ML20199G952
| ML20199G952 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 11/14/1997 |
| From: | NORTHEAST NUCLEAR ENERGY CO. |
| To: | |
| Shared Package | |
| ML20199G934 | List: |
| References | |
| NUDOCS 9711250340 | |
| Download: ML20199G952 (14) | |
Text
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Docket No. '50-423 :
L B16844 q
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Millstone Nuclear Power Station, Unit No. 3 Proposed Revision to Technical Specification Residual Heat Removal System Open Pressure interlock (PTSCR 3-36-97)
Marked Up Pane 1
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November 1997 l
9711250340 971114 PDR ADOCK 05000423 P
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l U.S. Nuclear Regulatory Commission -
B16844%ttachment 2\\Page 1 - -
MARKUP OF PROPOSED REVISION Refer _- to_ the attached markup of _ the __ proposed - revision _to the Technical
-Specifications. The attached markup reflects the currently issued version of the Technical Specifications listed below. Pending Technical Specification revisions or Technical Specification revisions issued subsequent to this submittal are not reflected in the enclosed markup.
The following Technical Specification changes are included in the attached markup.
The survaillance is modified to change the pressure from 390 psia to 412.5 psia to takeine bistable reset into account and delete the words "or actual Reactor Coolant System pressure",
4.5.2.d.1
8/28/97 tMERGENCY CORE COOLING SYSTEMS
. SURVEILLANCE REQUIREMENTS I
4.5.1 fach ECCS subsystem shall be demonstrated OPERABLE:
a.
At least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> by verifying that the following valves are in the indicated positions with power to the valve operators removed:
Valve Number Valve Function Valve Petitlen
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351H*MY8806 RWST Supply to 51 Pumps OPEN 351H*MV8802A
$1 Pump A to Hot Leg Injection CLOSED 351H'HV8802B SI Pump B to Hot Leg Injection CLOSED 3SIH*HV8835 SI Cold Leg Master Isolation OPEN 3SlH*MV8813 SI Pump Master Miniflow OPEN Isolation
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35!L*MV8840 RHR to Hot Leg Injection CLOSED j
3SIL*HV880gA RHR Pump A to Cold Leg OPEN Injection 3SIL*MV8809B RHR Pump B to Cold Leg OPEN Injection b.
At least once per 31 days by:
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1)
Verifying that the ECCS piping, except for the operating r'
centrifugal char pump, the RSS he'ging pump (s) and associated piping, the RSS at exchanger and associated piping, is full of water, and 2)
Verifying that each valve (manual, power operated, or automatic) in the flow path that is not locked, sealed, or otherwise secured in position, is in its correct position.
c.
By a visual inspection which verifies that no loose debris (rags, trash, clothing, etc.) is present in the containment which could be transported to the containment sump and cause restriction of the pump suctions during LOCA conditions. This visual inspection shall be performed:
1)
For all accessible areas of the containment prior to establish-ing CONTAINMENT INTEGRITY, and 2)
At least once daily of the areas affected (during each day) within containment by containment entry and during the final entry when CONTAINMENT INTEGRITY is established.
d.
At least once each REFUELING INTERVAL by:
"9 3)
Verifying automatic interlock action of the RHR System from the Reactor Coolant System by ensuring that with a simulated <sr3 I
rsEEUD P. enter ce6Ent:io T prevent the valves from being m're-swee) signal greater than or
'equar to psia the interl
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N!gl5T0HE-UNIT 3 3/4 5-4 Amendment No. pp. 7J 177, J U. 147 WQ
t Docket No. 50423 816844 I
I Millstone Nuclear ower Station, Unit No. 3 o
Proposed Revision to Technical Specification Residual Heat Removal System
+
Open Pressure Interlock (PTSCR 3-36-97)
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- 816844Wttachment 3Page1 o
RETYPE 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 submittel 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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EMERGENCY CORE. COOLING $Y$TEMS SURVEILLANCE REQUIREMENTS
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4.5.2 Each ECCS subsystem shall be demonstrated OPERABLE:
a.
