NL-11-1065, Response to CDBI - Backfit Appeal

Response to CDBI - Backfit Appeal

ML111680360
Person / Time
Site:	Hatch
Issue date:	06/17/2011
From:	Madison D Southern Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-11-1065
Download: ML111680360 (29)

Text

D. R. Madison (Dennis) Southern Nuclear Vice President Hatch Operating Company, Inc.

Plant Edwin L Hatch 11028 Hatch Parkway, North Baxley, Georgia 31513 Tel 912.537.5859 Fax 912.366.2077 June 17, 2011 SOUTHERN'\

COMPANY Docket Nos.: 50-321 Energy to Serve Your World""

50-366 NL-11-1065 U. S. Nuclear Regulatory Commission ATrN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant Response to CDBI - Backfit Appeal Ladies and Gentlemen:

On May 25, 2011, the Nuclear Regulatory Commission (NRC) staff issued a letter to Southern Nuclear Operating Company (SNC) providing Inspection Report 05000321 and 366/2011009, regarding the Component Design Bases Inspection (CDBI) performed at the Edwin I. Hatch Nuclear Plant (HNP) in July 2009. That letter documented actions taken to review unresolved item (URI) 05000321 and 366/2009006-08, "Degraded Voltage Protection," which concerned the degraded voltage protection system setpoints and analytical limits for the 4160 V buses at HNP.

At issue was the reliance on administrative controls and manual actions at HNP, as approved in a February 23, 1995 NRC Safety Evaluation Report (SER), for maintaining adequate voltage to protect Class 1E (safety related) electrical equipment in the event of degraded voltage conditions. In 1995, the NRC and staff recognized that this system's configuration represented a deviation from the guidance on degraded voltage protection provided in a NRC letter dated June 2, 1977, but after detailed review, the SER determined that the deviation was acceptable. Moreover, the NRC also reviewed and approved the configuration as part of a license amendment for Improved Technical Specifications (ITS), with an SER issued March 3, 1995. For over 16 years this configuration, including alarm annunciation in the control room, limiting conditions of operation, and action statements imposed by the more restrictive requirements of the 1995 SER have been HNP's licensing bases.

The NRC staffs May 25, 2011 letter concluded, however, that the measures in effect at HNP to demonstrate compliance with the applicable provisions of 10 CFR 50.55a(h)(2) and 10 CFR Part 50, Appendix A, General Design Criterion 17 are not acceptable. The staff recognizes that this changed position constitutes a backfit. However the staff also maintains that it does not need to perform a cost

U. S. Nuclear Regulatory Commission NL-11-1065 Page 2 justified substantial safety backfit analysis, as is required by 10 CFR 50.1 09(a)(3).

Instead, the staff states that its change in position falls within the "compliance exception" to the staff's backfit analysis obligation which is provided by 10 CFR 50.109(a)(4)(i).

SNC disagrees that a compliance backfit is necessary and that the compliance exception applies in this case. SNC appeals this decision for the following reasons:

1. The long history of discussions and correspondence between NRC and SNC, from 1976 through the 1995 issuance of the SERs (see Enclosure 2), documents the NRC's thorough understanding of the degraded voltage issue at HNP and the deliberate, thoughtful action which NRC took in response (i.e. determination that GOC 17 was met and consequent issuance of the SERs). The NRC staff made no error in this regard.

2. The NRC recognized in 1995 that plant operator ("manual") action to restore voltage in anticipation of degraded grid voltage conditions, thereby precluding unnecessary automatic separation of the plant from the grid at lower voltages. Reliance solely on an automatic grid separation function does not allow for correction of degraded grid voltage through manual action. More restrictive conditions were placed in the Technical Specifications, reflective of the plant configuration and the manual action.

3. The NRC May 25, 2011 letter references IEEE Std. 279-1971 and IEEE Std. 603-1991. Both units at HNP are committed to IEEE Std. 279 1971, which at Section 4.17 acknowledges the permissible use of manual actions. IEEE Std. 603-1991, which was under review for endorsement by NRC at the time the 1995 SERs were issued, provides in Section 4.5 explicit criteria for the use of manual actions. Although HNP is not committed to IEEE Std. 603-1991, the Section 4.5 criteria for use of manual action are satisfied by the HNP alternate approach approved in the 1995 SERs.

The NRC staff's new interpretation is that the use of manual operator actions is not an acceptable method of complying with the regulations.

However, GOC 17 and 10 CFR 50.55a do not expressly prohibit manual actions in all situations. 10 CFR 50.55a(h)(2) references both IEEE Std. 279-1971 and IEEE Std. 603-1991, which as noted above make clear reference to the use of manual actions for certain situations. IEEE Std. 603-1991 was endorsed by the NRC staff in 1996.

4. The current configuration of HNP with respect to degraded grid voltage response complies with NRC-approved legal requirements, GOC 17 and 10 CFR 50.55a. As a consequence, the "compliance exception" of 10 CFR 50.1 09(a)(4)(i) does not apply to this backfit. As SNC discussed with NRC staff representatives on prior occasions, the NRC backfit in this instance would require the licensee to amend its license.

U. S. Nuclear Regulatory Commission NL-11-1065 Page 3 As a result of the May 25, 2011 letter which announced a new staff position, HNP is placed in the position of needing to inform the staff by a specified deadline o'f how HNP intends to change its current license conditions in order to "comply" with the staff's new interpretation. The backfit rules were designed to avoid this result.

Irrespective of the result of this appeal, SNC will pursue the identification of a cost-effective resolution to the underlying technical issue, which concerns the margin - under worst-case circumstances and extremely degraded conditions between the minimum expected voltage on the safety-related 4160 V buses and the minimum voltage required to protect the safety-related equipment on these buses. To this end, SNC is evaluating options to increase this margin and by December 31, 2011 will provide a follow-up letter outlining the proposed technical solution with an implementation schedule.

A risk-informed evaluation estimates that the expected frequency of the pertinent technical issue, automatic actuation of safety-related equipment due to a loss of coolant accident concurrent with a degraded grid condition, is on the order of 1.0 E-9 per year and would not be considered to be safety significant by accepted risk criteria. SNC has determined this value through a best estimate approach with appropriate conservatism. Evaluation and implementation of corrective actions over an extended period is therefore considered to be acceptable 'from a nuclear safety perspective and will allow all options to be fully considered.

