 volts to protect all running motors.
The desy,a basis for this setting is contained in S&L Calculation 4266/19AZ13 (ref, 2).
The trip setpoint for the ESF Division 3' degraded voltage relays did not need to be j
changed. In'our discussions with the NRC during the EDSFI inspection, v,e indicated that
= the revised degraded voltage se' point of 3885 volts was conservative and did not include any instrumentation errors slacc the upper Technical Specification limit for this parameter eis 3890 volts (3814 + 76V).
Subsequent to our discussions with the NRC, we have perfoimed additional evaluations to determine the ir.nact of instrument error on the operation of safety related equipment and to expand the calibration setpoint tolerances for these relays. These analyses confirm that a setpoint of 3885 V is conservative.
Per references 3,4, and 5 Engineering increased the setpoint tolerances for the degraded voltage relays from 3885 +/- 5 volts to 3885 +5, -25 olts because the station indicated that these relays could not easily be calibrated to trip within the setpoint tolerances specified in reference 1, Our analysis' concluded that the lowest calibratico setting of 3860 volts (3885 - 2') would not impact the qqalified Hfe of continuously operating motors.
Reference 6 analyzed the affect of an instrument error of 40 volts (1.14 volts on the secondary side) on the operaticn of safety related equipment. While this value may not -
include all instrument errors associated with the degraded voltage relays, it does include the effect of repeatability, control voltage input variations, and temperature variations. To perform this analysis, voltage settings of 40 volts below the mini num allowable calibration setpoint of 3860 V and 40 volts above the maximum allowable calibration setpoint of 3890 V were evaluated. This analysis concluded that a drift in the setpoint of 40 volts in either direction ~will not degrade the level of protection.
A degraded voltage setpoint of 3820 volts (3860 - 40) will not adversely affect the operation of.any running equipment either during normal operation or a LOCA. If the bus voltage drops to 3820 volts during normal operation, only five motors will have terminal
-voltages of less than 90%, and minimum terminal voltage will be equal to 89.4% of motor rated voltage. If the bus voltage drops to 3820 volts during a LOCA, the worst case motor wi'l have a terminal voltage of 88.6% of rated. This terminst voltage is accceptable because it will only result in a small temperature r'se in the motor. In addition. the duration L
Il
{
NITACHMENT 13 of the egosure will be limited because the bus will either be declared inoperable or transferred to the EDG if a LOCA exists before the voltage drops to this level. _
Although a setpoir.t of 3930 volts (3890 + 40) for the degraded voltage relays is above the maximum allowable Technical Specification limit for this parameter, it is not a safety concern. The minimum expected switchyard voltage is 352 kV, and this corresponds to a 4 kV bus _ voltage of approximately 3955 volts at the maximum expected loading (normal full power operation phis LOCA) on the system with all of the loads being supplied by the SAT, Thus, an upward drift of 40 volts for these relays will not cause any unnecessaiy H
transfers to the diesel generators.
i As part of the long term solution for degraded voltage, setpoint calculations will be performed for the permanent degraded voltage trip setpoint, and a Technical Specification change reqilest will be s ibmitted if necessary. These calculation will address L, loown errors associated with these instruments. The schedule for completing this actici is.
j provided in our response to unresolved item (373/19019-06(DRS);374/19019-06(DRS)).
)
- References-
- 1. CECO letter dated October 2,1991 (CHRON # 173799).
- 2. S&L Calculation 4266/19AZ13, Rev. O, dated October 7,1991.
- 3. S&L letter SCE-5334 dated October 19, 1991.
- 4. CECO letter dated October 28,1991 (CHRON # 174756).
- 5. C12Co letter dated October 31,1991 (CHRON # 175386).
- 6. S&L Calculation 4266/19AZl7, Rev. O, dated October 31.1991, with supplemental memo dated November 6,1991.
4 s
AIfACHMENT U RESPONSE TO DEVIATION (373/91019-05C(DRS); 374/91019-05C)
EDG fuel oil inutsfer and Storage Systems Description of Candition The team identified th:ee deviations from ANSI N195 for Units 1 and 2 EDG fuel oil transfer and storage systerns that are not listed in the UFSAR Section 9..' 4.2. He team identined the following deviations:
- 1. The fuel oil storage tanks ID002T and 2D002T (Units 1 and 2 HPCS) have permanent piped connections to the diesel fire pump day tanks (1/2FP0lTA). ANSI N195,
. however, states, " Permanent interconnections between
- fuel oil storage tanks and auxiliary equipment other than the standby power system (for example, heating boilers and engine-driven fire pumps) shall not be used".
