ML101170607
| ML101170607 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 05/06/2010 |
| From: | Markley M Plant Licensing Branch IV |
| To: | Entergy Operations |
| Kalyanam N, NRR/DORL/LPL4, 415-1480 | |
| References | |
| TAC ME1622 | |
| Download: ML101170607 (10) | |
Text
UNITED NUCLEAR REGULATORY WASHINGTON, D.C. 20555*0001 May 6, 2010 Vice President, Operations Arkansas Nuclear One Entergy Operations, Inc. 1448 S.R. 333 Russellville, AR 72802 ARKANSAS NUCLEAR ONE, UNIT 2 -STAFF EVALUATION AND PROPOSED BASIS FOR DENIAL OF REQUEST FOR TECHNICAL SPECIFICATION CHANGE RELATED TO RELOCATION OF PRESSURIZER HEATER REQUIREMENTS TO TECHNICAL REQUIREMENTS MANUAL (TAC NO. ME1622)
Dear Sir or Madam:
By letter dated June 18, 2009, Entergy Operations, Inc. (Entergy, the licensee), submitted a license amendment request to revise the Arkansas Nuclear One, Unit 2, Technical Specifications (TSs). Specifically, the licensee proposed to relocate the pressurizer heater requirements in TS 3.4.4, "Pressurizer," to the licensee-controlled Technical Requirements Manual (TRM). TS 3.4.4 specifies operability requirements for both the water volume in the pressurizer and the electric heater capacity of the pressurizer.
Enclosed is the U.S. Nuclear Regulatory Commission (NRC) staff's evaluation and proposed basis for denial of the license amendment request. The staff's evaluation contains the NRC staff's conclusions on the proposed changes to the TSs and Entergy's position that the pressurizer heater requirements should be relocated from the TSs to the TRM. We request that your staff review the enclosed safety evaluation and provide comments within 15 days from the receipt of this letter.
-2 If you have any questions, please contact Kaly N. Kalyanam at (301) 415-1480 or via e-mail at kaly.kalyanam@nrc.gov.
Sincerely, Michael T. Markley, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-368
Enclosure:
As stated cc w/encl: Distribution via Listserv UNITED NUCLEAR REGULATORY WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PROPOSED BASIS FOR DENIAL OF TECHNICAL SPECIFICATION CHANGE RELATED TO RELOCATION OF PRESSURIZER HEATER REQUIREMENTS TO TECHNICAL REQUIREMENT MANUAL ENTERGY OPERATIONS, INC. ARKANSAS NUCLEAR ONE, UNIT 2 DOCKET NO. 50-398
1.0 INTRODUCTION
By letter dated June 18, 2009 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML091760204), as supplemented bye-mail dated July 30,2009 (ADAMS Accession No. ML101180105), Entergy Operations, Inc. (Entergy, the licensee), submitted a license amendment request to revise the Arkansas Nuclear One, Unit 2 (ANO-2), Technical Specifications (TSs). Specifically, the licensee proposed to relocate portions of the pressurizer heater requirements in TS 3.4.4, "Pressurizer," Limiting Condition for Operation (LCO) and Surveillance Requirements (SRs) to the licensee-controlled Technical Requirements Manual (TRM). TS 3.4.4 specifies operability requirements for both the water volume in the pressurizer and the electric heater capacity of the pressurizer.
According to the licensee, the heater bank and capacity requirements for the Pressurizer are not credited in the accident analyses and, therefore, are proposed for relocation to the station TRM. The licensee states that the proposed change is consistent with the intent of Section 50.36, "Technical specifications," in Title 10 of the Code of Federal Regulations (10 CFR) in that the heaters do not meet the requirements for inclusion in the TSs. The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review of the proposed amendment.
Our review has concluded that the proposed amendment should not be approved by the NRC staff. The basis for this finding are as explained below:
2.0 REGULATORY EVALUATION
In NUREG-1432, "Standard Technical Specifications, Combustion Engineering Plants," (STS, NUREG-1432) (ANO-2 is a CE plant type), LCO 3.4.9, "Pressurizer," specifies operability requirements for both the water volume in the pressurizer and the electric heater capacity of the pressurizer.
The Bases for LCO 3.4.9 state that the pressurizer satisfies Criterion 2 and Criterion 3 of 10 CFR 50.36(c)(2)(ii).