After reviewing this appeal, should the NRC still wish to pursue a backfit resolution to the underlying technical issue, the regulations do not permit the staff to use the 10 CFR 50.109(a)(4)(i) analysis exception for a compliance backfit.

Instead, as stated in 10 CFR 50.1 09(a)(3), " ... the commission shall require the backfitting of a facility only when it determines, based on the analysis described in paragraph (c) of this section, that there is a substantial increase in the overall protection of the public health and safety or the common defense and security to be derived from the backfit and that the direct and indirect costs of implementation for that facility are justified in view of this increased protection."

SNC is aware of no such analysis.

Consistent with NRC guidance for appealing an exception determination by the NRC staff, a copy of this letter is addressed to the Director of the Division of Reactor Safety, per NRC Management Directive 8.4, "Appeal Process". A copy of this appeal is also being sent to the NRC's Executive Director of Operations. of this letter provides additional discussion supporting the SNC appeal of this compliance backfit determination, while Enclosure 2 is a timeline and list of correspondence relating to the degraded voltage issue. Enclosure 3 provides the loss of power (LOP) instrumentation surveillance requirements for reference. Enclosure 4 lists apparent errors identi'fied in the May 25, 2011 letter from the NRC staff.

U. S. Nuclear Regulatory Commission NL-11-1065 Page 4 This letter contains no formal NRC commitments.

If you have any questions, please contact Doug McKinney at (205) 992-5982.

Respectfully submitted,

,

~7n~

D. R. Madison Vice President - Hatch DRMlDWD/lac : Response to CDBI - Backfit Appeal : Grid Voltage Issue Timeline I Correspondence List : Loss of Power Instrumentation Surveillance Requirements : Apparent Errors in NRC Letter of May 25, 2011 cc: Southern Nuclear Operating Company Mr. J. T. Gasser, Executive Vice President Mr. J. L. Pemberton, SVP & General Counsel Ms. P. M. Marino, Vice President - Engineering Mr. M. J. Ajluni, Nuclear Licensing Director RTYPE: CHA02.004 U. S. Nuclear Regulatory Commission Mr. R. W. Borchardt, Executive Director of Operations Mr. J. T. Munday, Director - Division of Reactor Safety Mr. V. M. McCree, Regional Administrator Mr. P. G. Boyle, NRR Project Manager Mr. E. D. Morris, Senior Resident Inspector - Hatch

Edwin I. Hatch Nuclear Plant Enclosure 1 Response to COBI - Backfit Appeal

Edwin I. Hatch Nuclear Plant Response to CDBI - Backfit Appeal Southern Nuclear Operating Company (SNC) appeals the NRC staff's imposition of a new staff position that differs from both the previous staff position applied to the Edwin I Hatch Nuclear Plant (HNP), and the commitments and conditions in the HNP license (Technical Specifications).

The NRC staff's May 25, 2011 letter recognizes that its change of position is a backfit. As the staff's letter states, the current NRC staff position is different than a previous position due to the NRC's 1995 acceptance of the voltage protection system configuration at HNP for degraded grid conditions. As recounted by the NRC staff, and documented in the long history of discussions and correspondence between NRC and SNC cited in Enclosure 2, this system's configuration was recognized as a deviation from staff guidance on degraded grid voltage protection provided in an NRC letter dated June 2, 1977, and formally accepted by the NRC as being in accordance with General DeSign Criterion (GDG) 17 in a Safety Evaluation Report (SER) dated February 23, 1995. SNC agrees that the NRC staff is imposing a backfit on HNP.

However, SNC disagrees with the staff's application of 10 CFR 50.1 09(a)(4)(i),

commonly referred to as a "compliance exception" to avoid the NRC staff's obligation to perform a cost-justified substantial safety benefit analysis prior to imposition of a backfit. In this matter, the compliance exception does not apply.

The compliance exception applies when a modification is "necessary to bring a facility into compliance with a license or rules or orders of the Commission." This is not the case here. The NRC specifically licensed HNP for its current design configuration in provisions and conditions in its Technical Specifications. SNC also disagrees with the NRC staff's "documented evaluation" that the staff "erroneously approved the use of manual action" to respond to degraded grid scenarios. At issue here is a new interpretation of law. The staff is disagreeing with the application of the law embodied in the HNP license (Technical Specifications). The staff may not simply declare that a new staff position must be met, when that position directly and irreconcilably conflicts with the plant's license.

SNC also contends that the staff may not rely on its assertion that "allowing the manual actions was a staff error applicable to a very limited number of plants."

To the extent that the staff has a history of allowing manual actions associated with GDC 17 compliance for a number of plants, the staff's back'fit is a new staff position.

SNC suggests that the previous deviation from the historic staff position approved by the NRC staff in 1995 is tantamount to an exemption issued in accordance with 10 CFR 50.12(a). SNC would welcome discussions with the staff on this latter point.

Although not required, in parallel with this appeal, SNC is evaluating technical approaches to address the new staff's pOSition that relying on manual operator Enclosure 1 Page 1 of 10

Edwin I. Hatch Nuclear Plant Response to CDBI - Backfit Appeal action to respond to degraded grid voltages above set pOints for the automatic separation of the plant from the grid is inconsistent with GDC 17. As the May 25, 2011 NRC letter correctly observes, the existing relay configuration and degraded voltage setpolnts at HNP are based on avoiding spurious separation of the offsite power supply. Offsite power is the preferred source of power over onsite emergency diesel generators. As the NRC recognized in 1995, use of operator manual actions to restore voltage in anticipation of degraded grid voltage conditions, thereby precluding the need for an unnecessary separation of the plant from the grid. Reliance solely on an automatic grid separation function does not allow for correction of degraded voltage through manual action.

The "Compliance Backlit" Exception 10 CFR 50.109(a)(4)(i) provides one of several exceptions to when the NRC staff must perform a cost-justified substantial safety backfit analysis; this exception is referred to as a "Compliance Backfit." If the exception does not apply. the staff must conduct the backfit analysis to justify its imposition. The components and factors for consideration in such a backfit analysis are set out in the NRC's Backfit Rule. They include installation and continuing costs associated with the backfit (including the cost of facility downtime) and the potential safety impact of changes in plant or operational complexity.

The NRC staff's position depends upon applying this Compliance Backfit exception. In its May 25,2011 letter, the NRC staff explains The staff's current position is that the licensee's analysis for the Hatch plant must show that the existing setpoints and time delays are adequate to ensure that all safety-related loads have required minimum voltage measured at the component terminal to start and operate safety-related equipment. .. without any credit for administratively controlled bus voltage levels."

