Text

IR 05000237-08-007, 05000249-08-007, on 12/03/2007 - 12/18/2007, Exelon Generation Company, Dresden Nuclear Power Station, Units 2 and 3, Component Design Bases Inspection Followup
	ML080170137
Person / Time
Site:	Dresden
Issue date:	01/17/2008
From:	Lara J F; Engineering Branch 3
To:	Pardee C G; Exelon Generation Co
References
	IR-08-007
	Download: ML080170137 (16)
	v • d • e

January 17, 2008

Mr. Charles Chief Nuclear Officer and

Senior Vice President Exelon Generation Company, LLC 4300 Winfield Road Warrenville IL 60555

SUBJECT: DRESDEN NUCLEAR POWER STATION, UNITS 2 AND 3 NRC INSPECTION REPORT 05000237/2008007; 05000249/2008007

Dear Mr. Pardee:

On December 18, 2007, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at your Dresden Nuclear Power St ation, Units 2 and 3. The enclosed inspection report documents the inspection findings, wh ich were discussed on December 18, 2007, with Mr. J. Ellis and other members of your staff.

The inspection examined activities conducted under your license as they relate to safety and compliance with the Commission's rules and regulations and with the conditions of your license. The inspectors reviewed selected procedures and records, observed activities, and interviewed

personnel.

Based on the results of this inspection, two NRC identified findings of very low safety significance (Green) were identified. All of these issues involved violations of NRC requirements. However, because of the very low safety significance and because they were entered into your corrective action program, the NRC is treating these violations as Non-Cited Violations (NCVs) consistent with Section VI.A.1. of the NRC Enforcement Policy.

If you contest the subject or severity of an NCV, you should provide a response within 30 days of the date of this inspection report, with the basis for your denial, to the U.S. Nuclear Regulatory Commission, ATTN: Document Control Desk, Washington, D.C. 20555-0001; with copies to the Regional Administrator, Region III, 2443 Warrenville Road, Suite 210, Lisle, IL 60532-4352; the Director, Office of Enforcement, U.S. Nuclear Regulatory Commission, Washington, D.C. 20555-0001; and the NRC Resident Inspector at the Dresden Nuclear Power Station. In accordance with 10 CFR 2.390 of the NRC's "Rules of Practice," a copy of this letter, its enclosure, and your response (if any), will be available electronically for public inspection in the NRC Public Document Room or from the Publicly Available Records System (PARS) component of NRC's Agencywide Documents Access and Management System (ADAMS), accessible from the NRC Web site at http://www.nrc.gov/reading-rm/adams.html (the Public Electronic Reading Room).

Sincerely,/RA by A. M. Stone Acting For/

Julio F. Lara, Chief Engineering Branch 3 Division of Reactor Safety

Docket Nos. 50-237; 50-249;72-037 License Nos. DPR-19; DPR-25

Enclosure:

1. Notice of Violation 2. Inspection Report 05000237/2008007; 05000249/2008007

w/Attachment:

Supplemental Information

cc w/encl: Site Vice President - Dresden Nuclear Power Station Plant Manager - Dresden Nuclear Power Station Regulatory Assurance Manager

- Dresden Nuclear Power Station Chief Operating Officer and Senior Vice President Senior Vice President - Midwest Operations Senior Vice President - Operations Support Vice President - Licensing and Regulatory Affairs Director - Licensing and Regulatory Affairs Manager Licensing - Clinton, Dresden, and Quad Cities Associate General Counsel Document Control Desk - Licensing Assistant Attorney General Illinois Emergency Management Agency State Liaison Officer Chairman, Illinois Commerce Commission

SUMMARY OF FINDINGS

IR 05000237/2008007; 05000249/2008007; 12/03/2007 - 12/18/2007; Exelon

Generation Company, Dresden Nuclear Power Station, Units 2 and 3, Component Design Bases Inspection Followup

This report covers a 2-week period of routine inspections by Region III inspectors. Two Green findings, involving Non-Cited Violations, (NCVs) were identified. The significance of most findings is indicated by their color (Green, White, Yellow, Red) using Inspection Manual Chapter 0609, "Significance Determination Process" (SDP). Findings for which the SDP does not apply may be Green or be assigned a severity level after NRC management review. The NRC's program for overseeing the safe operation of commercial nuclear power reactors is described in NUREG-1649, "Reactor Oversight Process," Revision 3, dated July 2000.

