ML20116J803
| ML20116J803 | |
| Person / Time | |
|---|---|
| Site: | 05200003 |
| Issue date: | 07/31/1996 |
| From: | WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML20116J585 | List:
|
| References | |
| SDG-2, NUDOCS 9608140079 | |
| Download: ML20116J803 (44) | |
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i BACKGROUND INFORMATION FOR AP600 j
i SHUTDOWN i
EMERGENCY RESPONSE GUIDELINE SDG-2 AP600 RESPONSE TO LOSS OF RNS DURING SHUTDOWN Rev.2 July 31,1996 l
WESTINGHOUSE ELECTRIC CORPORATION ENERGY SYSTEMS BUSINESS UNIT ADVANCED TECHNOLOGY BUSINESS AREA P.O. BOX 355 PITTSBURGH, PENNSYLVANTA 15230 O
wu88a masse F
PDR SDa m 3196 REVISION: 2
TAllLE OF CONTENTS Section Page
1.0 INTRODUCTION
1-1
2.0 DESCRIPTION
2-1 3.0 RECOVERY / RESTORATION TECHNIQUE 3-1 3.1 High-Level Action Summary 3-1 3.2 Key Utility Decision Points 3-3 4.0 DETAILED DESCRIPTION OF GUIDELINE 4-1 4.1 Detailed Description of Steps, Notes, and Cautions 4-1 4.2 Step Sequence Requirements 4-34 O
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1.0 INTRODUCTION
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Guideline SDG-2, RESPONSE TO LOSS OF RNS DURING SHUTDOWN, is a Shutdowr1 Guideline (SDG) that provides procedural guidance to maintain core cooling and to protect the reactor core in the event that Normal Residual Heat Removal System (RNS) cooling is lost dudng plant shutdown conditions.
There is only one explicit transition to guideline SDG-2. It is from the Shutdown Safety Status j
Tree, SDF-0.1, on an ORANGE priority when the operator determines that RNS is not in service.
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l After all of the appropriate actions in guideline SDG-2 are completed, the operator is instructed to i
retum to the appropriate plant procedure.
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l-1 REVislON: 2
2.0 DESCRIPTION
Iv Guideline SDG 2, RESPONSE TO LOSS OF RNS DURING SHUTDOWN, provides actions to respond if RNS shutdown core cooling is lost during Modes 5 and 6 plant shutdown conditions (i.e.,
when there is fuel in the reactor). This guideline is entered on an ORANGE priority fmm the Shutdown Safety Status Tree if the operator determines that RNS is not in service providing shutdown core cooling when required. Shutdown core cooling is needed at all times in Mode 5 and in Mode 6 when there is fuel in the vessel.
There are three plant conditions addressed in this guideline for a loss of RNS cooling. These are: 1) with the reactor refueling cavity flooded to refueling level; 2) an open RCS, with an open RCS being defined as any opening in the RCS that cannot be readily closed from the control room, including an opened SG manway isolated from the RCS via the SG nozzle dams; 3) a closed RCS, with a closed RCS being defined as an RCS secured (except for openings that can be closed from the control mom) and filled (including the SG and PRHR tubes) to/above the low pressurizer level CMT actuation setpoint.
The response is different for each of these three plant conditions; however, Oley all have the i
common goal of restoring RNS cooling. The operator can exit this procedure for the flooded cavity condition, if either spent fuel pool cooling to the cavity or long term makeup to the cavity is established, with a continuous action of trying to establish RNS cooling. The operator cannot exit p
this procedure for the other two plant conditions, unless a higher priority RCS inventory transition is made, without re-establishing RNS cooling.
Unless an altemate heat sink is established that directs reactor decay heat outside containment using either an SG or the spent fuel pit cooling system, decay heat is transferred to the containment atmosphere by allowing the RCS/IRWST or RCS/ refueling cavity fluid to heatup and boil. Potential actions with contml grade systems or components to cool the containment atmosphere include operation of the containment fan coolers which include operation of the Central Chilled Water System, Component Cooling System and Service Water System.
O sDc2m3196 2-1 REVisloN: 2
rx 3.0 RECOVERY / RESTORATION TECHNIQUE The objective of the recovery / restoration technique incorporated into guideline SDG-2 is to provide actions for responding to a loss of RNS cooling.
The following subsections provide a summary of the major action categories of operator actions and the key utility decision points for guideline SDG-2, RESPONSE TO LOSS OF RNS DURING SHUTDOWN.
3.1 High Level Action Summary A high level summary of the actions performed in SDG-2 is given on the following page in the form of major action categories. These are described below in more detail.
Check If Reactor Refueline Cavity Is Flooded If the reactor refueling cavity is flooded up to refueling height, then a large water volume with a large heat capacity (relative to boiling) is present to absorb decay heat temporarily.
Under these conditions, the operator either establishes refueling cavity /RCS cooling via one of the spent fuel pool cooling trains (as per design) or establishes a long term makeup water source to the refueling cavity to makeup for boil-off. The operator can exit this procedure p
after establishing one of these temporary cooling schemes with the continuous action of V
trying to re-establish RNS cooling as soon as possible.