This exception, however, only applies to avoid the need for a backfit analysis when it is found, as stated in 10 CFR 50.109(a)(4)(i):

That a modification is necessary to bring a facility into compliance with a license or the rules or orders of the Commission, or into conformance with written commitments by the licensee (emphasis added)

As these words reflect, the compliance exception does not apply where, as in this case, the licensee is following its license conditions. The compliance exception is intended to address situations in which the licensee has failed to meet known and established standards of the Commission because of omission or mistake of fact.

It should be noted that new or modified interpretations of what constitutes compliance would not fall within the exception and would require a backfit analysis and application of the standard." - 50 Federal RegisterNol. 50, No.

Enclosure 1 Page 2 of 10

Edwin I. Hatch Nuclear Plant Response to CDBI - Backfit Appeal 183/September 20, 1985/Rules and Regulations p. 38103. See alsoNUREG 1409, § 3.1 Question 4 at pg. 12 (which cites this statement from the Federal Register notice).

The NRC staff maintains that GDC 17 and 10 CFR 50.55a(h)(2) are not met for HNP. This staff position cannot be correct. Both regulations predate the Commission's specific approval of the variance approved by the staff in 1995. As explained earlier, GDC 17 was specifically applied in the staff's February 23, 1995 SER and 10 CFR 50.55a(h)(2) as applied to HNP incorporates by reference an industry standard that does not preclude the manual actions relevant here. If, in fact, those two regulations do not require the backfit, the staff is seeking to impose a new or modified staff position which does not come within the Compliance Backfit exception. As is well established, NRC staff positions are not rules and, absent written commitment by the licensee or an order or inclusion in a license, are not legal requirements. The law that governs HNP is the current license and its obligations, not the staff's new interpretation of historic staff positions from which HNP was explicitly granted variance.

The NRC Staff Did Not "Erroneously" Approve a Deviation from a Staff Position in 1995 The compliance exception is intended to address situations in which the licensee has failed to meet known and established standards of the Commission because of omission or mistake of fact. It should be noted that new or modified interpretations of what constitutes compliance would not fall within the exception and would require a backfit analysis and application of the standard." 50 Federal RegisterNol. 50, No.

183/September 20, 1985/Rules and Regulations p. 38103. See also NUREG 1409, § 3.1 Question 4 at pg. 12 (which cites this statement from the Federal Register notice).

The NRC staff now characterizes the 1995 NRC staff's approval of a deviation from the guidance on degraded grid voltage protection provided in an NRC letter dated June 2, 1977 as an "error" which "erroneously approved the use of manual actions ... " That characterization is not correct. To the contrary, the correspondence between SNC and the NRC, including the February 23, 1995 and March 3, 1995 SERs, unequivocally demonstrates that the NRC staff purposefully, extensively and formally reviewed the degraded grid voltage Loss of Offsite Power (LOP) and Loss of Coolant Accident (LOCA) scenarios for HNP, the sufficiency of voltage for concurrent LOP and LOCA, the positive safety consequences associated with additional degraded voltage alarms, operator monitoring and potential action, and the specific setpoints for degraded voltage relays that initiate automatic separation of the plant from the system. Ironically, the staff's February 23, 1995 SER reflects a risk-informed approach that considered the safety consequences of spurious separation, the potential range Enclosure 1 Page 3 of 10

Edwin I. Hatch Nuclear Plant Response to CDBI - Backfit Appeal of degraded voltages for certain postulated events where automatic protection would not occur, and the benefits of added design features and compensatory measures. In contrast, the current prescriptive staff backfit has one foundation: a reliance on the proposition that manual action is "clearly inconsistenf' with current and historic staff guidance. The following overview of the staff's historic approval of the degraded voltage configuration is not exhaustive, yet sufficiently shows the staff did not make an omission or error or a mistake of fact.

In February 1995 the NRC staff formally approved the design of the HNP protection system for assuring adequate voltage to safety-related equipment during LOP and degraded grid events. Both SNC and the staff expressly recognized that the design of the system was a deviation from the NRC staff guidance on degraded grid protection provided in an NRC letter dated June 2, 1977. By letter dated February 23, 1995 and the associated SER, the staff found that the deviation 1 from the guidance was acceptable. Significantly, the NRC staff imposed two additional conditions on SNC and, with SNC's commitment to the additional conditions, the NRC staff stated in the concluding test of the SER that:

With the alternate approach, the staff concludes that both an offsite and onsite power system is available, each with the capability of providing power for the required safety components in accordance with GDC 17 of 10 CFR Part 50, Appendix A.

III. CONCLUSION Based on its review, the staff finds that the requested deviation from the Generic Letters is acceptable because of the added design features and the compensatory measures at Hatch as discussed in the above Safety Evaluation.

Principal Contributors: D. Thatcher N. Trehan Proximate in time to the SER discussed above, the NRC staff also was reviewing Improved Technical Specifications (ITS) for HNP. The NRC approved the ITS and issued the associated license amendments by letter dated March 3, 1995.

1 Both SNC and the NRC staff expressly identified this deviation prior to this approval:

"Consequently, a deviation from the staff position stated in the June 2, 1977 letter exists relative to the initiation of an automatic disconnect from the offsite power source."

Georgia Power letter HL-4586, July 1, 1994, page 2. "At the conclusion of the meeting, the NRC staff stated that they will review GPC's submittal and the handouts with the view that the approach proposed by GPC constitutes a deviation from the recommendations of the Generic Letter dated June 2,1977". NRC Summary of December 7,1994 meeting with Georgia Power Company on Degraded Grid Voltage, dated January 10, 1994.

Enclosure 1 Page 4 of 10

Edwin I. Hatch Nuclear Plant Response to CDBI - Backfit Appeal The related SER examined Loss of Power (LOP) instrumentation, including the additional alarms and setpoints. As the SER explains, plant-specific issues, including plant-unique design features, plant-unique requirements, and plant unique operating practices were discussed during a series of meetings between SNC and the staff. Section 2.3.3.3.0 of the March 3, 1995 SER (pg. 118) addressed LOP Instrumentation. Subsection 4 of that Section states:

To satisfy Criterion 3 of the Final Policy Statement [for ITS review], HNP credits manual actions in the range of 78.8% to 92% of 4.16kV. Entry into this range is annunciated. The range specified for manual action indicates that sufficient power is available to the large ECCS pump motors. However, sufficient voltage for the equipment required for loss-of coolant accident (LOCA) conditions may not be available at lower voltages. The required channels of LOP annunciation instrumentation ensure the initiation of manual actions to protect the ECCS and other assumed systems from degraded voltage without initiating an unnecessary automatic disconnect from the preferred offsite power source. The LOP anticipatory annunciators are designed with a time delay of 65 seconds to reduce the possibility of nuisance annunciators while permitting prompt detections of potential low voltage conditions.