At least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> by verifying that the following valves are in the indicated positions with power to the valve operators removed:
Valve Number Valve Function Valve Position 3SIH*MV8806 RWST Supply to SI Pumps OPEN 3SlH*MV8802A SI Pump A to Hot leg Injection CLOSED 3SlH*MV8802B SI Pump B to Hot Leg Injection CLOSED 3SlH*MV8835 SI Cold Leg Master Isolation OPEN 3SIH*HV8813 SI Pump Master Miniflow OPEN
! solation 3SIL*MV8840 RHR to Hot leg Injection CLOSED 3SIL*MV8dO9A RHR Pump A to Cold Leg OPEN Injection 3SIL*MV80098 RHR Pump B to Cold Leg OPEN Injection b.
At least once per 31 days by:
1)
Verify!ng that the ECCS piping, except for the operating centrifugal charging pump (s) and associated piping, the RSS pump, the RSS heat exchanger and associated piping, is full of water, and 2)
Verifying that each valve (manual, power operated, or automatic) in the flow path that is not locked, sealed, or othe. wise secured in position, is in its correct position.
c.
By e visual inspection which verifies that no loose debris (rags, trash, clothing, etc.) is present in the containment which could be transported to the containment sump and cause restriction of the aump suctions during LOCA conditions. This visual inspection shall
)e performed:
1)
For all accessible areas of the containment prior to establish-ing CONTAINMENT INTEGRITY, and 2)
At least once dail,/ of the areas affected (during each day) within containment by containment entry and during the final entry when CONTAINMENT INTEGRITY is established, d.
At least once each REFUELING INTERVAL by:
1)
Verifying automatic interlock action of the RHR System from the Reactor Coolant System by ensuring that with a simulated signal greater than or equal to 412.5 psia the interlocks prevent the valves from being opened.
MILLSTONE - UNIT 3 3/4 5-4 Amendment No. pp. 77, Jpp, 17J, /J7, 0604
Docket No. 50-423 i
B16844 i
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Millstone Nuclear Powr Station, Unit No. 3 Proposed Revision to Technical Specification Residual Heat Removal System Ooen Pressure interlock (PTSCR 3-36-97)
Description of the Chanoe. Backaround and Safety Assessment 4
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November 1997 l
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U.S. Muclear Regulatory Commission B1684- \\ Attachment 4\\Page 1 Description of the Chance Technical Specification Surveillcoce Requirement 4.5.2.d.1 currently requires
" Verifying automatic interlock action of the RHR System from the Reactor Coolant System by ensuring that with a simc.;ted or actual Reactor Coolant System presture signal greater than or equal to 390 psia the interlocks prevent the valves from being opened." The proposed change will change the pressure f om 390 psia to 412.5 psia to take the bistable reset into account and delete the words 'or actual Reactor Coolant System pressure".
Backoround One function of the Residual Heat Removal (RHR) system is to provide cooling of the Reactor Coolant System and remove decay heat from the core. The RHR system is connected to the RCS at two locations to provide dual train cooling capability. The RHR system is a low pressure system with most of the piping and components rated at 600 psig. Since the RCS system operates at 2235 psig, the RHR system requires isolation valves to prevent over pressurization. These isolation valves are a series of 3 motor operated valves on each train. The open pressure interlock (OPI) is present on two of the three valves. The third valve, closest to the RCS loop, is normally closed with its power breaker locked out.
Technical Specifications do not provide a specific basis statement for the OPl. The obvious purpose of the OPl is to prevent an inadvertent opening of the valves when the RCS pressure signal is in excess of the RHR system design pressure limits.
Westinghouse provides the following description in WCAP-11736:
The OPl (Open Pressure Interlock-W acronym) prevents inadvertent openino cf the suction / isolation valves when the RCS pressure is above the design pressure of the RHRS considering RHR pump discharge pressure. The pressure setpoint is normally about 400 psig when instrument uncertainties are included.
In tha past there was an additional interlock, the Auto Closure Interlock (ACl). This feature was to protect the RHR system from pressure transients and automatically close the MOVs when pressure exceeded 750 psig (765 psla). This feature was removed from MP-3 alcng with numerous other plants when it was discovered that the increased instrumentation led to a number of spurious auto closures which isolated RHR cooling. Westinghouse provided Probabilistic Risk Assessment (PRA) analysis demonstrating that retaining the ACI feature was actually less safe the remeving it.
However, in the analysis, the OPl feature was credited for preventing valves from opening when pressure was above 390 psia. Plant specific analysis was conducted to assure that the capacity of the RHR relief valves was sufficient to relieve pressure while credited operator action was taken to close the valves.
