ML24215A208
| ML24215A208 | |
| Person / Time | |
|---|---|
| Site: | 05200050 |
| Issue date: | 08/02/2024 |
| From: | NuScale |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML24215A000 | List:
|
| References | |
| LO-169995 | |
| Download: ML24215A208 (1) | |
Text
Response to SDAA Audit Question Question Number: A-16.3.1.9-3 Receipt Date: 03/18/2024 Question:
Generic TS 3.1.9 Applicability is MODES 1, 2, and 3; Revision 5 of the NuScale US600 Generic TS 3.1.9 Applicability is MODES 1, 2, and 3 with any dilution source flow path in the CVCS makeup line not isolated.
In ACTIONS Condition B, the last Condition statement, about [module heating system (MHS)] flow paths to or from other module CVCS not isolated, warrants corresponding changes to the LCO, Applicability, and ACTION B. Following are suggested changes:
In the LCO, add a fourth statement using the logical connector AND that states: Module heatup system (MHS) flow paths to and from other module CVCS shall be isolated by a locked, sealed, or otherwise secured valve or device. Note that the phrase to and from is also used in SR 3.1.9.5.
In the Applicability statement, add a phrase, which is similar to the US600 GTS 3.1.9 Applicability statement, that states:
MODES 1, 2, and 3 with any dilution source flow path in the CVCS makeup line not isolated, and add an additional Applicability statement:
MODE 3 with CVCS flow aligned through the MHS.
In the Required Action column for Condition B, add Required Action B.2 using the logical connector AND that states:
B.2 Isolate MHS flow paths to and from other module CVCS by use of at least one locked, sealed, or otherwise secured valve or device. l 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> The applicant is requested to make changes consistent with the above suggested changes so that GTS 3.1.9 correctly addresses the need for isolating MHS flow paths to and from other module CVCS.
In order to provide more Condition-statement-specific Required Actions, the applicant is requested to consider separating the third, fourth, and fifth Condition statements of ACTION B NuScale Nonproprietary NuScale Nonproprietary
into dedicated ACTIONS, each having an action statement that more specifically remedies the associated condition statement. For example:
B. Required Action and associated Completion Time of Condition A not met. OR Two CVCS demineralized water isolation valves inoperable. l B.1 Isolate dilution source flow paths in the CVCS makeup line by use of at least one closed manual or one closed and de-activated automatic valve. l 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> C. Boric Acid supply boron concentration not within limits. l C.1 Isolate boric acid supply by use of at least one closed manual or one closed and de-activated automatic valve. l 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> D. CVCS makeup pump demineralized water flow path not configured to ensure maximum flowrate is within limits. l D.1 Stop one CVCS makeup pump so that only one CVCS makeup pump is in operation. l Immediately AND D.2 Verify CVCS makeup pump demineralized water flow path flowrate is within limits. l 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> E. MHS flow paths to or from other module CVCS not isolated by a locked, sealed, or otherwise secured valve or device. l E.1 Isolate MHS flow paths to and from other module CVCS by use of at least one locked, sealed, or otherwise secured valve or device. l 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> OR E.2 Isolate CVCS MHS flow path by use of at least one locked, sealed, or otherwise secured valve or device. l 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> The applicant is also requested to make appropriate changes to the LCO, Applicability, and Actions sections of the Bases for GTS 3.1.9.
Response
Item 1:
NuScale revises the LCO for GTS 3.1.9 to include the following statement:
Module heatup system (MHS) flow paths to and from cross-connected systems shall be isolated by a locked, sealed, or otherwise secured valve or device.
NuScale Nonproprietary NuScale Nonproprietary
NuScale revises the Bases for the GTS 3.1.9 LCO to address the addition of the MHS statement to the LCO.
Item 2:
NuScale revises the Applicability for GTS 3.1.9 to read:
MODES 1, 2, and 3 with any dilution source flow path not isolated.
The suggestion to add MODE 3 with CVCS flow aligned through the MHS to the Applicability was not adopted. The MHS requirements are applicable in all three modes because the cross-connected system requirements may apply to modules that are in Modes 1 or 2.
Item 3:
NuScale revises the Required Actions for GTS 3.1.9 to include the following new Required Action associated with MHS isolation:
B.2 Isolate MHS flows paths to and from cross-connected systems by use of at least one locked, sealed, or otherwise secured valve or device.
A one hour completion time has been assigned to this action.
NuScale revises the Bases for the GTS 3.1.9 Required Actions to address the addition of the MHS specific Required Action.
NuScale revises the MHS related condition in GTS 3.1.9 Condition B to read:
MHS flow paths to or from cross-connected systems not isolated by a locked, sealed, or otherwise secured valve or device.