HNP takes credit for the annunciators in restoring acceptable voltage levels. Therefore, improve TS Table 3.3.8.1-1 is being added to the CTS

[current Technical Specification] requirements. Additionally, ACTION B, addressing the annunciator function, is being added and the other functions are renumbered and amended to provide for the annunciation.

S(urveiliance]R[equirement]s are also being added for the annunciator bus undervoltage and associated time relays .... The Staff has reviewed these more restrictive requirements and believes they improve the CTS.

Therefore, these more restrictive requirements are acceptable.

The HNP License and its Conditions Take Precedence Over Staff Positions NUREG 1409 distinguishes between "legal requirements, as in explicit regulations, orders, and plant licenses and in amendments, conditions, and technical specifications," and "NRC staff positions that are documented explicit interpretations of more general regulations and are contained in documents such as the Standard Review Plan, branch technical positions, regulatory guides, generic letters, and bulletins." - NUREG 1409 §2.1.2 at pg. 3. See a/so id.§3.1 at pg. 13.

As noted above, the deviation from the June 1977 staff guidance has been incorporated into the HNP license. Although the NRC staff acts as if its current view of the historic staff positions have the force and effect of law, in actuality, the license and its conditions have the force and effect of law. SNC also points out that the NRC staff's May 25, 2011, letter as a practical matter will necessitate a license amendment related to trip setpoints, anticipatory alarms and related Enclosure 1 Page 5 of 10

Edwin I. Hatch Nuclear Plant Response to CDBI - Backfit Appeal requirements. To the extent that the new staff position may require a modification to the HNP license, SNC preserves its rights to a formal hearing under Section 189(a)(1) of the Atomic Energy Act, as amended, 42 U.S.C. § 2239(a)(1).

Attached to this letter in Enclosure 3 is a compilation of the provisions from current HNP Technical Specifications and conditions that implement the February 23, 1995 and March 3, 1995 SERs. These technical specifications ensure early detection of a degraded grid condition by requiring surveillance of the alarms, operability and LCO requirements, and an alarm setpoint of ~ 3825 V (corresponding to 92% of nominal bus voltage) for ~ 65 seconds.

The current HNP TS Bases also confirm that NRC committed no error in approving the 1995 SERs. The current HNP TS Bases for LOP Instrumentation (pg. B 3.3-187 - 3.3-188) explains:

... The 4.16kV undervoltage degraded voltage trip setpoints were determined in accordance with the NRC staff positions contained in an NRC letter dated June 2, 1977, except that manual actions are credited for restoring bus voltages or initiating a plant shutdown in the range of 78.8% to 92% of 4.16 kV .... The Bus Undervoltage Allowable Values are low enough to prevent inadvertent power supply transfer, but high enough to ensure that sufficient power is available to the large ECCS motors. The Time Delay Allowable Values are long enough for the offsite power supply to usually recover ... Manual actions are credited in the range of 78.8% to 92% of 4.16 kV to restore bus voltages or to initiate a plant shutdown.

The range specified for manual actions indicates that sufficient power is available to the large ECCS motors; however, sufficient voltage for equipment at lower voltages required for LOCA conditions may not be available ...

The Staff Seeks to Impose a Modified Interpretation of What Constitutes Compliance "It should be noted that new or modified interpretations of what constitutes compliance would not fall within the exception and would require a backfit analysis and application of the standard." 50 Federal RegisterNol. 50, No. 183/September 20, 1985/Rules and Regulations p. 38103, quoted with approval, NUREG 1409 §3.1 Question 4 at pg. 12.

The NRC staff's new position is that "manual actions" cannot be credited to restore bus voltages prior to actuation of the automatic disconnect of the plant from the grid. The staff asserts that a modification of the facility is necessary to Enclosure 1 Page 6 of 10

Edwin I. Hatch Nuclear Plant Response to CDBI - Backfit Appeal 50.55a(h)(2). Those regulations do not speak to manual action, however. 10 CFR 50.55a(h)(2) incorporates by reference certain IEEE Standard Criteria.

Protection systems. For nuclear power plants with construction permits issued after January 1, 1971, but before May 13, 1999, protection systems must meet the requirements stated in either IEEE Std. 279, "Criteria for Protection Systems for Nuclear Power Generating Stations,"

or in I EEE Std. 603-1991, "Criteria for Safety Systems for Nuclear Power Generating Stations," and the correction sheet dated January 30,1995.

For nuclear power plants with construction permits issued before January 1, 1971, protection systems must be consistent with their licensing basis or may meet the requirements of IEEE Std. 603-1991 and the correction sheet dated January 30, 1995. (bold supplied)

Thus, for HNP Unit 1, the licensing basis establishes the requirements for the protective system, while for HNP Unit 2, one of the IEEE standards applies. For both HNP units, however, the actual standard in effect is IEEE Std. 279-1971, and IEEE Std. 603-1991 does not apply.

On page 6 of the enclosure to the May 25,2011 NRC letter, the staff relies on provisions in IEEE standards 279-1971 and 603-1991 which address automatic actuation of protective systems and completion of those actuations for specific plant conditions without operator action. IEEE Std. 603-1991 at §6.1 on pg. 20 states that the operator is not required to take any action." IEEE Std. 603-1991 is not a standard to which HNP is committed, but even if applied to the HNP degraded grid protective system, the manual actions of operators are taken before the plant conditions for automatic actuation are reached. In addition, IEEE Std. 603-1991 Sec. 4.5 provides explicit criteria for the use of manual actions, and these criteria are satisfied by the HNP alternate approach approved in the February 23,1995 and March 3, 1995 SERs.

The November 22, 1993 GPC letter, July 1, 1994 GPC letter, January 10, 1995 NRC meeting notes, and February 23,1995 NRC SER address the broad universe of plant response to degraded grid conditions, setpoints for automatic disconnect, and anticipatory alarms and potential manual actions at below 92%.

