ML053620270
| ML053620270 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 12/12/2005 |
| From: | Vidal O BWR Owners Group, Southern Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation |
| Roth D | |
| References | |
| NUREG-1433, NUREG-1434 | |
| Download: ML053620270 (17) | |
Text
BW04 Proposed Solutions to Part 21 on Safety Limit 2.1.1.1, NUREG-1433/34 w
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Ozzie Vidal, Principal Engineer Southern Nuclear Operating Company Plant Hatch
- December 12, 2005 m
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Agenda
> Introduction and Purpose
> Presentation i Overview of SL 2.1.1.1 Part 21 i Description
- Evaluation i Subcommittee X Proposed Solutions
- Descriptions
- Advantages and Disadvantages X Schedule X Discussion IBWRI OWNERS'GROUP 2
Introduction and Purpose Meeting is intended to provide NRC with the current status of the SL 2.1.1.1 Part 21 issue, and to solicit some feedback. This involves discussion of:
- Two proposed Technical Specifications solutions Resolution schedule 3
Overview of Part 21/Description v GE Issued on March 29, 2005, as a reportable condition per 21.21(d)
- SL 2.1.1.1 requires that with reactor steam dome pressure below 785 psig or core flow below 10%0/ of rated, THERMAL POWER shall be < [25%] of rated (Value can be lower for extended power uprate plants)
- SL 2.1.1.1 intended to preclude the need for CPR calculations below 785 psig e SL provides conservative bounding conditions for fuel cladding integrity protection during start-up 4
Overview of Part 21/Description
- Problem discovered with at-power pressure regulator failure-open (PRFO) transient upon evaluation with newer models
- Early models predict a reactor level swell resulting in turbine trip and subsequent reactor scram
- Newer models predict that level may not increase to the turbine trip
- New models then predict the depressurization is terminated by MSIV closure scram at low pressure isolation setpoint OWNERS'GROUP 5
Overview of Part 21/Description
- Steam dome pressure could decrease to below 785 briefly with thermal power still above 25%
of rated, "violating" the SL A scram on MSIV closure position would occur, and, therefore, the time above 25% is very brief OWNERS' GROUP kj6
Overview of Part 21/Evaluation
- Depressurization transients increase the critical bundle power and decrease the bundle power
- This results in an increase in the critical power ratio, CPR=CP/AP
- Application of SL 2.1.1.1 is, therefore, overly conservative for this depressurization transient since the event does not threaten fuel cladding integrity 7
Subcommittee
- Subcommittee of Technical Specifications Issues Coordination Committee (TSICC) was formed in May, 2005
- Purpose to develop a proposed generic Technical Specifications (TS) change to the BWR NUREGs and to consider longer term solutions
Subcommittee
- Subcommittee has met four times
- Two proposed TS/Bases changes are currently under consideration
- TS Bases only change
- TS change which eliminates SL 2.1.1.1 and creates a new LCO in Power Distribution limits section 3.2
- A longer term solution is being discussed with GE which involves lowering the steam dome pressure value in the SL.
Other fuel vendors (Framatome/Westinghouse) already have lower acceptable value OWNERS' GROUP 9
Proposed Solutions/Description
- Proposed Solution #1, Bases only change--
- SL 2.1.1.1 stays as-is
- A paragraph is inserted into Applicable Safety Analysis section of B 2.1.1 indicating that SL 2.1.1.1 is not applicable during depressurization transients
- Similar wording added to Applicability section of B 2.1.1
- Eliminate tie to SL 2.1.1.1 in section B 3.3.6.1, Main Steam Line (MSL) Pressure-Low (Per part 21, MSL low pressure should not be an LSSS for protecting SL 2.1.1.1) 10 OWNERS'GROUP
Proposed Solutions/Description
- Proposed Solution #2^ TS and Bases change
- Eliminates SL 2.1.1.1 and corresponding Bases
- Creates new Limiting Condition of Operation (LCO) 3.2.5, "Reactor Steam Dome Pressure and Core Flow", and corresponding Bases
- Replaces references to SL 2.1.1.1 in Bases section B 3.3.1.1, "Average Power Range Monitor Neutron Flux-High, Setdown"
Proposed Solutions/Advantages and Disadvantages ProDosed Solution #1 Advantages J..
- Simple
- No changes necessary plant specific TS to NUREG TS or to l No changes necessary to longstanding TS SLs OWNERS' GROUP 12 w
Proposed Solutions/Advantages and Disadvantages Proposed Solution #1 Disadvantages
- TS Applicability unchanged
- No precedents for qualifying a TS Applicability in the Bases OWNERS' GROUP 13
Proposed Solutions/Advantages and Disadvantages e Proposed Solution #2. Advantages
- Eliminates any ambiguity with respect to Applicability of low pressure/low flow criteria OWNERS' GROUP 14
Proposed Solutions/Advantages and Disadvantages
- Proposed Solution #2 Disadvantages
- A more complex change, will require extensive re-formatting, re-numbering and re-writing of existing TS and Bases
- Requires each utility to submit a plant specific Technical Specifications change to NRC AM 15
Schedule
- Subcommittee will present their proposed TS/Bases solution to the full TSICC at the December full committee meeting
- Tentative schedule is to submit to NRC by June, 2006. Either proposed solution will require NRC review and approval 16
Discussion 0
]D0 Discussion! Questions / Comments from Participants 17