ML072560065
| ML072560065 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 08/10/2007 |
| From: | Susquehanna |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| Download: ML072560065 (14) | |
Text
Susquehanna Steam Electric Station NRC Meeting August 10, 2007 ATWS and Stability Implementation Agenda
- Long-Term Stability Solution Implementation Status
- Anticipated Transient Without Scram (ATWS)
" Emergency Operating Procedures (EOPs)
" Stability Mitigation Actions
- Effects of CPPU on ATWS and EOP's 1
Stability Long Term Solution Implementation
- Describe the process followed by Susquehanna to implement L/T Solutions.
- Strongly involved in BWROG Hardware Development committee (Hardware, Software, Tech Specs & Licensing)
- Member/Chairman on BWROG Detect & Suppress Methodology Committee
- Development of Option III Licensing Methodology (NEDO-32465-A) and DIVOM guide
- Resolutions for GE Safety Concerns
- Committee on 10CFR21 on Generic DIVOM (led td need for plant specific DIVOM analysis)
- 1996: ABB hardware installation began 3
Stability Long Term Solution Implementation
- Describe the process followed by Susquehanna to implement L/T Solutions.
" 1997 - 2002: Implementation delayed due to hardware and software issues, GE 10CFR21 Generic DIVOM Curve Issue
" Extensive testing/data collection on ABB system
" Several years of OPRM data prior to "arming" the trip function (startups and flow runbacks)
" November 2004: OPRM Operable (ABB Design)
" Power Range Neutron Monitor OPRM implemented March 2006: U1, March 2007 U2 (replaces ABB System) 4 2
Stability Long Term Solution .
Implementation
- Where is Susquehanna today in the implementation schedule and what is its implementation status?
PRNMS - General Description
- Hardware installed in existing instrument rack (lower relay room)
- Six analog APRM channels are replaced by four digital APRM channels
- APRM trip logic changed from one out of two taken twice to two out of four.
- Replaces existing GE APRM, LPRM, Flow Units, & RBM electronics with GE digital electronics Nuclear Measurement Analysis & Control (NUMAC).
- Removed existing ABB hardware, OPRM function now in APRM NUMAC Chassis 5
Stability Long Term Solution Implementation Where is Susquehanna today in the implementation schedule and what is its implementation status?
- 4 Trip Channels (GE PRNM)
- 2 out of 4 trip logic
- LPRM to OPRM assignments based on Arrangement 4P (NEDO-32465-A)
- Cycle Specific DIVOM analysis using AREVA RAMONA5-FA Methodology
- NEDO-32465-A Reload Methodology
- Amplitude Setpoints (Sp)
- 1.11 (Ul: non-MELLLA)
- 1.12 (U2: MELLLA) 6 3
Stability Long Term Solution p Implementation
- Where is Susquehanna today in the implementation schedule and what is its implementation status?
" Years of experience with ABB OPRM on both Units (pre- and post-"arming")
" GE PRNM OPRM Currently Operating on Both Units
" GE PRNM Technical Specifications in use
" Data taken during startups (confirmation counts & amplitudes) show comparable performance to ABB hardware
" System operating as expected - no spurious RPS actuations
" Implementation of Long Term Stability Solution is complete.
Stability Long Term Solution Implementation ""
Describe the Susquehanna CPPU L/T Solution Technical Specification/Operability requirements.
- OPRM operability requirements apply _Ž23% RTP
- Actions a 1.1Initiate alternate method to detect and suppress thermal hydraulic instability oscillations in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> AND
> 1.2 Restore required channels to OPERABLE in 120 days a Ifthe required action and associated Completion Time of 1.1and 1.2 are not met then reduce THERMAL POWER to <23% RTP in 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
- Surveillance Requirements Channel Check C
)C Calibrate local power range monitors Channel Functional Test C
)) Channel Calibration a Verify OPRM is not bypassed when APRM STP is ?25% and recirculation drive flow is 5 value equivalent to the core flow value defined in the COLR
>) Adjust recirculation drive flow to conform to reactor core flow 8
4
Stability Long Term Solution Implementation
- Describe the backup stability implementation (e.g. ICA) at Susquehanna.
