L-MT-22-049, Industry Groundwater Protection Initiative Special Report

Industry Groundwater Protection Initiative Special Report

ML22349A600
Person / Time
Site:	Monticello
Issue date:	12/15/2022
From:	Domingos C Northern States Power Company, Minnesota, Xcel Energy
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
L-MT-22-049, NEI 07-07
Download: ML22349A600 (1)

Text

fl Xcel Energy December 15, 2022 ATTN: Document Control Desk U.S. Nuclear Regulato ry Commission Washington, DC 2055 5-0001 Monticello Nuclear Generating Plant Docket No. 50-263 Renewed Facility Operating License No. DPR-22 Industry Groundwater Protection Initiative Special Repo rt Northern States Power Company, a Minnesota corporation, doing business as 2807 West County Road 75 Monticello, MN 55362 L-MT-22-049 NEI 07-07 Xcel Energy (hereafter "NSPM"), hereby submits a special report in accordance with Nuclear Energy Institute (NEI) 07-07 "Industry Groundwater Protection Initiative -Final Guidance Document." Samples contained in one on-site monitoring well indicated activity above the threshold for voluntary reporting per NEI 07-07.

If you have any questions about this submittal, please contact Carrie Seipp, Senior Regulatory Engineer, at 612-330-5576.

Summary of Commitments This letter m no new commitments and no revisions to existing commitments.

P Doe. -.o*s ------

Site Vice President, Monticello and Prairie Island Nuclear Generating Plants Northern States Power Company -Minnesota Enclosure cc: Administrator, Region Ill, USNRC Project Manager, Monticello, USNRC Resident Inspector, Monticello, USNRC State of Minnesota ENCLOSURE

MONTICELLO NUCLEAR GENERATING PLANT INDUSTRY GROUNDWATER PROTECTION INITIATIVE SPECIAL REPORT

This report is being submitted as part of the NEI Enhanced Groundw ater Protection Initiative.

During monthly Groundwater Protection Program (GWPP) well sampling, increased tritium levels were identified in a monitoring well. The monitoring well is located between the T urbine Building and R eactor Building; the well is used to sample the groundwater under the T urbine Building basemat. On 11/21/2022, the GWPP sample of Monitoring Well 9 (MW-9) showed an activity of 5,020,000 picocuries/liter. The same result was obtained following a resample on 11/22/2022. Subsequent samples resulted in similar tritium concentrations. The activity of 5,020,000 picocuries/liter exceeds the Offsite Dose Calculation Manual (ODCM) reporting limit of 30,000 picocuries/liter for non-drinking water. The information in this report is based on preliminary results through 12/8/2022; NSPM is waiting on certified vendor laboratory results.

Daily Gamma Spectroscopy testing was started on 11/21/2022 for the monitoring wells. The analysis determined the presence of Iodine-131 (I-131) in MW-9. The concentration on 11/21/2022 was 13.8 picocuries/liter. The concentration on 12/2/2022 was 20.1 picocuries /liter, exceeding ODCM reporting limit of 20 picocuries/liter for non-drinking water. The highest concentration identified in preliminary results was 27.5 picocuries/liter.

The leak is localized in the immediate vicinity under the Turbine Building b asemat. This was confirmed by sampling of the surrounding wells covering the R eactor Building and Turbine Building perimeters. Of note, down gradient monitoring wells MW-12A, MW -12B, MW-13A, and MW-13B were sampled and preliminary results were less than Minimum Detectable Concentration (MDC). The presence of I-131 was not detected in any of the surrounding wells.

A site troubleshooting team has been established to identify the source to eliminate further leakage. The investigation is on-going and daily samples will continue until the source has been identified and corrected.

The estimated potential or bounding annual dose for an adult that consumes 730 liters of water containing 5,020,000 picocuries/liter of tritium is a C ommitted Effective Dose Equivalent (CEDE) of 229 millirem/year. The estimated potential or bounding dose for an adult that consumes 730 liters of water containing 2 7.5 picocuries/liter of Iodine-131 is a Committed Dose Equivalent to the thyroid (CDEthyroid) of 33.5 millirem/year. This is based on assuming an individual consuming 730 liters of water over the course of a year per the ODCM and receives 5,000 millirem per 8E4 microcurie of tritium ingested and 50,000 millirem per 30 microcurie of Iodine-131 ingested per 10CFR20. However, no detectable tritium or Iodine-131 was found in any onsite or offsite drinking water wells monitored by the Radiological Environmental Monitoring Program (REMP).

This issue poses no immediate safety concerns for plant employees or the general public.

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