An automatiC degraded grid trip setpoint of 78.8% of bus voltage with a time delay of 21.5 seconds was approved, provided that the anticipatory alarm relays and degraded voltage relays came into the Technical Specifications. Manual action instead of automatic trip is applicable, then, only to a narrow band of voltages above the automatic trip level. Once the trip setpoint is reached, the actuation of the protection system goes to completion without manual intervention, in accordance with IEEE Std. 279-1971 at §4.16 on pg. 10.

Enclosure 1 Page 7 of 10

Edwin I. Hatch Nuclear Plant Response to CDBI - Backfit Appeal Manual Actions for ContrOlling Voltages at HNP HNP was operated by Georgia Power Company (GPC) until Southern Nuclear Operating Company, Inc. (SNC) was authorized to operate the plant on March 22, 1997 by license transfer amendments to the plant licenses. Both GPC and SNC are direct subsidiaries of Southern Company (Southern). Taking advantage of these relationships and an integrated Southern electric grid system, grid system operators monitor system voltage on a real-time basis to ensure that adequate voltage is provided to HNP. Because of the system's scale, integration, design and other characteristics, the system has high reliability and significant robustness. As with every licensed power reactor, HNP relies on the system operator to assure an offsite source of power at adequate voltage to safety related equipment to respond to an accident.

When evaluating the actual likelihood of sustained degraded grid voltage conditions, it is also proper to consider the system's attributes. The historic documentation associated with the February 13, 1995 SER observes that Ha sustained degraded grid does not represent the most probable event. Rather, a dynamic voltage excursion is more likely. For a dynamic voltage excursion, GPC

[then the licensee] believes that disconnecting both units from the offsite power supply and introducing dual unit scrams and reactor isolation transients through automatic voltage relays would be adverse to safety."

Contrary to the I\J RC staff's May 25, 2011, letter the NRC 1995 staff did not rely "in part, on measures implemented and maintained by their transmission operator to assure adequate voltage to safety-related equipment during an accident. .. " or "transmission system operator manual actions."

- NRC May 25, 2011 SER letter, Enclosure pg. 7 What the staff did in 1995 with respect to the transmission operator and offsite circuits was simply to require the licensee to document in the FSAR "the offsite system voltage levels and their significance with respect to the HI\JP approach to meeting the degraded grid requirements." The inclusion of this information in the FSAR was "so the impact of future changes will receive appropriate consideration." The manual actions "credited" for compliance with GDC-17 were limited to manual actions by plant operators in a specific band of degraded voltages followed by automatic controls.

"The NRC team determined that during a postulated design basis loss of coolant accident concurrent with the 4160 volt bus voltage in a narrow 3%

band between 91 % (3786 volts) and 88.34% (3675 volts) certain class 1E loads at voltage levels of 600 volts and below may not receive sufficient voltage." - SNC to NRC letter dated November 22,1993

"...the degraded grid protection system uses manual action instead of automatic disconnect in the range of the deadband. Accordingly, GPC Enclosure 1 Page 8 of 10

Edwin I. Hatch Nuclear Plant Response to CDBI - Backfit Appeal

[the licensee] has implemented an abnormal operating procedure to provide speci'fic actions to address a degraded offsite power supply. If the 4160 volt bus voltages were to degrade below approximately 92 percent,

[plant] operators will initiate a 'one hour to restore' action statement. If voltages are not restored within one hour, a plant shutdown is then initiated." - GPC to NRC letter dated July 1, 1994 Thus, the alternate approach approved by the NRC staff in the February 23, 1995 SER did not credit or approve manual actions for the offsite system operators; manual action response was limited to the plant operators and considered a failure to restore voltages.

The NRC staff's new interpretation is that the use of manual operator actions is not acceptable to demonstrate compliance with the regulations. However, GDC 17 and 10 CFR 50.55a do not expressly prohibit manual actions in all situations.

10 CFR 50.55a(h)(2) references both IEEE Std. 279-1971 and IEEE Std. 603 1991, which as noted above make clear reference to the use of manual actions.

IEEE Std. 603-1991 was endorsed by the NRC staff in 1996.

Current Configuration at HNP Complies with Commission-approved "Legal Reguirements" The NRC staff's May 25,2011, letter is premised on the theory that the February 23, 1995 SER, which approved a deviation from an NRC staff position, was "in error" and "inadequate." As explained above, this premise is incorrect and, in any event, the current configuration of HNP with respect to degraded grid voltage response complies with NRC-approved legal requirements. As a consequence, the "compliance exception" of 10 CFR 50.1 09(a)(4) (i) does not apply to this backfit.

NRC guidance observes that "applicable regulatory staff positions" are of several different types and sources:

• Legal requirements, such as in explicit regulations, orders, and plant licenses (amendments, conditions, technical specifications).

• Written commitments such as contained in docketed correspondence, including responses to Generic Letters.

• "NRC staff positions" that are explicit interpretations, and are contained in documents such as Generic Letters, and to which a licensee has previously committed. Positions contained in these documents are not considered applicable staff pOSitions to the extent that the staff has, in a previous licensing or inspection action, taCitly or expressly explicitly excepted the license from part or all of the pOSition. [fn]

Enclosure 1 Page 9 of 10

Edwin I. Hatch Nuclear Plant Response to CDBI - Backfit Appeal Imposition of a staff position to which a licensee has previously been excepted is a backfit.

(NUREG-1409, Appendix D, page 12 (NRC Manual Chapter 0514, NRC Program for Plant-Specific Backfitting of Nuclear Power Plants), emphasis supplied).

Thus, a clear distinction exists between legal requirements and NRC staff positions that may impose requirements on a licensee. For HNP, the license itself by Technical Specifications explicitly obligates HNP to implement the current plant configuration with respect to anticipatory alarms, alarm annunciation setpoints, trip setpoints, and action statements when the alarms are not functional. The NRC staff position set forth in the June 2, 1977 letter is not an "applicable regulatory staff position" because the staff in its February 23, 1995 SER on degraded grid setpoints and in the March 3, 1995 SER associated with the Improved Technical Specifications (ITS), expressly excepted HNP from the position. The staff's new position does not address the legal requirements contained in the HNP Technical Specifications and, as a consequence, fails to recognize that the current configuration of HNP complies with NRC-approved requirements. These express, clear and detailed legal requirements have the force and effect of law, whereas the new staff position is an interpretation of an industry standard referenced in more general regulations.