- 2. The Division 3 diesel generator fuel oil storage requirement is calculated using the expected load profile without a 10% margin. ANSI N195, however, allows the option of calculating the fuel storage requirements by assuming 100% load continuously or
' expected load profile plus 10% margin.
- 3. The diesel generator fuel oil storage tanks have low
' level alarms,' but not high level alarms. ANSI N195, however, calls for low and high level alarms for fuel oil tanks. The fuel oil day tanks have both low level and high level alarms,
' Emponse
. In response to Item #1, the permanent connection of the diesel fire pump to the day tant is not safety significant. The HPCS diesel generator fuel oil stomge tank is s! zed to ha sufficient capacity to run the HPCS diesel-generator for seven days of conservatively L
.c 1
9 4
ATTACHMELEll estimated Division 3 loads following a Loss-of-Coolant Accident (LOCA) and loss of off-site power, A fire in the plant is not postulated in addition to the LOCA scenario. The diesel fire pump day tank contains useable fuel to run the fire pump for more than 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> and will only remove luct from the HPCS diesel generator fuel oil storage tank when the day tank level has reached the low level setpoint to run the transfer pump. The lito from the storage tanks to the diesel fire pump day tank each have two isolation valves which are operated by fail-close solenoids.
In response to Item #2, the Division 3 fuel oil storage requirement calculations did not include a 10% design margin which could result in a shortage of fuel if the calculation has minor inaccuracies or is outdated. The calculation incorporates conservative assumptio.1s throughout which provides for sufficient design margin to accommodate minor inaccuracies, These conservatisms include the HPCS pump full load run time which
-is longer than realistic expectations, the use of the greatest pump brake horsepower (ahhough that is not a reasonable system condition) and the auxiliary loads are assumed to be operating 100% through the seven day period. The calculations includes a one thousand gallon margin for dieset testing and fuel sampling. Therefore, the Division 3 fuel oil storage requirements are sufficient, In response to Item #3, the lack of fuel oil storage tank high level alarms is not safety
- significant. The storage tank overflows to a diesel fuel sump which has a high level alarm to alert operators of an overflow situation, The sump level is also muitored by regular surveillance checks, UFSAll rection 9.5.4.2 will be revised to mention the fuel oil trnk interconnection (Item
- 1), Division 3 fuel oil storage requirement calculation (Item #2) and lack of storage tank
- high level alarms (item #3) and why these are deviations from ANSI N W L
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A'ITACHMENT C
'~
RESPONSE TO UNRESOLVED ITEM (373/91019-03(DRS); 374/91019-03(DRS))
125Vdc Voltage Drop Calculation
)
i Descriotion of Condition The team determined that 125Vdc voltage drop analyses were not available for Divisions 1,2, and 3. A pre-operational test was done for Divisions 1 and 2 to 1
ensure all required components operate satisfacterily with 105Vdc at the j
batteries. However, the team's position was that this test does not climinate the need for a calculation.
HOponse Even though pre-operational tests were uccessfully performed, the lice'isce has committed to the following course of action:
- 1. Perform calculations on all three 125Vdc safety related divisions for bcth units. Calculations are scheduled to be completed by Jan. 31,'1992.
Current results indicated that the Unit I and 2 "0" diesel generator main feed breaker closir.g circuits need significantly more than 105V at the battery terminals due to a large voltage drop, No other significant problems were identified.
- 2. Enginering work is being performed on an expedited basis to implement minor changes to reduce voltage drop. These minor changes add an interposing relay in the closing circuitry subsequently reducing the overall circuit length, The licensee's goal is to complete the design and installation during the current Unit 2 outage.