- Technical Requirements Manual contains requirements for the backup method Manual Scram and Exit regions defined on Power/Flow map
- Regions based on AREVA STAIF calculations plus ICA regions Most limiting of core wide and regional mode Analyses done over entire cycle exposure range Regions bound cycle step out exposures Scram Region (Region I) defined as STAIF DR = 1.0 Exit Region (Region II)includes STAIF uncertainties Regions generated to also bound ICA regions Stability Protection with OPRM Operable Scram Region becomes part of the Exit region Exit Region in force Technical Specifications require manual scram on dual recirculation pump trip g
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Stability Long Term Solution ""1 -
Implementation pp
- What is the Susquehanna experience with the PBDA? Noise, false positives ...
- Describe the implications for operator training. How are false alarms handled?
" SSES monitored OPRM / PRNMS during startups.
" SSES has not observed any false positive alarms or trips with the GE system.
11 Stability Long Term Solution Implementation
- Describe the acceptance testing process. Include a description of PBDA results where false alarms were detected
- Describe any Solution-Ill hardware implementation issues such as: location of the new hardware, periodic testing procedures, cable ringing for verification.
" SSES installed both the ABB system and subsequent GE PRNMS system in the original GE supplied APRM panels while using the installed LPRM cables and detectors.
" SSES performed continuity checks or functional tests of all input, output and interface terminations including all indication, alarms, and trip functions.
" SSES performed all surveillance tests including calibrations, functional, time response and logic system functional tests.
" SSES did not experience any notable OPRM installation issues.
12 6
Stability Long Term Solution Implementation
- Describe the effects, if any, of the proposed CPPU upgrade on the L/T Solution.
" No methods changes for CPPU
- Rod line not higher than current maximum rod line
- Cycle specific setpoint analysis will capture core design variations
- Full Cores of ATRIUM-10 fuel
" Option III LIT Solution remains unchanged except for CPPU cycle specific OPRM setpoints
" Option III OPRM setpoints will be developed based on the DIVOM curves from the CPPU cycle specific reload analysis 13 ATWS. ATWS/Stability, and EOPs
- Effect of the CPPU upgrade on ATWS and EOPs. How are EOP parameters that are affected by CPPU recalculated (e.g. cold shutdown boron weight, heat capacity temperature limit ... )
" Plant Specific Parameters affected by the CPPU changes are revised (i.e. reactor power, decay heat, boron enrichment, etc.)
" Work Sheets containing these revised parameters are recalculated
" EOPs are updated with changes associated with CPPU 14 7
ATWS, ATWSIStability, p and EOPs
- Effect of the CPPU upgrade on ATWS and EOPs. How are EOP parameters that are affected by CPPU recalculated (e.g. cold shutdown boron weight, heat capacity temperature limit ... )
" Hot Shutdown Boron Weight (HSBW) was revised for 88% enriched sodium pentaborate
" Heat Capacity Temperature Limit (HCTL) curves are slightly lower 15 ATWS, ATWS/Stability, and EOPs
- Summary of the EOPs that apply during ATWS (e.g. level control).