A. NRC-Identified and Self-Revealing Findings

Cornerstone: Mitigating Events

SL IV. The inspectors identified a Severity Level IV NCV associated with the failure to perform a safety evaluation in accordance with 10 CFR 50.59. Specifically, the licensee failed to perform a safety evaluation when non-conservatively changing the design basis loading for the emergency diesel generators (EDG) in the design calculation. This resulted in the expected loading during a design basis accident no longer being bounded by the EDG endurance testing requirements c ontained in the Tec hnical Specifications (TS). Because the licensee did not also evaluate the effect on the existing endurance test loading requirements, the testing no longer adequately verified the capability of the EDG to power its predicted loading during a LOOP/LOCA. This adverse change increased the probability of a malfunction of equipment important to safety EDG during a LOOP/LOCA event.

Because the issue affected the NRC

=s ability to perform its regulatory function, this finding was evaluated using the traditional enforcement process. The finding was determined to be more than minor because the inspectors could not reasonably determine that the change in EDG loading, which adversely affected equipment important to safety, would not have ultimately required NRC approval. The finding was determined to be of very low safety significance (Green) based on the results of the SDP Phase 1 screening worksheet. Specifically, the licensee was eventually able to demonstrate through an engineering evaluation, that the EDG loads would not exceed the bounding values contained in the endurance test criteria.

The inspectors determined that there was no cross cutting aspect to this issue. (Section 1R21.b.1)

Green.

The inspectors identified an NCV for the failure to meet the requirements contained in SR 3.8.1.15. Specifically, the testing that the licensee pe rformed to meet SR 3.8.1.15 did not test to a power factor as clos e to the accident load power factor as 2possible. These testing methods did not demonstrate the capability of the EDG to support the emergency core cooling system loading and were non-conservative. The issue was entered into the licensee

=s corrective action program.

3 The issue was more than minor because it was associated with the Mitigating System Cornerstone attribute of AEquipment Performance,@ and affected the cornerstone objective of ensuring the availability and reliability of the EDGs. Specifically, the licensee

=s testing methods for SR 3.8.1.15 did not demonstrate the capability of the EDG to support ECCS loading and was non-conservative. This finding was of very low safety significance, because the inspectors answered A No@ to all five questions under the Mitigating Systems Cornerstone column of the Phase 1 worksheet. Specifically, the licensee subsequently performed the required testing in SR 3.8.1.15 to the expected power factor, and the EDGs performed satisfactorily. The inspectors determined that there was no cross-cutting aspect to this issue.

(Section 1R21.b.2)

B. Licensee-Identified Violations

No findings of significance were identified.

4

REPORT DETAILS

REACTOR SAFETY

Cornerstones: Mitigating Systems

1R21 Component Design Basis Inspection

Main article: IP 71111.21

a. Inspection Scope

During this inspection period, inspector s completed followup inspection activities concerning URI 05000237/249/2002006-02. This URI contained two issues regarding whether the licensee's Technical Specifications (TS) surveillance provided reasonable assurance of the emergency diesel generator's (EDG) capability to carry design basis loads and whether operating the EDG at the reactive load for only 10 minutes of the 24-hour run met the supporting regulatory analysis and intent of the surve illance requirement.

b. Findings

b.1 Failure to Perform a 10 CFR 50.59 Evaluation for Exceeding Continuous Rating on the EDG

Introduction:

The inspectors identified a Severity Level IV Non-Cited Violation (NCV) of 10 CFR 50.59 having very low safety significan ce (Green) for the failure to perform an adequate safety evaluation in accordance with 10 CFR 50.59. Specifically, the licensee failed to perform a safety evaluation when non-conservatively changing the design basis loading for the plant EDGs in their design calculation.

Description:

The inspectors identified that the licensee

=s calculated design basis loads for a Loss of Offsite Power with a Loss of Coolant Accident (LOOP/LOCA) exceeded the continuous rating of the EDG. Dresden Technical Specification (TS) Surveillance Requirement (SR) 3.8.1.15 requires the following:

Verify each DG [diesel generator] operating within the power f actor limit operates for 24-hours:

a. For 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months loaded 2730 kW [kiloWatt] and 2860 kW (105 percent to 110 percent of continuous rating); and b. For the remaining hours of the test loaded 2340 kW and 2600 kW (90 percent to 110 percent of continuous rating)

The intent of this endurance test is to demons trate that each EDG is in operational readiness to assume the design-basis (LOOP/LOCA) lo ads even when the redundant EDG has failed.

