ML20205B778
| ML20205B778 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 03/23/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20205B772 | List: |
| References | |
| NUDOCS 9903310361 | |
| Download: ML20205B778 (9) | |
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g UNITED STATES NUCLEAR REGULATORY COMMISSION E
I WASHINGTON, D.C. - =1
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION l
RELATED TO AMENDMENT NO. 121 TO FACILITY OPERATING LICENSE NO. NPF-42 WOLF CREEK NUCLEAR OPERATING CORPORATION WOLF CREEK GENERATING STATION. UNIT 1 DOCKET NO. 50-482
1.0 INTRODUCTION
By application dated February 4,1998, as supplemented by letter dated October 20,1998, Wolf Creek Nuclear Operating Corporation (WCNOC, the licensee) requested changes to the Technical Specifications (TS) (Appendix A to Facility Operating License No. NPF-42) for the Wolf Creek Generating Station, Unit 1. The Wolf Creek TS Tables 3.3-3,3.3-4, and 4.3-2 identify operational, setpoint, and surveillance requirements respectively for the engineered safety features actuation system (ESFAS). These TS tables identify requirements for the ESFAS by functional unit.
The licensee proposed changes to ESFAS Functional Unit 6.f, " Loss of Offsite Power - Start Turbine-Driven Pump" requirements listed in TS Tables 3.3-3, 3.3-4, and 4.3-2 to create separate requirements for the analog and digital portion of the circuits associated with start of the turbine driven pump on a loss of offsite power. The analog portion in each TS table would be listed under new Functional Unit 6.f.1 and the digital portion under new Functional Unit 6.f.2.
Additionally, the licensee proposed a change to add a new action statement (#31) in TS Table 3.3-3 for Functional Unit 6.f.2, the digital functional unit. In their supplemental letter dated October 20,1998, the licensee revised the proposed action statement #31 to address staff concerns regarding the allowable outage time provided therein in addition, the licensee requested changes to the TS Table 4.3-2 to add a note to ESFAS Functional Unit 8.a and 8.b under " Loss of Power." The note would be added to the channel calibration and trip actuating device operational test (TADOT) surveillance requiremsnts. The note would indicate that the testing of time delays in the loss of power circuits would be completed as part of channel calibration surveillance requirements.
The October 20,1998, supplemental letter provided additional clarifying information, did not expand the scope of the application as originally noticed and did not change the staff's original proposed no significant hazards consideration determination published in the Federal Register on March 25,1998 (63 FR 14491).
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2.0 BACKGROUND
The ESFAS TS Table 3.3-3,3.3-4, and 4.3-2 requirements under Functional Unit 6.f, " Loss of Offsite Power - Start Turbine-Driven Pump," are applicable to the circuitry that starts the turbine-driven auxiliary feedwater (TDAFW) pump on a loss of offsite power. The Wolf Creek ESFAS Functional Unit 6.f involves the following three instrumentation systems:
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Loss of Offsite Power Instrumentation and Load Shedder and Emeraency Load Seouencer l-(LSELS) 1 The emergency diesel generators are designed to provide a source of emergency power when offsite power is either unavailable or !s ircafficiently stable to allow safe unit operation. If a loss l
of voltage or degraded voltage condition occurs at the 4.16 kV engineered safety features (ESF) buses, the undervoltage protection system will; (1) trip the 4.16 kV preferred normal and attemate bus feeder breakers to remove the two deficient offsite power sources to protect the Class 1E equipment from damage; (2) shed all loads from the ESF buses, except the Class 1E 480Vac load centers, to prepare the buses for re-energization by the LSELS; and (3) generate an emergency diesel generator (EDG) start signal.
There are two sets of undervoltage protective circuits, one for each 4.16 kV Class 1E system bus. Each set consists of a loss of voltage and degraded voltage functior,. Four potential transformers on each bus provide the necessary input voltages to the protective devices used l
to perform these functions. Four instantaneous undervoltage relays with an associated time delay are provided for each 4.16 kV Class 1E system bus for detecting a loss of bus voltage.
l Tne outputs are combined in a two-out-of-four logic to generate an undervoltage signal if the voltage is below approximately 70 percent. A brief time delay is employed to prevent false trips arising from transient undervoltage conditions. For degraded voltage protection, the above
_ potential transformers each provide an analog output signal of 0-120 volts. This signal (i.e.,
bistable output) is directed to logic circuits and processors that convert the analog signals into a l
two-out-of-four logic signal, whenever the signal drops below approximately 90 percent for a predetermined time.
