ML20216G988
| ML20216G988 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 04/14/1998 |
| From: | NORTHEAST NUCLEAR ENERGY CO. |
| To: | |
| Shared Package | |
| ML20216G986 | List: |
| References | |
| NUDOCS 9804210004 | |
| Download: ML20216G988 (25) | |
Text
l Docket No. 50-423 B17144 Millstone Nuclear Power Station, Unit No. 3 Proposed Revision to Technical Specification inadvertent Safety injection (TSCR 3-9-98)
Marked Up Pages April 1998 i
9804210004 980414 PDR ADOCK 05000423 P
U.S. Nuclear Regulatory Commission 1
B17144\\ Attachment 2\\Page 1
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MARKUP OF PROPOSED REVISION Refer to the attached rnarkup of the proposed revision to the Technical Specifications.
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l The attached markup reflects the currently issued version of the Technical J
l Specifications listed below.
Pending Technical Specification revisions or Technical l
l Specification revisions issued subsequent to this submittal are not reflected in the f
l enclosed markup.
4 The following Technical Specification changes are included in the attached markup.
Technical Specification 3/4.4.4 LCO Action entry conditions have been ' modified to l
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restrict continued plant operation to the case where the PORV is inoperable c'ue to 2
l excessive seat leakage considerations. Deletion of the references to manual cycling I
better reflects the additional crediting of automatic actuation. An editorial correction was also made in statement b.
Technical Specification Surveillance 4.4.4.1 adds quarterly and once per 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> Surveillance Requirements for PORV high pressure automatic opening capability i
l The Bases has been updated to reflect crediting PORV automatic actuation for Inadvertent ECCS Actuation at Power I
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12/16/93 REACTOR COOLANT SYSTEM
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3/4.4.4 RELIEF VALVES li LIMITING CONDITI0d FOR OPERATION
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'3.4.4.
Both power-operated relief valves (PORVs) and their associated tilock' valves shall be OPERABLE.
APPLICABILITY: MODES 1, 2, and 3.
ACTION:
With one or both PORV(s) inoperable ::d n; g:, f S:h;==:ll 6w o a.
O i
- y;':d, within I hour either restore the PORV(s) to OPERABLE status or close the associated block valve (s) with power maintained to the block valve (s); otherwise, be in at least HOT STAND 8Y within the
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q next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in 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 />. AL&
'A 9 MC k,. 40 ca.,>sa &4 eauss:n StJ f.
b.
With one PORY inoperable e=d =at etaele ef Mia; r rily cycl:d, within I hour either restore the PORV to OPERABLE status or close i
the associated block valve and remove power from the block valve; restore the PORV to OPERABLE status within the following 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in HOT STANDBY.wt4h4% the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in HOT SHUTDOWN within thefollowing6 hours./utA+
x With both PORVs inoperable h fo can ohhh*"-- * - - - - " - - ' ' ' - -- - " " " - "- '
d J
en.al,n. :H ed, c.
/
TC w s
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within I hour either restore at least one PORV to OPERABLE status g/
3 r:,. S, m:(. i or close its associated block valve and remove power from the. block
'" ' M "" '
i valve and be in 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 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 />.
d.
With one or both block valve (s) inoperable, within I hour restore the block valve (s) to OPERABLE status, or place its associated pvt.V(s) control switch to "CLOSE.* Restore at least one blo~ck valve to OPERABEE-status wi. thin the next hour if both block valves are v
inoperable; restore any remaining inoperable block valve to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />; otherwise, 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 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 />, e.
Entry into an OPERATIONAL MODE is permitted while subject to these ACTION requirements.
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MILLSTONE - UNIT 3 3/4 4-12 Amendment No. p,88 esas
2/19/97
, REACTOR COOLANT SYSTEM iO RELIEF VALVES I
i SURVE!LLANCE REQUIRENENTS 4.4.4.1 In addition to the requirements of Specification 4.0.5, each PORV shall be demonstrated OPERABLE st le::t :::e eid PSUELINC INTERVAL by:
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/
.tvs-
/
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a p
b.
trave,1 during 4.4.4.2 Each block valve shall be demonstrated OPERABLE at least once per 92 days by operating the valve through one complete cycle of full travel unless the block valve is closed with power removed in order to meet the requirements of ACTION b. or c. in Specification 3.4.4.
4.4.4.3 The emergency power supply for the PORVs and block valves shall be demonstrated OPERABLE at least once each REFUELING INTERVAL by operating the l valves through a complete cycle o' full travel.
e g
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We e
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M 3/4 4-13 Amendment No. JJ.133' gLSTONE-UNIT 3 I
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Insert C a.
