IR 05000282/2008007
| ML083590119 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 12/23/2008 |
| From: | Robert Daley Engineering Branch 3 |
| To: | Wadley M Northern States Power Co |
| References | |
| IR-08-007 | |
| Download: ML083590119 (20) | |
Text
December 23, 2008
SUBJECT:
PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNITS 1 AND 2, EVALUATION OF CHANGES, TESTS, OR EXPERIMENTS AND PERMANENT PLANT MODIFICATIONS BASELINE INSPECTION REPORT 05000282/2008007; 05000306/2008007(DRS)
Dear Mr. Wadley:
On December 5, 2008, the U.S. Nuclear Regulatory Commission (NRC) completed Evaluations of Changes, Tests, or Experiments and Permanent Plant Modifications at the Prairie Island Nuclear Generating Plant, Units 1 and 2. The enclosed report documents the results of the inspection, which were discussed with you and other members of your staff at the completion of the inspection on December 5, 2008.
The inspectors examined activities conducted under your license as they relate to safety and compliance with the Commissions 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 the inspection, one NRC identified finding of very low safety significance was identified, which involved a violation of NRC requirements.
However, because this violation was of very low safety significance and because it was entered into your corrective action program, the NRC is treating the issue as a Non-Cited Violation (NCV) in accordance with Section VI.A.1 of the NRCs 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, DC 20555-0001, with a copy to the Regional Administrator, U.S. Nuclear Regulatory Commission - Region III, 2443 Warrenville Road, Suite 210, Lisle, IL 60532-4352; the Director, Office of Enforcement, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001; and the Resident Inspector Office at the Prairie Island Nuclear Generating Plant, Units 1 and 2.
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 (PARS) component of NRC's document system (ADAMS), accessible from the NRC Web site at http://www.nrc.gov/reading-rm/adams.html (the Public Electronic Reading Room).
Sincerely,
/RA/
Robert Daley, Chief Engineering Branch 3 Division of Reactor Safety Docket Nos. 50-282; 50-306 License Nos. DPR-42, DPR-60 Enclosure: Inspection Report 05000282/2008007; 05000306/2008007(DRS)
w/Attachment: Supplemental Information cc w/encl: D. Koehl, Chief Nuclear Officer Regulatory Affairs Manager P. Glass, Assistant General Counsel Nuclear Asset Manager J. Stine, State Liaison Officer, Minnesota Department of Health Tribal Council, Prairie Island Indian Community Administrator, Goodhue County Courthouse Commissioner, Minnesota Department of Commerce Manager, Environmental Protection Division Office of the Attorney General of Minnesota Emergency Preparedness Coordinator, Dakota County Law Enforcement Center
SUMMARY OF FINDINGS
IR 05000282/2008007, 05000306/2008007; 11/17/2008 - 12/05/2008; Prairie Island Nuclear
Generating Plant, Units 1 & 2; Evaluations of Changes, Tests, or Experiments and Permanent Plant Modifications.
The inspection covered a two-week announced baseline inspection on evaluations of changes, tests, or experiments and permanent plant modifications. The inspection was conducted by three Region based engineering inspectors. One Severity Level IV Non-Cited Violation (NCV)was 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 may 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 4, dated December 2006.
A. Inspector-Identified and Self-Revealed Findings
Cornerstone: Mitigating Systems
- Severity Level IV. The inspectors identified a Severity Level IV NCV, having very low safety significance, of 10 CFR 50.59, Changes, Tests, and Experiments, for the licensees failure to perform a safety evaluation associated with installation of a bulk hydrogen storage facility. Specifically, the licensee had not evaluated the adverse affects on the Circulating Water System from a postulated hydrogen tank explosion in the bulk storage facility located directly above buried Circulating Water System return lines. The licensee stopped work on the installation of the bulk hydrogen facility and documented the NRC identified issues in the corrective action system. The inspectors concerns also prompted the licensee to identify above ground Cooling Water System pipe in the nearby Turbine Building, which had not been evaluated in the hydrogen blast analysis.