U.S. Nuclear Regulatory Commission P16844\\ Attachment 4\\Page 2 A number of factors are taken into account in the setting of the OP!. Additional system pretsure protection is provided by the RHR suction relief valves; 3RHS*RV8708A/B.
These valves have a setpoint of 440 +/- 3% psig (426.8 - 453.2 psig). Therefore, one of the restrictions in the OPl setpoint is tc not exceed the minimum setpoint of the RHR suction relief valve of 426.8 psig.
A second consideration will be the RHR pump discharge pressure developed when the pumps are operating. The combination of the existing RCS pressure (when the MOVs are open to the RCS,ystem) plus the pump discharge pressure m'ast not exceed the 600 psig piping system limit. As a result of recent RHR system tevng, the maximum t
developed purnp discharge pressures (dead head pressure) was determined to be 195 psi differential (psid), (Reference IST 3 97-000 ami 3 97-007). Based on this, the OPl setpoint could be no higher than 405 psig (600-195) or 420 psia. Differences in head height from the pressure transmitters to th9 RHR pump amount to less than 2 psig and are considered insignificant. Deadheading the RHR pump is not considered normal operation of the system. RHR is normally initiated by opening the valves without the RHR pumps running. Flow commences immediately on pump start and thus, system pressures are significantly lower than the deadheaded condition.
To increase the margin between the minimum relief valve setting of 426.8 psig (441.8 psia) and the maximum RHR system limit of 405 psig (420 psla), a value of 397.5 psi (412.5 psia) was chosen. This is the maximum value for the OPl bistable to 0
reset on increasing cignal pressure. The bistable will continue to be set :;o that during cooldown the valves can be opened when RCS signal pressure is reduced to 390 psia i calibration tolerances. Should RCS pressure subsequently increase, a high pressure alarm on the control room board notifies the operator to take action and close the valves.
(NOTE:
For the purposes of this description of proposed Technical Specification changes a standard conversion of psia = psig + 15 psi has been used for convenience.)
SAFETY ASSESSMENT LER 97-031-00 was submitted to the Nuclear Regulatory Commission describing an event which concluded '. hat the RHR System Open Pressure Interlock (OPI) did not comply with Technical Specification Surveillance Requirement 4.5.2.d.1. As a resu;t of inappropriate calibration techniques, the OPI bistable was calibrated to a nominal 390 psia decreasing pressure and didn't consider the effects of instrument uncertainties and reset tolerances. As a result, the bistables could prematurely trip on decreasing pressure signal (above 390 psia) and then reset on an increasing pressure signal at a
U.S. Nuclear Reguictory Commission B16844\\Attachme.nt 4\\Page 3 higher pressure. This does not meet the requirements of the Technical Specifications for a 390 psia interlock, in crder to account for instrument inaccuracies, deadbands, resets etc; a higher maximum allowable setpoint range is required. The 412.5 psia apper limit will be the maximum pressure signal at which the OPl bistables will reset after actuation and allow the RHR suction MOV's to be opened. At any pressure signal above 412.5 psia the OPl bistables will prevent the MOV's from opening. By accounting for bistable inaccuracles and reset deadbands, the bistable can continue to be calibrated so the valves can be opened at or below a nominal 390 psia.
The bistable receives an electric current to actuate. Therefore the bistable is not reading the " actual RCS pressure". This signal is generated from pressure transmitters which input into electronic sumrnation cards and is ultimately transmitted to indicators and the bistable. The OPl surveillance uses a simulated transmitter signal representative of the proass pressure.
Each train connecting RHR to RCS contains three valves which isolate the two systems from each other. One valve is directly controlled by the operators, the other two are interlocked with this RCS pressure permissive. On each train these two valves receive their permissive from signals derived through separata, independent sources. Although these instrumentation channels have inherent uncertainties associated with them it is unlikely that the uncertainties would bias both of these independent sources in a non-conservclive direction at the same time. Therefore, if one train erroneously permit its RHR valve to open, it is unlikely that the other train permissive would also exit the same time thereby allowing connection to the RCS at a higher pressure than (
cted.
Additionally, should both permissives be erroneously present, the RHR will be protected from over-pressurization by the suction relief valves.
