ML20147G662
| ML20147G662 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 03/21/1997 |
| From: | NORTHEAST NUCLEAR ENERGY CO. |
| To: | |
| Shared Package | |
| ML20147G661 | List: |
| References | |
| NUDOCS 9703280221 | |
| Download: ML20147G662 (9) | |
Text
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Docket No. 50-423 B16309 Millstone Nuclear Power Station Unit No. 3 Marked Uo Bases Paoes March 1997 9703280221 970321 PDR ADOCK 05000423:-
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PLANT SYSTEMS BASES 3/4.7.1.5 MAIN STEAM LINE ISOLATION VALVES The OPERABILITY of the main steam line isolation valves ensures that no more than one steam generator will blow down in the event of a steam line rupture. This restriction is required to:
(1) minimize the positive reac-i tivity effects of the Reactor Coolant System cooldown associated with the blowdown, and (2) limit the pressure rise within containment in the event the i
steam line rupture occurs within containment. The OPERABILITY of the main steam isolation valves within the closure times of the Surveillance Require-ments are consistent with the assumptions used in the safety analyses.
3/4.7.2 STEAM GENERATOR PRESSURE / TEMPERATURE LIMITATION The limitation on steam generator pressure and temperature ensures that the pressure-induced stresses in the steam generators do not exceed the maximum allowable fracture toughness stress limits. The limitations of 70*F and 200 psig are based on a steam generator RT m of 60*F and are sufficient to prevent brittle fracture.
l 3/4.7.3 REACTOR PLANT COMPONENT COOLING WATER SYSTEM The OPERABILITY of the Reactor Plant Component Cooling Water System ensures that sufficient cooling capacity is available for continued operation of safety-related equipment during normal and accident conditions. S e redundant cooling capacity of this system, assuming a single failure, is consistent with the assumptions used in the safety analyses.
3/4.7.4 SERVICE WATER SYSTEM The OPERABILITY of the Service Water System ensures that sufficient cooling capacity is avaliable for continued operation of safety-related equip-mont during normal and acc! dent conditions. The redundant cooling capacity of this system, assuming a single failure, is consistent with the assumptions used in the safety analyses.
3/4.7.5 ULTIMATE HEAT SINK 4
Backaround The ultimate heat sink (UHS) for Millstone Unit No. 3 is Long Island Sound.
It serves as a heat sink for both safety and nonsafety-related cooling systems.
j Sensible heat is discharged to the UHS via the service water and circulating water systems, i
limitina Condition for Operation The UHS is required to be OPERABLE and is considered OPERABLE if the average water temperature is less than or equal to 75'F. The limitation on the UHS temperature ensures that cooling water a less than the design temperature (75'F)
MILLSTONE - UNIT 3 B 3/4 7-3 Amendment No. 119
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PLANT SYSTEMS
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J,1ytitina Condition for Operation (Continued) is available to either (1) provide normal cooldown of the facility or (2) mitigate the effects of accident conditions within acceptable limits.
It is based on providing a 30-day cooling water supply to safety-related equiment without exceeding its design basis temperature and is consistent with tie recommendations of Regulatory Guide 1.27, " Ultimate Heat Sink for Nuclear g ht A Plants," March 1g74.
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Anolicability In MODES 1, 2, 3, AND 4, the UHS is required to support the OPERABILITY of the equipment serviced by the UHS and required to be OPERABLE in these N0 DES.
Action Statement j
When the UHS temperature is above 75'F, the Action Statement for the LCO requires that the UHS temperature be monitored for 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, and the plant be placed in at least HOT STAND 8Y within the next six hours and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> in the event the UHS temperature does not drop below 75'F during the 12-hour monitoring period.
The 12-hour interval is based on operating experience related to trending of the parameter variations during the applicable modes. During this period, the UHS temperature will be monitored on an increased frequency.
