IR 05000424/2019090
| ML19361A059 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 12/26/2019 |
| From: | Mark Franke Division of Reactor Safety II |
| To: | Gayheart C Southern Nuclear Operating Co |
| References | |
| EA-19-112 IR 2019090 | |
| Download: ML19361A059 (9) | |
Text
ber 26, 2019
SUBJECT:
VOGTLE ELECTRIC GENERATING PLANT - NRC INSPECTION REPORT 05000424/2019090 AND 05000425/2019090 AND PRELIMINARY WHITE FINDING AND APPARENT VIOLATION
Dear Ms. Gayheart:
The U.S. Nuclear Regulatory Commission has completed its preliminary significance determination of the finding and apparent violation discussed in inspection report 05000424/2019003 and 05000425/2019003 and determined the preliminary significance to be White with low safety significance based on the best available information. The enclosure provides the basis for the preliminary significance determination. The final resolution of this finding will be conveyed in separate correspondence.
We intend to issue our final significance determination and enforcement decision, in writing, within 90 days from the date of inspection report 2019-003 (issued November 14, 2019). The NRCs significance determination process (SDP) is designed to encourage an open dialogue between your staff and the NRC; however, neither the dialogue nor the written information you provide should affect the timeliness of our final determination.
Before we make a final decision, you may choose to communicate your position on the facts and assumptions used to arrive at the finding and assess its significance by either (1) attending and presenting at a regulatory conference or (2) submitting your position in writing. The focus of a regulatory conference is to discuss the significance of the finding. Written responses should reference the inspection report number and enforcement action number associated with this letter in the subject line.
If you choose to respond in writing, please mark your response "Pre-decisional Reply to EA-19-112, NRC Inspection Report 05000424/2019090 and 05000425/2019090 and Preliminary White Finding and Apparent Violation, and send it to the U.S. Nuclear Regulatory Commission, ATTN:
Document Control Desk, Washington, DC 20555-0001 with a copy to the Regional Administrator, Region II, and a copy to the NRC Resident Inspector at Vogtle Electric Generating Plant, within 30 days of the date of this letter. If you request a regulatory conference, it should be held within 40 days of your receipt of this letter. Please provide information you would like us to consider or discuss with you at least 10 days prior to any scheduled conference. If you choose to attend a regulatory conference, it will be open for public observation. If you choose not to request a regulatory conference or to submit a written response, you will not be allowed to appeal the NRCs final significance determination.
Please contact Mark Franke at 404-997-4600, or in writing using the Region II address above, within 10 days from the issue date of this letter to notify us of your intentions. If we have not heard from you within 10 days, we will continue with our significance determination and enforcement decision.
This letter, its enclosure, and your response (if any) will be made available for public inspection and copying at http://www.nrc.gov/reading-rm/adams.html and at the NRC Public Document Room in accordance with Title 10 of the Code of Federal Regulations 2.390, Public Inspections, Exemptions, Requests for Withholding.
Sincerely,
/RA/
Mark E. Franke, Director Division of Reactor Safety Docket Nos. 05000424 and 05000425 License Nos. NPF-68 and NPF-81
Enclosure:
As stated
Inspection Report
Docket Numbers: 05000424 and 05000425 License Numbers: NPF-68 and NPF-81 Report Numbers: 05000424/2019090 and 05000425/2019090 Enterprise Identifier: I-2019-090-0003 Licensee: Southern Nuclear Operating Company, Inc.
Facility: Vogtle Electric Generating Plant Location: Waynesboro, GA Inspection Dates: October 17 to December 2, 2019 Inspectors: Adam Nielsen Approved By: Brian R. Bonser, Chief Engineering Branch 3 Division of Reactor Safety Enclosure
SUMMARY The U.S. Nuclear Regulatory Commission (NRC) continued monitoring the licensees performance by conducting a NRC inspection at Vogtle Electric Generating Plant, in accordance with the Reactor Oversight Process. The Reactor Oversight Process is the NRCs program for overseeing the safe operation of commercial nuclear power reactors. Refer to https://www.nrc.gov/reactors/operating/oversight.html for more information.
List of Findings and Violations Failure to Calibrate Containment High-range Area Radiation Monitors Cornerstone Significance Cross-Cutting Report Aspect Section Emergency Preliminary White [H.1] - 71124.05 Preparedness AV 05000424,05000425/2019003-01 Resources Open EA-19-112 The inspectors identified an Apparent Violation (AV) of Technical Specification (TS) 3.3.3, for the failure to correctly calibrate the Vogtle Unit 1 (U1) and Unit 2 (U2) containment high-range area radiation monitors 1RE-0005, 1RE-0006, 2RE-0005, and 2RE-0006. Specifically, the source-to-detector geometry used for isotopic calibrations was not fixed and reproducible which resulted in radiation monitor indications in the main control room that were biased high. These radiation monitors are relied upon during an accident to provide release assessment for use by plant operators in determining the need to invoke site emergency plans.
