ML19327B435
| ML19327B435 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 10/23/1989 |
| From: | Loflin L CAROLINA POWER & LIGHT CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NLS-89-289, NUDOCS 8910310191 | |
| Download: ML19327B435 (12) | |
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1 Caroline Power & Light Company DCT 2 3 20 SERIAL: NLS.89 289 10CFR50.62 United States Nuclear Regulatory Commission ATTENTION: Document Control Desk Washington, DC 20555 BRUNSWICK STEAM ELECTRIC PIANT, UNIT NOS,1 AND 2 DOCKET NOS. 50 325 & 50 324/ LICENSE NOS. DPR-71 & Dri 62 ATUS ARI SYSTEM DESIGN (NRC TAC NOS. 73351/73352)
Centlemen:
In a letter dated August 21, 1989, the NRC informed Carolina Pcwer & Light Company (CP&L) of their conclusion that the $as built" alternate rod injection (ARI) system at Brunswick is not in agreement with the-ATWS Rule Cuidance.
Specifically, the ARI system is not powered independently from the reactor i
trip system (RTS).
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' Carolina Power & Light Company has performed a review of the ARI system design and, as a result of this review, determined that the "as built" alternate rod injection system at Brunswick meets the requirements of the ATWS Rule, the ATWS Rule Cuidance, and the Company's previous commitments.
provides a discussion and several simplified drawings which clarify the Brunswick design and demonstrate the basis for the Company's conclusions. We believe that this additional information will aid in your review and would welcomo an' opportunity for a meeting with your staff to discuss the Brunswick j
ARI design.
Since the Company has determined that the existing ARI design meets the ATWS Rule requirements, no plan or schedule for resolution of the issue, as committed to in the Company's September 7, 1989 submittal, is included in this response.
Please refer any questions regarding this submittal to Mr. M. R.
Oates at (919) 546-6063.
Yours very truly,
-) /)-QR Leonard I.
flin Manage Nuclear Licensing Section LIL/ MAT Enclosure cc:
Mr. S. D. Ebneter Mr. W. H. Ruland Mr. E. C. Tourigny C
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411 Fayetteville Street
- P. O. Dox 1551 e Raleigh. N C 27602 8910310191 891023 w-ammmmsemme=w-n-l PDR ADOCK 05000324 P
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I D i ENCLOSURE l-BRUNSWICK STEAM ELECTRIC PIANT, UNITS 1 AND 2 NRC DOCKETS 50 325 6 50 324 F
OPERATING LICENSES DPR-71 & DPR 62 i
ATWS ARI SYSTEM DESIGN (NRC TAC NOS, 73351/73352)
Staff PositiSD -
L The.following is the Staff's position as stated in~the August 21, 1989 letter j
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to Carolina Power & Light Company; a
.... the BSEP's,ARI logic and final actuetion devices (i.e., ARI i
solenoid valves) are powered from a DC distribution Panel 12A, feeder No. 2.
- The power to the RTS analog transmitter trip unit (ATTU) is also supplied from this same Distribution Panel 12A, on feeder No. 19, which is contrary to the commitment stated in the
-CP&L's letter dated April 14, 1987.
Furthermore, the staff concludes that the'"as-built" ARI system power supply arrangement is not in agreement with the ATWS Rule Guidance regarding System and Equipment Specifications. The ATWS Rule Guidance, published as " Supplemental Information" when the final rule was noticed in the Federal Register (49 FR 26036) on June 26, 1984, states, in part,.that the diverse reactor trip system (diverse scram system or. alternate rod injection) logic and actuation device power must be from an instrument power supply independent from the powet supplies for the existing reactor trip system.
Existing RTS and instrument channel power supplies may be used, provided the possibility of common mode failure is prevented.
. The staff has concluded that the "as-built" ARI system power supply arrangement at BSEP is not in agreement with the ATWS Rule Guidance or the commitment made in your April 14, 1987 letter that the'ARI system will be designed so the ARI power supply is independent of any RTS components.
Resoonse Carolina Power & Light Company believes that the ARI system, as designed and installed at Brunswick, meets the requirements of the ATWS Rule, the ATWS Rule Guidance, and the Company's April 14, 1987 commitment.