Check If RCS Is Open An open RCS is defined as any opening in the RCS that cannot be readily closed from control room, including an opened SG manway isolated from the RCS via the SG nozzle dams. The RCS should also be considered open, or the actions for an open RCS should be taken, if the RCS (including the SG and PRHR heat exchanger tubes) is not filled to the pressurizer low level CMT actuation setpoint.
The first action taken under open RCS conditions is checking and maintaining RCS inventory greater than the RCS hot leg low level IRWST actuation setpoint (SLO 2). If RCS hot leg level is less than SLO 2, then a higher priority transition to SDG-1, RESPONSE TO LOSS OF RCS INVENTORY DURING SHUTDOWN Step 1 is made. Subsequent to establishing / maintaining adequate RCS inventory, the actions taken include verifying ADS valves stages 1 to 3 are open and an attempt to restore RNS cooling. If RNS cooling cannot be established, then actions are initiated to protect personnel inside coatainment, establish containment closure and stan available containment fan coolers.
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sDG2 oM196 3-1 REV1sloN: 2
MAJOR ACTION CATEGORIES IN SDG-2 Check If Reactor Refueling Cavity Is Flooded
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Check If RCS Is Open
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Check If RCS Is Closed
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sDc2m3196 3-2 REVISION: 2
Check If RCS Is Closed
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The RCS is considered closed if RCS conditions are other than those as defined above for an open RCS. The actions taken under closed RCS conditions include checking and maintaining RCS inventory greater than the pressurizer low level CMT actuation setpoint (SL01) and an attempt to restore RNS cooling. If RNS cooling cannot be established, then actions are taken to establish an RCS heat sink using either the SGs or PRHR, and actions are also initiated to protect personnel inside containment, establish containment closure and start available containment fan coolers.
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3.2 Key Utility Decision Points There is one key utility decision point in this guideline when the operator must initiate actions to protect personnel inside containment. In Steps 10 and 19, the operator is instructed to evacuate non-essential personnel inside containment. The operator will have to determine which personnel must be evacuated from containment at this time in the guideline.
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4.0 DETAILED DESCRIPTION OF GUIDELINE This section provides a very detailed discussion of the generic guideline SDG-2 to facilitate procedure writing and training efforts. By presenting guideline background information in greater detail through the use of a structured fonnat (i.e., step description tables and step sequence tables),
applicability can be more easily determined. The separate and unique subsections containing this information follow, 4.I Detailed Description of Steps, Notes, and Cautions This section contains a one-page (or more) step description table for each separate guideline step, note, and caution. Notes and cautions are always presented relative to the step they precede.
The Step Description Tables for the steps and associated notes and cautions of guideline SDG 2 are presented on the following pages.
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sDG243196 4-1 REvlstoN; 2
STEP DESCRIPTION TABLE FOR SDG 2 STEP 1 STEP:
Check Reactor Cavity Level - FLOODED PURPOSE:
To de:crmine if the reactor refueling cavity is flooded to the refueling height BASIS:
If the reactor refueling cavity is flooded up to refueling height, then a large water volume with a large heat capadty (relative to boiling) is present to absorb decay heat temporarily. Under these conditions, the operator either establishes refueling cavity /RCS cooling via one of the spent fuel pool cooling trains (as per design) or establishes a long term makeup water source to the refueling cavity to makeup for boil-off. The operator can exit this procedure after establishing one of these temporary cooling schemes with the continuous action of trying to re-establish RNS cooling as soon as possible.
ACTIONS:
Determine if the reactor refueling cavity is flooded to the refueling height INSTRUMENTATION:
Reactor refueling cavity level indication CONTROL /EOUIPMENT:
N/A KNOWLEDCE:
N/A ADDITIONAL INFORM ATION:
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sDo2 073196 42 REVIs10N: 2
STEP DESCRII' LION TABLE FOR SDG.2 C
STEP 2 STEP:
Try To Restore RNS Flow PURPOSE:
To instruct the operator to attempt to restore RNS Flow BASIS:
A common concem, based on past plant designs, has been the loss of RNS because of inadequate water level above the RCS hot leg /RNS suction line interface. With an inadequate water level, air ingestion, caused by vortexing action, would cause the RNS pump to loose prime and therefore interrupt the RNS cooling function. With the refueling cavity flooded up to refueling level, this concem is not valid for this plant condition for the AP600 plant since the AP600 design incorporates specific features to address this concern. These design features are described in Step 9.
The RNS has redundant equipment. If a failure in one train occurs, the other train can be placed in service. The RNS pumps are automatically loaded onto the standby diesel generators if they were operating at the time of loss of normal power. The operator may have to manually load the RNS pumps onto the standby diesel generators if the automatic loading feature fails. The following supporting systems are also required to provide prompt restoration of RNS cooling: SWS, CCS and PLS.
With the reactor refueling cavity flooded up to refueling height, a large water volume with a large
[V9 heat capacity (relative to boiling) is present to absorb decay heat temporarily. Under these conditions, the operator can either establish refueling cavity /RCS cooling via one of the spent fuel pool cooling trains (as per design) or establish a long tenn makeup water source to the refueling cavity to makeup for boil-off. The operator can exit this pmcedure after establishing one of these temporary cooling schemes with the Continuous Action of trying to re-establish RNS cooling as soon as possible.