The finding was more than minor because the inspectors could not reasonably determine that this change would not have ultimately required prior approval from the NRC. This finding was categorized as Severity Level IV because the underlying technical issue for the finding was determined to be of very low safety significance based on a Phase 1 screening in accordance with IMC 0609, Appendix A, Significance Determination of Reactor Inspection Findings for At-Power Situation. Specifically, the inspectors answered No to the Mitigating Systems screening questions in the Phase 1 Screening Worksheet because the licensee had not yet filled the bulk storage facility with hydrogen, so no possibility of explosion and damage to plant equipment existed.
The cause of the finding is related to the cross-cutting element of Human Performance Decision Making, because the licensee failed to make conservative assumptions in decision making associated with the effects of a postulated hydrogen tank explosion (IMC 305, Section 06.07.c, Item H.1(b)). (Section 1R17.1.b)
Licensee-Identified Violations
No findings of significance were identified.
REPORT DETAILS
REACTOR SAFETY
Cornerstones: Initiating Events, Mitigating Systems, and Barrier Integrity
1R17 Evaluations of Changes, Tests, or Experiments and Permanent Plant Modifications
.1 Title 10 CFR 50.59 Evaluations and Screenings
a. Inspection Scope
From November 17 through December 5, 2008, the inspectors reviewed six safety evaluations performed pursuant to 10 CFR 50.59 to determine if the evaluations were adequate and that prior NRC approval was obtained as appropriate. The inspectors also reviewed 17 screenings and 2 equivalency evaluations where licensee personnel had determined that a 10 CFR 50.59 evaluation was not necessary. The inspectors reviewed these documents to determine if:
- the changes, tests, or experiments performed were evaluated in accordance with 10 CFR 50.59 and that sufficient documentation existed to confirm that a license amendment was not required;
- the safety issue requiring the change, test or experiment was resolved;
- the licensee conclusions for evaluations of changes, tests, or experiments were correct and consistent with 10 CFR 50.59; and
- the design and licensing basis documentation was updated to reflect the change.
The inspectors used, in part, Nuclear Energy Institute (NEI) 96-07, Guidelines for 10 CFR 50.59 Implementation, Revision 1, to determine acceptability of the completed evaluations, and screenings. The NEI document was endorsed by the NRC in Regulatory Guide 1.187, Guidance for Implementation of 10 CFR 50.59, Changes, Tests, and Experiments, dated November 2000. The inspectors also consulted Part 9900 of the NRC Inspection Manual, 10 CFR Guidance for 10 CFR 50.59, Changes, Tests, and Experiments.
This inspection constitutes six samples of evaluations and nineteen samples of changes as defined in Inspection Procedure 71111.17-05.
b. Findings
Failure to Perform a 10 CFR 50.59 Evaluation for Bulk Hydrogen Storage Facility
Introduction:
The inspectors identified a Severity Level IV Non-Cited Violation (NCV) of 10 CFR 50.59 having very low safety significance (Green) for the failure to perform a safety evaluation for installation of a bulk hydrogen storage facility. Specifically, the licensee had not evaluated the adverse affects on the Circulating Water (CW) System from a postulated hydrogen tank explosion in the bulk storage facility located directly above buried CW return lines.
Description:
On December 4, 2008, the licensee had mostly installed, (but not filled), a bulk hydrogen storage facility. The inspectors identified that the licensee had not considered the effects of a postulated hydrogen tank explosion on the buried CW return header pipes running directly under this facility.
The Updated Final Safety Analysis Report (UFSAR) Section 11.5.1 describes the design basis functions for the CW system and states that the CW system provides the heat sink for the generating plant. Specifically, excess heat from the steam leaving the turbine is transferred to circulating water flowing through the condenser tubes. The CW system also supplies the water for the Cooling Water System and Fire Protection Systems.
Water flows from the Intake Bay into the Plant Screenhouse. The Cooling Water pumps draw water from the screenhouse, pump it through the system and discharge to the warm circulating water leaving the condensers. Thus, the CW System indirectly cools the plant auxiliary equipment.