Additional Tracking Items None.
INSPECTION SCOPES Inspections were conducted using the appropriate portions of the inspection procedures (IPs) in effect at the beginning of the inspection unless otherwise noted. Currently approved IPs with their attached revision histories are located on the public website at http://www.nrc.gov/reading-rm/doc-collections/insp-manual/inspection-procedure/index.html. Samples were declared complete when the IP requirements most appropriate to the inspection activity were met consistent with Inspection Manual Chapter (IMC) 2515, Light-Water Reactor Inspection Program - Operations Phase. The inspectors reviewed selected procedures and records, observed activities, and interviewed personnel to assess licensee performance and compliance with Commission rules and regulations, license conditions, site procedures, and standards.
RADIATION SAFETY 71124.05 - Radiation Monitoring Instrumentation The inspectors convened a Significance Enforcement Review Panel to determine a preliminary significance for AV 2019003-01, "Failure to Calibrate Containment High-range Area Radiation Monitors" (EA 19-112).
INSPECTION RESULTS Failure to Calibrate Containment High-range Area Radiation Monitors Cornerstone Significance Cross-Cutting Report Aspect Section Emergency Preliminary White [H.1] - 71124.05 Preparedness AV 05000424,05000425/2019003-01 Resources Open EA-19-112 The inspectors identified an Apparent Violation (AV) of Technical Specification (TS) 3.3.3, for the failure to correctly calibrate the Vogtle Unit 1 (U1) and Unit 2 (U2) containment high-range area radiation monitors 1RE-0005, 1RE-0006, 2RE-0005, and 2RE-0006. Specifically, the source-to-detector geometry used for isotopic calibrations was not fixed and reproducible which resulted in radiation monitor indications in the main control room that were biased high. These radiation monitors are relied upon during an accident to provide release assessment for use by plant operators in determining the need to invoke site emergency plans.
Description: In October 2018, the inspectors identified potential errors in the calibration process used to perform in-situ isotopic calibrations on the Vogtle U1 and U2 containment high-range area radiation monitors (CHRMs) 1RE-0005, 1RE-0006, 2RE-0005, and 2RE-0006. Specifically, the methodology used to perform the calibrations failed to create a reproducible source-to-detector geometry from one surveillance to the next. Instead, the licensees calibration procedure involved moving the Cs-137-point source closer to the
detector surface over time in an attempt to maintain, as the source decayed, a target dose rate of 17 R/hr +/- 20%. Prior to each calibration, the distance to achieve 17 R/hr was determined on a benchtop using the calibration source and a small-volume, NIST-traceable ion chamber. As this distance decreased over time, the potential existed for the active detection volume of the CHRMs to be unevenly irradiated during the in-situ isotopic calibration. As a result, it is possible the CHRMs would under respond compared to the much smaller benchtop ion chamber. Therefore, the instrument gain may have been unnecessarily adjusted upward to compensate for low detector response over the course of several calibration surveillances. The inspectors documented an Unresolved Item (URI) in inspection report 05000424, 05000425/2018-004, and closed the URI to an apparent violation in inspection report 2019-003.
In response to this URI, the licensee performed an evaluation to determine the magnitude of the calibration error and presented the results to NRC inspectors on June 19, 2019. The evaluation consisted of irradiating spare containment high range ion chamber tubes in a gamma box calibrator to determine nominal response characteristics and then performing a transfer calibration using the Cs-137 calibration source in a fixed, direct contact geometry with both the spare detectors and those currently installed on Unit 2. Using this methodology, a gain factor (R/hr/Amp) was calculated for 2RE-0005 and 2RE-0006 and compared to the gain factors currently in use. In this manner, all sources of potential error described in the URI (i.e. inconsistency in measurement distance, uneven irradiation, and failure to decay-correct the source) were addressed in the evaluation.
The results showed that the gain factors currently in use were biased high by 60% for 2RE-0005 and 84% for 2RE-0006. Therefore, indications for these instruments in the main control room (MCR) would be biased high by a similar amount. In addition to the licensees evaluation, the inspectors performed a review of gain factors for both units going back to 2009. This showed that 1RE-0005, 1RE-0006, 2RE-0005, and 2RE-0006 have been operating with a positive bias between 46% and 128% during that time period. This bias exceeds the +/- 20% acceptance criteria in calibration procedures 24989-1, Isotopic Channel Calibration of the Containment High Range Area Radiation Monitors 1RE-0005 and 1RE-0006 and 24989-2, Isotopic Channel Calibration of the Containment High Range Area Radiation Monitors 2RE-0005 and 2RE-0006, and exceeds the accuracy range of +/- 20% of the actual radiation field described in UFSAR Section 12. In addition, as the Cs-137 calibration source continued to decay the source would be moved closer to the detector surface. As a result, the uneven irradiation would become more pronounced and could result in continued changes to the gain factor over time and an even larger positive bias in MCR indication.