An endurance test (24-hour run) is considered to be a reasonabl e duration to ascertain if the EDG capability continues to remain intact for a potentially long-term operation that would be 5needed to bring the plant to a safe shutdown following a design basis event. The test challenges whether the fuel system will continue to supply fuel in order to keep up with the maximum and varying load demand, the excitation system will produce sufficient magnetic field to maintain voltage, and the voltage regulator will maintain the voltage within acceptable limits. This can be achieved only when the diesel engine is loaded to its expected design basis loading conditions, and when the generator is producing sufficient voltage and current that reflect design basis accident loading. This endurance run verifies the EDG capability should a LOOP/LOCA occur.

Based on the above considerati ons, as well as review of pertinent regulatory guidance documents, the inspectors concluded that the surveillance test loading should bound the accident loading. However, at Dresden, anticipated LOOP/LOCA loading exceeded

the upper limit of the endurance test requirement (2600 kW). In the case of the No. 2 EDG, anticipated loading could be as high as 2851 kW for extended periods of time during such postulated events.

Originally, the licensee's design basis calculations and the facility's Final Safety Analysis Report (FSAR) predicted manual EDG loading to be below 2600 kW. However, during the life of the plant, the design basis EDG loading calculations we re revised such that predicted LOOP/LOCA loading increased. During that time period, Calculation Number 71317-33-19-2, Revision 17, was processed which changed the design and license basis predicted loading such that loads exceeded 2600 kW. Prior to this revision, the endurance testing fully demonstrated the capability of the EDGs during a LOOP/LOCA; however, once loads were predicted to be greater than 2600 kW, the testing performed under SR 3.8.1.15 no longer adequately demonstrated the capability of the EDG to power its predicted loading during a LOOP/LOCA.

The inspectors concluded that without changing the testing to reflect the new predicted loading, the probability of the EDGs being incapable of carrying predicted loads during a LOOP/LOCA was increased. The design basis reliability of the EDG had been re duced. At the time of the calculation revision, the licensee did not perform an evaluation pursuant to 10 CFR 50.59. The inspectors determined that had the licensee performed such an evaluation, the change would have required a license amendment because the probability of a malf unction of equipment important to safety (i.e., EDG)would have been increased.

The licensee provided the inspectors with historical documents that appeared to show that the NRC had accepted that the auto-connected loads could exceed the continuous rating of the EDG. However, the inspectors could not find any definitive information that would lead

them to conclude that the NRC had previously approved that manual loading of the EDG could exceed the continuous rating. The distin ction between the two is important, because auto-connected loads are only at their maximum during the initial stages of the event. Shortly

after the event initiation, the auto-connected load s become much less. This initial spike in loads is clearly bounded by the EDG testing, si nce 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months of the endurance run is performed between 105 percent and 110 percent of the EDG continuous rating. However, manually connected loads can last for the duration of the event. Therefore, if the manually connected loads exceeded the continuous rating, the 24-hour endurance run, if performed at the 6continuous rating, would not bound the actual loads that would be running for the duration of the event.

This issue was addressed by the licensee in a Dresden Engineering White Paper. In the White Paper, the licensee reassessed the loading values for the EDGs removing

conservatisms and loads that would not be used later (10 minutes into the event) in the LOOP/LOCA event. By doing this, the licensee was able to conclude that even though initial EDG loading may exceed 2600 kW, the loading at 10+ minutes would be sharply 7reduced below the 2600 kW value. Since SR 3.8.1.15 tests for 2 hour2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months s at levels above 2600 kW that bound the initial loading of the EDGs, the inspectors found this to be acceptable. The licensee planned to incorporate the results of this analysis into a

calculation revision. The licens ee entered the issue into their corrective action program as condition report (CR) 485889.

Analysis:

The inspectors determined that the licensee's failure to perform a safety evaluation in accordance with 10 CFR 50.59 for changes to their design and license basis was a performance deficiency warranting a significance determination. Specifically, Calculation 7317-33-19-2, Revision 17, was processed in 1994 which changed design and license basis predicted loading for the EDGs such that loads exceeded 2600 kW. Because the licensee did not evaluate this change pursuant to 10 CFR 50.59, the TS EDG surveillance testing in SR 3.8.1.15 no longer adequately verified the capability of the EDG to power its predicted loading during a LOOP/LOCA. This adverse change increased the probability of a malfunction of equipment important to safety (i.e., EDG) during a LOOP/LOCA event.

