ML20079B305
| ML20079B305 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 12/20/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20079B301 | List: |
| References | |
| NUDOCS 9501050404 | |
| Download: ML20079B305 (5) | |
Text
J gw%
p 4
UNITED STATES E
NUCLEAR RE2ULATORY COMMISSION u
%.....]f I
WASHINGTON, D.C. 20515 0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 174 TO FACILITY OPERATING LICENSE NO. DPR-51 ENTERGY OPERATIONS. INC.
ARKANSAS NUCLEAR ONE. UNIT NO. 1 DOCKET NO. 50-313
1.0 INTRODUCTION
By letter dated January 13, 1994, Entergy Operations, Inc. proposed changes to the Arkansas Nuclear One, Unit 1 (ANO-1) technical specifications (TSs) for Operating License No. DRP-51. The proposed changes would allow plant operation to continue indefinitely with one Reactor Protection System (RPS) channel placed in bypass. TS 3.5.1.3, the associated Bases for TS 3.5.1.3, TS 3.5.1.11, and TS Table 3.5.1-1 would be modified to allow this action.
i By letter dated July 8,1992, the staff approved Supplement 2 of Babcock and j
Wilcox Owners Group (BWOG) Topical Report BAW-10167, " Justification for Increasing the Reactor Trip System On-Line Test Interval-Additional Information on Allowed Outage Time".
In the July 8,1992, letter the staff approved placing one RPS channel in the bypassed state for an indefinite period for repairs and the licensee's proposed TS changes are based on this topical report.
The proposed changes would:
1.
Add additional requirements to ensure that only one RPS channel may be placed in channel bypass or contain inoperable functions or components in the unbypassed, untripped state.
I 2.
Add conservative requirements for conditions that involve multiple l
failures.
3.
Add Bases discussion of requirements upon discovery of inoperable I
functions or components in the RPS and available options for operating the RPS with inoperable functions.
4.
Add Bases discussion of operation of Emergency Feedwater Initiation I
and Control (EFIC) system maintenance bypass when any one RPS channel contains inoperable functions in the unbypassed, untripped state.
l 9501050404 941220 PDR ADOCK 05000313 P
i l
2.0 BACKGROUND
The ANO-1 RPS consists of four identical protection channels that operate in a two-out-of-four configuration. A trip in any two of the four channels would initiate a trip of all control rod power supply breakers and contactors.
Each channel is provided with a channel bypass key switch.
The channel bypass switch enables a channel to be bypassed without initiating a trip. The bypass switch is normally used to bypass one channel during on-line testing.
- Thus, during on-line testing the system would operate in a two-out-of-three configuration. The channel bypass switches are interlocked. Therefore, if one channel bypass switch is in bypass, the other channel bypass switches would be locked out.
When an RPS channel is bypassed, all functions in the channel are prevented from providing a trip signal.
However, the monitoring functions of the channel are not removed from service, but the trip logic is altered from a two-out-of-four configuration to a two-out-of-three configuration. When an RPS channel is placed in the tripped mode, all functions in the channel provide a trip signal.
The monitoring functions of the channel are removed from service and the trip logic is altered from a two-out-of-four configuration to a one-out-of-three configuration.
The BWOG topical report evaluated the two-out-of-three and one-out-of-three configurations.
The BWOG evaluation indicated that the two-out-of-three configuration provides acceptable reliability to trip on demand as well as protection against spurious trips. The one-out-of-three configuration is intolerant of single spurious trips.
In addition, testing the one-out-of-three configuration in the tripped mode requires more human actions to switch the channel from tripped to bypass mode and back again and, therefore, increases the susceptibility of the RPS trip logic to human error and thus may contribute to a higher RPS spurious trip rate.
The BWOG evaluation concluded that extended operation with an inoperable channel in bypass was safer than operation with the inoperable channel in the tripped mode.
3.0 EVALUATION Currently TS 3.5.1.3 requires that if a RrS channel is undergoing on-line testing or any protection instrument or channel fails, the RPS channel shall be placed in channel bypass.
The licensee has proposed changes that would allow the optional use of the channel bypass switch. Changes to TS 3.5.1.3 and the associated Bases for TS 3.5.1.3 would allow a single inoperable channel to be place" n channel bypass, in the manually tripped state, a to remain in ope. ^ en in a degraded condition as determined by evaluation, plant conditions, e tanagement approval.