" Containment Integrity", as used in the context of this step, means establishing a closed containment, including isolation of the spent fuel pool, such that the containment will contain the steam generated as a result of boiling in the reactor refueling cavity. The level of integrity intended is more than
" refueling closure", but less than " containment closure" or "at power containment integrity" ACTIONS:
Attempt to restore RNS cooling
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Determine if RNS cooling has been restored Align spent fuel pool cooling system to cool reactor refueling cavity Establish Containment Integrity Establish a long term source of makeup water to the reactor refueling cavity
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INSTRUMENTATION:
RNS cooling perfonnance status indication (D
q.)
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1 STEP DESCRII" TION TABLE FOR SDG-2 CONTROL /EOUIPMENT:
RNS controls required for RCS cooling Control for RNS support systems KNOWLEDGE:
The operator should understand the degree of " containment integrity" required for this step re-established.
This is a continuous action Step if RNS cooling cannot be re-established ADDITIONAL INFORM ATION:
Include AP600 specific details for restoring RNS flow e
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STEP DESCRIITION TABLE FOR SDG 2 STEP 3 STEP:
Go To Appropriate Plant Procedure PURPOSE:
To direct the operator to the proper procedure following completion of the first i
two steps in this guideline BASIS:
Now that the first two guideline steps have been completed, the operator should continue plant operation and/or recovery by going to the appmpriate normal or abnormal plant procedure while continuing to restore RNS cooling.
ACTIONS:
Go to appmpriate plant procedure l
Continue actions to restore RNS cooling INSTRUMENTATION:
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ADDITIONAL INFORMATION:
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STEP DESCRIPTION TABLE FOR SDG 2 STEP 4 - NOTE NOTE:
The RCS is considered open when an opening exists that cannot be closed from the control room such as a SG manway.
PURPOSE:
To remind the operator that the RCS is considered open if an opening exists that cannot for isolated from the control room.
BASIS:
An open RCS is defined as any opening in the RCS that cannot be readily closed from control room, including an opened SG manway isolated from the RCS via the SG nozzle dams.
ACTIONS:
N/A INSTRUMENTATION:
N/A CONTROL /EOUIPMENT:
N/A KNOWLEDGE:
N/A ADDITIONAL INFORM ATION:
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STEP DESCRIITION TABLE FOR SDG 2 N
STEP 4 l
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Check RCS Status - OPEN PURPOSE:
To determine if the RCS is open BASIS:
An open RCS is defined as any opening in the RCS that cannot be readily closed from control room, l
l including an opened SG manway isolated from the RCS via the SG nozzle dams. The RCS should l
also be considered open, or the actions for an open RCS should be taken, if the RCS (including the SG and PRHR heat exchanger tubes) is not filled to the pressurizer low level CMT actuation setpoint.
1 ACTIONS:
Determine if RCS is open 1
INSTRUMENTATION:
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N/A KNOWLEDGE:
l The operator should understand what is meant by an open RCS, j
ADDITIONAL INFORMATION:
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STEP DESCRIITION TABLE FOR SDG-2 STEP 5 STEP:
Check RCS Hot Leg Level - GREATER THEN (SLO 2)
PURPOSE:
To determine if RCS hot leg level is greater than the IRWST injection setpoint BASIS:
The first action taken under open RCS conditions is checking and maintaining RCS inventory greater than the RCS hot leg low level IRWST actuation setpoint (SLO 2). If RCS hot leg level is less than SLO 2, then a higher priority transition to SDG-1, RESPONSE TO LOSS OF RCS INVENTORY j
DURING SHUTDOWN, Step 1 is made. Adequate RCS hot leg level is required for RNS operation.
ACTIONS:
Determine if RCS hot leg level is greater than SLO 2 Go to SDG-1 RESPONSE TO LOSS OF RCS INVENTORY DURING SHUTDOWN, Step 1 INSTRUMENTATION-RCS hot leg level indication CONTROL /EOUIPMENT:
N/A KNOWLEDGE:
N/A ADDITIONAL INFORMATION:
SLO 2 - Enter RCS hot leg low level IRWST actuation setpoint sixna3196 4-8 REVISION: 2
STEP DESCRIPTION TABLE FOR SDG 2 STEP 6 STEP:
Verify Stage 1,2, and 3 ADS Valves - OPEN PURPOSE:
To ensure an adequate RCS vent path is open to containment BASIS:
In the April 10,1987 event at Diablo Canyon Unit 2, the RCS reached boiling in 30 to 45 minutes.
More importantly, this boiling caused RCS pressurization which was unanticipated. An RCS configuration can be postulated, with a blocked hot leg and a opening in the cold leg, which can result in the core being rapidly uncovered following initiation of boiling. Severe core damage can follow as soon as adiabatic heatup of the core reaches the point of rapid zirc-water chemical reaction.
By ensuring the Stage 1,2 and 3 ADS valves are open ensures an adequate RCS hot leg vent path (via the PRZR surge line) is provided to prevent RCS pressurization and possible core uncovery as described above.
ACTIONS:
Verify Stage 1. 2, and 3 ADS valves are open Manually open valves INSTRUMENTATION:
ADS valve position indication CONTROL /EOUIPhENT:
Manual ADS valve controls KNOWLEDGE:
If the Protection and Safety Monitoring System (PMS) is unsuccessful in opening the ADS valves, the operator should be aware that the Diverse Actuation System (DAS) has pmvisions for manually opening the ADS valves from the DAS panel.