Performance of a CilANNEL CALIBRATION at least once each REFUELING INTERVAL; and b.
Operating the valve through one complete cycle of full travel during MODES 3 or 4 at least once each REFUELING INTERVAL; and c.
Performance of an ANALOG CilANNEL OPERATIONAL TEST on the PORV high pressurizer pressure actuation channels, but excluding valve operation, at least once each quarter; and d.
Verify the PORV high pressure automatic opening function is enabled at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
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12/16/93 aEACTOR COOLANT SYSTEM BASEE
, outomaMe.or artIEF VRVES(Continued) adomaticaOg CHd Action st teneats a, b, and c dis tinguishes the inoperability of the power operated lief valves (PORV). !;pecifically, a PORV may be designated inoperable but it may be able to manually open and close and therefore, able S on yivvi - b ::t:::ti: c + -! p ;y be due to sea to perform its function. P0RV inoperability ma i
^
.1 ~ :S :th;r cec;; 4.. t d~
D#
fnstrument
. vent manuel use and de not create gpossibility for a small-break LOCA.
( n Jot
/*\\k For these reasons, the bT6ck valve may be closed but the action
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i This allows quick access to the PORV for U to be maintained to the valve.
e control. On the other hand if a PORV is inoperable and not capable g d pre of in manually cycled, it must be either restored or isolated by closing p
the associated block valve and removing power.
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IM) ~~%The prime importance for the capability to close the block valve is to isolate a stack-open PORV. Therefore, if the block valve (s) cannot be restored to operable status within I hour, the remedial action is to place the PORV in h
manual control (i.e. the control switch in the "CLOSE" position) to preclude its automatic opening for an overpressure event and to avoid the potential of The time a stuck-open PORV at a time that the block valve is inoperable.
allowed to restore the block valve (s) to operable status is based upon the remedial action time limits for inoperable PORV per ACTION requirements bn,and These-actions-de-not specify closure of the block valves because such
- c. ten would not likely be possible when the block valve is inoperable.
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hebos dda.w+ A. A.As I
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-l MILLSTONE - UNIT 3 83/44-2a Amendment No.88 at:4
Insert A Automatic operation of the PORVs is credited to allow more time for operators to terminate an inadvertant ECCS Actuation at Power. The PORVs and associated piping have been demonstrated to be qualified for water relief. Operation of the PORVs will prevent water relief from the pressurizer safety valves for which qualification for water relief has not been demonstrated. If the PORVs are capable of automatic operation but have been declared inoperable, closure of the PORV block valve is acceptable since the Emergency Operating Procedures provide guidance to assure that the PORVs would be available to mitigate the event. Operability and setpoint controls for the safety grade PORV opening logic are maintained in the Technical Requirements Manual Insert B For the same reasons, reference is not made to Action statements b. and c. for the required remedial actions.
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i Docket No. 50-423 B17144 i
l Millstone Nuclear Power Station, Unit No. 3 Proposed Revision to Technical Specification
]
l Inadvertent Safety injection (TSCR 3-9-98)
)
i Retyped Pages l
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4 April 1998
U.S. Nucitar Regulatory Commission B17144\\ Attachment 3\\Page1 RETYPJ OF PROPOSED REVISION Refer to the attached retype of the proposed revision to the Technical Specifications.
The attached retype reflects the currently issued version of the Technical Specifications. Pending Technical Specification revisions or Technical Specification revisions issued subsequent to this submittal are not reflected in the enclosed retype.
The enclosed retype should be checked for continuity with Technical Specifications prior to issuance.
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REACTOR C0OLANT SYSTEN 3/4.4.4-ItELIEF VALVES LINITING C0051 TION FOR OPERATION 3.4.4.
Both power-operated relief valves (PORVs) and their associated block valves shall be OPERABLE.
APPLICABILITY: MODES 1, 2, and 3.
l ACTION:
l a.
With one or both PORV(s) inoperable because of excessive seat l
1eakage, within I hour either restore the PORV(s) to OPERABLE status or close the associated block valve (s) with power maintained to the block valve (s); otherwise, 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 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 />.
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b.
With one PORV inoperable due to causes other than excessive seat leakage, within I hour either restore the PORV to OPERABLE status or close the associated block valve and remove power from the block valve; restore the PORV to OPERABLE status within the following l
72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in 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 HOT l
SHUTDOWN within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
c.
