Exelon Generation Company, LLC; LaSalle County Station, Units 1 and 2

AGENCY:

Nuclear Regulatory Commission.

ACTION:

Environmental assessment and finding of no significant impact; issuance.

SUMMARY:

The U.S. Nuclear Regulatory Commission (NRC) is considering issuance of amendments to Renewed Facility Operating License Nos. NPF-11 and NPF-18 issued to Exelon Generation Company, LLC (Exelon, the licensee) for operation of LaSalle County Station, Units 1 and 2 (LaSalle), located in Brookfield Township, LaSalle County, Illinois. The proposed action would revise the technical specifications (TS) for the plant to allow for an average, rather than absolute, ultimate heat sink (UHS) sediment level and would modify the UHS temperature curve to increase the allowable TS diurnal temperature limits of the cooling water supplied to the plant from the UHS. The NRC is issuing an environmental assessment (EA) and finding of no significant impact (FONSI) associated with the proposed license amendments.

DATES:

The EA and FONSI referenced in this document are available on March 12, 2021.

ADDRESSES:

Please refer to Docket ID NRC-2021-0034 when contacting the NRC about the availability of information regarding this document. You may obtain publicly available information related to this document using any of the following methods:

• Federal Rulemaking Website: Go to https://www.regulations.gov and search for Docket ID NRC-2021-0034. Address questions about Docket IDs in Regulations.gov to Stacy Schumann; telephone: 301-415-0624; email: Stacy.Schumann@nrc.gov. For technical questions, contact the individuals listed in the FOR FURTHER INFORMATION CONTACT section of this document.
• NRC's Agencywide Documents Access and Management System (ADAMS): You may obtain publicly available documents online in the ADAMS Public Documents collection at https://www.nrc.gov/reading-rm/adams.html. To begin the search, select “Begin Web-based ADAMS Search.” For problems with ADAMS, please contact the NRC's Public Document Room (PDR) reference staff at 1-800-397-4209, 301-415-4737, or by email to pdr.resource@nrc.gov. For the convenience of the reader, the ADAMS accession numbers are provided in a table in the “Availability of Documents” section of this document.
• Attention: The PDR, where you may examine and order copies of public documents, is currently closed. You may submit your request to the PDR via email at pdr.resource@nrc.gov or call 1-800-397-4209 or 301-415-4737, between 8:00 a.m. and 4:00 p.m. (EST), Monday through Friday, except Federal holidays.

FOR FURTHER INFORMATION CONTACT:

Briana Grange, Office of Nuclear Material Safety and Safeguards, telephone: 301-415-1042; email: Briana.Grange@nrc.gov; and Bhalchandra Vaidya, Office of Nuclear Reactor Regulation, telephone: 301-415-3308; email: Bhalchandra.Vaidya@nrc.gov. Both are staff of the U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001.

SUPPLEMENTARY INFORMATION:

I. Introduction

The NRC is considering issuance of amendments to Renewed Facility Operating License Nos. NPF-11 and NPF-18 issued to Exelon for LaSalle located in LaSalle County, Illinois. Exelon submitted its license amendment request in accordance with section 50.90 of title 10 of the Code of Federal Regulation (10 CFR), by letter dated July 17, 2020, as supplemented by letters dated September 11, 2020, and October 22, 2020.

In accordance with 10 CFR 51.21, the NRC staff prepared the following EA that analyzes the environmental impacts of the proposed licensing action. Based on the results of this EA, the NRC staff did not identify any significant environmental impacts associated with the proposed amendments and the NRC staff is, therefore, issuing a FONSI in accordance with 10 CFR 51.32.