ADDITIONAL INFORMATION:
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SDG2c3196 49 REvlsloN: 2
I STEP DESCRIITION TABLE FOR SDG-2 i
l STEP 7 - CAUTION - 1 CAUTION - 1:
Personnel working in containment should be warned before refilling the RCS to i
avoid inadvertent contamination of personnel working near RCS openings PURPOSE:
To avoid personnel contamination from potentially radioactive gases or steam vapor when filling an open RCS BASIS:
Refilling the RCS may purge out radioactive vapors or gases from any open RCS vents and contaminate personnel in the area. Therefore personnel working in the vicinity of any RCS openings should clear the area prior to filling the RCS.
ACTIONS:
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N/A CONTROL /EOUIPMENT:
N/A KNOWLEDGE:
The operator should be cognizant of RCS opening locations and any work going on in these areas ADDITIONAL INFORMATION:
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soc 2m3196 4-10 REVIsloN: 2
STEP DESCRIITION TABLE FOR SDG 2 O
STEP 7 - CAUTION 2 CAUTION - 2:
Only borated water should be added to the RCS to maintain adequate shutdown margin PURPOSE:
To infonn the operator that inadvenent dilution of the RCS, without RNS, may result in a loss of (localized) shutdown margin while adding RCS makeup BASIS:
Although the coolant boron should remain in the RCS (as opposed to transferring with the boiled-off steam) borated makeup should be added to the RCS to maintain localized shutdown margin since mixing in the RCS will be minimal under these loss of RNS conditions. The decay heat / boil-off rates during this time are low enough that boron precipitation is not a concem.
ACTIONS:
i N/A INSTRUMENTATION:
N/A CONTROL /EOUIPMENT:
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N/A ADDITIONAL INFORM ATION:
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sDG2a3196 4 11 REVISION: 2
STEP DESCRIPTION TABLE FOR SDG-2 STEP 7 STEP:
Maintain RCS Hot Leg Level - GREATER THAN (SLO 2)
PURPOSE:
To maintain RCS hot leg level greater than the IRWST injection setpoint BASIS:
The preferred makeup source is CVS makeup so that the CMTs and IRWST remain available for injection if needed. Maintaining RCS level greater than SLO 2 prevents unnecessary automatic 1RWST injection.
ACTIONS:
Maintain RCS hot leg level using CVS makeup pumps Maintain RCS hat leg level using CMTs, gravity feed from IRWST to RNS suction, gravity feed from IRWST INSTRUMENTATION:
RCS hot leg level indication CVS RCS makeup instrumentation IRWST injection via RNS suction instrumentation IRWST injection instnamentation CONTROL /EOUIPMENT:
Controls for:
CVS RCS makeup IRWST injection via RNS suction IRWST injection KNOWLEDGE:
N/A ADDITIONAL INFORM ATION:
SLO 2 - Enter RCS hot leg low level IRWST actuation setpoint O
sDG2@3196 4 12 REVislON: 2 l
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STEP DESCRIPTION TABLE FOR SDG 2 STEP 8 STEP:
Identify And Isolate Any RCS Leakage PURPOSE:
To prevent RCS inventory loss due to RCS leakage or RCS interfacing systems BASIS:
To prevent RCS inventory loss due to RCS leakage or RCS interfacing systems.
ACTIONS:
Identify / isolate any RCS leakage INSTRUMENTATION:
N/A CONTROL /EOUIPMENT:
N/A KNOWLEDGE:
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STEP DESCRIPTION TAllLE FOR SDG-2 STEP 9 CAUTION CAUTION:
Staning an RNS pump may result in an RCS level decrease due to shrink or void collapse PURPOSE:
To warn the operator that an RCS level decrease, due to shrink or void collapse, may occur BASIS:
Since RCS boiling (voiding) was used for temporary core cooling, initiation of RNS cooling may cause a void collapse with a resulting RCS level decrease.
ACTIONS:
N/A INSTRUMENTATION:
RCS hot leg level indication CONTROIEOUIPMENT:
N/A KNOWLEDGE:
N/A ADDITIONAL INFORMATION:
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soa: 07 196 4 14 RrvisioN: 2
STEP DESCRIITION TABLE FOR SDG 2 t
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STEP 9 i
STEP:
Try To Restore RNS Flow i
PURPOSE:
To instruct the operator to attempt to restore RNS Flow
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BASIS:
A common concem, based on past plant designs, has been the loss of RNS because of inadequate water level above the RCS hot leg /RNS suction line interface. With an inadequate water level, air i
ingestion, caused by vortexing action, would cause the RNS pump to loose prime and therefore j
interrupt the RNS cooling function. The AP600 design incorporates specific features to address this j
concem consisting of: 1) a stepped nozzle RCS hot leg /RNS suction line interface which limits i
entrained air to no greater than five percent,2) a sloped RNS suction line without any local i
highpoints to permit easy line efill after hot leg level is reestablished,3) RCS layout is such that i
draining the SG primary side can he accomplished with a higher hot leg level and 4) Hot leg level indication. Therefore, hot leg leve: is maintained greater than SLO 2 to provide adequate RNS i
suction.