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Balance-of-Plant (BOP) ESFAS The BOP ESFAS processes signals from the solid-state protection system, signal processing equipment, and plant radiation monitors to actuate certain ESF equipment. There are two redundant trains or separation groups, identifieH1 as BOP-ESFAS 1 and BOP-ESFAS 4. These trains provide actuation for the motor-driven auxiliary feedwater pumps and reposition automatic valves as required. A third separation group (BOP-ESFAS 2) actuates the TDAFW pump by repositioning automatic valves as required.
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3-TDAFW Pumo Start on Loss of Offsite Power (LOP)
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A LOP is indicated by the undervoltage relays detecting (analog portion) a loss of voltage on each ESF bus, as discussed above. Upon satisfying the two-out-of-four loss of voltage logic (digital portion hereafter) in the LSELS cabinets, LSELS output relays feed the redundant 4
separation groups 1 and 4 BOP-ESFAS cabinets. The separation groups 1 and 4 BOP-ESFAS cabinets perform several functions, but on a LOP signal, these cabinets perform only two 4
functions (1) isolate the steam generator blowdown and sample lines, and (2) provide electrically isolated outputs to the separation group 2 BOP-ESFAS cabinet. The separation group 2 BOP-ESFAS cabinet is associated with the TDAFW pump alone and is considered to be part of that end device, i.e., the TDAFW pump. On a LOP signal, the turbine trip and throttle I
i valve and turbine steam supply valves are opened to start the TDAFW pump.
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The ESFAS F. 'ctional Unit 6.f, circuitry that starts the TDAFW purap on a loss of offsite power includes both (
iH and analog portions. The analog portion of Functional Unit 6.f consists of I
circuitry from ths
.ervoltage relays on the two redundant 4kV Class 1E buses to the output j
relays in the LSELS cabinets in separation groups BOB-ESFAS 1 and 4. The digital portion of 4
ESFAS Functional Unit 6.f consists of the output relays from the LSELS cabinets and that portion of the separation groups BOP-ESFAS 1,2 and 4 circuits that are associated with the j
start of the TDAFW pump during a LOP.
The licensee has concluded that the current TS Table 3.3-3 provides opor#io%I requirements i
for Functional Unit 6.f written only for the digital portion of the circuitry. The ucensee has also concluded that TS Table 4.3-2 provides surveillance requirements which can only be j
reasonably performed at the frequency specified for the analog portion of the Functional 6.f circuitry. Furthermore, TS Table 3.3-4 currently lists as "not applicable" setpoint requirements i
for Functional Unit 6.f. The licensee has concluded that setpoint requirements are not applicable to the digital portion of Functional Unit 6.f; however, setpoint requirements are applicable to the analog portion. The licensee has proposed changes to create separate digital y
and analog functional units for 6.f in thase TS tables to correct these inconsistencies.
Specifically, in TS Tables 3.3-3, 3.3-4, and 4.3-2, the licensee has proposed replacing the j
current Functional Unit 6.f, " Loss of Offsite Power-Start Turbine Driven Pump," with analog Functional Unit 6.f.1, "4 kV Bus Undervoltage - Loss of Voltage," and digital Functional Unit j
6.f.2, " Automatic Actuation Logic and Actuation Relays (LSELS and BOP ESFAS)."
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TS Table 4.3-2 also provides surveillance requirements for Functional Unit 8.a, "4 kV Undervoltage - Loss of Voltage," and Functional Unit 8.b, '4 kV Undervoltage - Degraded Grid Voltage." The licensee has proposed adding a note to Table 4.3 2 under these functional units to clarify that the associated time delay in these circuits is verified during the channel calibration surveillance.
i 3.0 EVALUATION i
i The staff has evaiusted the changes to TS Tables 3.3-3, 3.3-4, and 4.3-2 to identify requirements applicable to the analog and digital portions of the ESFAS Functional Unit 6.f 4
circuitry. The evaluation of the changes is presented by affected TS table in the following sections (Section 3.1,3.2 and 3.3). Within each section, the changes are presented, followed by an evaluation of the proposed changes for the analog portion (6.f.1), and an evaluation of i
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' the proposed changes for the digital portion of the circuitry (6.f.2). Section 3.4 concludes the evaluation with a review of proposed changes to ESFAS Functional Units 8.a and 8.b in TS l
Table 4.3-2.
