ML20101D225
| ML20101D225 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 03/14/1996 |
| From: | Lesniak M COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9603200127 | |
| Download: ML20101D225 (5) | |
Text
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Commonweahh Edison Company 1400 Opus Place i
Downers Grove, n. @515 501 March 14,1996 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555
Subject:
Request to Use American Society of Mechanical Engineers (ASME) Code Case N-514 in the Determination of Low Temperature Overpressure Protection System (LTOPS) Setpoints Byron Station Units 1 and 2 NRC Docket Nos. 50-454/455
References:
- 1. " Exemption from Requirements of 10 CFR 50.60 - Braidwood Station, Unit 1, R. Assa (NRC) to D. L. Farrar (Comed), dated July 13,1995.
- 2. " Acceptance for Referencing of Topical Report WCAP-14040, Revision 1,
" Methodology Used to Develop Cold Overpressure Mitigating System Setpoints and RCS Heatup and Cooldown Limit Curves C. I. Grimes (NRC) to R. A. Newton, Westinghouse Owner's Group, dated October 16,1995.
- 3. NRC Generic Letter 96-03, " Relocation of the Pressure Temperature Limit Curves and Low Temperature Overpressure Protection System Limits,", dated January 31,1996.
Commonwealth Edison (Comed) requests an exemption, per 10 CFR 50.12, to use the American Society of Mechanical Engineers (ASME)Section XI, Code C' se N-514, a
" Low Temperature Overpressure Protection Section XI, Division 1," in the determination of Low Temperature Overpressure Protection System (LTOPS) Setpoints for Byron Nuclear Station Units 1 and 2. 10 CFR 50.12(a) (2) (iii) allows for the Commission to consider granting an exemption under special circumstances; specifically, if compliance with current regulations would result in undue hardship to a licensee.
Code Case N-514 (Attachment 1) was approved by the ASME on February 12,1992, and the guidance of this code case has been incorporated into the 1993 Addenda to the ASME Boiler and Pressure Vessel Code,Section XI, Appendix G. Code Case N-514 provides guidance on when LTOPS shall be in operation and the maximum pressure to which 9603200127 960314 PDR ADOCK 05000454 P
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NRC Document Control Desk March 14,1996 LTOPS shall limit Reactor Vessel pressure. In particular, Code Case N-514 states:
"LTOP systems shall limit the maximum pressure in the vessel to 110% of the pressure determined to satisfy Appendix G paragraph G-2215 of Section XI, Division 1."
In Attachments 2 and 3, Comed requested approval to use Code Case N-514 in the l.
' development of LTOPS setpoints for Braidwood Units 1 and 2. The NRC granted l
. approval of the exemption request in Reference 1.
Per the requirements of 10 CFR 50.12 (a) (2) (iii), cc npliance with the current requirements for determination of LTOPS setpoints included in 10 CFR 50 Appendix G will result in future hardship for Byron Station without a concurrent increm in the level of quality and safety. The hardship is that the operating window between the. maximum allowed RCS pressure for LTOPS and the minimum RCS pressure required for Reactor Coolant Pump (RCP) operation is significantly restricted when physical conditions such as PORV overshoot, RCP pump APs, and static head corrections' are taken into account in the setpoint determination. In the future, maintaining the current restrictions will increase the likelihood of LTOPS actuation at lower setpoints. This has the potential to endanger the RCP seals.
1 As documented in the Braidwood request and subsequent clarification letter (Attachments 2 and 3), Comed has reviewed ASME Code Case N-514 and determined that its use would provide an acceptable level of quality and safety. There are many conservatisms incorporated into the pressure-temperature (PT) limits calculated using the current methodology of ASME Code Section XI, Appendix G. ASME explicitly recognized the amount of margin inherent in the Appendix G PT limits by incorporating Code Case N-514 in the 1993 Addenda to ASME Code Section XI, Appendix G. Similar to the Braidwood circumstance, use of Code Case N-514 will not result in any design changes or plant modifications at Byron Station. LTOPS will still function to limit Reactor Pressure Vessel pressure and the use of Code Case N-514 will still ensure that the Reactor Pressure Vessel is protected from brittle fracture.