Hydrogen gas is used as the heat transfer medium to cool the main generators and for reducing the oxygen concentration in the volume control tank to less than 5 percent by volume. As described in the UFSAR Section 9.3.2.1.5, this hydrogen gas was supplied by ten portable banks of gas cylinders. In accordance with Engineering Change (EC)12191 Hydrogen Storage Replacement Modification, the licensee changed the original storage configuration and located the new bulk hydrogen tank storage facility directly over the Unit 1 and Unit 2 buried CW header pipes. The new bulk storage facility was comprised of three (non-portable) banks of cylindrical tanks that were designed to contain approximately twice the volume of hydrogen of the original storage facility.
These banks of tanks were attached to a metal framework supported by concrete piers, which allowed for distribution of the tank weight around the buried circulating water pipes located beneath this facility. The buried CW return headers for each unit running beneath this facility were large diameter concrete pipes located several feet below the slab elevation. The licensee had completed calculation 2008-11997 Hydrogen Blast Analysis to evaluate the affect of a postulated hydrogen explosion on structures identified within a the predicted blast radius that could affect plant operation. However, the inspectors identified the following concerns with this calculation:
1) The effect of a blast induced shockwave on the buried CW pipes directly beneath the facility was not evaluated. If the blast shock wave was sufficient to collapse and block the buried headers, the station would experience a loss of CW, which could also disrupt the normal operation of the safety-related Cooling Water System.
2) The calculation evaluated the blast effects from only one individual tank explosion within a given bank based on a hydrogen explosion event which occurred on a portable hydrogen trailer bank at Los Alamos National Laboratory. The licensee had not compared their storage configuration with that involved in the Los Alamos event to ensure that multiple tanks would not explode. Because, the licensees bulk storage tanks were larger than those used on the portable trailer tanks, they would generate a larger explosive force which may be sufficient to trigger additional tank explosions.
On August 11, 2008, the licensee approved screening 3015 Hydrogen Tank Farm which evaluated and determined that a 10 CFR 50.59 evaluation was not required to install EC 12191. This screening was inadequate, because, it failed to identify the need for a full safety evaluation to evaluate the impact of a postulated tank farm blast on the CW System and Cooling Water System functions. Specifically, a postulated hydrogen tank explosion would create a shock wave into the ground which could damage the buried CW piping and adversely affect the functions of this system. Further, if sufficient blockage occurred in the CW System, it would disrupt the normal flow of the Cooling Water System that discharges into the CW return header piping.
The inspectors concluded that location of the bulk hydrogen storage facility directly over the circulating water lines without a demonstrated analysis to assess the effect on these lines would not have been acceptable under 10 CFR 50.59 and would have required approval from the NRC (e.g., license amendment). Specifically, NEI 96-07 Section 4.3.6 identifies that a new or common cause failure not bounded by previous analysis would not meet the 10 CFR 50.59 screening criteria and hence would require a license amendment. As a corrective action, the licensee stopped work on the installation of the bulk hydrogen facility and documented the NRC identified issues in Assignment Report (AR) 01161382 and AR 01161364. The inspectors concerns subsequently prompted the licensee to identify above ground Cooling Water System piping in the nearby Turbine Building which had also not been evaluated in the hydrogen tank blast analysis (AR 01161373).
Analysis:
The inspectors determined that the licensees failure to perform a safety evaluation in accordance with 10 CFR 50.59 for changes to their design basis associated with bulk hydrogen storage was a performance deficiency warranting a significance determination. Specifically, the licensee had installed a bulk hydrogen storage system at a location that could adversely affect the design basis function of the CW System.
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 licensees design basis would not have ultimately required NRC prior approval.
The inspectors completed a significance determination of the underlying technical issue using NRCs inspection manual chapter (IMC) 0609, Appendix A, Significance Determination of Reactor Inspection Findings for At-Power Situations, and answered No to the Mitigating Systems screening questions in the Phase 1 Screening Worksheet (Table 4a). The inspectors answered No, because the licensee had not yet filled the bulk storage facility with hydrogen, so no possibility of explosion and damage to plant equipment existed. Based upon this Phase 1 screening, the inspectors concluded that the issue was of very low safety significance (Green).