Following discussions, a subsequent licensee evaluation showed that loading would have remained below 2600 kW at time = 10+ minutes. However, this did not change the impact of the initial change to the design and license basis loading. The changes to the loading calculation changed the accident analyses such that exceeding 2600 kW on the EDGs was determined to be acceptable with no further regulatory reviews performed. The inspectors

concluded that the calculation revision resulted in a change to the analyses that would not have been acceptable under 10 CFR 50.59 and w ould have required e ither approval from the NRC or a license amendment for a change to the loading requirement for SR 3.8.1.5.

Because violations of 10 CFR 50.59 are considered to be violations that potentially impede or impact the regulatory process, they are dispositioned using the traditional enforcement process instead of the significance determination process (SDP). The finding was determined to be more than minor because the inspectors could not reasonably determine that the changes to the licensee's design basis would not have ultimately

required NRC prior approval.

The inspectors completed a significance determination of the underlying technical issue using NRC=s inspection manual chapter (IMC) 0609, Appendix A, ASignificance Determination of Reactor Inspection Findings for At-Power Situations,@ and answered A No@ to the Mitigating Systems screening questions in the Phase 1 Screening Worksheet. Based upon this Phase 1 screening, the inspectors concluded that the issue was of very low safety significance (Green). In accordance with the Enforcement Policy, the violation was therefore classified as a Severity Level IV vi olation. The inspectors determined that there was no cross cutting aspect to this issue.

Enforcement:

Title 10 CFR 50.59(d)(1) states, in pa rt, that the licensee shall maintain records of changes in the facility, of changes in procedures, and of tests and experiments.

8These records must include a written evaluation which provides a basis for the determination that the change, test, or expe riment does not require a license amendment.

Contrary to the above, the licensee failed to perform a safety evaluation when increasing the design basis load on the EDGs while revising Calculati on 7317-33-19-2, Revision 17, in 1994. Since the EDG load testing required by the facility's TS was no longer bounding 9after this change, the probability of a malfunction of equipment important to safety (i.e., EDGs) was affected. In accordance with the Enforcement Policy, this violation of the

requirements of 10 CFR 50.59 was classified as a Severity Level IV Violation because the underlying technical issue was of very low safety significance. Because this violation was of very low safety significance, was not repetitive or willful, and it was entered into the licensee=s corrective action program (CR 485889), this violation is being treated as an NCV consistent with VI.A.1 of the NRC Enforcement Policy (NCV). (NCV 05000237/2008007-01; 05000249/2008007-01)

b.2 Failure to Meet the EDG Power Factor Testing Requirements

Introduction:

The inspectors identified an NCV having a very low safety significance (Green) for the failure to meet the EDG power factor testing requi rements contained in TS SR 3.8.1.15. Specifically, the testing that the licensee performed to meet SR 3.8.1.15 did not test to a power factor

(pf) as close to the accident load power factor as possible.

These testing methods did not demonstrate the capability of the EDG to support ECCS loading and were non-conservative.

Description:

Dresden Technical Specification (TS) Surveillance Requirement (SR) 3.8.1.15 requires the following:

Verify each DG [diesel generator] operating within the power fact or limit operates for 24-hours:

a. For 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months loaded 2730 kW and 2860 kW (105 percent to 110 percent of continuous rating); and b. For the remaining hours of the test loaded 2340 kW and 2600 kW (90 percent to 110 percent of continuous rating).

This SR is modified by a note which states, AIf grid conditions do not permit, the power factor limit is not required to be met. Under this conditi on, the power factor shall be maintained as close to the limit as practicable.

@

The Bases for this TS SR states, AIn order to ensure that the DG is tested under load conditions that are as close to design conditions as possible, testing must be performed at a power factor as close to the accident load power factor as practicable. When synchronized with offsite power, the power factor limit is 0.85. This power factor is chosen to bound the actual worst case inductive loading that the DG could experience under design basis accident conditions.

@ The licensee developed surveillance pro cedure DOS 6600-12, "Diese l Generator Tests Endurance and Margin/Full Load Rejection/ECCS

/Hot Restart," to demonstrate compliance with SR 3.8.1.15. In this surveillance test, the diesel is connected to the grid and operated for 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months at a load between 2730 and 2860 kW for the remaining 22 hours2.546296e-4 days 0.00611 hours 3.637566e-5 weeks 8.371e-6 months of the test.

