ML14339A765
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PAM Instrumentation B 3.3.3 McGuire Unit 1 and 2 B 3.3.3-1 Revision No. 122 B 3.3 INSTRUMENTATION B 3.3.3 Post Accident Monitoring (PAM) Instrumentation BASES BACKGROUND The primary purpose of the PAM instrumentation is to display unit variables that provide information required by the control room operators during accident situations. This information provides the necessary support for the operator to take the manual actions for which no automatic control is provided and that are required for safety systems to accomplish their safety functions for Design Basis Accidents (DBAs).
The OPERABILITY of the accident monitoring instrumentation ensures that there is sufficient information available on selected unit parameters to monitor and to assess unit status and behavior following an accident.
The availability of accident monitoring instrumentation is important so that responses to corrective actions can be observed and the need for, and magnitude of, further actions can be determined.
These essential instruments are identified by unit specific documents (Ref. 1) addressing the recommendations of Regulatory Guide 1.97 (Ref. 2) as required by Supplement 1 to NUREG-0737 (Ref. 3).
The instrument channels required to be OPERABLE by this LCO include two classes of parameters identified during unit specific implementation of Regulatory Guide 1.97 as Type A and Category I variables.
Type A variables are included in this LCO because they provide the primary information required for the control room operator to take specific manually controlled actions for which no automatic control is provided, and that are required for safety systems to accomplish their safety functions for DBAs.
Category I variables are the key variables deemed risk significant because they are needed to:
Determine whether other systems important to safety are performing their intended functions; Provide information to the operators that will enable them to determine the likelihood of a gross breach of the barriers to radioactivity release; and
PAM Instrumentation B 3.3.3 BASES McGuire Unit 1 and 2 B 3.3.3-2 Revision No. 122 BACKGROUND (continued)
Provide information regarding the release of radioactive materials to allow for early indication of the need to initiate action necessary to protect the public, and to estimate the magnitude of any impending threat.
These key variables are identified by the unit specific Regulatory Guide 1.97 analyses (Ref. 1). These analyses identify the unit specific Type A and Category I variables and provide justification for deviating from the NRC proposed list of Category I variables.
The specific instrument Functions listed in Table 3.3.3-1 are discussed in the LCO section.
APPLICABLE The PAM instrumentation ensures the operability of Regulatory Guide SAFETY ANALYSES 1.97 Type A and Category I variables so that the control room operating staff can:
Perform the diagnosis specified in the emergency operating procedures (these variables are restricted to preplanned actions for the primary success path of DBAs), e.g., loss of coolant accident (LOCA);
Take the specified, pre-planned, manually controlled actions, for which no automatic control is provided, and that are required for safety systems to accomplish their safety function; Determine whether systems important to safety are performing their intended functions; Determine the likelihood of a gross breach of the barriers to radioactivity release; Determine if a gross breach of a barrier has occurred; and Initiate action necessary to protect the public and to estimate the magnitude of any impending threat.
PAM instrumentation that meets the definition of Type A in Regulatory Guide 1.97 satisfies Criterion 3 of 10 CFR 50.36 (Ref. 4). Category I, non-Type A, instrumentation must be retained in TS because it is intended to assist operators in minimizing the consequences of accidents.
Therefore, Category I, non-Type A, variables are important for reducing public risk.
PAM Instrumentation B 3.3.3 BASES McGuire Unit 1 and 2 B 3.3.3-3 Revision No. 122 LCO The PAM instrumentation LCO provides OPERABILITY requirements for Regulatory Guide 1.97 Type A monitors, which provide information required by the control room operators to perform certain manual actions specified in the unit Emergency Operating Procedures. These manual actions ensure that a system can accomplish its safety function, and are credited in the safety analyses. Additionally, this LCO addresses Regulatory Guide 1.97 instruments that have been designated Category I, non-Type A.
The OPERABILITY of the PAM instrumentation ensures there is sufficient information available on selected unit parameters to monitor and assess unit status following an accident. This capability is consistent with the recommendations of Reference 1.