NuScale revises GTS SR 3.1.9.5 to read:
Verify MHS flow paths to and from cross-connected systems are isolated by a locked, sealed, or otherwise secured valve or device.
The phrase other module CVCS was replaced with cross-connected systems to clarify that GTS 3.1.9 only applies to the module associated with the unit specific technical specifications.
NuScale Nonproprietary NuScale Nonproprietary
The suggestion to separate the third, fourth, and fifth Condition statement of Action B into dedicated Actions has not been adopted. With the addition of Action B.2 to address MHS isolation, Required Action B.1 adequately addresses the Required Actions for the other Conditions.
Markups of the affected changes, as described in the response, are provided below:
NuScale Nonproprietary NuScale Nonproprietary
Boron Dilution Control 3.1.9 NuScale US460 3.1.9-1 Draft Revision 2 3.1 REACTIVITY CONTROL SYSTEMS 3.1.9 Boron Dilution Control LCO 3.1.9 Two CVCS demineralized water isolation valves shall be OPERABLE.
AND Boric Acid supply boron concentration shall be within the limits specified in the COLR.
AND Maximum CVCS makeup pump demineralized water flow path flowrate shall be within the limits specified in the COLR.
AND Module heatup system (MHS) flow paths to and from cross-connected systems shall be isolated by a locked, sealed, or otherwise secured valve or device.
APPLICABILITY:
MODES 1, 2, and 3 with any dilution source flow path not isolated.
ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. One CVCS demineralized water isolation valve inoperable.
A.1 Restore CVCS demineralized water isolation valves to OPERABLE status.
72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />
Boron Dilution Control 3.1.9 NuScale US460 3.1.9-2 Draft Revision 2 ACTIONS (continued)
CONDITION REQUIRED ACTION COMPLETION TIME B. Required Action and associated Completion Time not met.
OR Two CVCS demineralized water isolation valves inoperable.
OR Boric Acid supply boron concentration not within limits.
OR CVCS makeup pump demineralized water flow path not configured to ensure maximum flowrate is within limits.
OR MHS flow paths to or from other module CVCScross-connected systems not isolated by a locked, sealed, or otherwise secured valve or device.
B.1
NOTE------------
Flow paths may be unisolated intermittently under administrative controls.
B.1 Isolate dilution source flow paths in the CVCS makeup path by use of at least one closed manual or one closed and de-activated automatic valve.
AND B.2 Isolate MHS flows paths to and from cross-connected systems by use of at least one locked, sealed, and otherwise secured valve or device.
1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> 1 hour
Boron Dilution Control 3.1.9 NuScale US460 3.1.9-3 Draft Revision 2 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.1.9.1 Verify that CVCS makeup pump demineralized water flow path is configured to ensure that the maximum demineralized water flowrate remains within the limits specified in the COLR.
In accordance with the Surveillance Frequency Control Program SR 3.1.9.2 Verify each automatic CVCS demineralized water isolation valve that is not locked, sealed, or otherwise secured in the isolated position, actuates to the isolated position on an actual or simulated signal.
In accordance with the Surveillance Frequency Control Program SR 3.1.9.3 Verify Boric Acid supply boron concentration is within the limits specified in the COLR.
In accordance with the Surveillance Frequency Control Program SR 3.1.9.4 Verify each CVCS makeup pump maximum flowrate is 25 gpm.
In accordance with the Surveillance Frequency Control Program SR 3.1.9.5
NOTE--------------------------------
- 1. Only required to be met when CVCS flow is aligned through the module heatup system (MHS).
- 2. Isolation devices that are locked, sealed, or otherwise secured may be verified by use of administrative means.
Verify MHS flow paths to and from cross-connected systemsother module CVCS are isolated by a locked, sealed, or otherwise secured valve or device.
In accordance with the Surveillance Frequency Control Program
Boron Dilution Control B 3.1.9 NuScale US460 B 3.1.9-3 Draft Revision 2 BASES LCO The requirement that two demineralized water isolation valves be OPERABLE assuresensures that there will be redundant means available to terminate an inadvertent boron dilution event. The requirement that the boron concentration of the boric acid supply be maintained within the limits specified in the COLR ensures that the supply is not a source to the CVCS that could result in an inadvertent boron dilution event.
The limits on maximum CVCS makeup pump demineralized water flow path flowrate are established by restricting the flow that can be provided during system operation to within the limits in the COLR. The restrictions may be implemented by use of at least one closed manual or one closed and de-activated automatic valve, or by removing the power supply from one CVCS makeup pump.
The requirement that Module heatup system (MHS) flow paths to and from cross-connected systems are isolated by a locked, sealed, or otherwise secured valve or device prevents CVCS flow between units via the module heating system (MHS) headers that could result in unplanned changes to the boration of a unit aligned to the MHS.