Byron and Braidwood Stations intend to submit a License Amendment Request in August, 1996, for review and approval of the Improved Technical Specifications (ITS), which includes the relocation of the pressure temperature (P/T) limit curves and the low temperature overpressure protection (LTOP) system setpoints to a pressure temperature limits report (PTLR). The request to implement the PTLR will be consistent with the recommendations contained in Generic Letter (GL) 96-03 (Reference 2). Also
' documented in GL 96-03, the NRC indicated that licensees must request an exemption from Appendix G for ASME Code Case N-514 until the NRC completes the rulemaking process for revisions to 10 CFR 50.55a and 10 CFR Pan 50, Appendix G.
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NRC Document Control Desk March 14,1996 Work is currently ongoing for Byron and Braidwood Stations to generate revised Reactor Coolant System (RCS) heatup and cooldown curves and LTOPS setpoints using the methodology documented in Westinghouse Owner's Group WCAP-14040-NP-A, Rev. 2.
WCAP-14040 was reviewed and approved by the NRC (Reference 3) The PTLR would use the WCAP methodology along with station specific instrument uncertainty analyses per Instrument of America (ISA) Standard S67.04-1994. The generation of the LTOPS setpoints would also include implementation of ASME Code Case N-514. This would ensure that the reactor pressure vessel is protected from brittle fracture but would allow for adequate operational flexibility between the maximum allowed LTOPS RCS pressure and the minimum RCS pressure for RCP operation Approval of this exemption request to use ASME Code Cas N-514 in the development of LTOPS setpoints for use at Byron Station is requested by August 30,1996.
If you have any questions regarding this correspondence, please contact this office.
Sincerely, 4th Marcia T. Lesniak Nuclear Licensing Administrator :
Code Case N-514, dated February 12,1992 :
" Request to use American Society of Mechanical Engineer's Code Case N-514 in the Determination of Low Temperature Overpressure Protection System Setpoints for Braidwood Station Units 1 and 2," NRC Docket Nos.
50-456/457, D. M. Saccomando - Comed to NRR, dated November 30, 1994. :
" Clarification ofInformation Regarding Braidwood Station's Request to use American Society of Mechanical Engineers Code Case N-514 in the Determination of Low Temperature Overpressure Protection System Setpoints," NRC Docket Nos 50-456/457, D. M. Saccomando - Comed to NRR, dated May 11,1995.
cc:
G. Dick, Byron Project Manager-NRR H. Peterson, Senior Resident Inspector-Byron H. Miller, Regional Administrator-RIII Illinois Department of Nuclear Safety-IDNS k:\\nla\\ byron \\n514 req. doc /3
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l ATTACHMENTS-Code Case N-514, dated February 12,1992 i
" Request to use American Society of Mechanical Engineer's Code Case N-514 in the Determination of Low Temperature Overpressure Protection System Setpoints for Braidwood Station Units 1 and 2," NRC Docket Nos. 50-456/457, D. M. Saccomando - Comed to NRR, dated November 30,1994.
" Clarification ofInformation Regarding Braidwood Station's Request to use American Society of Mechanical Engineers Code Case N-514 in the Determination of Low Temperature Overpressure Protection System Setpoints," NRC Docket Nos. 50-456/457, D. M. Saccomando - Comed to NRR, dated May 11,1995.
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CASE N-514 CASES OF ASME BOILER AND PRESSURE VESSEL CODE 4
Approval Date: February 12,1992 See NumericalIndex for expiration and any reaffirmation dates.
t Case N 514 protection against failure during reactor start-up and Low Temperature Overpressure Protection shutdown' operation due to low temperature over.
Section XI, Division 1 pressure events that have been classified as Service Level A or B events. LTOP systems shall be effective Inquiry: Section XI, Division 1, IWB-3730, re-at coolant temperatures less than 200*F or at coolant quires that during reactor operation, load and tem-temperatures' corresponding to a reactor vessel perature conditions be maintained to provide pro-metal temperature less than RTm,r + 50'F, which-d 2
tection against failure due to the presence of ever is greater. LTOP systems shall limit.the maxi-postulated flaws in the ferritic portions of the reactor mum pressure in the vessel to 110% of the pressure coolant pressure boundary. For those plants having determined to satisfy Appendix G, para. G-2215 of low temperature overpressure protection (LTOP)
Section XI, Division 1.
systems, what load and temperature conditions under IWB-3730 may be used to provide protection against failure during reactor start-up and shutdown opera.