With both PORVs inoperable due to causes other than excessive seat leakage, within I hour either restore at least one PORV to OPERABLE status or close its associated block valve and remove power from the block valve and be in 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 HOT l
SHUTDOWN within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
d.
With one or both block valve (s) inoperable, within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> restore the block valve (s) to OPERABLE status, or place its associated
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PORV(s) control switch to "CLOSE." Restore at least one block valve to OPERABLE status within the next hour if both block valves are inoperable; restore any remaining inoperable block valve to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />; otherwise, 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 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 />.
e.
Entry into an OPERATIONAL MODE is permitted while subject to these ACTION requirements.
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J MILLSTONE - UNIT 3 3/4 4-12 Amendment No. 77, pp.
0687 j
REACTOR C0OLANT SYSTEN RELIEF VALVES 9
SURVEILLANCE REQUIRENENTS 4.4.4.1 In addition to the requirements of Specification 4.0.5, each PORV shall be demonstrated OPERABLE by:
l a.
Performance of a CHANNEL CALIBRATION at least once each REFUELING INTERVAL; and b.
Operating the valve through one complete cycle of full travel during l
MODES 3 or 4 at least once each REFUELING INTERVAL; and c.
Performance of an ANALOG CHANNEL OPERATIONAL TEST on the PORV high pressurizer pressure actuation channels, but excluding valve operation, at least once each quarter; and L
d.
Verify the PORV high pressure automatic opening function is enabled at 1 east once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
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4.4.4.2 Each block valve shall be demonstrated OPERABLE at least once per 92 days l
by operating the valve through one complete cycle of full travel unless the block j
valve is closed with power removed in order to meet the requirements of ACTION b.
or c. in Specification 3.4.4.
4.4.4.3 The emergency power supply for the PORVs and block valves shall be demonstrated OPERABLE at least once each REFUELING INTERVAL by operating the valves through a complete cycle of full travel.
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i NILLSTONE - UNIT 3 3/4 4-13 Amendment No. pp, 177, om
4 REACTOR COOLANT SYSTEM BASES RELIEF VALVES (Continued)
Action statements a, b, and c distinguishes the inoperability of the power operated relief valves (PORV). Specifically, a PORV may be designated inoperable but it may be able to automatically and manually open and close and l
therefore, able to perform its function.
PORV inoperability may be due to seat i
leakage which does.not prevent automatic or manual use and does not create the i
possibility for a small-break LOCA.
For these reasons, the block valve may be closed but the action requires power to be maintained to the valve. This allows quick access to the PORV for pressure control. On the other hand if a PORV is inoperable and not capable of being automatically and manually cycled, it must be l either restored or isolated by closing the associated block valve and removing l
power.
Automatic operation of the PORVs is created to allow more time for operators to terminate an Inadvertent ECCS Actuation at Power. The PORVs and associated piping have been demmistrated to be qualified for water relief. Operation of the PORVs will prevent water relief from the pressurizer safety valves for which qualification for water relief has not been demonstrated.
If the PORVs are capable of automatic operation but have been declared inoperable, closure of the PORV block valve is acceptable since the Emergency Operating Procedures provide guidance to assure that the PORVs would be available to mitigate the event.
Operability and setpoint controls for the safety grade PORV opening logic are maintained in the Technical Requirements Manual.
The prime importance for the capability to close the block valve is to isolate a stuck-open PORV. Therefore, if the block valve (s) cannot be restored to j
l operable status within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, the remedial action is to place the PORV in manual control (i.e. the control switch in the "CLOSE" position) to preclude i
its automatic opening for an overpressure event and to avoid the potential of a stuck-open PORV at a time that the block valve is inoperable.
The time l
allowed to restore the block valve (s) to operable status is based upon the 4
remedial action time limits for inoperable PORV per ACTION requirements b. and c.
Action statement d. does not specify closure of the block valves because such action would not likely be possible when the block valve is inoperable. For the same reasons, reference is not made to Action statements b. and c. for the required remedial actions.
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MILLSTONE - UNIT 3 B 3/4 4-2a Amendment No. pp, 0688
r Docket No. 50-423 B17144 i
Millstone Nuclear Power Station, Unit No. 3 Proposed Revision to Technical Specification inadvertent Safety injection (TSCR 3-9-98)
Background and Safety Summary 1
April 1998
1 U.S. Nuctur Regulatory Commission
'B17144\\ Attachment 4\\ Pag 01 Backaround FSAR Section 15.5.1 Inadvertent Operation of the Emergency Core Cooling System During Power Operation, states in the Conclusions that "With respect to pressurizer filling, the pressurizer will not reach a water solid condition, with or without PORV actuation, prior to 10 minutes from event initiation."