LCO 3.3.3 requires two OPERABLE channels for most Functions. Two OPERABLE channels ensure no single failure prevents operators from getting the information necessary for them to determine the safety status of the unit, and to bring the unit to and maintain it in a safe condition following an accident.
Furthermore, OPERABILITY of two channels allows a CHANNEL CHECK during the post accident phase to confirm the validity of displayed information.
In some cases, the total number of channels exceeds the number of required channels, e.g., pressurizer level has a total of three channels, however only two channels are required OPERABLE. This provides additional redundancy beyond that required by this LCO, i.e., when one channel of pressurizer level is inoperable, the required number of two channels can still be met. The ACTIONS of this LCO are only entered when the required number of channels cannot be met.
Category I variables are required to meet Regulatory Guide 1.97 Category I (Ref. 2) design and qualification requirements for seismic and environmental qualification, single failure criterion, utilization of emergency standby power, immediately accessible display, continuous readout, and recording of display.
Listed below are discussions of the specified instrument Functions listed in Table 3.3.3-1.
- 1.
Neutron Flux - (Wide Range)
Wide Range Neutron Flux indication is provided to verify reactor shutdown.
PAM Instrumentation B 3.3.3 BASES McGuire Unit 1 and 2 B 3.3.3-4 Revision No. 122 LCO (continued)
Neutron flux is used for accident diagnosis, verification of subcriticality, and diagnosis of positive reactivity insertion.
Two channels of wide range neutron flux are required OPERABLE.
2, 3.
Reactor Coolant System (RCS) Hot and Cold Leg Temperatures RCS Hot and Cold Leg Temperatures are Category I variables provided for verification of core cooling and long term surveillance.
RCS hot and cold leg temperatures are used to determine RCS subcooling margin. RCS subcooling margin will allow termination of safety injection (SI), if still in progress, or reinitiation of SI if it has been stopped. RCS subcooling margin is also used for unit stabilization and cooldown control.
In addition, RCS cold leg temperature is used in conjunction with RCS hot leg temperature to verify the unit conditions necessary to establish natural circulation in the RCS.
Reactor coolant hot and cold leg temperature inputs are provided by fast response resistance elements and associated transmitters in each loop.
Two channels of RCS Hot Leg Temperature and two channels of RCS Cold Leg Temperature are required OPERABLE by the LCO.
RCS Hot Leg and Cold Leg Temperature are diverse indications of RCS temperature. Core exit thermocouples also provide diverse indication of RCS temperature.
- 4.
Reactor Coolant System Pressure (Wide Range)
RCS wide range pressure is a Category I variable provided for verification of core cooling and RCS integrity long term surveillance.
RCS pressure is used to verify delivery of SI flow to RCS from at least one train when the RCS pressure is below the pump shutoff head. RCS pressure is also used to verify closure of manually closed spray line valves and pressurizer power operated relief valves (PORVs).
PAM Instrumentation B 3.3.3 BASES McGuire Unit 1 and 2 B 3.3.3-5 Revision No. 122 LCO (continued)
In addition to these verifications, RCS pressure is used for determining RCS subcooling margin. RCS pressure can also be used:
to determine whether to terminate actuated SI or to reinitiate stopped SI; to determine when to reset SI and shut off low head SI; to manually restart low head SI; as reactor coolant pump (RCP) trip criteria; and to make a determination on the nature of the accident in progress and where to go next in the procedure.
RCS pressure is also related to three decisions about depressurization. They are:
to determine whether to proceed with primary system depressurization; to verify termination of depressurization; and to determine whether to close accumulator isolation valves during a controlled cooldown/depressurization.
A final use of RCS pressure is to determine whether to operate the pressurizer heaters.
RCS pressure is a Type A variable because the operator uses this indication to monitor the cooldown of the RCS following a steam generator tube rupture (SGTR) or small break LOCA. Operator actions to maintain a controlled cooldown, such as adjusting steam generator (SG) pressure or level, would use this indication.
Furthermore, RCS pressure is one factor that may be used in decisions to terminate RCP operation.