3.1 Chanaes to TS Table 3.3-3 TS Table 3.3-3, Functional Unit 6.f. " Loss of Offsite Power - Start Turbine-Driven Pump,"
identifies operational requirements for the circuit in terms of total number of channels, channels to trip, channels required to be operable, applicable operating mode, and action to be taken if operability requirements are not met. Current requirements are lined through in the following excerpt from Table 3.3-3. The licensee has proposed replacing the current requirements with analog circuit (6.f.1) and digital circuit (6.f.2) requirements as shown.
TABLE 3.3-3 (Functional Unit 6.f ontv) i ENGINEERED SAFETY FEATURES ACTUATION SYSTEM INSTRUMENTATION MINIMUM TOTAL NO. CHANNELS CHANNELS APPLICABLE FUNCTIONAL UNLI CHANNELS TO TRIP OPERABLE MODES ACTION
- f. Loss-of-Offsite Power-
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Start Turbine-Driven 2-
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4 4 9;B ff 7
pump
- 1) 4 kV Bus Undervoltage
- Loss of Voltage 4/ Bus 2/ Bus 3/ Bus 1,2,3 19*
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2 1,2,3 31 3.1.1. TS Table 3.3-3. Ooerational Reauirements for Analoa Circuitry (6.f.1) in consideration of the design of the 4 kV undervoltage relays, its actuation logic (two-out-of-four), and accessibility for surveillance and maintenance, the licensee has determined that the 4 l
kV bus undervoltage relays comprise the analog portion of the circuitry. The licensee proposed l-a new Functional Unit 6.f.1, to provide requirements for this analog portion of the circuitry.
Since TS Table 3.3-3 Functional Unit 8.a, " Loss of Power," already provides operational requirements for the 4 kV undervoltage relays, the licensee proposed these same requirements under Functional Unit 6.f.1. However, the differences in applicable operational mode between i
current Functional Unit 6.f and 8.a (Modes 1,2,3 verses Modes 1,2,3,4,5,6) require a separate entry in Table 3.3-3 for Functional Unit 6.f.1. The staff has reviewed the change for Functional Unit 6.f.1 and finds the requirements to be the same as Functional Unit 8.a for the same 4 kV l
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5-undervoltage relays, with an exception of applicable plant operational mode. Therefore, the staff concludes that the Functional Unit 6.f.1 is acceptable.
'3.1.2 TS Table 3.3-3. Ooerational Reauirements for Diaital Circuitrv (6.f.2)
The output relays for the LSELS cabinets and the portion of the separation group BOP-ESFAS 1,4, and 2 circuitry associated with starting the TDAFW pump on a LOP are considered digital circuitry. The licensee has determined that the requirements currently provided in TS Table 3.3-3, Functional Unit 6.f address the digital portions of this circuitry. Therefore, the licensee has proposed that the current requirements in Functional Unit 6.f be moved to new Functional Unit 6.f.2, " Automatic Actuation Logic and Actuation Relays (LSELS and BOP ESFAS)."
However, the licensee has proposed a new action statement (#31) in place of the current action statement (#22). (Action Statement 22 would still be used in other functional unit requirements s
in TS Table 3.3-3).
1 Action Statement 22 states:
With the number of OPERABLE channels one less than the Total Number of Channels, 5
restore the inoperable channel to OPERAB!.E status within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> or be in at least HOT i
STANDBY within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in at least HOT SHUTDOWN within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
Action Statement 22 allows 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> to restore one inoperable channel (i.e., train) to operability, but results in entry into TS Limiting Condition for Operation (LCO) 3.0.3 if both channels are determined to be inoperable. LCO 3.0.3 allows only one hour to restore operability before initiating a plant shutdown. The licensee has proposed Action Statement 31 in Functional Unit 6.f.2 in place of the current Action Statement 22. Action Statement 31 would read as follows:
With the number of OPERABLE channels less than the Total Number of Channels,
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restore the inoperable channel (s) to OPERABLE status within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in at least HOT SHUTDOWN within the i
following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
Action Statement 31 would consider all of the digital circuitry that is associated with the TDAFW 1
pump alone as a single functional unit, i.e., Functional Unit 6.f.2. The licensee's basis for the 48-hour allowable outage time (AOT) is that the 48-hour AOT would be a reasonable restoration time considering the nature of this functional unit and the available redundancy provided by the motor-driven auxiliary feedwater pumps. The 48-hour AOT is consistent with that allowed by the existing Action Statement 22 for the existing Functional Unit 6.f, as well as the AOT allowed by action statements for other automatically initiated functions. For the inoperability of any part or multiple parts of Functional Unit 6.f.2, a 48-hour AOT will be allowed j
in which to restore the entire Functional Unit 6 f.2 to operability. Thus, Action Statement 31 pronies for the elimination of the transient imposed on the plant from an unnecessary shutdown under the requirements of Specification 3.0.3. On the basis of the foregoing discussion, the staff concludes that t% changes to the digital portion (6.f.2) in Table 3.3-3 are acceptable.