. Figures 1 through 4 provide simplified diagrams of the existing Brunswick design.
Figure 1 is a schematic of the Reactor Protection System (RPS) power supply, also included is a discussion of the RPS power supply.
Figure 2 provides the layout of the ARI system power supply including a discussion of the ARI power supply. Figures 1 and 2 are intended to provide a brief 21 overview of the system designs as they relate to this issue.
Figure 3 is a block diagram which expands Figure 1 of the NRC's August 21, 1989 letter.
Figure 4 provides a sketch of ARI/RPS sensor power supply interface.
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The ATWS Rule Guidance, published as " Supplemental Information" when the final rule was noticed in the Federal Register (49 FR 26036) on June 26, 1984, states, in part, that the diverse reactor trip system (diverse scram system or alternate rod injection) logic and actuation device power must be from an instrument power supply independent from the power supplies for the existing reactor trip system. As demonstrated by Figures 1 and 2, the existing Brunswick design fulfills this requirement. The RPS logic and actuation devices are supplied with'AC control power from Motor Generator Sets C71(72)-S011A and B.
Control power for the ARI logic and actuation devices is supplied from a noninterruptible, Class 1E DC source.
As shown on Figure 4, some sensors which supply trip signals to the RPS are powered through Distribution Panel 12A by the same noninterruptible, Class 1E DC source as that supplying the control power for the ARI system. This is acceptable based on the ATWS Rule Guidance, General Electric's Topical Report "NEDE 31096 P-A, Anticipated. Transients Without Scram, Response to NRC ATWS Rule 10 CFR 50.62," and the staff SER on the Topical Report, dated October 21, 1986.
The ATWS Rule Guidance required electrical independence of the ARI system from the existing RTS from sensor output to the final actuation device at which point non-safety related circuits must be isolated from safety related circuits. The ATWS Rule Guidance also states that the power supply for the ARI system need not be safety related, however, existing RTS sensor and instrument channel power supplies'may be used provided the possibility of commen mode failure is prevented.
GE Topical Report NEDE-31096-P-A, as approved by the NRC, states that it is acceptable to utilize RPS sensors to initiate the ARI provided proper isolation is maintained and ARI control power is separate from the RPS control power. The NRC October 21, 1986 SER expands upon this stating that if the ARI system has to use a safety related power supply, then proper isolation consists of two qualified Class 1E breakers in series with proper relay coordination (two fuses in series or a combination of one fuse and one breaker will also be acceptable).
As shown in Figures 2 and 4 the ATWS ARI system is powered from a noninterruptible, Class 1E DC source which is diverse from the RPS.
Figure 4 demonstrates the configuration of qualified isolators used in the Brunswick design. There are least two qualified isolators, in series, between the ARI control logic and the DC power supply, between the ARI control logic and the associated sensors, and between the RPS control logic and the associated sensors.
This preven.:s the possibility of common mode failure.
Summary Carolina Power & Light Company believes that the existing design of the Brunswick ARI system meets the requirements of the ATWS Rule, the ATWS Rule Cuidance, and the Company's previous commitments.
This is achieved by powering the control power for the ARI logic and actuation devices from a noninterruptible, Class 1E DC source which is diverse from the AC control El-2
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. power for the RPS logic and actuation devices which is supplied from
. Motor Generator Sets C71(72) S011A and B.
Proper isolation devices, as defined in the staff's SER for CE Topical Report NEDE-31096-P A, are provided i?
between the non Class 1E AR1 system and the Class lE power supply.
The only commonality is introduced when some sensors which supply' trip signals to the i':
RPS-are' powered"through Distribution Panel 12A via the same noninterruptible, f
Class.1E DC source as that supplying the control power for.the ARI system.
I Since the ATWS Rule allows use of the same sensors for~ actuation of both the r
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'RPS and the ARI system and proper isolation is provided between the ARI i
control logic and the associated sensors, and between the RPS control logic and the associated sensors, the existing design is acceptable.
' Carolina Power 6 Light Company is cognizant'of the discussions under way
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between the NRC and the BWROG regarding analog transmitter trip units (ATTUs).