Two channels of wide range RCS pressure are required OPERABLE.
PAM Instrumentation B 3.3.3 BASES McGuire Unit 1 and 2 B 3.3.3-6 Revision No. 122 LCO (continued) 5, 6.
Reactor Vessel Water Level Reactor Vessel Water Level is provided for verification and long term surveillance of core cooling. It is also used for accident diagnosis and to determine reactor coolant inventory adequacy.
The Reactor Vessel Water Level Monitoring System provides a direct measurement of the collapsed liquid level above the fuel alignment plate. The collapsed level represents the amount of liquid mass that is in the reactor vessel above the core.
Measurement of the collapsed water level is selected because it is a direct indication of the water inventory.
Two channels of Reactor Vessel Water Level are provided in both the core region (lower range) and the head region (wide range) with indication in the unit control room. Each channel uses differential pressure transmitters and a microprocessor to calculate true vessel level or relative void content of the primary coolant.
- 7.
Containment Sump Water Level (Wide Range)
Containment Sump Water Level is provided for verification and long term surveillance of RCS integrity.
Containment Sump Water Level is used to determine:
containment sump level accident diagnosis; and when to continue the recirculation procedure.
Two channels of wide range level are required OPERABLE. Each channel consists of wide range level indication and two level switches.
- 8.
Containment Pressure (Wide Range)
Containment Pressure (Wide Range) is provided for verification of RCS and containment OPERABILITY.
Containment pressure is used to verify closure of main steam isolation valves (MSIVs), containment spray operation, and Phase B containment isolation when Containment Pressure - High High is reached.
PAM Instrumentation B 3.3.3 BASES McGuire Unit 1 and 2 B 3.3.3-7 Revision No. 122 LCO (continued)
Two channels of wide range containment pressure are required OPERABLE.
- 9.
Containment Atmosphere Radiation (High Range)
Containment Atmosphere Radiation is provided to monitor for the potential of significant radiation releases and to provide release assessment for use by operators in determining the need to invoke site emergency plans. Containment radiation level is used to determine if a high energy line break (HELB) has occurred, and whether the event is inside or outside of containment.
Two channels of high range containment atmosphere radiation are provided. One channel is required OPERABLE. Diversity is provided by portable instrumentation or by sampling and analysis.
- 10.
Not Used
- 11.
Pressurizer Level Pressurizer Level is used to determine whether to terminate SI, if still in progress, or to reinitiate SI if it has been stopped.
Knowledge of pressurizer water level is also used to verify the unit conditions necessary to establish natural circulation in the RCS and to verify that the unit is maintained in a safe shutdown condition.
Three channels of pressurizer level are provided. Two channels are required OPERABLE.
- 12.
Steam Generator Water Level (Narrow Range)
SG Water Level is provided to monitor operation of decay heat removal via the SGs. The Category I indication of SG level is the narrow range level instrumentation.
PAM Instrumentation B 3.3.3 BASES McGuire Unit 1 and 2 B 3.3.3-8 Revision No. 122 LCO (continued)
SG Water Level (Narrow Range) is used to:
identify the faulted SG following a tube rupture; verify that the intact SGs are an adequate heat sink for the reactor; determine the nature of the accident in progress (e.g., verify an SGTR); and verify unit conditions for termination of SI during secondary unit HELBs outside containment.
Four channels per SG of narrow range water level are provided.
Only two channels are required OPERABLE by the LCO.
13, 14, 15, 16.
Core Exit Temperature Core Exit Temperature is provided for verification and long term surveillance of core cooling.
Adequate core cooling is ensured with two valid Core Exit Temperature channels per quadrant with two CETs per required channel. Core inlet temperature data is used with core exit temperature to give radial distribution of coolant enthalpy rise across the core. Core Exit Temperature is used to determine whether to terminate SI, if still in progress, or to reinitiate SI if it has been stopped. Core Exit Temperature is also used for unit stabilization and cooldown control.