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6-3.2 Chanaes to TS Table 3.3-4 TS Table 3.3-4, Functional Unit 6.f, " Loss of Offsite Power - Start Turbine-Driven Pump,"
identifies trip setpoint requirements for the circuitry that accomplishes this function. Current requirements are lined through in the following excerpt from TS Table 3.3-4. The licensee has proposed replacing the current lined through setpoint requirements with analog circuit (6.f.1) and digital circuit (6.f.2) setpoint requirements as shown.
TABLE 3.3-4 (Functional Unit 6.f onlv)
ENGINEERED SAFETY FEATURES ACTUATION SYSTEM INSTRUMENTATION TRIP SETPOINTS Total Sensor Trip Allowable FUNCTIONAL UNIT Mgwance Z
Error (s)
Setooint Value
- f. Loss-of-Offsite Power-Start Turbine -
Driven Pump RA-N-A-N-A-RA-N-A;
- 1) 4 kV Bus Undervoltage
-Loss of Voltage See item 8.a below for Trip Setpoints and Allowable Values.
- 2) Automatic Actuation Logic and Actuation N.A.
N.A.
N.A.
N.A.
N.A.
Relays (LSELS and BOP ESFAS) i 3.2.1 TS Table 3.3-4. Setooint Reauirements for Analoa Circuitrv (6.f.1)
For Functional Unit 6.f Table 3.3-4 currently indicates setpoint requirements are "not applicable." The licensee has concluded that'this is only appropriate for the digital portion of the circuitry. Setpoint requirements are applicable to the analog portion (4 kV undervoltage relays) of the circuit. Therefore the licensee has proposed trip setpoint and allowable value requirements for the 4kV undervoltage relays under a new Functional Unit 6.f.1. These requirements for trip setpoint and allowable value are the same as those already specified for the 4kV undervoltage relays under existing Functional Unit 8.a. Since the change (new line item 6.f.1) would not affect any existing analysis, there would be no need to change the current trip setpoints and allowable values. Therefore, the staff concludes that the change is acceptable.
3.2.2 TS Table 3.3-4. Setooint Reauirements for Diaital Circuitrv (6.f.2)
The current setpoint requirements in TS Table 3.3-4, Functional Unit 6.f are "not applicable."
This is applicable to the digital portion of the circuit and is proposed to be transferred i
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. unchanged to the new Functional Unit 6.f.2. The staff concludes that this is acceptable as the existing "N.A." requirement still pertains to the digital portion of the circuitry.
3.3 Chanaes to TS Table 4.3-2 TS Table 4.3-2, Functional Unit 6.f. " Loss of Offsite Power - Start Turbine-Driven' Pump,"
identifies surveillance requirements. Current requirements are lined through in the following excerpt from Table 4.3-2. The licensee has proposed replacing the current requirements with analog circuit (6.f.1) and digital circuit (6.f.2) requirements as shown.
TABLE 4.3-2 (Functional Unit 6.f oniv)
ENGINEERED SAFETY FEATURES ACTUATION SYSTEM INSTRUMENTATION SURVEILLANCE REQUIREMENTS Trip Analog Actuat Modes Chani Device Actuatn Mastr Slave forWhich Chant Chan!
Operat Operat Lode Relay Relay Surveilis Functional Unit Check Qa[ih M
Inst Tgit M Impf Reauired
- f. LOOP Start Turbine -
Driven Pump N.A.
R N.A.
M N.A.
N.A.
N.A.
1, 2, 3
- 1) 4 kV Bus Undervoltage -
Loss of Voltage N.A.
R N.A.
M N.A.
N.A.
N.A.
1,2,3
N.A.
N.A.
N.A.
R N.A.
N.A.
N.A.
1,2,3 3.3.1 TS Table 4.3-2. Surveillance Reauirements for Analoa Circuitrv (6.f.1)
The surveillance requirements for the current Functional Unit 6.f require a channel calibration at least once per 18 months and a trip actuating device operational test (TADOT) at least once per 31 days. Since the performance of a trip actuation device operational test (TADOT) on the digital portion of the circuit at power is not possible without the use of jumpers and lifted leads, the licensen concluded that the current TS Table 4.3-2 surveillance requirement for Functional Unit 6.f are meant only for the analog circuitry (4 kV undervoltage relay circuitry). Therefore,
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. the licent.ee proposed that the current surveillance requirements under Functional Unit 6.f be separated into analog and digital line items, with the current surveillance requirements moved to new Functional Unit 6.f.1, which is applicable only to the analog portion of the circuitry.