As SNC discussed with NRC staff representatives on prior occasions, the NRC backfit in this instance would require the licensee to amend its license. As a result of the May 25, 2011 letter which announced a new staff position, HNP is placed in the untenable position of needing to inform the staff by a specified deadline of how HNP intends to change its current license conditions in order to "comply" with the staff's new interpretation. The backfit rules were designed to avoid this result.

Enclosure 1 Page 10 of 10

Edwin I. Hatch Nuclear Plant Enclosure 2 Grid Voltage Issue Timeline I Correspondence List

Edwin I. Hatch Nuclear Plant Grid Voltage Issue Timeline I Correspondence List

1. August 11, 1976 NRC Letter to Georgia Power Company (GPC)

Subject:

Request for information (prompted by the Millstone degraded grid event of July 5, 1976) regarding plant operation during periods of degraded grid voltage

2. September 17,1976 GPC Letter to NRC

Subject:

"Operation During Degraded Grid Voltage Conditions" Comments: Responding to the NRC request for information dated August 11, 1976, GPC told the NRC that HNP Unit 1 (Unit 2 was still under construction) had the following:

a. Loss of Voltage relays (no degraded grid voltage relays installed) are set at 70%.

b. Proposed to raise degraded grid voltage 4160 setpoints to 90%.

c. The letter contained graphs which showed that 600 V buses were less than 90% using a minimum grid 230 kV voltage of 99.4%. The letter showed that much safety related equipment had minimum voltage levels of 90%,

thus a deadband was obvious.

3. June 2, 1977 NRC Generic Letter to GPC

Subject:

"Statement of Staff Positions Relative to Emergency Power Systems for Operating Reactors" Comments: This letter required that the degraded voltage setpoints be determined based on "an analysis of the voltage requirements of the safety related loads at all on site distribution levels" and required an automatic transfer when the voltage setpoint was exceeded. These requirements later became embodied in NRC position PSB-1. Also, the NRC required that the undervoltage relays be incorporated into the technical specifications.

4. July 22, 1977 GPC Letter to NRC

Subject:

Response to NRC Generic Letter of June 2, 1977 Comments: In this letter, GPC stated that their current system design met all NRC requirements and that no plant modifications were required. As required by the NRC, a Technical Specifications revision was proposed which provided a degraded grid setpoint of 3744 volts at 8 seconds. This corresponded to the same CV-7 relay setting of the loss of voltage setpoints Enclosure 2 Page 1 of 7

Edwin I. Hatch Nuclear Plant Grid Voltage Issue Timeline I Correspondence List which were proposed to be at 2496 volts at 2.6 seconds. Graphs supplied to show the effect of the minimum grid voltage (99%) on the distribution levels indicated the 600 V system would be at 88% and 208 V system would be similarly marginal. With a degraded grid setpoint of 90%

proposed there was therefore a broad dead band.

5. August 8, 1979 NRC Generic Letter (GL) 79-36 to GPC

Subject:

"Adequacy of Station Electric Distribution Systems Voltages" Comments: The following points in the generic letter apply to this issue:

- NRC defined the scenario to be an evaluation of the offsite grid with no diesels available.

NRC wanted to assure that plant equipment was operable at grid minimum voltage.

- NRC wanted to assure that analysis showed no spurious trips.

- NRC tied this letter to the June 2, 1977 Generic Letter as an additional information request.

6. September 18, 1979 NRC Letter to G PC

Subject:

RFI on HNP LOSP event October 30,1979 GPC Letter to NRC

Subject:

Provides TS surveillance changes November 27,1979 GPC Letter to NRC

Subject:

Response to September 18, 1979 NRC request Comments: The above three letters relate to degraded grid issues but do not directly relate to degraded grid setpoint issues.

7. December 7,1979 GPC Letter to NRC

Subject:

"Adequacy of Station Electric Distribution System Voltage" Comments: Responding to NRC Generic Letter dated August 8, 1979, GPC stated that grid voltage would not drop below 98% and provided an analysis based on a minimum voltage of 98% on the 230 kV bus. The detailed analysis showed that at 98% on the 230 kV bus the 208 V system was marginal at 90%.

Enclosure 2 Page 2 of 7

Edwin I. Hatch Nuclear Plant Grid Voltage Issue Timeline / Correspondence List

8. February 29, 1980 NRC Letter to GPC

Subject:

Questions on GPC December 7, 1979 response Comments: Focus of NRC concerns rests on the basis for equipment operability at a 230 kV grid minimum voltage of 98%.

9. April 28, 1980 GPC Letter to NRC

Subject:

"Adequacy of Station Electric Distribution System Voltage" Comments: Response to NRC Questions of February 29, 1980; main issues related to concern are as follows:

a. Provided details regarding system indicating why 98% was a valid grid minimum voltage number.

b. Committed to reaffirm the acceptability of all plant safety related equipment voltage levels based on a 98% 230 KV minimum and to immediately notify the NRC if a concern was identified.

c. Revised submittal of 1217179 and again submitted detailed drawing which clearly showed 208 voltage levels approaching 90% for a minimum 230 KV grid level of 98%.

10. October 9, 1980 GPC Letter to NRC

Subject:

Response to Request for Additional Information Comments: Again revised submittal of 12/7/79 and again submitted detailed drawing which clearly showed 208 voltage levels approaching 90% for a minimum 230 KV grid level of 98%. Told the NRC that degraded grid voltage settings would change to a time dial of 5 based on the results and that these changes would be discussed in more detail when the technical specifications revisions were submitted.

11. May 21, 1981 GPC Letter to NRC

Subject:

Provides revised technical specifications per 10/9/80 Comments: Revises the setpoint of degraded grid from 3744 volts at 8 sec to 3120 volts at 17 seconds among other TS changes. Letter states this will result in linearly 10% more margin against a sustained degraded voltage condition while providing protection from spurious disconnection Enclosure 2 Page 3 of 7

Edwin I. Hatch Nuclear Plant Grid Voltage Issue Timeline 1 Correspondence Ust from offsite power as a result of momentary voltage dips on the emergency buses."

12. October 2, 1981 GPC Letter to NRC

Subject:

Amends submittal of 5/21/81 with additional changes and amends 3120 volts at 17 seconds to 3280 volts at 21.5 seconds (Same curve in that tap setting of 105v at time dial of 5 is same for both).

13. December 2,1981 GPC Letter to NRC

Subject:

Amends submittal of 5/21/81 with additional changes.