Two OPERABLE channels of Core Exit Temperature are required in each quadrant to provide indication of radial distribution of the coolant temperature rise across representative regions of the core.
Two sets of two thermocouples (1 set from each redundant power train) ensure a single failure will not disable the ability to determine the radial temperature gradient.
- 17.
Auxiliary Feedwater Flow AFW Flow is provided to monitor operation of decay heat removal via the SGs.
PAM Instrumentation B 3.3.3 BASES McGuire Unit 1 and 2 B 3.3.3-9 Revision No. 122 LCO (continued)
The AFW Flow to each SG is determined by flow indicators, pump operational status indicators, and NSWS and condensate supply valve indicators in the control room. The AFW flow indicators are category 2, type D variables which are used to demonstrate the category 1 variable of AFW assured source.
AFW flow is used three ways:
to verify delivery of AFW flow to the SGs; to determine whether to terminate SI if still in progress, in conjunction with SG water level (narrow range); and to regulate AFW flow so that the SG tubes remain covered.
- 18.
RCS Subcooling Margin Monitor RCS subcooling is provided to allow unit stabilization and cooldown control. RCS subcooling will allow termination of SI, if still in progress, or reinitiation of SI if it has been stopped.
The margin to saturation is calculated from RCS pressure and temperature measurements. Display of the RCS subcooling margin values is provided via the Inadequate Core Cooling Monitor Subcooling Margin Monitor (ICCM SMM) and the Plant Computer.
The plant computer is the primary indication for RCS subcooling margin. Backup indication of the RCS subcooling margin consists of two qualified redundant channels each consisting of one ICCM plasma display and one ICCM cabinet, with each ICCM cabinet receiving inputs from 20 core exit thermocouples, one wide range RCS pressure transmitter, and two wide range hot leg RTDs all associated with that channel (train) of ICCM SMM. Therefore, a single train of ICCM SMM including the associated RCS subcooling margin field inputs is equivalent to a single channel of the RCS Subcooling Margin Monitor technical specifications function.
Each train of ICCM SMM uses the average of the five highest core exit thermocouples and the wide range RCS pressure for that train to determine primary system conditions. The primary system conditions are then compared to saturation curves to calculate and display the margin to subcooling. Each train of ICCM SMM also calculates subcooling values for each of the two wide range hot leg temperature RTDs associated with that train.
PAM Instrumentation B 3.3.3 BASES McGuire Unit 1 and 2 B 3.3.3-10 Revision No. 122 LCO (continued)
Therefore, a single train (channel) of SMM provides three diverse subcooling margin values. The diversity of temperature inputs for a channel (train) of the RCS Subcooling Margin Monitor function minimizes the impact to this function resulting from the failure of a single field input.
A graphic display on the ICCM over the required range gives the operator a representation of primary system conditions compared to various curved of importance (saturation, etc.).
Note: Each trains RCS Subcooling Margin values are displayed on the respective trains ICCM SMM display and the Plant Computer.
In addition to displaying the subcooling values received from the ICCM SMM, the plant computer performs independent RCS Subcooling Margin calculations using the average of the five highest core exit thermocouples and wide range RCS pressure to determine primary system conditions. The plant computer compares the primary system conditions to plant computer saturation curves to calculate and display the core margin to subcooling. The plant computer also calculates and displays subcooling values based on the wide range hot leg and cold leg temperature RTDs.
A graphic display on the plant computer over the required range gives the operator a representation of primary system conditions compared to various curves of importance (saturation, NDT, etc.).
A backup program exists to ensure the capability to accurately monitor RCS subcooling. The program includes training and a procedure to manually calculate subcooling margin, using control room pressure and temperature instruments.
- 19.
Steam Line Pressure Steam Line Pressure is provided to monitor operation of decay heat removal via the SGs. Steam line pressure is also used to determine if a high energy secondary line rupture occurred and which SG is faulted.
Two channels of Steam Line Pressure are required OPERABLE.
PAM Instrumentation B 3.3.3 BASES McGuire Unit 1 and 2 B 3.3.3-11 Revision No. 122 LCO (continued)
- 20.