If the trend shows improvement, and if the trend of the UHS temperature gives reasonable expectations that the temperature will decrease below 75'F during the 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> monitoring period, the UHS temperature will be continued to be monitored during the remaining portion of the 12-hour period. However, if it becomes apparent that the UHS temperature will rrmain above 75'F throughout the 12-hour monitoring period, conservative action regarding compliance with the Action Statement should be taken.
An evaluation was conducted to qualify the risk significance of various Chapter 15 initiating events and eartSquakes during periods of elevated UHS temperature.
It concluded that a seismi event was not credible for the ti p ds with elevated.. UHS temperature.
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A NILLSTONE - UNIT 3 B 3/4 7-4 Amendment No. 119
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j PLANT SYSTEMS nAsEs 1
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j Action Sta F --t (Continued)
I With respect to the service water loads, the limiting Condition II and III Chapter 15 event initiators are those that add additicnal heat loads to the l
service water system. A loss of offsite power etent i.; limiting because of the i
i added loads due to the diesel generator and the residuel heat removal heat exchanger. A steam generator tube rupture event is limiting because of the addition of the safety injection and diesel generator loads without isolation of the turbine plant component cooling water loads (n oss of fsite power or Letb !
containment depressurization actuation signal)..;th _:....:::, scenarios have g
been evaluated with the additional consideration o a single failure. The l
evaluation investigated whether or not these events could te resolved with an elevated UHS temperature.
It was determined that Millstone Unit No. 3 could i
j recover from these events, even with an elevated temperature of 77'F.
This evaluation provides the basis for the action statement requirement to place l
the plant in HOT STAND 8Y with six hours and in COLD SHUTDOWN within the next i
J 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />, if the UHS temperature goes above 77'F during the 12-hour monitoring i
period.
l Surveillance Reauiraments l
i For the surveillance requirements, the UHS temperature is measured at the j
j locations described in the LCO write-up provided in this section.
1 i
Surveillance Requirement 4.7.5.a verifies that the UHS is capable of providing a 30-day cooling water supply to safety-related equipment without exceeding its design basis temperature. The 24-hour frequency is based on operating experience related to trending of the parameter variations during the applicable modes.
l This surveillance requirement verifies that the average water temperature of the l
UHS is less than or equal to 75'F.
l Surveillance Requirement 4.7.5.b requires that the UHS temperature be monitored on an increased frequency whenever the UHS temperature is greater than 70*F during the applicable modes. The intent of this Surveillance Requirement is to increase the awareness of plant personnel regarding UHS temperature trends above j
70*F.
The frequency is based on operating experience related to trending of the parameter variations during the applicable modes.
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s NILL 5 TONE - UNIT 3 3 3/4 7-5 Amendment No. 119 i
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Insert A The Circulating Water System has six condenser inlet waterboxes, each contains a temperature measurement device. The average UHS temperature is normally obtained from the plant process computer by averaoing the six Circulating Water System j
condenser inlet waterbox temperature measurements.
Given potential condenser waterbox temperature instrumentation failure (s), or that a waterbox is not operating, or a process computer failure, other methods may be used to determine the average UHS temperature.
For example, if one condenser waterbox instrument has failed, the average UHS temperature may be based on five condenser inlet waterbox temperature measurements.
For the purposes of determining average UHS temperature, if condenser waterbox inlet temperature is used, the average should be based on no less than 3 measurements. If the process computer condenser waterbox inlet temperature average is based on less than three measurements, the average is automatically flagged to users as potentially in error. Using local Service Water System temperature instruments (two or more) is an acceptable alternative for determining average UHS i
temperature.
It has been concluded that using the average of multiple condenser waterbox inlet temperature measurements is sufficiently representative of the UHS temperature to assure OPERABILITY of the UHS. The only exception to this conclusion is when a
[
condenser thermal backwash evolution is being conducted. During this evolution, there is a potential for significant intake structure temperature stratification.
Therefore, during condenser thermal backwashing evolutions, the average UHS temperature shall l
be monitored by temperature instruments in the service water system to assure OPERABILITY of the UHS.