The RNS has redundant equipment. If a failure in one train occuis, the other train can be placed in service. The RNS pumps are automatically loaded onto the standby diesel generators if they were j
operating at the time of loss of normal power. The operator may have to manually load the RNS pumps onto the standby diesel generators if the automatic loading feature fails. The following j
O supporting systems are also required to provide prompt restoration of RNS cooling: SWS, CCS and PLS. After RNS is restored, the desired cooldown rate is established ard the operator transitions to j
the appropriate plant procedure.
ACTIONS:
Start an RNS pump Maintain RCS hot leg level greater than SLO 2
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Determine if RNS cooling has been restored Establish desired RCS cooldown rate Go to appropriate plant pmcedure a
INSTRUMENTATION:
RNS cooling perfonnance status indication RCS hot leg level indication CONTROL /EOUIPMENT:
l RNS controls required for RCS cooling Controls for RNS support systems KNOWLEDGE:
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STEP DESCRII' TION TABLE FOR SDG 2 ADDITIONAL INFORM ATION:
Include AP600 specific details for staning one RNS pump SLO 2 - Enter RCS hot leg low level IRWST actuation setpoint 1,
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STEP DESCRII" TION TABLE FOR SDG 2 STEP 10 STEP:
Initiate Actions To Protect Personnel Working In Containment PURPOSE:
To ensure personnel inside containment are protected from a potential adverse radiological environment BASIS:
When the core starts boiling, steam and/or gases may be released into containment through vents in the RCS. The release of steam into containment can create a habitability (temperature) concem for operators who may be in the area to perform recovery actions. The potential exists for release of radioactive materials from the RCS into containment causing a personnel contamination pmblem.
Any non essential personnel inside containment should be evacuated. As an additional precautionary measure, essential personnel entering containment may need to take additional protective measures such as respirators, breathing air or special protective clothing. Containment radiation should be periodically monitored and at some point, it may be necessary to evacuate essential personnel from containment.
ACTIONS:
Initiate actions to protect personnel working in containment
,.3 INSTRUMENTATION:
Containment radiation monitoring CONTROL /EOUIPMENT:
N/A KNOWLEDGE:
N/A ADDITIONAL INFORMATION:
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STEP DESCRIPTION TABLE FOR SDG 2 STEP 11 STEP:
Initiate Actions To Establish Containment Closure PURPOSE:
To establish a boundary to prevent the release of fission products BASIS:
Since RNS cooling has been lost, and initial attempts to restore RNS cooling have been unsuccessful, actions must be taken to address the possibility of core uncovery and subsequent fuel damage due to RCS inventory loss. Since two of the three radiological barriers may be open (the RCS and containment), actions must be taken to close containment and pmvide a barrier to the release of radioactive materials should the event pmceed to core damage. Containment closure must be accomplished before the onset of core damage. Once containment closure is initiated, closure should continue until controlled and stable decay heat removal has been restored (either RNS cooling or stable heat removal via the secondary plant) and the RCS is retumed to a controlled and stable condition.
ACTIONS:
Initiate actions to establish containment closure INSTRUMENTATION:
N/A CONTROL /EOUTPMENT:
N/A KNOWLEDGE:
Means to establish containment closure ADDITIONAL INFORMATION:
Specific guidelines for establishing containment closure during typical shutdown conditions.
Containment closure as discussed in this step includes establishing the desired position of available containment isolation valves to minimize release outside containment.
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1 STEP DESCRIPTIOS TABLE FOR SDG 2 O
STEP 12 STEP:
Start Available Containment Fan Coolers PURPOSE:
To ensure all available containm:nt fan coolers are runnhlg to remove containment heat BASIS:
The intent of this step is to remove heat from containment resulting from coolant boiling off in the RCS. Note that steam vented off via ADS stages L 2 and 3 will be condensed and captured via the ADS spargers in the IRWST. Therefore, until the IRWST starts steaming. the heat load on the containment fan coolers should be minimal.
ACTIONS:
Stan available containment fan coolers INSTRUNENTATION:
Containment fan cooler instnunentation CONTROldEOUIPMENT:
Controls for containment fan coolers KNOWLEDGE:
N/A ADDITIONAL INFORMATION:
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STEP DESCRIPTION TABLE FOR SDG-2 STEP 13 STEP:
Retum to Step 4 PURPOSE:
To re-evaluate RCS opened / closed status and transition to aipmpriate procedure actions as required BASIS:
To continue attempts to restore RNS cooling.
ACTIONS:
N/A INSTRUMENTATION-l N/A CONTROL /EOUIPNENT:
N/A KNOWLEDGE:
N/A ADDITIONAL INFORMATION:
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SDG24/3196 4-20 REVisloN: 2
STEP DESCRIFFION TABLE FOR SDG-2 STEP 14 STEP:
Check PRZR Level - GREATER THAN (SLOl)
PURPOSE:
To detennine if PRZR level is greater than the low PRZR level CMT actuation setpoint BASIS:
Step 14 stans the mitigating response procedure loop for a closed RCS conditions. See Step 4 for a description of what is considered an open RCS. For closed RCS conditions, the SL01 setpoint is used as a basis for action to an inadequate RCS inventory condition since a full RCS is needed to maintain the SGs and PRHR heat exchanger tubes full for core decay heat removal purposes. If PRZR level is less than SL01, then a higher priority transition to SDG-1, RESPONSE TO LOSS OF RCS INVENTORY DURING SHUTDOWN, Step 1 is made.