10Sometime during this 22-hour period, the power factor is adjusted by increasing KVARs to a band of 1550 to 1600 (0.83 - 0.86 pf) if possible, keeping the voltage on the emergency bus less than 4300 volts. This is held for only 10 minutes before returning to the 300 kVAR band. The inspectors were concerned, because this testing did not meet the intent of the TS SR because it did not bound the actual worst case inductive loading that the 11EDG could experience under design basis accident conditions. The licensee only tested to 0.85 pf for 10 minutes during the performance of SR 3.8.1.15. While the TS did provide provisions to accommodate cases when the plant conditions cannot allow generation of sufficient kVAR to match design basis kVAR loading, the licensee

=s testing methodology did not follow these provisions. Prior to EDG testing, the licensee did not perform any evaluation as to the condition of the grid, with respect to whether or not the power factor limit can be achieved. Rather, regardless of whether the grid conditions may support testing at the power factor limit, the licensee had established a testing practice that only tests at this limit for 10 minutes.

The inspectors determined that the licensee

=s testing methods did not demonstrate the capability of the EDG to support ECCS loading and was non-conservative. The licensee entered this issue into their corrective action program as CR 485889.

Analysis:

The inspectors determined that the licensee's failure to meet the EDG power factor testing requirements contained in TS SR 3.8.1.15 was a performance deficiency warranting a significance determination. Specifically, the testing that the licensee performed to meet SR 3.8.1.15 did not test the EDG at a power factor as close to the accident load power factor as possible. The issue was more than minor because it was associated with the Mitigating System Cornerstone attribute of AEquipment Performance,@ and affected the cornerstone objective of ensuring the availability and reliability of the EDGs. Specifically, the licensee

=s testing methods for SR 3.8.1.15 did not demonstrate the capability of the EDG to support ECCS loading and was non-conservative.

The finding screened as having very low significance (Green) using IMC 0609, Appendix A, ASignificance Determination of Reactor Inspection Findings for the At-Power Situations,@ because the inspectors answered A No@ to all five questions under the Mitigating Systems Cornerstone column of the Phase 1 worksheet. Specifically, the licensee subsequently performed the required testing in SR 3.8.1.15 to the expected power factor, and the EDGs performed satisfactorily. The inspectors determined that there was no cross cutting aspect to this issue.

Enforcement

Dresden SR 3.8.1.15 states, in part, that the licensee is required to verify each EDG operates within the power factor limit for 24-hours. This testing methods for this SR should demonstrate the capability of the EDG to support ECCS loading. This capability includes the operating at the power factor that would be expected during the design basis accident (LOCA) event.

Contrary to the above, the testing that th e licensee performed to meet SR 3.8.1.15 did not test to a power factor as close to the accident load power factor as possible. The inspectors determined that the licensee

=s testing methods did not demonstrate the capability of the EDG to support ECCS loading and was non-conservative. Because this failure to comply with the requirements in SR 3.8.1.15 was determined to be of very low safety significance and because it was entered in the licensee

=s corrective action program 12as CR 485889, this violation is being treated as an NCV, consistent with Section VI.A.1 of the NRC Enforcement Policy. (NCV 05000237/2008007-02; 05000249/2008007-02)

OTHER ACTIVITIES (OA)

4OA5 Other Activities

.1 (Closed) Unresolved Item (URI) 0500237/249/2002006-02:

Non-Conservative Emergency Diesel Generator Testing This URI contained two issues regarding whether the licensee's Technical Specifications (TS) surveillance provided reasonable assurance of the emergency diesel generator's (EDG) capability to carry design basis loads and whether operating the EDG at the reactive load for only 10 minutes of the 24-hour run met the supporting regulatory analysis and intent of the surveillance requirement. This URI had been previously

updated in inspection report 0500237/249/2005-009. Based on the information discussed in Section 1R21.b of this report, two NCVs were identified. Therefore, this URI is closed.

4OA6 Meetings

.1 Exit Meetings

The inspectors presented the inspection results to Mr. James Ellis and other licensee

members at the conclusion of the insp ection on December 18, 2007. The inspectors asked the licensee whether any materials examined during the inspection should be considered proprietary. No proprietary information was identified.

ATTACHMENT: