ML063180569
| ML063180569 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 11/13/2006 |
| From: | Howe A NRC/NRR/ADES/DE/EICB |
| To: | Raghavan L NRC/NRR/ADRO/DORL/LPLII-2 |
| NORBERT CARTE, NRR/DE/EICB, 415-5890 | |
| References | |
| TAC MC9565, TAC MD3048 | |
| Download: ML063180569 (7) | |
Text
November 13, 2006 MEMORANDUM TO: Lakshminaras Raghavan, Chief Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation FROM:
Allen G. Howe, Chief /RA/
Instrumentation and Controls Branch A Division of Engineering Office of Nuclear Reactor Regulation
SUBJECT:
BROWNS FERRY UNIT 1 REVISION TO TECHNICAL SPECIFICATION TO INCLUDE OSCILLATION POWER RANGE MONITOR (TAC NO. MD3048)
Plant Name:
Browns Ferry Nuclear Plant Unit 1 (BFN1)
Licensee:
Tennessee Valley Authority (TVA)
TAC No.:
MC9565 Docket No.:
50-259 Operating License:
DPR-33 Project Directorate:
PD II-2 Responsible PM:
Margaret H Chernoff Review Branch:
EICB A Review Status:
Complete By letter dated January 6, 2006 (ML060180477) Tennessee Valley Authority (the licensee) proposed license amendments to change the technical specifications (TS) for Browns Ferry Nuclear Plant Unit 1 to activate the Oscillation Power Range Monitor (OPRM). By letter dated August 14, 2006 (ML062220537), the staff requested additional information which was provided by letter dated October 2, 2006 (ML062790140). The OPRM is designed to detect the onset of reactor core power oscillations resulting form thermal-hydraulic instability and suppress them by initiating a reactor scram via the reactor protection system trip logic. The OPRM trip function ensures protection of the minimum critical power ratio safety limit in the event of thermal-hydraulic power oscillations, and thereby, provides compliance with general design criteria 10 and 12 of Title 10 Code of Federal Regulation 50, Appendix A.
CONTACT: Norbert Carte, DE/EICA 415-5890
L. Raghavan The Instrumentation and Control staff has reviewed the licensees submittal and approves the proposed revisions.
Enclose is the safety evaluation report documenting staffs approval of the licensees request.
Docket No: 50-259
Enclosure:
As stated
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 443 TO FACILITY OPERATING LICENSE NO. DPR-33 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT, UNIT 1 DOCKET NO. 50-259
1.0 INTRODUCTION
By application dated January 6, 2006 (ML060180477) as supplemented by a response to a request for additional information (RAI), dated October 2, 2006 (ML062790140), Tennessee Valley Authority (the licensee) requested changes to the Technical Specifications (TS-443) for the Browns Ferry Nuclear Plant, Unit 1.
The proposed changes (TS-443) revise the TS to activate the thermal-hydraulic stability monitoring instrumentation, referred to as oscillation power range monitor (OPRM). The Tennessee Valley Authority (TVA) identified that this request (TS-443) must be coordinated with previous proposed changes (TS-430: Installation of the OPRM and TS-433: Transition to 24 month fuel cycle). The two previously proposed changes (TS-430 & TS-433) that were necessary for the approval of TS-443, were implemented by the Nuclear Regulatory Commission (NRC) (ML062170007 & ML062170002 respectively).
1.1 BACKGROUND
Under certain conditions, boiling water reactors (BWRs) may be susceptible to coupled neutronic/thermal-hydraulic instabilities. These instabilities are characterized by periodic power and flow oscillations. If these power and flow oscillations become large enough, the fuel cladding integrity minimum critical power ratio (MCPR) safety limit requirements may be challenged.
To detect core instabilities automatically and provide a reactor scram signal to the reactor protection system (RPS), the licensee selected Boiling Water Reactor Owners Group (BWROG) Stability Option III as the long-term stability system solution (LTSSS) for Browns Ferry Nuclear Plant Unit 1 (BFN1). The LTSSS Option III approach consists of detecting and suppressing stability-related power oscillations by automatically inserting control rods (scramming) to terminate power oscillations, thereby complying with the requirements of General Design Criteria (GDC) 10 and GDC 12.