Upon completion cf the two previeus i ems, all loads requiring more than 105V will t
be evaluated for further actions.
g vi ATTACHMENT C a
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RESPONSE TO UNRESOLVED ITEM-
- (373/91019-06(DRS);374/91619-06(DRS))
-l 41'60 YOLT DEGRADED VOLTAGE 4
1 Rescription of Condition l
During the team's review of the degraded voltage protection - the licensee provided an October 2,1991,-letter containing the results of prelintinary Sargent and Lundy and_Bechtel calculations intended to verify the adequacy of the existing degraded voltage relay _setpoint (3814 +/- 76 volts). These preliminary caldulations indicated that the current setpoint may be non-conservative in that at least 4040 volts is required to start selected emergency loads and that greater
. than 4040_ volts is required to ensure that all motor control circuits will have adequate voltage.
In response to the October 7,1991, calculation results, the licensee took the following compensatory measures:
- LIncreased the degraded voltage relay setpoints to 3885 volts.
- Increased undervoltage alarm setpoint to 4040 volts.
- Will declare _4160 volt bus inoperable if voltage is below 4040 volts.
' * -Will notify the load dispatchers to raise LaSalle switchyard voltage if voltage is '--
-less than 4(MO.:
- Will verify proper operation of equipment that required greater that 4040 ' volts if voltage was below 4040.
Also, the licensee committed to the following future actions:
- Complete motor control circuit (120 volt) voltage drop analysis for Division 3 -
by November 27,19P
- Revise preliminary calculations.uiilizing actual equipment data by December 31,1991.
- Finalize dates for all future actions (design changes, Technical Specification
a l
ATTACHMENT C changes, etc.) required to correct any issues resulting from revised calculations by April 30,1992, i
Pending NRC review of the licensee's evahiation of this issue, this is considered an unresolved item (373/91019-06(DRS); 374/91019-06(DRS)).
Response
A. Compensatory Measures A summary of the compensatory measures that were proceduralized at LaSalle are listed below:.
1.
The trip setpoint for the ESF Division 1 and 2 degraded voltage relays,
'1427(2427)-AP270A/B and AP271 A/B, was increased from 3814 V.to 3885 V. The trip setpoint for the ESF Division ' degraded voltage relays did not need to be increased and remains at 3814 V.
T The trip setpoint for the ESF Division I and 2 SAT winding undervoltage relays, 1427(2427)-Al J39 and AP251, was increased from 3500 V to 4040 V,
. Note: The function of these relays is to annunciate an alarm in the control room and prevent the SAT feed breakers to busses 141Y(241Y) and 142Y(242Y) from closing on. low SAT voltage. ESF Division 3 does not have a SAT winding undervoltage relay.
3.
If the SAT winding undervoltage alarm annunciates and a LOCA does not -
exist, the control room operators will immediately check the voltage on 4160V switchgears 141Y(241Y),142Y(242Y), and 143 (243). If the bus
' voltage'is verified to be less than 4040 V and the bus is connected to the SAT, the following actions will be taken:
- a. The load dispatcher will be notified to raise the switchyard voltage.
L
- b. If the Unit is in Run or Starmp, any bus with a voltage level less than 4040 V will be declared inoperable and action will be taken as specified g
E in the Technical Specification. The bus can be declared operable when its voltage increases to 4040 V or the Unit is placed in Hot Shutdown, Cold Shutdown, or Refuel.
1
)
-s ATIGIMENIf
- c. :If the Unit is in Hot Shutdown, Cold Shutdown or Refuel, the Unit will not be placed in Stanup.or Run until the bus voltages are raised above 4040 V. However, the busses are not inoperable under these conditions.
- d. No evolutions which will increase bus loading will be performed.
- 4. -
If the SAT winding undervoltage alarm annunciates and a LOCA condition
- exists, the SAT feed breakers to all three ESF 4 kV busses will be tripped.
This will cause the t usses to de-energize and connect to their anociated diescl ' generator.
B. FSF Divison 3 Motor CoatmLcircuit Voltaggyrop Analysis The preliminary calculations for the ESF Division 3 motor contol circuit voltage
-drep were preparcd by S&L and submitted to CECO for review on December 6, 1991J These calculations were revised to incorpora.. our comments and finalized on January 15,1992. The reason for the delay in meeting the above schedule is that not all of the information required to perform these calculations was received
~ from the vendor until December 3,1991.
The calculations show that the compensatory incasures that were implemented in response to the October 2,1991, letter cover the ESF Division 3 motor control circuits. That is, all ESF Division 3 motor control circuits have adequate voltage to
' pickup the motor starter contactor at a bus volta of 4040 volts.