The inspectors noted that 1RE-0005, 1RE-0006, 2RE-0005, and 2RE-0006 are used during an accident to assist in making EAL declarations, as described in the licensees Emergency Action Level (EAL) implementing procedure NMP-EP-141-003, Vogtle 1 & 2 Emergency Action Level and Basis. Specifically, the instruments are used in the Fission Product Barrier Degradation matrix (EALs FA1, FG1 and FS1) and Cold Shutdown/refueling System Malfunction Reactor Pressure Vessel Level accident scenario (EALs CG1 and CS1). Since the monitors were biased high compared to actual radiological conditions in containment, these emergency declarations would be made earlier than necessary or when a lower classification was more appropriate. In some cases, this would result in an Offsite Response Organization (ORO) implementing unnecessary protective actions for the public.
Corrective Actions: The licensee is revising their procedures for performing calibrations on the containment high range area radiation monitors.
Corrective Action References: Condition Reports 10621148 and 10621284 Performance Assessment:
Performance Deficiency: The licensees failure to calibrate containment high range area radiation monitors, as required by TS 3.3.3, was a performance deficiency.
Screening: The inspectors determined the performance deficiency was more than minor because it was associated with the Plant Facilities/Equipment and Instrumentation attribute of the Emergency Preparedness cornerstone and adversely affected the cornerstone objective to ensure that the licensee is capable of implementing adequate measures to protect the health and safety of the public in the event of a radiological emergency. Specifically, main control room indications relied upon to make EAL declarations, per the site emergency plan, were biased high due to improper instrument calibration methods.
Significance: The inspectors utilized IMC 0609, Appendix B, Emergency Preparedness Significance Determination Process, to determine the significance of the performance deficiency. Due to a long-standing positive bias in MCR indication for the containment high range area radiation monitors 1RE-0005, 1RE-0006, 2RE-0005, and 2RE-0006, the initiating conditions for Fission Product Barrier Degradation matrix EALs (FA1, FG1 and FS1) and Cold Shutdown/Refueling System Malfunction Reactor Pressure Vessel Level EALs (CG1 and CS1) would be met appreciably earlier than required by actual conditions inside containment (overly-conservative). Since the EAL schemes associated with these instruments contain events that would result in a General Emergency, the inspectors determined the performance deficiency would result in an over-classification that would lead to protective action recommendations (PARs) being provided to off-site response organizations who would then take unnecessary actions to protect the public. Therefore, the performance deficiency resulted in a degraded Risk Significant Planning Standard (RSPS) function associated with 10 CFR 50.47(b)(4), Emergency Classification System. The Emergency Preparedness SDP states that unnecessary public protective actions caused by an over-classification are a concern since the public could be placed at increased health risks without realizing the dose avoidance benefit of a necessary protective action. Based on the RSPS degraded function examples (over-classification that includes unnecessary PARs) provided in Table 5.4-1 and Figure 5.4-1 of the Emergency Preparedness SDP, this issue was determined by the NRC staff to be a White finding.
Cross-Cutting Aspect: H.1 - Resources: Leaders ensure that personnel, equipment, procedures, and other resources are available and adequate to support nuclear safety. The event was a direct result of the licensees failure to provide adequate calibration procedures.
Enforcement:
Violation: Technical Specification 3.3.3 requires the licensee to perform periodic channel calibrations for post-accident monitoring equipment, including radiation monitors 1RE-0005, 1RE-0006, 2RE-0005, and 2RE-0006. Section 1.1 of the TS states that A channel calibration shall be the adjustment, as necessary, of the channel so that it responds within the required range and accuracy to known inputs. Contrary to this, since plant startup, the licensee has failed to periodically calibrate containment high-range area monitors 1RE-0005, 1RE-0006, 2RE-0005, and 2RE-0006 so that they responded within the required accuracy to known inputs. Upon identification, the licensee took action to revise their calibration procedures.
Enforcement Action: This violation is being treated as an apparent violation pending a final significance (enforcement) determination.
EXIT MEETINGS AND DEBRIEFS The inspectors verified no proprietary information was retained or documented in this report.
- On December 23, 2019, the inspectors presented the NRC inspection results to Keith Taber, Site Vice President and other members of the licensee staff.
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