However, a Configuration Management Program review questioned the operator response time assumed in the analysis. Specifically, in the Inadvertent SI, the analysis assumed that the operator terminates the injection flow to avoid an overfill of the system (i.e., solid pressurizer).
However, the operator experience at the simulator may not support this assumption in i
all cases. In order to provide more time for operator action, it was decided to qualify the PORVs and the associated piping for water relief.
J In Standard Review Plan Section 15.5.1, one of the acceptance criteria for this event is that an incident of moderate frequency should not generate a more serious plant condition without other faults occurring independently. Since the pressurizer safety valves are not qualified for water relief, operator action was credited to terminate the event prior to a water solid condition being reached. Water relief from the pressurizer safety valves could lead to valve failure and a resultant unisolable RCS leak. In order for the operator to terminate the event, the operator must terminate ECCS injection, re-align charging to the normal flow path and re-establish letdown. While the operators have successfully mitigated actual events in the past, the simulator data indicates that the operator respcase to prevent pressurizer overfill is marginal. Thus, to increase the available operator response time, the PORVs and associated piping have been qualified for water relief.
Thus, with the PORVs automatically maintaining RCS pressure, the pressurizer safety valves would not be challenged, even if the pressurizer j
becomes water solid.
4 A new analysis for the inadvertent ECCS Actuation at Power Operation has been performed to define the conditions necessary for qualifying the PORVs and piping and to define the time frame for which the PORVs must be available for mitigation. The new analysis also corrects an error in the modeling of the sprays and heaters during this event. The new analysis shows that a water solid condition will be reached within approximately 8.5 minutes. However, with one PORV available to automatically control RCS pressure at 10.75 minutes, challenges to and subsequent water relief from the pressurizer safety valves is prevented. In order to credit the PORV in this analysis, both PORVs must be available to function automatically, taking into account the i
potential for a random single failure.
Included in the new analysis was the calculation of mass and energy releases from the PORV for one hour. This was used to demonstrate that the PORVs and associated
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.U,S. Nuclear Regulatory Commission B17144\\ Attachment 4\\Page 2 l
, piping are qualified for one hour of water relief for an inadvertent ECCS Actuation at Power Operation. This provides sufficient margin for the operator to terminate the event. In addition, the PORV actuation logic has been upgraded to safety grade and single failure proof.
For the current design, the PORV opening logic is control grade circuitry that actuates on a 1/1 logic. A selectable control is provided so that either one of two channels can be selected to control each PORV opening. One PORV is programmed to open at a set pressure of 2350 psia. The other PORV is part of the pressurizer pressure control logic that controls pressurizer spray, heaters and the one PORV. This PORV would open 100 psi above the controller pressure setting. The current PORV closing logic is safety grade based upon a 2/4 pressurizer pressure low logic.
For the upgrade, the safety grade closing logic will be used for the safety grade open logic. A 2/4 logic will be used to open the PORVs based on pressurizer pressure greater than 2350 psia.
The PORV closure logic will be 3/4 that actuates when pressurizer pressure drops 20 psi below the opening setpoint. Since the stroke time for the PORV is very short, the closing pressure is adequate to assure that the valve will cycle as designed. The PORV open circuitry is designed to require energization to open. This minimizes the potential for spurious opening of the PORVs. However, with the new logic, two failed high channels of pressurizer pressure will result in an inadvertent opening of both PORVs. With the current logic, while a single channel failing high would open the PORV, the closure logic woulo close the PORV when pressurizer pressure dropped below 2200 psia. It would take three channels failed high for the PORVs to open and remain open.
Currently, TS 3.4.4 allows indefinite operation with one or both PORVs INOPERABLE, provided that the PORV can be manually cycled and the PORV block valve is closed.
This is inconsistent with the new analysis assumption which credits automatic PORV operation. Thus, the TS 3.4.4 is being changed to allow indefinite operation only if the PORV is inoperable due to excessive seat leakage.
fr. addition, an Emergency Operating Procedure (EOP) change is being made to ensure that the PORV block valves are opened within ten minutes from event initiation. The new analysis shows that, with a PORV block valve stroke time of 45 seconds and credit for operator action to open the block valves within ten minutes, the safety valves will not be challenged by water relief and the PORV will maintain RCS pressure below the safety valve setpoint.