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insert B i
Although the risk significance of a Condition IV accident occurring during the period of elevated UHS temperature is considered to be negligibly small compared to that of Condition 11 and ill events, Loss cf Coolant Accident with or without a LOP was also evaluated. These...
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Docket No. 50-423 i
B16309 i
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Millstone Nuclear Power Station Unit No. 3 Retvoed Bases Prqqa j
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i March 1997 l
PUWT SYSTEMS
' BASES i
)
4 3/4.7.1.5 MAIN STEAM LINE ISOLATION VALVES The OPERABILITY of the main steam line isolation valves ensures that no l
more than one steam generator will blow down in the event of a steam line rupture. This restriction is required to:
(1) minimize the positive reac-j tivity effects of the Reactor Coolant System cooldown associated with the blowdown, and (2) limit the pressure rise within containment in the event the l
a l
steam line rupture occurs within containment. The OPERABILITY of the main steam isolation valves within the closure times of the Surveillance Require-ments are consistent with the assumptions used in the safety analyses, j
3/4.7.2 STEAM GENERATOR PRESSURE / TEMPERATURE LIMITATION 1
i The limitation on steam generator pressure and temperature ensures that i
the pressure-induced stresses in the steam generators do not exceed the maximum a
allowable fracture toughness stress limits. The limitations of 70*F and l
200 psig are based on a steam generator RTuor of 60*F and are sufficient to
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prevent brittle fracture.
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l 3/4.7.3 REACTOR PLANT COMPONENT COOLING WATER SYSTEM r
The OPERABILITY of the Reactor Plant Component Cooling Water System ensures that sufficient cooling capacity is available for continued operation of safety-related equipment during normal and accident conditions. The redundant cooling j
capacity of this system, assuming a single failure, is consistent with the j
assumptions used in the safety analyses.
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3/4.7.4 SERVICE WATER SYSTEM The OPERABILITY of the Service Water System ensures that sufficient cooling capacity is available for continued operation of safety-related equip-ment during normal and accident conditions. The redundant cooling capacity of this system, assuming a single failure, is consistent with the assumptions used in the safety analyses.
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3/4.7.5 ULTIMATE HEAT SINK
Background
The ultimate heat sink (UHS) for Millstone Unit No. 3 % Long Island Sound.
It serves as a heat sink for both safety and nonsafety-rei ted cooling systems.
Sensible heat is discharged to the UHS via the service w.+er and circulating water systems.
Limitino Condition for Operation The UHS is required to be OPERABLE and is considered OPERABLE if the average water temperature is less than or equal to 75'F. The limitation on the UHS temperature ensures that cooling water at or less than the design temperature l
NILLSTONE - UNIT 3 B 3/4 7-3 Amendment No. JJ7, ones
PLAPT SYSTEMS
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BASES Limitina Condition for Operation (Continued)
(75'F) is available to either (1) provide normal cooldown of the facility or (2) mitigate the effects of accident conditions within acceptable limits.
It is based on providing a 30-day cooling water supply to safety-related equi ment l
without exceeding its design basis temperature and is consistent with tie recommendations of Regulatory Guide 1.27, " Ultimate Heat Sink for Nuclear Plants," March 1974.
The Circulating Water System has six condenser inlet waterboxes, each contains a temperature measurement device. The average UHS temperature is normally obtained from the plant process computer by averaging the six Circulating Water System condenser inlet waterbox temperature measurements. Given potential condenser waterbox temperattre instrumentation failure (s), or that a waterbox is not operating or a pro:ess computer failure, other methods may be used to determine the average UHS teamerature.
For example, if one condenser waterbox instrument has failed, the average UHS temperature may be based on five condenser inlet waterbox temperature measurements.
For the purposes of determining average UHS temperature, if condenser waterbox inlet temperature is used, the average should be based on no less than 3 measurements.
If the process computer condenser waterbox inlet temperature average is based on less than three measurements, the average is automatically flagged to users as potentially in error. Using local Service Water System temperature instruments (two or more) is an acceptable alternative for determining average UHS temperature.