- RPV Control
- Level and Power Control
- PC Control
- RPV Flooding 16 8
- .* ****~~
ATWS EOPs PpI EO-000-002 RPV Control
- Step RC-1
. If a Rx Scram has not been initiated, initiate a Rx Scram
- Step RC-2
- If more than 1 Control Rod >00 then enter EO-000-1 13 Level/Power Control 17
- .* ~
i 'I.--
EO-000-1 13 Level/Power Control
- Step LQ-4
. Ensure Rx Mode Switch in Shutdown
- Step LQ-5
. Ensure ARI initiated
- Step LQ-6
. Record initial ATWS power level
- Perform Power/Level/Pressure legs concurrently 18 9
EO-000-1 13 Level/Power Control
- Power Leg (LQ/Q steps)
" Is initial ATWS power >5% or cannotbe determined
" If Rx power is <5% and before Supp Pool temperature exceeds 150OF inject SBLC and inhibit ADS
" Inject SBLC and inhibit ADS
" Ensure SRMs and IRMs inserted
" Ensure Recirc Pumps run back to minimum speed
" If initial ATWS power >5%, trip both Recirc Pumps
" Maximize CRD (drift control rods into 00)
" Insert Control Rods (see Sheet 2 of EOP-000-1 13)
" Stop SBLC pumps at "0"gallons in tank (CSBW) 19 ATWS EOPs PP1 "
EO-000-1 13 Level/Power Control
- Level Leg (LQ/L steps)
- If level cannot be determined go to RPV Flooding
- Reset Main Generator Lockouts (if turbine tripped)
- If initial ATWS power level >5%, lower Rx level to target band
- Bypass MSIV and CIG interlocks
- When HSBW is injected restore Rx level to normal
- If Rx level cannot be restored and maintained >TAF (-161), go to Rapid Depressurization and restore Rx level to -60 to -161 20 10
- ~
EO-000-1 13 Level/Power Control
- Pressure Leg (LQ/P steps)
" Before depressurizing <700 psig, prevent uncontrolled Condensate injection
" Before depressurizing <400 psig, prevent RHR and CS injection not required to assure adequate core cooling
" If initial ATWS power < 5%, maintain RPV pressure less than HCTL curve
" Stabilize RPV pressure <1087 psig 21 P
ATWS EOPs EO-000-1 13 Level/Power Control
- Sheet 2 Control Rod Insertion
- Maximize CRD to drift control rods with cooling water pressure
- Drive control rods manually
- Bypass RSCS and RWM and establish drive pressure
- Individually Scram control rods
- De-energize Scram solenoids
- Venting CRD overpiston volume 22 11
ATWS EOPs P EO-000-103 PC Control
- SP Temperature Leg
" When initial ATWS power _ 5% or shutdown with control rods, ensure SBLC injected as required (150OF Supp Pool temp)
" Maintain HCTL requirements
- PC Pressure Leg
- If Supp Chamber pressure cannot be maintained within the Pressure Suppression Limit and initial ATWS power _ 5% or shutdown with control rods, go to Rapid Depressurization 23 i
EO-000-114 RPV Flooding
- After Rapid Depressurization and with more than 1 control rod
>00
" Isolate MSIVs and drains
" When RPV pressure is less than Minimum Steam Cooling Pressure (MSCP) injection is started to maintain RPV pressure just above MSCP 24 12
ATWS. ATWSlStability, and EOPs
- ATWS/Stability Mitigation Actions implemented in Susquehanna EOPs ON-178(278)-002 Core Flux oscillations
- NOTE: Enter the ON when in Region I or Region II- with or without oscillations
- Operator Actions (per procedure)
Monitor LPRM alarms & readings
" Monitor APRM readings
" Increase flow or insert rods
- Indications ii Trending Towards 10% peak-to-peak on LPRMs or APRMs i 2 or more LPRM upscale alarms alarming and clearing w/1 to 5 sec. period
- With OPRM operable ii Suppress oscillations by increasing core flow or inserting control rods
- With OPRM not operable, immediately Scram the Rx if:
a) IfRegion 1 of Power/Flow map entered
)a If Region 2 of Power/Flow map entered with <50% of required LPRM Upscale Alarms operable a Thermal instabilities are occurring 25 ATWS, ATWS/Stability, and EOPs
- What is the effect on plant equipment of high suppression pool temperatures (e.g. NPSH)?
" EPU Calculated Peak Suppression Pool Temperature during an ATWS Event - 206°F
- Design Temperature for Wetwell Components - 220°F
- Residual Heat Removal System
- Components (i.e. pump, heat exchanger, pump seals, etc.)
are qualified to 340°F
- Available NPSH is acceptable for the ATWS event (Reference PUSAR Section 4.2.6) 26 13
ATWS, ATWS/StabiIity, and EOPs
- What is the effect on plant equipment of high suppression pool temperatures (e.g. NPSH)?
" Core Spray System
- Components (i.e. pump, pump seals, etc.) are qualified to 212°F
- Available NPSH is acceptable for the ATWS event (Reference PUSAR Section 4.2.6)
" Suppression Pool remains below local-to-bulk temperature (NUREG-0783) limit of 2161F 27
SUMMARY
pp
- Long -Term Stability Solution Implementation Status
- Anticipated Transient Without Scram (ATWS)
" Emergency Operating Procedures (EOPs)
- Stability Mitigation Actions