Operator ability to open the PORV block valves per the EOP change within 10 minutes has been validated in the Millstone Unit 3 plant simulator.
1 A Technical Requirements Manual (TRM) change will specify the nominal opening setpoint for the PORV required to support the analysis assumption which credits automatic operation. The TRM change will specify that operability of the PORVs
U.S. Nuclear Regulatory Commission
'B17144\\Attachmsnt 4\\Page 3 l
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requires at least three pressurizer pressure channels operable. This allows for plant l
' operation with one inoperable pressurizer pressure channel.
W4th one inoperable
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pressurizer pressure channel, the PORV opening logic will change from a 2/4 to 1/3 logic. This means that, when one pressurizer pressure channel is inoperable, a single failure of a pressurizer pressure channel high would cause both PORVs to open. A time limit for plant operation of 30 days will be included in the TRM change to limit the l
period that the plant will be operated when a single failure of a pressurizer pressure l
channel high would cause both PORVs to open.
This proposed change (with the addition of surveillance requirements)is similar to a l
license change which was previously approved at Salem Generating Station, Dockets 50-272 and.50-311. The Safety Evaluation Report for Salem was dated June 4,1997.
SAFETY
SUMMARY
The proposed changes provide added assurance that the pressurizer safety valve and associated piping will not be damaged due to water relief. Currently, timely operator action is required to prevent the pressurizer from filling and potentially challenging the pressurizer safety valves under water relief. The proposed TS changes provide added assurance that the safety valves will not be challenged by minimizing the time that the PORVs would not be available for automatic pressure control as well as by adding Surveillance Requirements to ensure the automatic function of the PORVs is operable.
If the automatic capability of one PORV is INOPERABLE for more than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, shutdown is required. If the automatic capability of both PORVs is INOPERABLE for more than one hour, shutdown is. required. If the block valves have been closed but the automatic capability of the PORVs is OPERABLE, an EOP change has been made to assure that the PORV block valves would be opened within ten minutes of an inadvertent ECCS actuation at power. The new analysis shows that this is sufficient to assure that the PORVs would control RCS pressure if water relief is experienced and the safety valves would not be challenged. Thus, it is concluded that the change
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provides added assurance that the safety valves would not fail due to water discharge.
Evaluations and analysis have been performed to demonstrate that the PORVs and the j
associated piping are qualified for water relief from an inadvertent ECCS Actuation at i
Power Operation for _one hour from event initiation. The PORV actuation logic has been upgraded to be safety grade and single failure proof. This provides significant margin for operator action to terminate the event.
The EOP change will direct the operator to open the PORV block valve if it has been closed due to excessive PORV seat leakage that does not affect the ability for automatic or manual cycling. The EOP change will not result in the opening of the PORV block valve when the power has been removed when required to prevent a small i
U.S. Nuclear Regulatory Commission B17144\\ Attachment 4\\Page 4 break, LOCA. This includes leakage from the PORV such that there is no assurance that the PORV would re-close as required to control RCS pressure. Thus, the PORV block valve would be opened only when there is assurance that the PORV will open and re-close as required.
l Credit is now being taken for the PORVs to prevent challenges to pressurizer safety valves under water relief. If the PORVs were to fail to control RCS pressure, it is possible for water relief through the safety valves to occur. This also can result if both l
of the PORV block valves cannot be opened or the operator fails to open the block valves within the required time frame. While operator action was always credited for mitigation, the actions were associated with termination of ECCS injection, realignment of charging to the normal flow path and establishment of letdown. These actions are consistent with the generic Westinghouse Owners Group Emergency Response Guidelines that have been reviewed by the NRC. On the other hand, the operator l
action to open the PORV block valves for this event is a different credited action that l
represents a deviation from the generic guidance. Since the safety valves and the l
associated piping are not qualified for water relief the valves may be damaged and may l
not reseat, resulting in an unisolable RCS leak. As such, it is concluded that the failure of the PORVs to control pressure, the failure of the PORV to open and the failure of the operator to open the PORV block valve within the required time frame represent malfunctions of a different type.