The staff has reviewed the change that would move the current surveillance requirements of Functional Unit 6.f to new Func4ional Unit 6.f.1 as shown in Table 4.3 2. The staff finds that the surveillance requirements of Functional Unit 6.f.1 for the analog portion are identical to those of Functional Unit 8.a, "4 kV Undervolta0e - Loss of Voltage." Therefore, the change represents no material change to current surveillance requirements. The staff concludes that mov:ng the current Functional Unit 6.f to Functional Unit 6.f.1 is acceptable.
3.3.2 TS Table 4.3-2. Surveillance Reauirements for Dioital Circuitry (8.f.21 The licensee proposed two changes to the existing surveillance requirements under the current Functional Unit 6.f line item as applied to the digital portion of the circuitry. First, the surveillance interval for the channel calibration surveillance requirement is revised from "R" (at least once per 18 months) to "N.A" (not applicable) since there is no channel calibration for digital circuitry. Second, under the TADOT surveillance requirement, the surveillance interval is revised from "M" (at least once per 31 days) to "R" (at least once per 18 months). This would require a refueling interval TADOT for the digital portion of the TDAFW pump start circuitry on a LOP. The licensee currently performs this TADOT surveillance as part of the 18-month diesel generator / sequencer surveillance testing. To be consistent, the licensee has proposed to revise the TADOT surveillance frequency in the new Functional Unit 6.f.2. The surveillance testing currently being completed will not be altered by this proposed change in surveillance test j
frequency. The staff finds that the changes to Table 4.3-2, Functional Unit 6.f.2 are editorial in nature because they do not change existing procedures and are, therefore, acceptable.
3.4 Chanaes to TS Table 4.3-2. ESFAS Functional Unit 8. " Loss of Power" Functional Unit 8.a "4 kV Undervoltage - Loss of Voltage" and 8.b, "4 kV Undervoltage -
Degraded Grid Voltage," in TS Table 3.3-4 specify voltage trip setpoints and associated time delays, with tclerances, for the undervoltage relays that detect loss of voltage or degraded voltage conditions on the 4 kV Class 1E system buses. TS Table 4.3-2 identifies surveillance requirements for these ESFAS functional units. In TS Table 4.3-2, the licensee proposed to add notations to the 18 month channel calibration and monthly TADOT surveillance requirements for Functional Units 8.a and 8.b to clarify that the time delays for the 4 kV undervoltage relays would be tested as part of the channel calibration.
The licensee has tested the time delay relays as part of the 18 month channel calibration to ensure that safety-related systems, subsystems, and components would not be adversely affected by drift within the permissible tolerance band. The licensee's review of the data obtained from past surveillance supports that the time delay relays have remained within the TS tolerances. On this basis, the licensee concluded that the proposed change will not affect the ability of any safety-related equipment to perform its intended function, thus concluding that the proposed change is acceptable.
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' The staff reviewed the corresponding Surveillance Requirement 3 3 5 3 in NUREG-1431 j
. Revision 1, " Standard Technical Specification - Westinghouse Plants," dated April 1995, and 4
finds that the channel calibration, including voltage setpoint and time delay verification, is to be performed every 18 months. On this basis, the staff concludes that the notation that clarifies that verification of the time delay for Functional Units 8.a and 8.b is to be performed as part of the channel calibration is acceptable.
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4.0 STATE CON 3QLTATION In accordance with the Commission's regulations, the Kansas State official was notified of the proposed issuance of the amendment. The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
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The amendment changes a requirement with respect to installation or use of a facility j
component located within the restricted area as defined in 10 CFR Part 20 and changes i
surveillance requirements. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that i
may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued proposed findings that the amendment involves no significant hazards consideration, and there have been no public 1
comment on such findings (63 FR 14491). Accordingly, the amendment meets the eligibility j
criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b)
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no environnsental impact statement or environtrental assessment need be prepared in
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connection with the issuance of the amendment.
6.0 CONCi USION j
i The Commission has concluded, based on the considerations discussed above, that (1) there is 1
reasonable assurance that the health and safety of the public will not be endangered by operation 1.1 the proposed manner, (2) such activities w,Il be conducted in compliance with the e
Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principle Contributors: Peter Kang Ke!'h Mortensen Date: March 23, 1999
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