- The coolant temperature is the reactor coolant inlet tempera.
1 tion due to low temperature overpressure events that have been classified as Setvice Level A or B events?
2 The vessel metal temperature is the temperature at a distance one-fourth of the vessel section thickness from the inside surface in the vessel beltline region. RT.7 is the highest adjusted refe-Reply: It is the opinion of the Committee that for rence temperature for weld or base metal in the beltline region at a distance ne-f urth of the vessel section thickness from the those P ants havin8 TOP systems the followin8 oad l
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vessel inside surface, as determined by Regulatory Guide 1.99, and temperature conditions may be used to provide Rev. 2.
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Commonwealth Edloon
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1400 Opus Place
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Downers Grove. Enos 60515 November 30, 1994 Office of Nuclear Reactor Regulation i
U.
S. Nuclear Regulatory Commission Washington D.C. 20555 Attention:
Document Control Desk
Subject:
Request to Use American Society of Mechanical Engineers Code Case N-514 in the Determination of Low Temperature Overpressure Protection System Setpoints.
Braidwood Station Units 1 and 2 NPF-72/77 NRC Docket Nos. 50-456/457 Commonwealth Edison '(Comed) requests approval, per Title 10 Code of Federal Regulations, Section 55a, subsection a, paragraph 3 (10 CFR 50.55a (a) (3 )) to use American Society of Mechanical Engineers (ASME)Section XI Code Case N-514, " Low Temperature Overpressure Protection Section XI,' Division 1,"
in the determination of Low Temperature Overpressure Protection System (LTOPS) Setpoints for Braidwood Nuclear Station Units 1 and 2.
Code Case N-514 war approved by ASME on February 12, 1992.
Although the use of this Code Case is currently not referenced in Regulatory Guide 1.147, " Inservice Inspection Code Case Acceptability," Revision 10, dated July, 1993, the guidance in Code Case N-514 has been incorporated into the 1993 Addenda to the ASME Boiler and Pressure Vessel Code,Section XI, Appendix G.
Code Case N-514 provides guidance on when LTOPS shall be in effect, and the maximum pressure to which LTOPS shall limit Reactor Vessel pressure.
In particular, Code Case N-514 states:
"LTOP systems shall limit the maximum pressure in the vessel to 110% of the pressure determined to satisfy Appendix G paragraph G-2215 of Section XI, Division 1."
A copy of Code Case N-514 has been included with this request as Attachment 1.
Comed has reviewed Code Case N-514 and determined that its use would provide an acceptable level of quality and safety.
There are many conservatisms incorporated.into the pressure-temperature (PT) limits calculated using the current methodology of ASME Code Section XI Appendix G.
The ASME explicitly recognized the amount of margin inherent in the Appendix G PT limits by incorporating Code Case N-514 in the 1993 Addenda to ASME Code Section XI Appendix G.
Use of this code case will not result in any design changes to Braidwood Station.
No new equipment will be installed and no existing equipment will be modified or removed.
The LTOPS system will still function to limit Reactor Pressure Vessel pressure and the use of Code Case N-514 will still ensure that the Reactor Pressure Vessel is protected from brittle fracture.
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Document Control Desk November 30, 1994 Compliance with the current requirements for determination of LTOPS setpoints included in 10 CFR 50 Appendix G results in hardships for Braidwood Station without a concurrent increase in the level of 1
quality and safety.
Application of the current LTOPS setpoint determination method reduces operating flexibility by reducing the margin between the maximum allowed Reactor Coolant System (RCS) pressure and the minimum RCS pressure for Reactor Coolant Pump (RCP) operation with no concurrent increase in protection against non-ductile failure of the Reactor Pressure Vessel.
The current methodology also increases the likelihood of LTOPS actuation at lower setpoints, and reduces the amount of separation of the setpoints for the Power Operated Relief Valves (PORV) used in the LTOPS system.
This endangers the RCP seals as actuation of LTOPS i
setpoints determined by the current methodology may cause RCS at pressure to drop below the minimum needed to maintain proper RCP seal differential pressure.