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Water relief from the PORVs for the inadvertent ECCS actuation event would result in a larger discharge of RCS..wentory than currently analyzed. However, the accident analysis has shown that Departure from Nucleate Boiling (DNB) is not a concern and thus, there would be no failed fuel associated with this event. In addition, any RCS l
leakage would be inside containment. Thus, it is concluded that there would be no impact on offsite doses for this event.
l With the upgrade of the PORV control logic and added surveillance requirements, there l
is added assurance that the PORVs will be capable of providing automatic pressure l
control and preventing challenges to the safety valves, particularly under water solid j
conditions. However, there is a small impact due to multiple channel failures resulting in an increase in the probability of inadvertent opening of both PORVs. With the new safety grade PORV actuation logic, two failed high pressurizer pressure channels will result in inadvertent opening of both PORVs. With the current logic, a single failed high l
pressurizer pressura channel would result in opening one PORV. However, the 2/4 l
closure logic would re-close the PORV when pressurizer pressure drops below approximately 2200 psia. With the current logic three failed high pressurizer pressure channels are required for the PORVs to inadvertently open and remain open. Thus it is concluded that there is an increase in the probability that the PORVs will inadvertently open and remain open. However, multiple failures are required for this malfunction. In addition, for failure modes such as loss of power for the transmitter or a failure of the L
U.S. Nuclear Regulatory Commission
'B17144\\ Attachment 4\\Page 5 instrument tubing, the channel will fail low. Failure modes that would result in multiple
' channels failing high are highly unlikely. Further, the new logic energizes to actuate in order io open the PORVs, further minimizing the potential for inadvertent opening. In addition, these failures which result in the PORVs automatically opening and remaining open do not disable the ability of the operators to close the PORVs by taking their control switch to the close position. Thus, it is concluded that the increase is negligible.
The consequences of inadvertent opening of both PORVs is bounded by the analysis provided in Chapter 15.6.1 Inadvertent Opening of Pressurizer Safety or Relief Valve.
Thus, while the change does increase the probability of a previously evaluated accident and constitutes an unreviewed safety question, the change is safe.
l The TRM change requires at least three pressurizer pressure channels OPERABLE in order for the PORVs to be OPERABLE. This allows continued plant operation with one inoperable pressurizer pressure channel. An inopeiable pressurizer pressure channel will be placed in the tripped condition. This will change the PORV opening logic from a l
2/4 to a 1/3 logic. This means that when a pressurizer pressure channel is inoperable, a single failure of a pressurizer pressure channel high will result in the opening of both l
PORVs. This represents an increase in the probability of opening both PORVs over the i
existing design.
However, additional failures would be required to prevent the operators from closing the PORVs by placing the PORV control switches in the close position. Although allowing plant operation with a 1/3 logic for PORV opening when one pressurizer pressure channel is inoperable is an unreviewed safety question, establishing a 30 day time period to limit risk assures that the change is safe.
l The EOP change has been designed to minimize the impact on mitigation of other l
accidents. The PORV block valve will be opened following a Safety injection actuation only after it has been determined that RCS pressure is above the HPSI shut off head.
This means that Charging is sufficient to maintain RCS pressure well above the RCS pressure predicted for the limiting LOCA analysis. Further, the PORV block valve would not be opened when power has been removed because of the potential for operation of the PORV to result in a small break LOCA. Finally, the EOP change will l
not affect the capability of the operators to perform the required actions within the l
required time frames to mitigate any other accident.
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i in summary, the proposed changes will provide added assurance that the operators will I
be able to mitigate an inadvertent ECCS actuation at power without challenging the i
pressurizer safety valves during water solid conditions for which they are not qualified.
While the changes involve crediting the PORVs and additional operator actions, thus introducing the potential for malfunctions of a different type, these malfunctions would result in the current situation where reliance would be placed on the operators to terminate the event before pressurizer overfill occurred. In addition, while the change in i
the PORV logic does increase the probability that the PORVs will inadvertently open and remain open, multiple failures are necessary for this to occur and the
,0.S. Nuclear Regulatory Commission Bi7144\\ Attachment 4\\Page 6 consequences are bounded by the current accident analysis. The changes do not
' affect the mitigation of any other accident and do not impact the probability that any other accident will occur. The changes in operator actions necessary to mitigate the inadvertent ECCS event can be accomplished within the required time frame and do not affect the mitigation of other events. Thus, it is concluded that while the changes are an unreviewed safety question, they are safe to implement.
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,c Docket No. 50-423 B17144 1
l Millstone Nuclear Power Station, Unit No. 3 i
Inadvertent Safety injection (TSCR 3-9-98)
Significant Hazards Consideration and Environmental Considerations April 1998
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,0.S. Nuclear Regulatory Commission B17144\\ Attachment 5\\Page 1
' Sianificant Hazards Consideration NNECO has reviewed the proposed revision in accordance with 10CFR50.92 and has concluded that the revision does not involve a significant hazards consideration (SHC).