14. December 7,1981 NRC Letter to GPC

Subject:

NRC Questions on degraded grid voltage Comments: NRC specifically requested for GPC to verify that the 208 V contactors will work at the "minimum grid voltage." Also, GPC was to submit a graph which showed the worst case voltage transient and the combined characteristics of the degraded grid and the loss of-voltage relays. Finally, GPC was asked to verify that the Unit 2 design was identical to Unit 1 .

15. January 12,1982 GPC Letter to NRC

Subject:

Response to NRC Questions of 1217/81 Comments: Provided all requested information.

16. February, 1982 EGG Report to NRC

Subject:

Degraded Grid Protection for Class 1 E Power Systems Comments: EGG stated that the HNP design met the NRC requirements.

Specifically, in response to the issue that GPC should select degraded grid setpoints based on analysis of the voltage requirements of the safety related loads at all onsite distribution levels, the EGG report stated that GPC have performed this analysis and that these analyses "have contributed to the selection of the proposed relay settings,"

Enclosure 2 Page 4 of 7

Edwin I. Hatch Nuclear Plant Grid Voltage Issue Timeline 1Correspondence List

17. April 5, 1982 NRC Letter to GPC

Subject:

Safety Evaluation Report on Degraded Grid Comments: NRC referenced the EGG report for their conclusions that HNP had met the requirements.

18. May 6, 1982 NRC Letter to GPC

Subject:

Safety Evaluation and Approval of Degraded Grid Voltage Technical Specifications Comments: NRC SER concluded that "The relay setpoints selected are supported by analyses which indicate adequate protection is provided to ensure that acceptable voltage will be available to all Class IE equipment under the worst case degraded grid voltage conditions analyzed. The licensee has additionally shown that spurious operation of the first and second level undervoltage relays would not occur during anticipated grid swings and starting of large loads." The relay setpoints were stated in this letter to be at 78.8% with a time delay of 21.5 seconds for degraded grid.

19. MaylJune 1991 Electrical Distribution System Functional Inspection (EDSFI) performed by NRC NRC team questioned whether the undervoltage relay setpoints were too low to ensure minimum voltage prior to disconnect from offsite power supply.

20. August 6,1991 - GPC meeting with NRC on Degraded Grid Issues Discussed offsite system controls, extremely low probability of a sustained degraded grid concurrent with LOCA, and operating enhancements. NRC Staff indicated agreement with GPC's conclusions.

21. August 22, 1991 - NRC Inspection Report 50-321/91-202 & 50-366/91-202 Restated EDSFI Team's concern.

22. October 7,1991 - Notice of Violation; NRC Inspection Report 50-321/91 202 & 50-366/91-202 Identified deficiencies in undervoltage protection for degraded grid voltage, and certain other electrical distribution concerns.

Enclosure 2 Page 5 of 7

Edwin I. Hatch Nuclear Plant Grid Voltage Issue Timeline I Correspondence List

23. November 6, 1991 - GPC Letter to NRC

Subject:

Response to Notice of Violation Comment: GPC denied the violation, determining that no violation of NRC requirements existed.

24. November 16, 1992 - GPC meeting with NRC

Subject:

HNP Degraded Grid Issues Comment: GPC provided objectives and criteria used in assessment. GPC also provided a detailed discussion of offsite system monitoring and control.

Cost estimates were provided for conceptual modifications.

25. November 22,1993 - GPC letter to NRC

Subject:

Degraded Grid Protection Provided basis for existing setpoints, and basis for concerns about unnecessary disconnects.

26. July 1, 1994 - GPC letter to NRC

Subject:

Degraded Grid Protection Comment: Provided basis for alarm setpoints. GPC also committed to include alarm in Improved Technical Specifications.

27. January 10, 1995 - NRC letter to GPC

Subject:

Summary of December 7, 1994 meeting Comment: GPC met with NRC to discuss degraded grid issues.

28. February 23, 1995 - NRC letter to GPC

Subject:

SER for Degraded Grid Voltage Relay Setpoints Comment: SER accepted GPC approach (Le. that dynamic voltage excursion rather than sustained degraded grid represented most probable event, and automatic undervoltage relays would be adverse to safety) with the following conditions, which GPC agreed to:

Enclosure 2 Page 6 of 7

Edwin I. Hatch Nuclear Plant Grid Voltage Issue Timeline 1 Correspondence List Include degraded voltage alarm relays in the Tech Specs along with degraded voltage relays which initiate automatic actions Document offsite system operating voltage levels vs. HNP degraded voltage requirements in the FSAR (ref. sec. 8.2.1) so future changes receive appropriate consideration

29. March 3,1995 - NRC letter to GPC

Subject:

SER for Improved Tech Specs Comment: Revision of TS 3.3.8.1 to add Table 3.3.8.1-1 with surveillance requirements for Loss of Power Instrumentation was made as part of the ITS submittal (thus implementing the condition to include degraded voltage alarm relays in Tech Specs that NRC included in their February 23, 1995 SER). The SER states on pg. 119 that "The staff has reviewed these more restrictive requirements and believes they improved the CTS. Therefore, these more restrictive requirements are acceptable."

30. August 17, 2009 - NRC letter to SNC

Subject:

NRC Component Design Basis Inspection

-Inspection Report 05000321/2009006 and 05000366/2009006 Comment: Report included an Unresolved Item regarding the HNP degraded voltage protection scheme (URI 05000321/2009006-08 and 05000366/2009006-08, Degraded Voltage Protection). It stated, The existing automatic degraded voltage protection scheme employs automatic setpoints that are too low to assure operability of safety related electrical equipment in case of a sustained degraded grid condition, and instead relies on administrative controls to assure adequate voltage to safety related equipment during an accident."

31. May 25, 2011 - NRC letter to SNC

Subject:

NRC Component Design Basis Inspection

-Inspection Report 05000321/2011009 and 05000366/2011009 Comment: Advises of change in staff position on acceptability of relying on manual operator action to demonstrate compliance with the applicable provisions of GDC-17 and 10 CFR 50.55a(h)(2) and asserts that a compliance backfit is required.