Enclosure
-2 The regulations in 10 CFR 50.36(c)(2)(ii) require that a TS LCO of a nuclear reactor must be established for each item meeting one or more of the four criteria specified in the regulation.
Specifically, Criterion 2 of 10 CFR 50.36(c)(2)(ii)(B), states, A process variable, design feature, or operating restriction that is an initial condition of a design basis accident or transient analysis that either assumes the failure of or presents a challenge to the integrity of a fission product barrier. Criterion 3 in 10 CFR 50.36(c)(2)(ii)(C) states, A structure, system, or component that is part of the primary success path and which functions or actuates to mitigate a design basis accident or transient that either assumes the failure of or presents a challenge to the integrity of a fission product barrier. Criterion 4 in 10 CFR 50.36(c)(2)(ii)(D) states, A structure, system, or component which operating experience or probabilistic risk assessment has shown to be significant to public health and safety. The LCO 3.4.9 Bases further state, Safety analyses presented in the FSAR [Final Safety Analysis Report] do not take credit for pressurizer heater operation; however, an implicit initial condition assumption of the safety analyses is that the RCS [reactor coolant system] is operating at normal pressure.
Although the heaters are not specifically used in accident analysis, the need to maintain subcooling in the long term during loss of offsite power, as indicated in NUREG-0737
["Clarification on Post-TMI Requirements"]
is the reason for their inclusion.
There are no specific 10 CFR Part 50, Appendix A, General Design Criteria (GDC) associated with pressurizer heaters. 3.0 TECHNICAL EVALUATION 3.1 Background The pressurizer provides a point in the RCS where liquid and vapor are maintained in equilibrium under saturated conditions for pressure control purposes to prevent bulk boiling in the remainder of the RCS. Key functions include maintaining required primary system pressure during steady state operation and limiting the pressure changes caused by reactor coolant thermal expansion and contraction during normal load transients.
The pressure control components addressed by this LCO include the pressurizer water level, the required heaters and their backup heater controls, and emergency power supplies.
-3Current TS 3.4.4 Current TS 3.4.4 through Amendment No. 234 states, PRESSURIZER LIMITING CONDITION FOR OPERATION The pressurizer shall be OPERABLE with a water volume of :s; 910 cubic feet (equivalent to :s; 82% of wide range indicated level) and both pressurizer proportional heater groups shall be OPERABLE.
APPLICABILITY:
MODES 1, 2 and 3. ACTION: With the pressurizer inoperable due to water volume 910 cubic feet, be in at least HOT SHUTDOWN with the reactor trip breakers open within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. With the pressurizer inoperable due to an inoperable emergency power supply to the pressurizer heaters, either restore the inoperable emergency power supply as required by TS 3.8.1.1 action b.3 or be in at least HOT SHUTDOWN within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. SURVEILLANCE REQUIREMENTS The pressurizer water volume shall be determined to be within its limits at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. The pressurizer proportional heater groups shall be determined to be OPERABLE. At least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> by verifying emergency to the heater groups, and power is available At least once per 18 months by verifying that the summed power consumption of the two proportional heater groups is 150 KW.
Revised TS 3.4.4 Revised TS 3.4.4 would state, PRESSURIZER LIMITING CONDITION FOR OPERATION The pressurizer shall be OPERABLE with a water volume of S 910 cubic feet. APPLICABILITY:
MODES 1, 2 and 3. ACTION: With the pressurizer to water volume 910 cubic feet, be in at least HOT SHUTDOWN with the reactor trip breakers open within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. SURVEILLANCE REQUIREMENTS 4.4.4.1 The pressurizer water volume shall be determined to be within its limits at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. Regulatory Precedence There is no regulatory precedence where the NRC staff has approved the removal of the pressurizer heaters from the TS. NRC Staff Evaluation Discussion on Initial Conditions In its letter dated June 18, 2009, the licensee states, in part, that, Although it is preferable to maintain the Pressurizer heaters to enhance operation during natural circulation cooldown, the associated limits and surveillance requirements do not meet the intent of 10 CFR 50.36 for inclusion in the TSs in that they are not installed instrumentation that is used to detect, and indicate in the control room, a significant abnormal degradation of the reactor coolant pressure boundary, they are not a process variable, design feature, or operating restriction that is an initial condition of a Design Basis Accident (DBA) or transient analysis that either assumes the failure of or presents a challenge to the integrity of a fission product barrier, and they are not a structure, system or component that is part of the primary success path and which functions or actuates to mitigate a DBA or transient that either assumes the failure of or presents a challenge to the integrity of a fission product barrier. In addition, the Pressurizer heaters are not a structure, system, or component which operating experience or probabilistic risk assessment has shown to be significant to public health and
-5 safety. As discussed above, the Pressurizer heaters are not required to prevent or mitigate any DBA, nor are they required to successfully complete a natural circulation cooldown through Mode 3. In Mode 4 (RCS temperature
<300 OF), Shutdown Cooling (SOC) may be placed in service as desired to exit natural circulation cooldown conditions." A letter dated May 9, 1988 (ADAMS Legacy Library Accession No. 8805240041), from Mr. Thomas E. Murley, NRC, to each of the pressurized-water and boiling-water reactor owners groups (inclUding the CE Owners Group), documents the NRC staff's conclusions as to which current STS requirements must be retained in the new STS and which can be relocated to other licensee-controlled documents.