The licensee is replacing the existing power range portion of the existing Neutron Monitoring System with a General Electric Nuclear Measurement Analysis and Control-Power Range Neutron Monitor System (GE NUMAC-PRNMS), including the Option III OPRM function (See TS-430). A reactor trip occurs when two or more of the four OPRM functions calculate a trip condition.
The GE NUMAC-PRNMS design was approved by the staff in its safety evaluation of GE licensing topical report (LTR), Document No. NEDC-32410P, Nuclear Measurement Analysis and Control Power Range Neutron Monitor (NUMAC-PRNM) Retrofit Plus Option III Stability Trip Function,dated September 5, 1995. The safety evaluation was subsequently included in the approved version of the LTR (ML9605290009). Supplement 1 of the LTR was approved by the staff in its safety evaluation dated August 15, 1997. The safety evaluation was subsequently included in the approved Supplement 1 of the LTR (ML9806120242). The LTR and Supplement 1 address the Boiling Water Reactor (BWR) power instability issue discussed in GE licensing topical report NEDO-31960, BWROG Long-Term Stability Solutions Licensing Methodology (ML9106100443).
By letter dated June 29, 2001, GE submitted a Part 21 notification about the concern that stability reload licensing calculations using the generic delta critical power ratio (CPR) over initial minimum CPR MCPR versus oscillation magnitude (DIVOM) curve could result in OPRM reactor trip system RPS trip setpoints which may not protect MCPR safety limit.
By letter dated September 30, 2003 (ML032751632), the BWROG submitted a resolution for the Part 21 notification. The resolution required the licensee to use the plant-specific Delta Critical Power Ratio Over Initial Minimum Critical Power Ratio Versus Oscillation Magnitude (DIVOM) curve, which are generated or confirmed for each reload fuel cycle consistent with the process described in NEDO-32465A. The plant-specific curves will be reasonably conservative but not necessarily bounding for a particular fuel cycle. In conjunction with the 95/95 statistical approach of the licensing methodology, the plant-specific DIVOM curves will result in a high probability that the fuel cladding integrity safety limit will not be violated as a result of anticipated instability events.
It was previously proposed that the OPRM trip function would be operated in the indicate only test mode (See TS-430). During this test period, the interim corrective actions described in the above-referenced topical reports for determining and mitigating power oscillations would have been in effect. Upon completion of the OPRM test period, the licensee was to propose revisions to incorporate the OPRM into the BFN1 TS using the staff approved guidance in Supplement 1 to NEDC-32410P-A. However, due to extensive experience with OPRM on similar plants (Units 2 & 3) TVA has proposed activation OPRM for the startup of Unit 1.
The staff approved use of the NUMAC-PRNMS with the OPRM functions in BWR design plants.
The NUMAC-PRNMS with the Option III LTSSS function, when installed and operated in accordance with the approved guidance provided in the above-referenced LTR, addresses the requirements of GDC 10 and GDC 12.
2.0 REGULATORY EVALUATION
GDC 10, in Appendix A to 10 CFR 50, Reactor design, requires that the reactor core and associated coolant, control, and protection systems be designed with appropriate margin to assure that specified acceptable fuel design limits are not exceeded during any condition of normal operation, including the effects of anticipated operational occurrences.
GDC 12, in Appendix A to 10 CFR 50, Suppression of reactor power oscillations, requires that the reactor core and associated coolant, control, and protection systems be designed to assure that power oscillations which can result in conditions exceeding specified acceptable fuel design limits are not possible or can be reliably and readily detected and suppressed.
The staff used these regulatory requirements for its evaluation of the license amendment request.
3.0 TECHNICAL EVALUATION
TVA has requested ten (10) changes to the Technical Specifications (TS),Sections 3.3.1.1 and Section 3.4. EICB has reviewed the changes related to TS Section 3.3.1.1. The EICB review compared the changes to Section 3.3.1.1 against those of Supplement 1 of NEDC-32410P-A, which was approved by the NRC (ML9806120242).