The increase in the Technical Specification OPl setting will not result in changes to the operation of the RHR system. The increased pressure is simply taking into account the reality of bistable setpoint and reset tolerances. The RHR system will still be administratively controlled by the Operating Procedures to initiate RHR/RCS cooldown at less than 390 psla/350 degrees F.
Increasing the pressure vs. decreasing the Technical Specification pressure was required in order to avoid impacting reactor coolant pump NPSH. Therefore, not decreasing the pressure setpoint maintains the current NPSH margin for the RCPs at 350 degrees F.
In summary, the Technical Specification requirement to provide an Open Pressure Interlock (OPI)is to protect the RHR piping system from inadvertent c>pening of Motor Operated Valve (MOV) isolation valves. The OPl will remain in use. However, the
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U.S. Nuclear RegulClory Commission B16844Wttacnment 4\\Page 4 m! 'e oressure increase is necessary to account for instrument calibration tolerances and rei at deadbands. The deletion of ' actual RCS oressure" is to clarify that the OPl generotes instrument sianals derived from pressure transmitters measuring RCS pressure. There is no direct pressure reading to the bistable. These changes more i
accurately describe the verification test used for thc OPl. The RHR piping remains properly protected from inadvertent valve opening.
i Based on the above, the proposed Technical Specification change is safe.
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1 Docket No. 50-423 B16844 i
Millstone Nuclear Power Station, Unit No. 3 Proposed Revision to Technical Specification Residual Heat Removal System Open Pressure Interlock i
(PTSCR 3-36-97)
Slanificant Hazards Consideration and Environmental Considerations 5
i November 1997 I
e U.S. r4uclear Regulatory Commission B16844\\ Attachment 5\\Page 1 Sianificant Hazards Consideration NNECO has reviewed the proposed revision in accordance with 10CFR50.92 and has i
concluded that the revision does not involve a significant hazerds consideration (SHC).
The basis for this conclusion is that the three criteria of 10CFR50.92(c) are not satisfied. The proposed revision does not involve a SHC because the revision would not:
1.
Involve a significant increase in the probability or consequence of an accident previously evaluated.
Increasing the Technical Specification Open Pressure Interlock (OPI) pressure to 412.5 psia will still maintain the required function of preventing the MOVs from opening inadvertently. The increased pressure is within the design limits of the RHR piping system and components. The pressure signal is generated from a transmitter and results in an electronic input to the bistable.
This is a clarification of the conditions under which the OPl is tested.
Therefore, the proposed revision does 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.
Theie is no change to the function of the OPl. The protection provided by the interlock remains intact. The Technical Spacification OPl pressure has been raised to take into account instrument accuracies and reset deadbands. The RHR system design pressure remains protected from being exceeded by inadvertent opening of the isolation MOVs. The method for the OPI surveillance is clarified by clearly stating that the bistable receives a simulated transmitter signal representative of the process pressure.
Therefore, the proposed revision does not create the possibility of a new or different kind of accident from any accident previously evaluated.
3.
Involve a significant reduction in a margin of safety.
The design pressure of the RHR system is 600 psig. The most limiting case is to prevent the RHR pump developed head pressure from exceeding the design pressure when aligned to the RCS as suction pressure. RHR pump testing has determined that a maximum pump differential pressure of 195 psi exists for deadhead /no flow conditions. Therefore, to maintain the 600 psig design pressure limit, RCS/ suction pressure must be limited to 405 psig (420 psia, assuming a 15 psi conversion from psig to psla). The proposed maximum pressure, including setpoint tolerances and reset deadbands, is less than this
U.S.' Nuclear Regulatory Commission B16844Wttachment SPage 2 value; i.e. 412.5 psia.
Head corrections due to elevation differences are considered to be insignificant.
Therefore, the proposed revision does not involve a significant reduction in a margin of safety, in conclusion, based on the information provided,'it is determined that the proposed i
revision does not involve en SHC.-
2 i
Q1Yk9amattaLGenalder.allana NNECO has reviewed the proposed license amendment against the criteria of 10CFR51.22 for environmental onsiderations. The proposed revision does not involve l
a SHC, does not significantiy increase the type and emot.nts 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 revision meets the criteria delineated in 10CFR51.22(c)(9) for categorical exclusion from the requirements for environmental review.
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