Enclosure 2 Page 7 of 7

Edwin I. Hatch Nuclear Plant Enclosure 3 Loss of Power Instrumentation Surveillance Requirements

Edwin I. Hatch Nuclear Plant Loss of Power Instrumentation Surveillance Requirements LOP Instrumentation Surveillance Requirements Source: Hatch Units 1 & 2 Technical SpeCifications Table 3.3.8.1-1 REQUIRED ALLOWABLE CHANNELS SURVEILLANCE VALUE FUNCTION PER REQUIREMENTS FUNCTION (% 4.16 kV)

1. 4.16 kV Emegency Bus Undervoltage (Loss of Voltage)

a. Bus Undervoltage 2 SR 3.3.8.1.2  ;:: 2800 V (67.3%)

SR 3.3.8.1.3 SR 3.3.8.1 .4

b. Time Delay 2 SR 3.3.8.1 .2 S 6.5 seconds SR 3.3.8.1.3 SR 3.3.8.1.4

2. 4.16 kV Emegency Bus Undervoltage (Degraded Voltage)

a. Bus Undervoltage 2 SR 3.3.8.1.2  ;:: 3280 V (78.8%)

SR 3.3.8.1.3 SR 3.3.8.1.4

b. Time Delay 2 SR 3.3.8.1.2 s 21.5 seconds SR 3.3.8.1.3 SR 3.3.8.1.4

3. 4.16 kV Emegency Bus Undervoltage (Annunciation)

a. Bus Undervoltage 2 SR 3.3.8.1.1  ;:: 3825 V (92%)

SR 3.3.8.1.2 SR 3.3.8.1.3 SR 3.3.8.1.4

b. Time Delay 2 SR 3.3.8.1.1 s 65 seconds SR 3.3.8.1.2 SR 3.3.8.1.3 SR 3.3.8.1.4 Enclosure 3 Page 1 of 1

Edwin I. Hatch Nuclear Plant Enclosure 4 Apparent Errors in !\IRC Letter of May 25, 2011

Edwin I. Hatch Nuclear Plant Apparent Errors in NRC Letter of May 25,2011 The following is a list of factual errors noted in the Enclosure to the NRC staff's letter of May 25, 2011, some of which may have affected the staff's backfit analysis:

1. There are a number of instances where it is stated that HNP relies on measures implemented and maintained by their transmission system operator. It should be noted, however, that HNP does not rely on the offsite transmission system operators to assure adequate voltage, but instead credit is taken for the onsite HNP licensed operating staff to initiate action to assure adequate voltage.

This error in portraying the role of the transmission system operator is noted to occur as follows:

Pg. 4, second paragraph closes with: Therefore, Hatch currently relies, in part, on measures implemented and maintained by their transmission system operator to assure adequate voltage to safety-related equipment during an accident."

Pg. 7, first full paragraph begins: The 1995 SER approving Hatch's reliance, in part, on measures implemented and maintained by their transmission system operator to assure adequate voltage to safety-related equipment during an accident was inconsistent with Staff guidance (identified above) in effect at the time of that SER."

Pg. 7, second full paragraph states: Therefore, the degraded voltage relay setpoints must be determined and used in component design bases calculations such that proper voltage levels as defined by GL 79-36 will be supplied to Class 1E equipment without reliance on the plant or transmission system operator manual actions."

2. Pg. 5, last paragraph makes reference is made to IEEE 603-199. The report states: The criteria of IEEE Std. 279-1971 and IEEE 603-199 apply to the establishment of minimum requirements for the safety-related functional performance and reliability of protection systems for nuclear power plants."

Based on other references to IEEE 603-1991 in the inspection report, SNC believes this is a typographic error and the report should correctly refer to IEEE 603-1991. Additionally, the subsequent sentence refers to "IEEE Std. 279 and 603 ... ," omitting the year designator for each standard. (It should be noted that HNP is not committed to IEEE Std. 603-1991.)

3. Pg. 6, at the second IEEE standard citation there is an error in quoting IEEE Std. 279-1971, Section 4.16, "Completion of Protective Action Once Initiated,"

where the section is stated as follows (quotation marks not in original text):

"The protection system shall be so designed that, once initiated, a protection system action shall go to completion. Return to operation shall require subsequent deliberate operator action." The correct quotation of this section (with restored text in italics) is: The protection system shall be so designed Enclosure 4 Page 1 of 3

Edwin I. Hatch Nuclear Plant Apparent Errors in NRC Letter of May 25, 2011 that, once initiated, a protective action at the system level shall go to completion. Return to operation shall require subsequent deliberate operator action."

4. Pg. 6, at the third IEEE standard citation, the text intended to be quoted was apparently omitted. The following is stated: "IEEE Std 279-1968171, Section 1, "Scope," states the following:" but the referenced text is not identified as quoted text and is misplaced into a subsequent discussion paragraph.

5. Pg. 6, at the fourth IEEE standard citation, there is an error in quoting IEEE Std. 603~ 1991 Section 6.1, in that the quoted text omits references to Section 4.5 (which discusses the minimum criteria for each safety function and corresponding protective actions whose operation may be controlled by manual means initially or subsequent to initiation). The following is stated in the report: "IEEE Std. 603~1991 states that means shall be provided to automatically initiate and control all protective actions ~~~-The safety system design shall be such that the operator is not required to take any action prior to the time and plant conditions following the onset of each deSign basis event."

Section 6.1 of IEEE Std. 603~ 1991 actually states the following (restored text in italiCS): "Automatic Control. Means shall be provided to automatically initiate and control all protective actions except as justified in 4.5. The safety system design shall be such that the operator is not required to take any action prior to the time and plant conditions specified in 4.5 following the onset of each design basis event."

For convenient reference, IEEE Std. 603-1991 Section 4.5 reads as follows:

4.5 The following minimum criteria for each action identified in 4.2 whose operation may be controlled by manual means initially or subsequent to initiation. See IEEE Std 494-1974 (R1990) [8].

4.5.1 The points in time and the plant conditions during which manual control is allowed.

4.5.2 The justification for permitting initiation or control subsequent to initiation solely by manual means.

4.5.3 The range of environmental conditions imposed upon the operator during normal, abnormal, and accident circumstances throughout which the manual operations must be performed.

4.5.4 The variables in 4.4 that shall be displayed for the operator to use in taking manual action.

Enclosure 4 Page 2 of 3

Edwin I. Hatch Nuclear Plant Apparent Errors in NRC Letter of May 25,2011

6. Pg. 6, second from last paragraph, "IEEE 603" is cited, but the applicable year of the standard (presumably 1991) is not included.

7. Pg. 6, last paragraph (under Technical Evaluation), the first sentence states that " ...administrative controls at the Hatch plant for maintaining adequate voltage at the terminals of Class 1E equipment is not in accordance with IEEE Std. 279-1971/IEEE Std. 603/1991 ..." As noted earlier, HNP is committed only to I EEE Std. 279-1971.

Enclosure 4 Page 3 of 3