In order to address the Part 21 notification, the licensee stated, that the OPRM system will be implemented using a plant-specific DIVOM calculation of setpoints, in accordance with the resolution of the Part 21 notification, and in this respect is acceptable.
The licensee, TVA, also operates Brown Ferry Units 2 & 3. Browns Ferry Units 2 & 3 are very similar to BFN1 and have been operating with the OPRM Option III system enabled since the spring of 1999 and 2000 respectively. Therefore based on the licensees experience with OPRM on Units 2 & 3, the staff finds it acceptable to activate the OPRM on BFN1 without the previously proposed trial period.
1 TS Section 3.3.1.1 - Addition to Note in Conditions A and B TS-430 (ML033300129) added a note to conditions A and B of Section 3.3.1.1 of the TS.
TS-443 (the TS change) modifies this note to include the added function 2.f of TS Table 3.3.1.1-1 in the list of functions in the note. This change is in accordance with Supplement 1 of NEDC-32410P-A, and is therefore acceptable.
2 TS Section 3.3.1.1 - Addition of Condition I and J to 3.3.1.1 Action table Conditions I and J were added. However, the conditions added are more conservative that those in Supplement 1 of NEDC-32410P-A. Condition J is more conservative than that in Supplement 1, and eliminates the need for required action I.2 of Supplement 1. Therefore, since the changes as proposed are more conservative than Supplement 1, they are acceptable.
Condition J of Supplement 1 required that the THERMAL POWER be reduced to below [25]
percent RTP within [4] hours if the completion time of Condition I was not met.
TVAs more conservative approach to Condition J is to be in Mode 2 within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> if the required action and associated completion time of Condition I were not met. This approach eliminated the need for required action I.2 of Supplement 1, which restored to OPERABLE the required channels within 120 days.
3 TS Section 3.3.1.1 - Addition of Surveillance Requirement (SR) No. 3.3.1.1.17 SR 3.3.1.1.17 is added to the TS, and is consistent with SR 3.3.1.1.18 in Supplement 1 of NEDC-32410P-A, as modified by TS-430 & TS-433, and is therefore acceptable.
The thermal power value in SR 3.3.1.1.17 is consistent with SR 3.3.1.1.18 of Supplement 1 of NEDC-32410P-A as modified by TS-431, and is more conservative for any licensed power level below that. The 24 month surveillance frequency is consistent with SR 3.3.1.1.18 of Supplement 1 of NEDC-32410P-A as modified by TS-433, and is therefore acceptable.
SR 3.3.1.1.18 of Supplement 1 (page H-8) verifies that the OPRM is not bypassed when Average Power Range Monitor (APRM) Simulated Thermal Power is greater than or equal to 30 percent Licensed Thermal Power (LTP). The 30 percent power boundary for OPRM bypass is based on the Original Licensed Thermal Power (OLTP). The proposed value of 25 percent for the equivalent surveillance (SR 3.3.1.1.17) more conservative and therefore is acceptable.
4 TS Section 3.3.1.1 - Addition to TS Table 3.3.1.1-1 The function added (2.f OPRM Upscale) to Table 3.3.1.1-1 is consistent with that on page H-10 of Supplement 1 of NEDC-32410P-A, and is therefore acceptable. Consistent with Supplement 1 of NEDC-32410P-A, the allowable value is not applicable, and is therefore indicated as NA.
The SR numbers in the TVA BFN1 TS are not identical to those in Supplement 1 of NEDC-32410P-A, however the same SRs are listed in both locations.
4.0 CONCLUSION
The staff has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: Norbert Carte EICB:DE (301) 415-5890 Date: 10/31/06
L. Raghavan The Electrical Instrumentation and Control staff has reviewed the licensees submittal and approves the proposed revisions.
Enclose is the safety evaluation report documenting staffs approval of the licensees request.
Docket No: 50-259
Enclosure:
As stated DISTRIBUTION P. Hiland M. Chernoff C. Lauron ACCESSION NUMBER:
OFFICE DE/EICA DE/EICA DE/EICA/BC NAME N. Carte H. Garg A. Howe DATE 10/31/06 10/31/06 11/13/06