Refueling Water Storage Tank Level RWST level monitoring is provided to ensure an adequate supply of water to the ECCS pumps during the switchover to cold leg recirculation.
Three channels of RWST level are provided. Two channels are required OPERABLE by the LCO.
- 21.
DG Heat Exchanger NSWS Flow Flow indicators are provided in each of the NSWS trains to indicate cooling water flow through the respective train DG. These indicators are provided for operators to manually control flow to the DG heat exchanger. One flow indicator is required OPERABLE on each train.
- 22.
Containment Spray Heat Exchanger NSWS Flow Flow indicators are provided in each of the NSWS trains to indicate cooling water flow through the respective train containment spray heat exchangers. These indicators are provided for operators to manually control flow to the heat exchanger. One flow indicator is required OPERABLE on each train.
APPLICABILITY The PAM instrumentation LCO is applicable in MODES 1, 2, and 3.
These variables are related to the diagnosis and pre-planned actions required to mitigate DBAs. The applicable DBAs are assumed to occur in MODES 1, 2, and 3. In MODES 4, 5, and 6, unit conditions are such that the likelihood of an event that would require PAM instrumentation is low; therefore, the PAM instrumentation is not required to be OPERABLE in these MODES.
ACTIONS A Note has been added in the ACTIONS to clarify the application of Completion Time rules. The Conditions of this Specification may be entered independently for each Function listed on Table 3.3.3-1. When the Required Channels in Table 3.3.3-1 are specified (e.g., on a per steam line, per loop, per SG, etc., basis), then the Condition may be entered separately for each steam line, loop, SG, etc., as appropriate.
The Completion Time(s) of the inoperable channel(s) of a Function will be ACTIONS (continued)
PAM Instrumentation B 3.3.3 BASES McGuire Unit 1 and 2 B 3.3.3-12 Revision No. 122 tracked separately for each Function starting from the time the Condition was entered for that Function.
A.1 Condition A applies to all PAM instrument Functions. Condition A addresses the situation when one or more required channels for one or more Functions are inoperable. The Required Action is to refer to Table 3.3.3-1 and take the appropriate Required Actions for the PAM instrumentation affected. The Completion Times are those from the referenced Conditions and Required Actions.
B.1 Condition B applies when one or more Functions have one required channel that is inoperable. Required Action B.1 requires restoring the inoperable channel to OPERABLE status within 30 days. The 30 day Completion Time is based on operating experience and takes into account the remaining OPERABLE channel, the passive nature of the instrument (no critical automatic action is assumed to occur from these instruments), and the low probability of an event requiring PAM instrumentation during this interval. Condition B is not applicable to functions with a single required channel.
C.1 Condition C applies when the Required Action and associated Completion Time for Condition B are not met. This Required Action specifies initiation of actions in Specification 5.6.7, which requires a written report to be submitted to the NRC immediately. This report discusses the results of the root cause evaluation of the inoperability and identifies proposed restorative actions. This action is appropriate in lieu of a shutdown requirement since alternative actions are identified before loss of functional capability, and given the likelihood of unit conditions that would require information provided by this instrumentation.
PAM Instrumentation B 3.3.3 BASES McGuire Unit 1 and 2 B 3.3.3-13 Revision No. 122 ACTIONS (continued)
D.1 Condition D applies when a single require channel is inoperable.
Required Action D.1 requires restoring the required channel to OPERABLE status within 7 days. The Completion Time of 7 days is based on the relatively low probability of an event requiring PAM instrument operation and the availability of alternate means to obtain the required information. Continuous operation with the required channel inoperable is not acceptable. Therefore, requiring restoration of the required channel to OPERABLE status limits the risk that the PAM function will be in a degraded condition should an event occur.
E.1 Condition E applies when one or more Functions have two inoperable required channels (i.e., two channels inoperable in the same Function).
