ML17297B745
| ML17297B745 | |
| Person / Time | |
|---|---|
| Site: | Technical Specifications Task Force |
| Issue date: | 10/24/2017 |
| From: | Mann B Excel Services Corp, Technical Specifications Task Force |
| To: | Michelle Honcharik, Jennifer Whitman NRC/NRR/DSS/STSB |
| Honcharik M | |
| References | |
| TSTF-484, TSTF-542 | |
| Download: ML17297B745 (4) | |
Text
From: Brian Mann <Brian.Mann@excelservices.com>
Sent: Tuesday, October 24, 2017 2:47 PM To: Honcharik, Michelle; Whitman, Jennifer Cc: llwilliams@energy-northwest.com; PHLashley; Rabenold, Alan D.;
bvictor@jagwireless.net
Subject:
[External_Sender] Input to Friday's call on TSTF-542 Attachments: Oct 27 2006 Notice of Availabilty TSTF-484 .pdf; TSTF-484-ARev0.pdf; Pages from TSTF-542-A,Rev2.pdf
- Michelle, We looked into the staff's question regarding TSTF-542 and TSTF-484. We want to provide the results of our investigation before the call to facilitate the discussion.
Brian We reviewed TSTF-484 and the NRC's safety evaluation. Annotated versions are attached.
Since at least Revision 0 of the ISTS, the TS have allowed hydrostatic testing when >
200 F and applying the Mode 4 requirements using Special Operation 3.10.1. TSTF-484 only added the allowance to do control rod testing, but doesn't really affect the issue.
In the Applicable Safety Analysis section of the 3.10.1 Bases, it states (starting in Revision 0 of the ISTS):
In the event of a large primary system leak, the reactor vessel would rapidly depressurize, allowing the low pressure core cooling systems to operate. The capability of the low pressure coolant injection and core spray subsystems, as required in MODE 4 by LCO 3.5.2, "ECCS -
Shutdown," would be more than adequate to keep the core flooded under this low decay heat load condition. Small system leaks would be detected by leakage inspections before significant inventory loss occurred.
The justification for TSTF-484 makes a similar statement, "Small system leaks would be detected by leakage inspections before significant inventory loss occurred. In the event of a large primary system leak, the reactor vessel would rapidly depressurize, allowing the low-pressure core cooling systems to operate. The capability of the low pressure coolant injection and core spray subsystems, as required in MODE 4 by LCO 3.5.2, "ECCS - Shutdown," would be more than adequate to keep the core flooded under this low decay heat load
Condition."
The NRC safety evaluation for TSTF-484 was more explicit (even though TSTF-484 had no effect on this aspect of the existing provision) (emphasis added):
Since the tests are performed with the reactor pressure vessel (RPV) nearly water solid, at low decay heat values, and near Mode 4 conditions, the stored energy in the reactor core will be very low. Small leaks from the RCS would be detected by inspections before a significant loss of inventory occurred. In addition, two low-pressure emergency core cooling systems (ECCS) injection/spray subsystems are required to be operable in Mode 4 by TS 3.5.2, ECCS Shutdown.
In the event of a large RCS leak, the RPV would rapidly depressurize and allow operation of the low pressure ECCS. The capability of the low pressure ECCS would be adequate to maintain the fuel covered under the low decay heat conditions during these tests.
Under TSTF-542, only one ECCS subsystem is required to be operable in Mode 4. This appears to be the crux of the NRC staff's concern.
The TSTF-542 justification discussed the change from two ECCS subsystems to one:
In developing the requirements, no additional single failure or operator error beyond the initiating event is considered. This is consistent with other TS applicable during shutdown, such as TS 3.8.2, "AC Sources - Shutdown", which requires a single offsite and onsite power source and do not require redundant features to address a limiting single failure.
Consistent with TS 3.8.2, a loss of offsite power is considered. In addition, common mode failures (i.e., single initiating events that affect more than one RPV penetration flow path) are considered when appropriate.
Unlike the current LCO 3.5.2 requirement, the primary purpose of the LCO is to prevent an unexpected draining event through the controls on Drain Time. However, in order to provide defense-in-depth against an unexpected draining event, one ECCS injection/spray subsystem is
also required to be operable. The existing TS 3.5.2 "Applicable Safety Analysis" Bases states that two ECCS injection/spray subsystems are required to provide redundancy.
However, this redundancy is not required for a defense-in-depth measure when, consistent with other events considered during shutdown, no additional single failure is assumed. The Drain Time controls, in addition to the required ECCS injection/spray subsystem, provide reasonable assurance that an unexpected draining event can be prevented or mitigated before the RPV water level would be lowered to the TAF.
This justification is equally applicable during hydrostatic testing.
TSTF-542 revised the Bases of TS 3.10.1 to reflect the change to TS 3.5.2 as shown in the attached page. Section 3.3, "EVALUATION OF ADDITIONAL BASES CHANGES,"
subsection 3.3.4, "Other Affected Bases," of the staff's SE lists 3.10.1 as being reviewed and concluded:
The NRC staff reviewed the revised Bases sections and concluded that the revisions accurately reflect the changes contained in the associated LCOs. The Applicability, Actions and Applicable Safety Analyses sections continue to contain information regarding the reasons for each of the LCO requirements. The NRC staff determined that the Bases for the LCOs continue to satisfy the guidance in the Final Policy Statement.
Therefore, the TSTF believes the changes in TSTF-542 are applicable when applying Special Exception 3.10.1, without or without adoption of TSTF-484, and the change from two to one ECCS subsystems does not affect the applicability of TSTF-542, TSTF-484, or Special Exception 3.10.1.
We look forward to discussing this issue with the staff on October 27.
Brian D. Mann Vice President of Industry Programs and Services EXCEL Services Corporation Direct (240) 880-0490 Mobile (804) 339-7034 Main (301) 984-4400
E-mail: brian.mann@excelservices.com Web: www.excelservices.com Web: www.nukapedia.com