In the letter, the staff's conclusions were based on the Commission's Interim Policy Statement on Technical Specification Improvements, issued February 6, 1987 (52 FR 3788), and on several interpretations of how to apply the screening criteria contained in that Policy Statement.
The letter further states that the NRC staff considered comments made by industry at a meeting on March 29, 1988, between the NRC, the Nuclear Management and Resources Council (now Nuclear Energy Institute), and each Owners Group in making these interpretations.
One of the concerns raised in the letter was the interpretation of "initial conditions" to which the letter provides the following conclusions: The "initial conditions" captured under Criterion 2 should not be limited to only "process variables" assumed in safety analyses.
They should also include certain active design features (e.g., high pressure/low pressure system valves and interlocks) and operating restrictions (e.g., temperature operating limit curves), needed to preclude unanalyzed accidents.
In this context, "active design features" include only design features under the control of operations personnel (Le., licensed operators and personnel who perform control functions at the direction of licensed operators).
This position is consistent with the conclusions reached by the staff during trial application of the criteria to the Wolf Creek [Generating Station] and Limerick [Generating Station] Technical Specifications. The "initial conditions" of design-basis accidents (DBA) and transients, as used in Criterion 2, should not be limited to only directly "monitored and controlled" from the control room. Initial conditions should also include other features/
characteristics that are specifically assumed in DBA and transient analyses even if they can not be directly observed in the control room. For example, initial conditions (e.g., moderator temperature coefficient and hot channel factors) that are periodically monitored by other than licensed operators (e.g., core engineers, instrumentation and control technicians) to provide licensed operators with the information required to take those actions necessary to assure that the plant is being operated within the bounds of design and analysis assumptions, meet Criterion 2 and should be retained in the Technical Specifications.
Initial conditions do not, however, include things that are purely design requirements.
-6 While the NRC staff notes that the ANO-2's safety analyses do not take explicit credit for pressurizer heater operation, an implicit initial condition (as explained above) assumption of the safety analyses is that the RCS is operating at normal pressure.
Inability to control RCS pressure during natural circulation flow could result in loss of single phase flow and decreased capability to remove core decay heat. The need to maintain subcooling in the long term during loss of offsite power, as indicated in NUREG-0737, is the basis for their inclusion in the TSs. Based on the above, the heaters maintain RCS pressure (process variable), and are periodically monitored to assure that the plant is being operated within the bounds of design and analysis assumptions, meet the Criterion 2, and therefore, should be retained in the TSs. The NRC staff disagrees with the statement in the licensee's application dated June 18, 2009, that "they (the pressurizer heaters) are not a process variable, design feature, or operating restriction that is an initial condition of a Design Basis Accident." 3.5.2 Discussion on 10 CFR 50.36 Criteria Selection Appendix C to the NRC letter dated May 9, 1988, from Mr. Thomas E. Murley provides a listing of LCOs and identifies the Policy Statement selection criteria that required that the LCO must be retained in the STS, and LCOs that may be wholly or partially relocated to licensee-controlled documents.