CP&L concurs'with the BWROC position that the trip units are' considered to be i
n part of the sensor.
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Reactor Protection System Equipment and Logic l
l The Reactor Protection System (RPS) contains two l
independent, fail-safe trip systems, each of which controls the continuity or discontinuity of electrical j
power to one of the two solenoid-operated scram pilot i
valves associated with each control rod.
1 Each trip system (designated A and B) is housed in a separate panel (H12-P609 and H12-P611. respectively) in the electronic equipment room and is furnished 120 Vac power, via an individual RPS bus, which is powered by a motor-generator set located in the battery room, m e
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Motor-Generator Sets C71(721-S011A and B t.
Power to each of the two reactor protection trip systems is supplied, via a separate bus, by its own high inertia AC motor-generator set.
Each set consists of a 48O yolt induction drive motor coupled to a 120 vol: synchronous generator and a flywheel.
The flywheel functions to permit the sets to " ride through" momentarv interruptions in input power. Sufficient inertia is provided to maintain output voltage and frequency within 5 percent of rated values for at least one second following a total loss of power to the drive motor.
The MG net A and B output voltages'are set at 117 Vac to ensure that safety related scran solenoids and relay coil voltages do not r
exceed 115 1 2 Vac when supplied by the MG sets.
These motor-generator sets, designated MG set A and MG set B, are located in the battery room and are powered from MCC CA and MCC CB, respectively.
Their control panels with all operating components are mounted on top of the generator.
In addition to supplying power to the RPS buses, the MG sets also supply power to the Neutron Power Range Monitoring, Process Radiation Monitoring and Nuclear Steam Supply Shutoff Systems.
RPS Alternate Power Source A backup, or alternate power source is previded so that one MG set can be removed from service during plant operation.
For Unit 1, either emergency bus E5 or E6 can provide,120 volt power transformer and 120V voltage regulator, 120 volt power to either RPS bus, and for Unit 2 the power source is supplied through a stepdown transformer and 120V voltage regulator to either RPS bus, from either bus E7 or E8.
The alternate power supply voltage regulator is a single phase, 25 kVA unit. The regulator is set to regulate voltage at 117 Vac and will maintain this output voltage 1", from no load to full load. The voltage regulator maintains the output setpoint 1% for an input voltage range of -12%/+20%, with a load that has a 0.7=8 power at i
. factor (lagging). The regulator will respond to input voltage variations within 10 cycles. The output voltage contains a maximum of 5% harmonics.
A three-position power source selector switch (alternate A - normal - alternate B), located on simultaneous supply of power to a given MG set could be the same emergency has supplying power through the stepdown transformer to the other RPS bus.
I RPS Power Distribution Panel C71(C72)-P0001 Output from the MG sets is to the RPS power distribution panel. This panel contains circuit breakers which connect each RPS Trip system to its respective RPS bus.
Circuit breakers which connect the neutron monitoring power range buses, the Nuclear Steam Supply Shutoff System, and the Process Radiation Monitoring System to the RPS buses are also contained in this panel.
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t Alternate Rod Injection System Equipment and Logic The Alternate Rod Injection System provides a path i
for reactor shutdown which is diverse and independent from the Reactor Protection System.
It is conunon to i
the normal shutdown components only in the scram inlet and discharge valves, the control rod drives, and the control rods themselves. The automatic signal to initiate the ARI function will come from l
high reactor vessel pressure or low reactor vessel water level.
'ARI System logic uses existing recirculation pump trip initiation instrumentation. The high reactor l
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vessel pressure setpoint will be such that a normal scram should have already been initiated at the time its setpoint is reached, and the low reactor vessel water level setpoint will be set lower than the reactor vessel low water level scram setpoint.
The ARI System performs a function redundant to the backup scram system, although the ARI System has a different design basis. The ARI System is not redundant in itself.
Control switches for manual ARI System initiation, resetting the initiation logic, and annunciation are located on panel 1112-P603. The ARI System logic circuitry
.and valves are energized to trip.
ARI System Power Source The ARI System logic circuitry and valves are energized to function and are powered from a noninterruptible de source.
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