The basis for this conclusion is that the three criteria of 10CFR50.92(c) are not l
satisfied. The proposed revision does not involve a SHC because the revision would
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not:
1.
Involve a significant increase in the probability or consequence of an accident previously evaluated.
Currently, timely. operator action is required to prevent the pressurizer from filling and potertially challenging the pressurizer safety valves under water relief. The proposed TS changes provide added assurance that the safety valves will not be l
challenged by requiring the POR\\/s to be available for automatic pressure control. The changes to the Surveillance Requirements add the appropriate requirements to provide assurance that the automatic capability of the PORVs is OPERABLE. The quarterly analog channel operational test for the PORV high pressurizer pressure channels will not include valve operation. However, it does involve changing the opening logic from 2/4 to 1/3 and, thus, performing the surveillance increases the probability of the PORVs opening inadvertently. If the automatic capability of one PORV is INOPERABLE for more than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, shutdown is required.
If the automatic capability of both PORVs is INOPERABLE for more than one hour, shutdown is required. If the block valves have been closed but the automatic capability of the PORVs is OPERABLE, an EOP change has been made to assure that the PORV block valve would be opened within ten minutes of an inadvertent ECCS actuation at power. The new analysis shows-that this is sufficient to assure that the PORVs would control RCS pressure if water relief is experienced and the safety valves would not be challenged. Thus, it is concluded that the change provides added assurance that the safety valves would not fail due to water discharge.
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Evaluations and analysis have been performed to demonstrate that the PORVs i
and the associated piping are qualified for water relief from an inadvertent ECCS Actuation at Power Operation for one hour from event initiation. This provides significant margin for operator action to terminate the event.
The PORV control logic has been upgraded to be safety grade and single failure proof. A 2/4 logic is used for opening and 3/4 logic is used for subsequent closure. With the upgrade of the PORV control logic, there is added assurance that the PORV will be capable of providing automatic pressure control and preventing challenges to the safety valves, particularly under water solid conditions. However, there is a small impact on the probability of inadvertent
U.S. Nuclear Regulatory Commission
' B'l7144\\ Attachment 5\\Pags 2
' opening of both PORVs resulting from multiple channel failures. With the new safety grade PORV control logic, two failed high pressurizer pressure channels will result in inadvertent opening of both PORVs. With the current logic, a single failed high pressurizer pressure channel would result in opening a PORV.
However, the 2/4 closure logic will re-close the PORV when pressurizer pressure drops below 2200 psia. With the current logic three failed high pressurizer pressure channels are required for the PORVs to inadvertently open and remain open. Thus it is concluded that there is an increase in the probability that the PORVs will inadvertently open and remain open.
However, multiple channels failing high are required for the PORVs to inadvertently open and remain open. For failure modes such as loss of power for the transmitter or a failure of the instrument tubing, the channel will fail low.
Failure modes that can result in the channel failing high are highly unlikely.
Further, the new logic will require energization in order to open the PORVs, further minimizing the potential for inadvertent opening. These failures, which result in the PORVs automatically opening and remaining open, do not disable the ability of the operators to close the PORVs by taking their control switch to the close position. Thus, it is concluded that the increase in risk is negligible.
The consequences of inadvertent opening of both PORVs is bounded by the analysis provided in Chapter 15.6.1 Inadvertent Opening of Pressurizer Safety or Relief Valve.
In the event of an inoperable pressurizer pressure channel, the channel will be placed in the tripped condition. This will change the opening logic from 2/4 to 1/3 and the subsequent closure logic from 3/4 to 3/3. This means that, when a pressurizer pressure channel is inoperable, a single failure of a pressurizer pressure channel high will cause both PORVs to open and remain open. Thus it j
3 is concluded that the Technical Requirements Manual (TRM) change which addresses specific surveillance controls, also results in an increase in the probability that the PORVs willinadvertently open and remain open. However, procedural controls will be implemented and controlled in the TRM that will require a plant shutdown if the channel is inoperable for more than thirty days.
l The setpoint for the PORV opening logic has been selected to assure that the PORVs will open prior to the safety valves, taking into account instrument uncertainties. The setpoint will be specified and controlled in the Technical Requirements Manual.
This minimizes the potential challenges to the pressurizer safety valves under steam as well as water solid conditions. The PORV closure logic will be 3/4 that actuates when pressurizer pressure drops 20 psi below the opening setpoint. Since the stroke time for the PORV is very short, the closing pressure is adequate to assure that the valve will cycle as designed.