Required Action E.1 requires restoring one channel in the Function(s) to OPERABLE status within 7 days. The Completion Time of 7 days is based on the relatively low probability of an event requiring PAM instrument operation and the availability of alternate means to obtain the required information. Continuous operation with two required channels inoperable in a Function is not acceptable because the alternate indications may not fully meet all performance qualification requirements applied to the PAM instrumentation. Therefore, requiring restoration of one inoperable channel of the Function limits the risk that the PAM Function will be in a degraded condition should an accident occur.
Condition E does not apply to hydrogen monitor channels and functions with single channels.
F.1 Not Used G.1 and G.2 If the Required Action and associated Completion Time of Conditions D or E are not met, the unit must be brought to a MODE where the requirements of this LCO do not apply. To achieve this status, the unit must be brought to at least MODE 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and MODE 4 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
The allowed Completion Times are reasonable, based on operating experience, to reach the required unit conditions from full power conditions in an orderly manner and without challenging unit systems.
PAM Instrumentation B 3.3.3 BASES McGuire Unit 1 and 2 B 3.3.3-14 Revision No. 122 ACTIONS (continued)
H.1 Alternate means of monitoring Containment Area Radiation have been developed and tested. These alternate means may be temporarily installed if the normal PAM channel cannot be restored to OPERABLE status within the allotted time. If these alternate means are used, the Required Action is not to shut down the unit but rather to follow the directions of Specification 5.6.7, in the Administrative Controls section of the TS. The report provided to the NRC should discuss the alternate means used, describe the degree to which the alternate means are equivalent to the installed PAM channels, justify the areas in which they are not equivalent, and provide a schedule for restoring the normal PAM channels.
SURVEILLANCE A Note has been added to the SR Table to clarify that REQUIREMENTS SR 3.3.3.1 and SR 3.3.3.3 apply to each PAM instrumentation Function in Table 3.3.3-1.
Performing the Neutron Flux Instrumentation and Containment Atmosphere Radiation (High-Range) surveillances meets the License Renewal Commitments for License Renewal Program for High-Range Radiation and Neutron Flux Instrumentation Circuits per UFSAR Chapter 18, Table 18-1 and License Renewal Commitments Specification MCS-1274.00-00-0016, Section 4.44.
SR 3.3.3.1 Performance of the CHANNEL CHECK ensures that a gross instrumentation failure has not occurred. A CHANNEL CHECK is normally a comparison of the parameter indicated on one channel to a similar parameter on other channels. It is based on the assumption that instrument channels monitoring the same parameter should read approximately the same value. Significant deviations between the two instrument channels could be an indication of excessive instrument drift in one of the channels or of something even more serious. A CHANNEL CHECK will detect gross channel failure; thus, it is key to verifying the instrumentation continues to operate properly between each CHANNEL CALIBRATION. The high radiation instrumentation should be compared to similar unit instruments located throughout the unit.
PAM Instrumentation B 3.3.3 BASES McGuire Unit 1 and 2 B 3.3.3-15 Revision No. 122 SURVEILLANCE REQUIREMENTS (continued)
Agreement criteria are determined by the unit staff, based on a combination of the channel instrument uncertainties, including isolation, indication, and readability. If a channel is outside the criteria, it may be an indication that the sensor or the signal processing equipment has drifted outside its limit. If the channels are within the criteria, it is an indication that the channels are OPERABLE.
As specified in the SR, a CHANNEL CHECK is only required for those channels that are normally energized.
The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
SR 3.3.3.2 Not Used SR 3.3.3.3 CHANNEL CALIBRATION is a complete check of the instrument loop, including the sensor. The test verifies that the channel responds to measured parameter with the necessary range and accuracy. This SR is modified by a Note that excludes neutron detectors. The calibration method for neutron detectors is specified in the Bases of LCO 3.3.1, "Reactor Trip System (RTS) Instrumentation." The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
REFERENCES
- 1.
UFSAR Section 1.8.
- 2.
Regulatory Guide 1.97, Rev. 2.
- 3.
NUREG-0737, Supplement 1, "TMI Action Items."
- 4.
10 CFR 50.36, Technical Specifications, (c)(2)(ii).