In the letter, the new STS contain only those requirements that are consistent with 10 CFR 50.36 and have a sound safety basis. LCO 3.4.3.1 on 'Pressurizer,'
is one of the LCOs identified in the letter, which must be retained in the STS since it satisfies Criterion 2 and Criterion
- 3. For pressurizer and pressurizer heaters, this LCO addresses operating requirements similar to those specified in CE's NUREG-0212 (LCO 3/4.4.2), NUREG-1432 (LCO 3.4.9), as well as ANO-2's TS LCO 3.4.4. It should be noted that the heater design and operating requirements which were reviewed by the NRC staff, and approved by the Commission, were originally submitted by the Pressurized-Water Reactor Owners Group for meeting the Criteria.
The proposed amendment does not provide new technical information and/or justification on how the criteria will be met if the heater requirements are relocated to the licensee-controlled document.
The NRC staff position on compliance with 10 CFR 50.36(c)(2)(ii) considers that the heaters are (a) the design feature of the pressurizer, (b) required to be operable to satisfy Criterion 2, and (c) though the heaters are not specifically used in accident analysis, as indicated in NUREG-0737, the heaters are powered from emergency power supply and are needed to maintain subcooling in the long term during loss of offsite power. Therefore, the NRC concludes that the appropriate place for the LCO, Actions, and SRs for the pressurizer heaters is in the TS. 3.5.3 Discussion on Post-TMI Requirements Furthermore, NUREG-0737 specifies a set of requirements for the post-Three Mile Island (TMI) requirements for operating reactors, which have been approved for implementation by the NRC. Specifically, Post-TMI Action Plan item II.E.3.1 provides the NRC staff position on the design and operating requirements for Emergency Power Supply for Pressurizer Heaters. This item further states that the NRC staff position is consistent with satisfying the requirements of General Design Criteria 10, 14, 15, 17, and 20 of Appendix A to 10 CFR Part 50 for the event of
-7 loss of offsite power. The item lists specific actions for the licensee to implement in order to comply with the staff position.
In addition, NUREG-0737 specifically calls for TSs, as one of the minimum documentation required from the licensee, to support a reasonable assurance finding by the NRC that the staff position stated in the NUREG is met. The licensee's proposed amendment does not provide sufficient safety or risk justification or provide new information on how the NRC staff position will be met if the proposed heater requirements are relocated to a licensee-controlled document.
3.5.4 Discussion on "Feed and Bleed" as a Cooling Source The licensee's e-mail of July 30, 2009, indicated that ANO-2 does not rely on the pressurizer heaters as vital equipment for safe operation during NCC. The e-mail stated that "No matter what the plant conditions, the credited end-all cooling source is feed and bleed." It should be noted that the NRC position is that the feed-and-bleed method is not a preferred mitigation strategy.
Instead, it should be used as the last resort for accident mitigation.
This NRC position is correctly reflected in CEN-152, Revision 3, "Combustion Engineering Emergency Procedure Guidelines" (ADAMS Legacy Accession No. 8710090286).
3.5.5 Probabilistic Risk Assessment Perspective The licensee has not provided any information related to the licensee's plant-specific probabilistic risk assessment that demonstrates that the proposed revision does not satisfy Criterion 4 in 10 CFR 50.36(c)(ii)(D).
3.5.6 Acceptance Review by the NRC Staff Please note that that in the NRC staff e-mail dated August 17, 2009, "Acceptance Review of ANO-2 LAR, Technical Specification Changes to Relocate Pressurizer Heater," pointed out that supplemental information, in the areas discussed above, will be required for the NRC staff to complete the detailed technical review.
4.0 CONCLUSION
The proposed amendment concerns relocation of the pressurizer heater requirements from the TS to the licensee-controlled document.
Per the Commission's Interim Policy Statement, these requirements must be retained in the licensee's TSs. The license amendment request application dated June 18, 2009, as supplemented bye-mail dated July 30, 2009, does not contain sufficient safety or risk justification and does not state (a) how the 10 CFR 50.36(c)(2)(ii)
Criteria 2, 3, and 4 will be satisfied, and (b) how the NRC staff position specified in NUREG-0737 for the pressurizer heaters, will be met. Therefore, based on the above, the NRC staff has proposed to deny the amendment request. Principal Contributor:
Ravi Grover Date: May 6, 2010
-2 If you have any questions, please contact Kaly N. Kalyanam at (301) 415-1480 or via e-mail at kaly.kalyanam@nrc.gov.
Sincerely, IRA by Carl F. Lyon fori Michael T. Markley, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-368
Enclosure:
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