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,U.S. Nuclear Regulatory Commission B'l7144\\ Attachment 5\\Page 3 An EOP change will direct the operator to open the PORV block valve if it has been closed due to excessive seat leakage. The EOP change will not result in the opening of the PORV block valve when the power has been removed when required to prevent a small break LOCA. This includes leakage from the PORV such that there is no assurance that the PORV would re-close as required to control RCS pressure. Thus, the PORV block valve would be opened only when there is assurance that the PORV will open and re-close as required. Thus, the EOP change does not impact the probability of a failed open PORV.
Credit is now being taken for the PORVs to prevent challenges to pressurizer safety valves under water relief. If the PORVs were to fail to control RCS i
pressure, it is possible for water relief through the safety valves to occur. This l
also can result if both of the PORV block valves cannot be opened. Since the safety valves and the associated piping are not qualified for water relief, the valve may be damaged and may not reseat, resulting in an unisolable RCS leak.
However, this would require multiple failures since the PORVs are redundant. The accident analysis has shown that DNB is not a concern and thus, there would be no failed fuel associated with this event. In addition, any RCS leakage would be inside containment. The analysis provided in FSAR Section 15.6.1 for an inadvertent Opening of a Pressurizer Safety or Relief Valve bounds the opening of both PORVs since the capacity of two PORVs is equivalent to one pressurizer safety valve.
Thus it is concluded that the proposed changes do not involve a significant increase in the probability or consequence of an accident previously evaluated.
2.
Create the possibility of a new or different kind of accident from any accident previously evaluated.
The changes provide added assurance that an inadvertent ECCS Actuation at Power Operation will be mitigated and meet the requirement that a moderate frequency event will not lead to a more serious event without additional failures.
The PORVs and associated piping have been qualified for water relief.
In i
addition the PORVs are QA equipment and are single failure proof. The TS changes provide assurance that the PORV automatic function will be OPERABLE or the plant will be shutdown. By crediting the PORVs, there is added assurance that the operators will terminate the event and prevent water relief from the safety valves for which they are not qualified. Since all criteria are met for this event, this does not represent the possibility of an accident of a different type.
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^ B17144\\Attachmsnt 5\\Page 4
' Because of the change in the PORV automatic actuation circuitry and the changes in the channel operability and surveillance requirements, the change does increase the probability of an inadvertent Opening of both' PORVs but the consequences are bounded by the analysis provided in FSAR Section 15.6.1 for inadvertent Opening of a Safety or Relief Valve. Thus, this does not represent an accident of a different type.
Credit is being taken for the operator to open a PORV block valve if it has been closed due to excessive PORV seat leakage. The PORV block valve will be opened following a Safety injection actuation only after it has been determined that RCS pressure is above the HPSI shut off head. This means that charging is sufficient to maintain RCS pressure well above the RCS pressure predicted for the limiting LOCA analysis. Further, the PORV block valve would not be opened when power has been removed because of the potential for operation of the PORV to result in a small break LOCA. Further, the potential for opening the PORV block valve when the PORV is needed for accident mitigation is already addressed in the TS and is part of the licensing basis. Thus, this does not create the possibility of an accident of a different type.
3.
Involve a significant reduction in a margin of safety.
With the proposed changes, all criteria for the inadvertent ECCS actuation at Power Operation are met.
The changes provide added assurance that a moderate frequency event would not result in a more serious event without additional failures. The TS changes and EOP change provide added assurance that the PORVs would be available to mitigate this event. Opening the block valve when the PORV can be used to mitigate an accident without the potential for a small break LOCA is already addressed in the TS and is part of the licensing basis. Inadvertent Opening of both PORVs is bounded by the Chapter l
15 accident analysis. Thus, it is concluded that the changes have no impact on l
the margin of safety.
In conclusion, based on the information provided, it is determined that the proposed revision does not involve an SHC.
Environmental Considerations NNECO has reviewed the proposed license amendment against the criteria of 10CFR51.22 for environmental considerations. The proposed revision does not involve a SHC, does not significantly increase the type and amounts of effluents that may be released offsite, nor significantly increase individual or cumulative occupational radiation exposures. Based on the foregoing, NNECO concludes that the proposed L,
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,1).S. Nucinar Regulatory Commission Efl7144%ttachmsnt 5\\Paga 5
' revision meets the criteria delineated in 10CFR51.22(c)(9) for categorical exclusion from the requirements for environmental review.
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