APPLICABILITY The requirement that two demineralized water isolation valves be OPERABLE, and that the boric acid storage tank boron concentration and maximum CVCS makeup pump demineralized water flow path flowrate is within the limits specified in the COLR is applicable in MODES 1, 2, and 3 with any dilution source flow path in the CVCS makeup line not isolated. In these MODES, a boron dilution event is considered possible, and the automatic closure of these valves is assumed in the safety analysis. The boron concentration of the boric acid sources are not assumed to be capable of causing a dilution event by the boron dilution event analysis. The maximum CVCS makeup pump demineralized water flow path flowrate is an assumption of the boron dilution event.
In MODE 1 < 15% RTP, the detection and mitigation of a boron dilution event would be signaled by a High Source or Intermediate Range Log Power Rate or a High Source Range Count Rate.
In MODE 1 15% RTP, the detection and mitigation of a boron dilution event would be signaled by a High Power Range Rate or High Power Range Linear Power. In MODES 2 and 3, the detection and mitigation of a boron dilution event would be signaled by a Source Range High Count Rate trip, a trip on Source Range High Log Power Rate, or a trip on High Subcritical Multiplication, or low RCS flow.
Boron Dilution Control B 3.1.9 NuScale US460 B 3.1.9-4 Draft Revision 2 BASES APPLICABILITY (continued)
In MODES 4 and 5, a dilution event is precluded because the CVCS RCS injection and discharge flow paths are not connected to the RCS, thus eliminating the possibility of a boron dilution event in the RCS.
Pool volume is sufficient to minimize the potential for boron dilution during MODE 5 within the surveillance intervals provided by LCO 3.5.3, Ultimate Heat Sink.
ACTIONS A.1 If one CVCS demineralized water isolation valve is inoperable, the valve must be restored to OPERABLE status in 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The allowed Completion Time is considered acceptable because the safety function of automatically isolating the dilution source can be accomplished by the redundant isolation valve.
B.1 If the Required Action and associated Completion Time is not met, or if both CVCS demineralized water isolation valves are not OPERABLE (i.e., not able to be closed automatically), then the demineralized water supply flow path to the RCS must be isolated to preclude a boron dilution event. Isolation can be accomplished by manually isolating the CVCS demineralized water isolation valve(s) or by positioning the manual 3-way combining valve to only take suction from the boric acid tank. Alternatively, the dilution path may be isolated by closing appropriate isolation valve(s) in the flow path(s) from the demineralized water storage tank to the RCS.
If the boric acid concentration in the boric acid supply or if the CVCS makeup pump demineralized water flow path flowrate are not within the limits specified in the COLR, then the flow path to the RCS must be isolated to preclude a boron dilution event. Condition B permits indefinite operation with the boric acid storage tank or the boric acid batch tank not meeting the COLR concentration limits with the source isolated from the CVCS.
The Required Actions B.1 and B.2 are is modified by a Note allowing either flow paths to be unisolated intermittently under administrative controls. These administrative controls consist of stationing a dedicated operator at the valve controls, who is in continuous communication with the main control room. In this way, the flow path can be rapidly isolated when a need for isolation is indicated.
Boron Dilution Control B 3.1.9 NuScale US460 B 3.1.9-5 Draft Revision 2 BASES ACTIONS (continued)
B.2 If the MHS flow paths to or from cross-connected systems are not isolated, the unisolated flow paths must be isolated by a locked, sealed, or otherwise secured valve or device.
SURVEILLANCE REQUIREMENTS SR 3.1.9.1 This Surveillance verifies that CVCS makeup pump demineralized water flow path is configured to ensure that the maximum dilution flow rate that can exist during makeup pump operation remains within the limits specified in the COLR. The Surveillance accomplishes this by assuring that when the maximum demineralized water flowrate is restricted to that of a single CVCS makeup pump, at least one closed manual or one closed and de-activated automatic valve is correctly configured, or verifying that the power supply has been removed from one CVCS makeup pump. The Surveillance Frequency is controlled under the Surveillance Frequency Control Program.
SR 3.1.9.2 This Surveillance demonstrates that each automatic CVCS demineralized water isolation valve actuates to the isolated position on an actual or simulated actuation signal. This Surveillance is not required for automatic valves that are locked, sealed, or otherwise controlled under administrative controls.
In addition to this Surveillance, the automatic actuation logic is tested as part of Engineered Safety Features Actuation System Actuation and Logic testing, and valve performance is monitored as part of the INSERVICE TESTING PROGRAM.
The Surveillance Frequency for this test is controlled under the Surveillance Frequency Control Program.
SR 3.1.9.3 This Surveillance ensures that the boric acid supply is not a potential source of dilution water.