However, the contactors for thc tollowing equipment will be field inspected to
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' deterinine whether nuclear grade or commercial grade models are installed:
1.' HPCS Diesel Generator Cochng Water Pump,1(2)E22-C002
- 2. HPCS Pump 71scharge _ Valve,1(2)E22-F004 -
- 5. HPCS Cubicle Cooler Fan,1(2)VY02C At a bus voltage of 4040 volts the S&L calculations indicate that the terminal
' voltages at the coils of these contactors are between 75% and 85% of rated.
- Vendor dceumentation for these contactors indicates that the minimum pickup voltage is at least 75% of rated for their nuclear grade models and 85% of rated for their commercial grade models. However, they also indicate that their
ATTACEMIiNI C commercial grade models have a very high probability (>90%) of being able to pickup at a voltage J 75% of rated.
If the field inspection indicates that a " nuclear grad " model is not installed, a nuclear grade contactor will be procured and installed during the subsequent refueling outage. The Unit 2 contactors for the above equipment will be inspected during the current refueling outage, and the Unit I contactors will be inspected during the next refueling outage.
The results of this voltage drop analysis are documented in S&L Calculations 4266/19AZl9 and 4266/19AZ20.
C. Revision of the l'relimj_n3rv Degradsdlohage Calculations n
The scheduled completion date for revising the preliminary degraded voltage calculations has been changed to April 30,1992. The reason for the delay is that equipment data has not been received from the various motor vendors yet.
Letters have been issued to the motor vendors requesting this information but no responses have been received as of this date. The main renson for obtaining this information is that we believe the actual equipment data will show that a lower starting voltage requirement can be utilized in the degraded voltage calculations.
D. Final ACliRILElBB The schedule for develop;ng the long term action plan for resolving the degraded voltage issue has not been revised. This action plan will identify the design changes and Technical Specification changes that are required for removing the compensatory measures describeo above and the schedule for ccmpleting them.
The Icng term schition for degraded voltage will also address the safety related motor starting voltage issue, Deviation 373/91019-05A(DRS); 374/91019-OM(DRS), and the degraded voltage setpoint methodology issue, Dcviation 373/91019- 05D(DRS);374/91019-05D(DRS).
A1TACHMENT D 4
RESPONSE TO OPEN ITEM (373/91019 08(DRS); 374-91019-08(DRS))
Ilattery Sl7Ng Calculatten i
Descriotion of Condition j
- The team's review of the battery sizing calculations (426619D3) indicated that temperature, design, and aging margins were not applied when sizing the Unit 2, Division 2,125Vdc battery.
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Responss -
The referenced calculr. tion applies to the orig nal LaSalle FPS-15 cells. Three of
- those original batteries ( Baticry 1 A: IB and 2A) have already been replaced with NCX-17 cells as ptri of the LaSalle DC Upgrade project. These new batteries are sized in excess of the requirements ofIL 4485 including all the design margins, even though LaSalle is not committed to IEEE-485 in its design basis.
Calculation 4266-19D3 does apply to the current 2B battery and docc not meet the current recommendations in IEEE-485. However, the latest service test indicated that the battery is capab!c of supplying its design basis lords. A
" performance" test to demonstrate the battery's capacity, performed on 4-16-91, indicated that the battery capacity is greater than 105%. In addition, the Electrical Load Monitoring System (ELMS) run using the current load profile independently indicates that the battery has sufficient capacity to meet its design load profile.
The Unit 2, Division 2 battery will b6 replaced during the unit refueling outage for LaSalle which commenced in early January 1992, at which time calculation 4266-19D3 will cease to apply at LaSalle.
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' ATTACHMENT D RESPONSE TO OPEN ITEM
- (373/91019-02(DRS);374/91019-02(DRS))
4KV ESF CIRCUIT BREAKER OVERCURRENT PROTECTION E
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._ Description of Conryn 1The team ' determined that the overcurrent protection relays for the Division 3 4kV ESF feedcr breakers were not properly set to clear a fault when powered fmm the -
- Division-3 EDO.1 In addition, the licensee could not demonstrate that the overcurrent protection relays for the Division 1. and 2 4kV ESF feeder breakers twould not clear a fault when powered from the Division 1 and 2 EDGs. The team
' determined that the licensee had set the Division _3 relays to protect the 4kV
- busses and loads from the higher' fault currents that would be expected when the
' busses were supplied by offsite power. Lin the event of a fault, the failure to isolate
- Class lE components from the resulting fault currents could lead to component
' degradation or failure.