These changes would also allow a channel undergo. g testing to be placed in either channel bypass or in the manually tripped state as determined by existing plant conditions and management review. To preserve the minimum trip logic of the two-out-of-three configuration, the licensee has proposed
i t
. tha, 'iS 3.5.1.3 be further revised to require that only one channel shall contain inoperable functions in the unbypassed, untripped state at any one l
t time.
The licensee has also proposed to modify TS 3.5.1.3 to require the operator to l
tag the remaining channel bypass switches when operating with an inoperable function unbypassed in the untripped state. This requirement ensures that one l
of the remaining channels will not be placed in bypass without prior management approval consistent with the requirements of TS Table 3.5.1-1.
Upon discovery of an inoperable component or function in any channel, the 1
condition would be evaluated for channel and system operability as required by
)
existing plant administrative procedures and TSs. This review would look at both the failure itself and an evaluation of the effect of the failure on interconnected systems. Should this evaluation determine that the failure would prevent the functioning of another system, the appropriate actions for i
the additional affected system would be implemented.
l Ti 161e 3.5.1-1 calls for the minimum number of operable channels to be three ior S e following:
I High Pressure Injection System reactor coolant pressure instrument channels and reactor building 4 psig instrument channels Low Pressure Injection System reactor coolant pressure instrument channels and reactor building 4 psig instrument channels Reactor Building Isolation reactor building 4 psig instrument channels Reactor Building Cooling System reactor building 4 psig instrument channels Reactor Building Spray Pumps reactor building 30 psig instrument channels Reactor Building Spray Valves reactor building 30 psig instrument channels.
This table also references TS Table 3.5.1-1 Note 6 which currently allows the minimum number of operable channels to be reduced to two, provided that the system is reduced to one-out-of-two configuration.
In the event that these channels cannot be placed in a one-out-of-two configuration Note 6 requires the operator to apply TS 3.3.
TS 3.3 defines the conditions necessary to assure immediate availability of the emergency core cooling system and does not have applicability in an RPS bypass situation.
l
- - l
i l The licensee has proposed changes to TS 3.5.1-1 Note 6 that would direct the
[
operator to apply the actions specified by TS Table 3.5.1-1 Column 5 if these channels cannot be placed in a one-out-of-two configuration. TS Table 3.5.1-1 Column 5 refers to TS Table 3.5.1-1 Notes 1 and 5.
Note 1 requires the reactor to be in hot shutdown within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> if the minimum number of operable channels or the minimum degree of redundancy are not met. Note 5 requires that if the minimum number of operable channels or the minimum degree of redundancy cannot be met within an additional 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, the reactor be placed in cold shutdown within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. This change would remove a misleading reference to place the plant in a mode where the affected instrumentation system is not required.
The licensee also proposed changes to the Bases for TS 3.5.1-1 regarding the EFIC system to discuss operation of the EFIC system maintenance bypass when one RPS channel contains an inoperable function in the unbypassed, untripped l
state.
An EFIC channel may be placed in maintenance bypass by use of a bypass key switch, but only one channel may be placed in maintenance bypass at a time.
Currently when an inoperable RPS channel is placed in bypass only the associated EFIC channel may also be placed in maintenance bypass.
if a i
failure occurred in an RPS function that is not an input to the EFIC, only the associated EFIC channel would be allowed to be placed in maintenance bypass.
The licensee's proposed changes would allow, based on plant conditions and management approval, for any of the EFIC channels to be placed in maintenance bypass teen an inoperable RPS function is in the unbypassed, untripped state, l
l but is not an input to the EFIC system.
Based on the above evaluation, the staff concludes that with the proposed changes the RPS and EFIC will remain single-failure proof.
Therefore, the proposed changes are acceptable.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Arkansas State official was notified of the proposed issuance of the amendment. The State official had no comments.
i
5.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The NRC staff has determined 6
that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards i
consideration, and there has been no public comment on such finding (59 FR 10005).
Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR Y
i f
! 'l 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
+
6.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such I
activities will be conducted in compliance with the 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.
Principal Contributor:
B. Marcus Date: October 24, 1994 i
t l
i
. ~ -
_