It has been concluded that using the average of multiple condenser waterbox inlet temperature measurements is sufficiently representative of the UHS temperature to assure OPERABILITY of the UHS. The only exception to this conclusion is when a condenser thermal backwash evolution is being conducted. During this evolution, there is a potential for significant intake structure temperature stratification.
Therefore, during condenser thermal backwashing evolutions, the average UHS temperature shall be monitored by temperature instruments in the service water system to assure OPERABILITY of the UHS.
Anolicability In MODES 1, 2, 3, AND 4, the UHS is required to support the OPERABILITY of the equipment serviced by the UHS and required to be OPERABLE in these MODES.
Action Statement When the UHS temperature is above 75'F, the Action Statement for the LC0 requires that the UHS temperature be monitored for 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, and the plant be placed in at least HOT STANDBY within the next six hours and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> in the event the UHS temperature does not drop below 75'F during the 12-hour monitoring period.
The 12-hour interval is based on operating experience related to trending of the parameter variations during the applicable modes. During this period, the UHS temperature will be monitored on an increased frequency.
If the trend shows improvement, and if the trend of the UHS temperature gives reasonable expectations that the temperature will decrease below 75'F during the 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> MI.LLSTONE - UNIT 3 B3/47-4 Amendment No. JJP,
PLANT SYSTEMS x
)
j Action Stat-- t (Continued) i i
monitoring period, the UHS temperature will be continued to be monitored during the remaining portion of the 12-hour period. However, if it becomes apparent that the UHS temperature will remain above 75'F throughout the 12-hour monitoring j
period, conservative action regarding compliance with the Action Statement should be taken.
i i
An evaluation was conducted to qualify the risk significance of various i
L Chapter 15 initiating events and earthquakes during periods of elevated UHS temperature.
It concluded that a seismic event was not credible for the time j
periods with elevated UHS temperature.
With respect to the service water loads, the limiting Condition II and III l
1 Chapter 15 event initiators are those that add additional heat loads to the l
service water system. A loss of offsite power event is limiting because of the added loads due to the diesel generator and the residual heat removal heat i
exchanger. A steam generator tube rupture event is limiting because of the addition of the safety injection and diesel generator loads without isolation of the turbine plant component cooling water loads (no loss of offsite power or j
containment depressurization actuation signal). Although the risk significance i
of a Condition IV accident occurring during the period of elevated UHS temperature is considered to be negligibly small compared to that of Condition II and III events, a Loss of Coolant Accident with or without a LOP was also 4
evaluated. These scenarios have been evaluated with the additional consideration j
of a single failure. The evaluation investigated whether or not these events could be resolved with an elevated UHS temperature.
It was determined,that Nillstone Unit No. 3 could recover from these events, even with an elevated temperature of 77'F.
I This evaluation provides the basis for the action statement requirement to place the plant in HOT STANDBY with six hours and in COLD SHUTDOWN within the next 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />, if the UHS temperature goes above 77'F during the 12-hour monitoring j
period.
Surveillance Reauirements 1
\\
i For the surveillance requirements, the UHS temperature is measured at the l
locations described in the LCO write-up provided in this section.
o Surveillance Requirement 4.7.5.a verifies that the UHS is capable of providing a i
30-day cooling water supply to safety-related equipment without exceeding its
~
design basis temperature. The 24-hour frecuency is based on operating experience related to trending of the parameter variations during the applicable modes.
This surveillance requirement verifies that the average water temperature of the UHS is less than or equal to 75'F.
Surveillance Requirement 4.7.5.b requires that the UHS temperature be monitored on an increased frequency whenever the UHS temperature is greater than 70*F during the applicable modes. The intent of this Surveillance Requirement is to increase the awareness of plant personnel regarding !SS temperature trends above 70'F.
The frequency is based on operating experience rel ted to trending of the parameter variations during the applicable modes.
NI.LLSTONE - UNIT 3 5 3/4 7-5 Amendment No. JJ7,
.