II. Environmental Assessment

Plant Site and Environs

LaSalle is a two-unit nuclear power plant located in Brookfield Township in LaSalle County, Illinois, approximately 75 miles (mi) (120 kilometers (km)) southwest of downtown Chicago, Illinois. The LaSalle site lies in a rural area predominantly used for agriculture and wind-power generation. An onsite 2,058 acre (ac) (833-hectare (ha)) cooling pond provides condenser cooling. Cooling water that is not otherwise lost from the pond through evaporation or seepage is recirculated from the cooling pond through the condenser systems in a continuous loop. Underground pipelines approximately 3.5 mi (5.6 km) long connect the cooling pond to the Illinois River, which is the source of the plant's makeup water and the receiving body of water for plant blowdown. A small screen house located on the river provides makeup water to the cooling pond, and a portion of the water in the cooling pond is discharged as blowdown to the river on a near continuous basis.

A dedicated portion of the cooling pond located immediately adjacent to the LaSalle intake canal serves as the plant's UHS. The UHS is also known as the core standby cooling system (CSCS) pond, and it directly supplies water to the CSCS cooling water system equipment. The UHS provides a heat sink for process and operating heat from safety-related components during the UHS design basis event. The UHS design basis event includes a failure of the cooling pond dike. In such an event, the UHS would become the remaining source of cooling water to plant safety systems. In such an event, the UHS allows for the safe shutdown and cooldown of both LaSalle units for a 30-day period with no additional makeup water source. The UHS also provides a source of emergency makeup water for the spent fuel pools and can provide water for fire protection equipment.

The cooling pond is a wastewater treatment works as defined by Section 301.415 of Title 35 of the Illinois Administrative Code (35 IAC 301.415). Under this definition, the cooling pond is not considered waters of the State under Illinois Administrative Code (35 IAC 301.440) or waters of the United States under the Federal Clean Water Act (40 CFR 230.3(s)), and so the cooling pond is not subject to Federal or State water quality standards.

Exelon leases a large portion of the cooling pond to the Illinois Department of Natural Resources (IDNR), which maintains the leased portion of the pond as an outdoor recreation area for public use and fishing. IDNR has actively managed fish populations in the cooling pond since 1984. The cooling pond can be characterized as a highly managed ecosystem in which IDNR fish stocking and other human activities primarily influence the species composition and population dynamics. IDNR surveys the cooling pond each year and determines which fish to stock based on fishermen preferences, fish abundance, different species' tolerance to warm waters, predator and prey dynamics, and other factors. Currently, commonly stocked species include largemouth bass (Micropterus salmoides), smallmouth bass (M. dolomieu), black crappie (Pomoxis nigromaculatus), white crappie (P. annularis), channel catfish (Ictalurus punctatus), blue catfish (I. furcatus), striped bass hybrid (Morone saxatilis x M. chrysops), walleye (Sander vitreus), and bluegill (Lepomis macrochirus). Because cooling pond temperatures are high in the summer months, the introductions of warm-water species, such as largemouth bass and blue catfish, has been more successful than the introductions of cool-water species, such as walleye and muskellunge (Esox masquinongy). In addition to the stocked species, gizzard shad (Dorosoma cepedianum) and threadfin shad (D. petenense) also occur in the cooling pond. Shad are not recreationally fished, and IDNR does not currently stock these fish. IDNR stocks some recreationally fished species that consume shad (e.g., catfish and striped bass) in part to limit the size of shad populations.

The plant site and environs are described in greater detail in Chapter 3 of the NRC's August 2016, “Generic Environmental Impact Statement for License Renewal of Nuclear Plants: Regarding LaSalle County Station, Units 1 and 2, Final Report” (NUREG-1437, Supplement 57; (herein referred to as the “LaSalle FSEIS” [Final Supplemental Environment Impact Statement]). Figures 3-3 and 3-4 on pages 3-4 and 3-5 of the LaSalle FSEIS, respectively, depict the plant layout. Figure 3-6 on page 3-9 depicts the cooling pond, including the portion of the pond that constitutes the UHS, as well as the blowdown line to the Illinois River.

Description of the Proposed Action

If approved, the proposed action would revise TS Surveillance Requirement (SR) 3.7.3.2 concerning the UHS sediment level verification requirement to allow for an average, rather than absolute, sediment level. The proposed action would also modify the temperature curve associated with TS SR 3.7.3.1 to increase the allowable TS diurnal temperature limits of the cooling water supplied to the plant from the UHS. Other conforming TS changes would also be made.