The licensee rergonded by stating that the consequences of an uncleared fault
- would be limited to one division.1 The team concurred with the licensee, However, the team c'insidered this condition to be a design weakness.. This item is
- : considered open pend.ing additional licensee analysis (373/91019--
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iResponse
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CECO document RPS-TG-36 requires protective relay pettings to be t)ased on _
both the minimum and maximum available fault currents, However, no industry standards exist that specifically detail.the methodology for preparing circuit
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breaker protective relay settings for busses which are fed from several sources of power. Noimat engineering practice is to de: ermine the instantarteous settings from the power source that can supply the greatest fault current because this--
technicue minimizes potential damage to the system, The LaSalle 4kV SSF circuit breaker relay settings were determined with the busses fed from the System Auxiliary Transformer (SAT) which provides the largest source of fault current 4
The design bases for these settings were based upon Sargent and Lundy (S&L) n'
- calculations 4266;EAD-4 and 4266-19AN-1.
- During the LaSalle ED5FI audit, an analysis was performed by S&L of the existing protective relay settings for the 4 kV LSF circuit breakers. This analysis y;
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ATTACHMENT D concluded that the overcurrent protection relays for the ESF Division 1, 2, and 3 j
breakers would clear a fault when powered from the associated emergency diesel i
generator (EDG). This analysis is summarized below.
The LnSalle diesel generators have a subtransient reactance of 6.1% at 3562.5 kVA. Based on this subtransient reactance, the maximum 3 phase fault current from the dicsel generator is 8511 A The corresponding line-to-line fault current value is 87% _of the 3-phase fault current (1.732/2 x 8511 A = 7371 A).
Following a LOCA and a loss of offsite power, the only 4 kV loads that are automatically connected to the EDGs are the ECCS pumps and 480 V unit substations.
For ESF Divisions 1 and 2 the maximum instantaneous setting for the 4 kV ECCS pump motors is 3120A for the Low Pressure Core Spray (LPCS) pump _ motor.
Based on fault current decrement curves for a diesel generator that is nearly identical to those installed at LaSalle, the DG fault current output drops to about 73% within 0.01 second (0.6 cycle). This corresponds to a line-to-line fault current value of 5381 A (0.73 x 7371 A). Since the relay instantaneous units j
typically operate within half a cycle (0.008 second), bolted (maximum) faults in the ESF Division 1 and 2 ECCS pump motors or their associated cables would be cleared by the motor instantaneous units.
1 The 480 V unit substations on ESF Divisions 1 and 2 are protected by CO-4 relays with instantaneous units set at 5000A and high drop out instantaneous units set at
. 800A. As noted in the previous paragraph, the relay instantaneous units typically _
trip wi'hin half a cycle. The high drop out instantaneous units normally trip within 0.6 sewnds, and DG fault current decrement curves show that the fault current output drops to 33% at 0.64 seconds. This corresponds to a line-to-line fault current value of 2432A (0.33 x 7371 A). Therefore, bolted faults in these loads
-would also be cleared by either the instantaneous units or high drop out instantaneous units in the unit substation phase overcurrent relays.
ESF Division 3 has only two 4 kV feeder circuit breakers - the HPCS pump motor and the 480 V unit substation. A similar analysis of the protective relay settings for these two breakers also shows that faults in these loads would be cleared when powered from the the EDG.
Thisjustification concludes that faults on feeders will he cleared if the ESF buses are fed from the diesel generators. Not withstanding this conclusion which is based on technically defensible engineeri%udgement, it is our position that a fault in dr.: safety related distribution system cons:itutes a single failure that may, i
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ATTACHMENT D a;
1 depending upon its location, magnitude, configuration, etc., render the entire division inoperable whether or not the protective devices are able to isolate and disconnect the faulted component. This'is especially true for ESF Division 3 which has only two 4 KV feeder cir: ult breakers. Should either of these breakers trip due to a fault, the entire division ~ would become inoperable. However, the plant is designed for a single failure. Therefore, CECO believes that no further actions are warranted at this time.
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