ACTIONS:
Detennine if PRZR level is greater than SL01 Go to SDG-1, RESPONSE TO LOSS OF RCS INVENTORY DURING SHUTDOWN, Step 1 INSTRUNENTATION:
PRZR level indication CONTROL /EOUIPhENT:
N/A KNOWLEDGE:
N/A ADDITIONAL INFORMATION:
SL01 - Enter PRZR level CMT actuation setpoint during shutdown i
O SDG2G3196 4 21 REvls!ON: 2
STEP DESCRIPTION TABLE FOR SDG-2 STEP 15 - CAUTION - 1 CAUTION -1:
Personnel working in containment should be warned before refilling the RCS to avoid inadvertent contamination of personnel working near RCS openings PURPOSE:
To avoid personnel contamination fmm potentially radioactive gases or vapors when filling an open RCS BASIS:
Refilling the RCS may purge out radioactive vapors or gases from any open RCS vents and contaminate personnel in the area. Therefore, personnel working in the vicinity of any RCS openings should clear the area prior to filling the RCS.
ACTIONS:
N/A INSTRUMENTATION:
N/A CONTROL /EOUIPMENT:
1 N/A KNOWLEDGE:
The operator should be cognizant of RCS opening locations and any v/ork going on in these areas ADDITIONAL INFORMATION-N/A j
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soc 2-on196 4-22 REvlsioN: 2
1 STEP DESCRIPTION TABLE FOR SDG 2 i
STEP 15 - CAUTION - 2 CAUTION - 2:
Only borated water should be added to the RCS to maintain adequate shutdown margin PURPOSE:
To inform the operator that inadveitent dilution of the RCS, without RNS, may result in a loss of (localized) shutdown margin while adding RCS makeup BASIS:
Although the coolant boron should remain in the RCS (as opposed to transferring with the boiled-off steam) borated makeup should be added to the RCS to maintain localized shutdown margin since mixing in the RCS will be minimal under these loss of RNS conditions. The decay heat /boilmff rates during this time are low enough that boron precipitation is not a concem.
ACTIONS:
N/A INSTRUMENTATION:
N/A CONTROL /EOUIPMENT:
N/A KNOWLEDGE:
N/A ADDITIONAL INFORMATION:
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STEP DESCRIPTION TABLE FOR SDG-2 STEP 15 STEP:
Maintain PRZR Level Greater Than (SLOI) Using CVS Makeup Pumps As Necessary PURPOSE:
To maintain PRZR level greater than the CMT injection setpoint BASIS:
The preferred makeup source is CVS makeup so that the CMTs remain available for injection if needed. Maintaining RCS level greater than SLOl prevents unnecessary automatic CMT injection if RCS makeup is capable of providing makeup.
ACTIONS:
Maintain PRZR level greater than SLOl using CVS makeup INSTRUMENTATION:
PRZR level indication CVS RCS makeup instrumentation CONTROL /EOUIPMENT:
Controls for CVS RCS makeup KNOWLEDGE:
N/A ADDITION AL INFORMATION:
SL01 - Enter PRZR level CMT actuation setpoint during shutdowm
)
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i sna2m3196 4 24 REVISION: 2 I
l STEP DESCRIFFION TABLE FOR SDG 2 l
l l
l STEP 16 - CAUTION CAUTION:
Staning an RNS pump may result in an RCS level decrease due to shrink or void' collapse I
PURPOSE:
To wam the operator that a PRZR level decrease, due to shrink or void collapse, may occur l
BASIS:
i Since RCS boiling may occur as a result of loosing RNS cooling and without any other RCS heat sunk, re-initiation of RNS cooling may cause a void collapse with a resulting PRZR level decrease.
ACTIONS:
l N/A INSTRUMENTATION:
PRZR level indication CONTROL /EOUIPMENT:
N/A l
KNOWL EDGE:
N/A ADDITIONAL INFORMATION:
N/A 1
t i
I i
iO 1
l sno2m3196 4-25 REVISION: 2
STEP DESCRIITION TABLE FOR SDG-2 STEP 16 STEP:
Try To Restore RNS Flow PURPOSE:
To instmet the operator to attempt to restore RNS Flow BASIS:
A common concern, based on past plant designs, has been the loss of RNS because of inadequate water level above the RCS hot leg /RNS suction line interface. With an inadequate water level, air ingestion, caused by vortexing action, would cause the RNS pump to loose prime and therefore interrupt the RNS cooling function. With the refueling cavity flooded up to refueling level, this concern is not valid for this plant condition for the AP600 plant since the AP600 design incorporates specific features to address this concern. These design features are described in Step 9.
The RNS has redundant equipment. If a failure in one train occurs, the other train can be placed in service. The RNS pumps are automatically loaded onto the standby diesel generators if they were operating at the time of loss of normal power. The operator may have to manually load the RNS pumps onto the standby diesel generators if the automatic loading feature fails. The following supporting systems are also required to pmvide prompt restoration of RNS cooling: SWS, CCS and PLS.