Approval of this request to use Code Case N-514 in the determination of LTOPS setpoints is necessary to allow Braidwood Station to obtain approval of new LTOPS Technical Specification curves which will be submitted in a future Technical Specification Amendment request.
These curves allow Braidwood Unit 1 to exceed 5.37 Effective Full Power Years (EFPY) of operation.
Braidwood is currently predicted to reach 5.37 EFPY on July 16, 1995.
Accordingly, Comed requests that this request to use Code Case N-514 in the determination of LTOPS setpoints be approved prior to i
July 10, 1995.
Please direct any questions to this office.
['
Sincerely, e
.,/ l Kr.. ~ / ' /. - f m _,_ Aw Denisb M. Saccomando Nuclear Licensing Administrator Attachment cc:
R. R. Assa, Braidwood Project Manager - NRR S. G.
DuPont, Senior Resident Inspector - Braidwood J.
B. Martin, Regional Administrator - RIII Office of Nuclear Safety-IDNS k:nla\\bwd\\n514x
Osmmonwealth Edi3on Company l4tM Opus Place Downers Gnne, lL (oils May 11, 1995 Office of Nuclear Regulation, U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Attn:
Document Control Desk
Subject:
Clarification of Information Regarding Braidwood Stations Request to Use American Society of Mechanical Engineers Code Case N-514 in the Determination of Low Temperature Overpressure Protection System Setpoint Braidwood Station Units 1 and 2 NRC Docket Numbers 50-456/457
References:
1.
D. Saccomando letter to NRC dated November 30, 1994, Transmitting Request to Use ASME Code Case N-514 2.
D. Saccomando letter to NRC dated December 16, 1995, transmitting Technical Specification Amendment Request for Nominal PORV Pressure Relisl3f Setpoint Versus RCS Temperature for the Cold Overpressure Protection System 3.
Teleconference dated May 2 between Commonwealth Edison Company and the Nuclear l
Regulatory Commission Regarding the December 16, 1995, Technical Specification Submittal During the Reference Teleconference it was noted that Commonwealth Edison Company (Comed) needed to clarify that it is requesting an exemption request per 10CFR50.12 to use American Society of Mechanical Engineers (ASME)Section XI Code Case N-
- 514, " Low Temperature Overpressure Protection Section XI, Division 1,"
in the determination of Low Temperature Overpressure Protection System (LTOPS) Setpoints for Braidwood Nuclear Station Units 1 and 2.
10CFR50.12 (a) (2 ) (iii) allows for the Commission to consider l
granting an exemption under special circumstances; specifically, 1
if compliance would result in undue hardship.
As stated in l
Reference letter 1,
" Compliance with the current requirements for determination of LTOPS setpoints incfuded in 10CFR50 Appendix G results in hardships for Braidwood Station without a concurrent increase in the level of quality and safety.
Application of the current LTOPS setpoint determination method reduces operating flexibility by reducing the margin between the maximum allowed Reactor Coolant System (RCS) pressure and 4
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NRC Document Control Desk -May ll, 1995 the minimum RCS pressure for Reactor Coolant Pump (RCP) operation with no concurrent increase in protection against non-ductile failure of the Reactor Pressure Vessel.
The current methodology also increases the likelihood of LTOPS actuation at lower setpoints, and reduces the amount of separation of the setpoints for the Power Operated Relief Valves (PORV) used in the LTOPS system.
This endangers the RCP seals as actuation of LTOPS at setpoints determined by the current methodology may cause RCS pressure to drop below the minimum needed to maintain proper RCP seal differential pressure."
i Approval of this request to use Code Case N-514 in the determination of LTOPS setpoints is necessary to allow Braidwood Station to obtain approval of new LTOPS Technical Specification curves which was submitted in Reference 2.
If you have any questions regarding this correspondence, please contact this office.
i 1
Sincerely, C
sd Denise M. hbcomando Nuclear Licensing Administrator cc:
R. Assa, Braidwood Project Manager-NRR S. Dupont, Senior Resident Inspector-Braidwood J. Martin, Regional Administrator-RIII Office of Nuclear Safety-IDNS j
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