In accordance with IMC 305 Operating Reactor Assessment Process, the inspectors identified a cross-cutting aspect for this finding, using available causal information. The cause of this finding was related to the cross-cutting element of Human Performance, Decision Making, because the licensee failed to make conservative assumptions in decision making. In accordance with IMC 305, Section 06.07.c, Components Within the Cross-Cutting Areas, the inspectors identified Item H.1.b as applicable for this finding.
Specifically, the licensees decision to ignore the effect of a blast induced shock wave on CW piping was not conservative, and the assumption that only one cylinder in a bank of hydrogen cylinders could explode without establishing an adequate basis was non-conservative.
Enforcement:
Title 10 CFR 50.59(d)(1) states, in part, that the licensee shall maintain records of changes in the facility, of changes in procedures, and of tests and experiments. These records must include a written evaluation which provides a basis for the determination that the change, test, or experiment does not require a license amendment.
Contrary to the above, as of December 5, 2008, the licensee failed to perform a written safety evaluation for installation of the bulk hydrogen storage facility (EC 12191). 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 licensees corrective action program (AR 01161382 and AR 01161364), this violation is being treated as an NCV consistent with VI.A.1 of the NRC Enforcement Policy (NCV).
(NCV 05000282/2008007-01; 05000306/2008007-01).
.2 Review of Permanent Plant Modifications
a. Inspection Scope
From November 17, 2008 through December 5, 2008, the inspectors reviewed ten permanent plant modifications that had been installed in the plant during the last three years. This review included in-plant walkdowns for portions of the modified Turbine Generator Control Systems, Emergency Diesel Generator Ventilation Systems, Bulk Hydrogen Storage System and the Condensate Storage Tank Freeze Protection System. The modifications were selected based upon risk significance, safety significance, and complexity. The inspectors reviewed the modifications selected to determine if:
- the supporting design and licensing basis documentation was updated;
- the changes were in accordance with the specified design requirements;
- the procedures and training affected by the modification have been updated;
- the test documentation as required by applicable test programs has been updated; and
- post-modification testing specified was sufficient to ensure functionality of the component modified, its associated system, and any support systems.
This inspection constitutes ten samples as defined in Inspection Procedure 71111.17-05.
b. Findings
No findings of significance were identified.
OTHER ACTIVITIES (OA)
4OA2 Identification and Resolution of Problems
.1 Routine Review of Condition Reports
a. Inspection Scope
From November 17, 2008 through December 5, 2008, the inspectors reviewed Corrective Action Process documents that identified or were related to 10 CFR 50.59 evaluations and permanent plant modifications. The inspectors reviewed these documents to evaluate the effectiveness of corrective actions related to permanent plant modifications and evaluations for changes, tests, or experiments issues. In addition, corrective action documents written on issues identified during the inspection were reviewed to verify adequate problem identification and incorporation of the problems into the corrective action system. The specific corrective action documents that were sampled and reviewed by the inspectors are listed in the attachment to this report.
b. Findings
No findings of significance were identified.
4OA6 Management Meeting(s)
.1 Exit Meeting
The inspectors presented the inspection results to Mr. M. Wadley and others of the licensees staff, on December 5, 2008. Licensee personnel acknowledged the inspection results presented and did not identify any proprietary content. The inspectors returned proprietary material reviewed during the inspection to the licensee staff.
ATTACHMENT:
SUPPLEMENTAL INFORMATION
KEY POINTS OF CONTACT
Licensee Personnel
- M. Wadley, Site Vice President
- S. Myers, Design Engineering Manager,
- M. Hopman, Engineering Supervisor
- J. Connors, Mechanical Design Engineer
- C. Sansome, Design Engineer
- J. Kivi, Regulatory Compliance Engineer
LIST OF ITEMS OPENED, CLOSED, AND DISCUSSED
Opened and Closed
- 05000282/2008007-01; NCV Failure to Perform a 10 CFR 50.59 Evaluation for Bulk
- 05000306/2008007-01 Hydrogen Storage Facility (Section 1R17.1.b)
Discussed
None Attachment