ACTIONS:
Stan an RNS pump Maintain PRZR level greater than SLO 1 Determine if RNS cooling has been re-established Establish desired RCS cooldown rate Go to appropdate plant procedure INSTRUMENTATION:
RNS cooling performance status indication PRZR level indication CONTROL /EOUIPMENT:
RNS controls required for RCS cooling Controls for RNS suppon systems KNOWLEDGE:
N/A ADDITIONAL INFORMATION:
Include AP600 specific details for staning one RNS pmnp SL01 - Enter PRZR level CMT actuation setpoint dudng shutdowm soc 2m3196 4-26 REVISloN: 2
STEP DESCRIPTION TABLE FOR SDG-2
/N STEP 17 k
STEP:
Establish RCS Heat Sirk Using SGs PURPOSE:
To provide an RCS heat sink using available SG(s)
BASIS:
The plant condition required for this step is a " closed" RCS which has already been determined. By definition, a closed RCS requires that the RCS (including the SG tubes) be filled to at least the PRZR CMT actuation level setpoint (SL01). In addition to a closed RCS, an SG must be available.
An SG is available if the secondary side of a non-ruptured, non-faulted SG is filled to approximately normal level, and atmospheric steam release capability via the SG power operated relief valves (PORVs) is operable (with the plant shutdown, steam dump to the condenser would not be available).
The ADS valves remain in the position they were in at the time this step is reached. Subcooled core cooling will take place until the RCS and SGs reach saturation based on SG secondary side atmospheric pressure. With the ADS valves and RCS closed, the RCS will slightly pressurize above atmospheric pressure to an equilibrium value required to remove core decay heat. This plant configuration will permit RCS/SG natural circulation to transfer core decay heat to the SGs. The SGs remain at atmospheric pressure with steam release to the atmosphere. Since SG pressure will be maintained at atmospheric pressure via the open SG PORVs, saturated core cooling will take
()
place.it approximately 212 F. RCS inventory will be monitored and controlled via Step 15. SG
)
V feedwater will be required, as necessary, depending on the length of time RNS cooling is lost to maintain secondary inventory.
i If the ADS valves remain open, this method of saturated core cooling will not be effective since no temperature gradient will develop to promote natural circulation. Very little, if any, temperature i
gradient between the RCS and SG will exist because both the RCS and SG(s) will irmain at atmospheric pressure when the ADS valves and SG PORVS are open.
ACTIONS:
Detennine if any SGs are available Try to restore SGs to service Feed SGs to establish and maintain SG level Open respective SG PORVs INSTRUMENTATION:
SG level indication SFW operation instmmentation RCS hot leg, cold leg and SG temperature indication
=
SG PORV position indication ADS valve position indication Hot leg level indication b
soo2 m 3196 4-27 Revision: 2
m.
STEP DESCRIPTION TABLE FOR SDG-2 CONTROL /EOUIPMENT:
Controls for:
SFW operation SG PORV operation KNOWLEDGE:
N/A ADDITIONAL INFORM ATION:
N/A i
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O soc 2m3196 4-28 REVISION: 2
STEP DESCRIfTION TABLE FOR SDG-2 STEP 18 STEP:
Establish RCS Heat Sink Using PRHR PURPOSE:
To provide an RCS heat sink using the PRHR heat exchanger BASIS:
The passive residual heat removal system (PRHRS) is designed to cool the RCS using natural circulation from the RCS through the PRHR heat exchanger (PRHRHX) during the initial cooldown phase (of plant shutdown) before RNS cooling is initiated. The PRHR heat exchanger uses the IRWST as a heat sink normally maintained at containment ambient temperature. Aligning the PRHRS to cool the RCS will provide a heat sink for the RCS although it may not be very effiective until the RCS heats up. If PRHR cooling can not be placed in service; at an RCS temperature of (ST03) F, the operator is instructed to open all ADS valves to initiate a feed and bleed mode of cooling for the RCS and to prevent further pressurizatioa of the RCS.
1 i
ACTIONS:
Detennine if PRHR is available Align PRHR to cool RCS Open all ADS valves when RCS temperature reaches (ST03) F INSTRUMENTATION:
w/
Instrumentation for:
PRHR operability status PRZR level indication CONTROL /EOUIPMENT:
Controls for:
PRHR operation ADS valves KNOWLEDGE:
The operator should be aware of IRWST cooling capabilities provided by RNS, SFP and containment fan coolers. If PMS is unsuccessful in opening / closing the ADS valves or actuating PRHR, the operator should be aware that the Diverse Actuation System (DAS) has provisions for manually opening / closing the ADS valves or actuating PRHR from the DAS panel.
ADDITIONAL INFORMATION:
STV3 - Enter nonnal RNS cut-in temperature sDc2m3196 4 29 REVIslON: 2
STEP DESCRII'rION TAIILE FOR SDG 2 STEP 19 STEP:
Initiate Actions To Protect Personnel Working la Containment PURPOSE:
To ensure personnel inside containment are protected from a potential adverse radiological environment BASIS:
When the core /IRWST stans boiling, steam and/or gases may be released into containment through vents in the IRWST. The release of steam into containment can create a habitability (temperature) concem for operators who may be in the area to perform recovery actions. The potential exists for release of radioactive materials from the RCS/lRWST into containment causing a personnel contamination problem.
Any non essential personnel inside contMnment should be evacuated. As an additional precautionary measure, essential personnel entering containment may need to take additional prote.ctive measures such as respirators, breathing air or special protective clothing. Containment radiation should be periodically monitored and at some point, it may be necessary to evacuate essential personnel from containment.
ACTIONS:
Initiate actions to protect personnel working in containment INSTRUMENTATION:
I Containment Temperature indication Containment radiation monitoring CONTROlJEOUIPMENT:
N/A KNOWLEDGE:
N/A
]
ADDITIONAL INFORMATION:
N/A O
spa 2m3196 4-30 REVisloN: 2
STEP DESCRTTION TABLE FOR SDG 2 STEP 20 v
STEP:
Initiate Actions To Establish Containment Closure PURPOSE:
To establish a boundary to prevent the release of fission products BASIS:
Since RNS cooling has been lost, and initial attempts to restore RNS cooling have been unsuccessful, actions must be taken to address the possibility of core uncovery and subsequent fuel damage due to RCS inventory loss. Since two of the three radiological baniers may be open (the RCS and containment), actions must be taken to close containment and provide a barrier to the release of radioactive materials should the event proceed to core damage. Containment closure must be accomplished before the onset of core damage. Once containment closure is initiated, closure should continue until controlled and stable decay heat removal has been restored (either RNS cooling or stable heat removal via the secondary plant) and the RCS is returned to a controlled and stable condition.
ACTIONS:
Initiate actions to establish containment closure O
INSTRUMENTATION:
V 1
N/A CONTROL /EOUIPMENT:
N/A i
i KNOWLEDGE:
Means to establish containment closum l
1 ADDITIONAL INFORMATION:
Specific guidelines for establishing containment closure during shutdown conditions and using the t
passive core cooling systems (i.e., PXS/PRHR and PCC). Containment closure as discussed in this l
step includes establishing the desired position of available containment isolation valves to minimize release outside containment.
1 (V
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suc2m3196 4 31 REVisloN: 2
STEP DESCRIITION TABLE FOR SDG-2 STEP 21 STEP:
Start Available Containment Fan Coolers PURPOSE:
To ensure all available containment fan coolers are running to remove containment heat BASIS:
The intent of this step is to remove heat from containment resulting from the IRWST boiling off to containment. Note that subcooled PRIIR cooling will occur, and steam vented off via ADS stages 1, 2 and 3 will be condensed and captured via the ADS spargers in the IRWST. Therefore, until the IRWST starts steaming, the heat load on the containment fan coolers should be minimal.
ACTIONS:
Start available containment fan coolers INSTRUMENTATION:
Containment fan cooler instrumentation CONTROL /EOUIPMENT:
Controls for containment fan coolers KNOWLEDGE:
N/A ADDITIONAL INFORM ATION:
N/A O
stxum3196 4-32 REVISloN: 2
STEP DESCRII" TION TABLE FOR SDG 2 O
STEP 22 STEP:
Retum To Step 14 PURPOSE:
To retum to the initial procedure step that addresses recovery with a cloced RCS BASIS:
Steps 14 to 22 form a loop of recovery actions with closed RCS conditions. Since RNS cooling has not been re-established, the operator is sent back to the beginning of this loop to re-evaluate the
{
status of RCS cooling and restoration of RNS cooling of the RCS.
t ACTIONS:
l' N/A INSTRUNENTATION:
N/A CONTROL /EOUIPMENT:
N/A IV KNOWLEDGE:
N/A ADDITIONAL INFORMATION:
N/A I
1 AV sna2.on196 4 33 REVis!ON: 2
4.2 Step Sequence Requirements j
This section consists of a table which presents the existing guideline sequence and identifies the interchangeability of guideline steps for the benefit of the procedure writer.
The Step Sequence Table for SDG-2 is provided on the following page. The interchangeability of guideline steps is identified by the numbers in the column to the right of each guideline step.
O l
O sDG2413196 4 34 REVis!ON: 2 i
STEP SEQUENCE FOR SDG-2 STEP SEOUENCE t
1.
Check Reactor Cavity Level - Flooded 1
2.
Try To Restore RNS Flow 2
3.
Go To Appropriate Plant Procedure 3
i J
4.
Check RCS Status - OPEN 4
S.
Check RCS Hot Leg Level - GREATER THAN (SLO 2) 5 6.
Verify Stage 1,2 and 3 ADS Valves - OPEN 6
7.
Maintain RCS Hot Leg Level - GREATER THAN (SLO 2) 7 8.
Identify And Isolate Any RCS Leakage 8
9.
Try To Restore RNS Flow 9
- 10. Initiate Actions To Protect Personnel Working In Containment 10 11.
Initiate Actions To Establish Containment Closure 10
- 12. Start Available Containment Fan Coolers 10
- 13. Retum To Step 4 11 14.
Check PRZR Level - GREATER THAN (SL01) 12
- 15. Maintain PRZR Level Greater Than (SLOI) Using CVS Makeup Pumps As Necessary 13
- 16. Try To Restore RNS Flow 14 1
- 19. Initiate Actions To Protect Personnel Working In Containment 16 i
SDG2@3196 4 35 REVISION: 2
STEP SEQUENCE FOR SDG-2 (Cont.)
STEP SEOUENCE i
20.
Initiate Actions To Establish Containment Closure 16 21.
Start Available Containment Fan Coolers 16
- 22. Retum to Step 14 17 O
O SDG2-073196 4 36 REVISION: 2
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