Specifically, the proposed action would modify TS SR 3.7.3.2. This TS currently requires Exelon to verify that the sediment level in the intake flume and CSCS pond is less than or equal to (≤) 1.5 feet (ft) (18 inches (in.) or 0.5 meters (m)). This TS would be modified to allow an average, rather than absolute, sediment level. The revised requirement would state, “Verify average sediment level is 6 inches in the intake flume and the CSCS pond.”

The proposed action would also modify the temperature curve associated with TS SR 3.7.3.1. This requirement currently states, “Verify cooling water temperature supplied to the plant from the CSCS pond is within the limits of Figure 3.7.3-1.” Under the proposed action, Figure 3.7.3-1 would be modified to specify new diurnal temperature limits. The revised TS temperature limits would continue to vary with the diurnal cycle and would continue to limit the maximum temperature of the UHS supplied to plant safety systems to below 107 degrees Fahrenheit (°F) (41.7 degrees Celsius (°C)), the design limit of the plant. The revised limits would increase the allowable maximum UHS temperature of cooling water by 1.54 to 3.54 °F (0.85 to 1.97 °C) as compared to current limits and depending on time of day. Table 1 lists the current and proposed temperature limits, and Figure 1 depicts these limits graphically.

Additionally, the proposed action would make conforming changes to the LaSalle TS as described in the licensee's application dated July 17, 2020, as supplemented by letters dated September 11, 2020, and October 22, 2020. The proposed action would be in accordance with the licensee's application.

Need for the Proposed Action

The licensee has requested the proposed amendments in connection with recent meteorological and atmospheric conditions that have resulted in challenges to the TS UHS temperature. These conditions include elevated air temperatures, high humidity, and low wind speed. The proposed action would provide the licensee with operational flexibility during periods of high UHS temperatures in order to prevent plant shutdown.

Environmental Impacts of the Proposed Action

With regard to radiological impacts, the proposed action would not result in any changes in the types of radioactive effluents that may be released from the plant offsite. No significant increase in the amount of any radioactive effluent released offsite or significant increase in occupational or public radiation exposure is expected from the proposed action. Separate from this EA, the NRC staff is evaluating the licensee's safety analyses of an accident that may result from the proposed action. The results of the NRC staff's evaluation will be documented in a safety evaluation (SE). If the NRC staff concludes in the SE that all pertinent regulatory requirements are met by the proposed amendments, then the proposed action would result in no significant radiological impact to the environment. The NRC staff's SE will be issued with the license amendments, if approved by the NRC.

With regard to potential non-radiological impacts, raising the maximum allowable UHS diurnal temperature limits could cause the UHS portion of the cooling pond to experience increased water temperatures. Because the proposed action would not affect LaSalle's licensed thermal power level, the temperature rise across the condensers as cooling water travels through the cooling system would remain constant. Thus, if water in the UHS were to rise to the proposed allowable limits according to the proposed temperature curve, heated water returning to the cooling pond would also experience a corresponding 1.54 to 3.54 °F (0.85 to 1.97 °C) increase compared to current limits and depending on time of day. That additional heat load would dissipate across some thermal gradient as discharged water mixes within the cooling pond.

Many freshwater fish, such as those species that inhabit the cooling pond, experience thermal stress and can die when they encounter water temperatures at or above 95 °F (35 °C). Fish kills tend to occur when water temperatures rise above this level for some prolonged period of time and fish are unable to tolerate the higher temperatures or cannot retreat into cooler waters. Fish that experience thermal effects within the region of the cooling pond that is thermally affected by LaSalle's effluent discharge (e.g., the discharge canal, the flow path between the discharge canal and UHS, and the UHS itself) are experiencing effects that are, at least in part, attributable to plant operation.

Under current operating conditions, LaSalle's cooling pond occasionally experiences fish kills. Such events only occur in the summer months and tend to be correlated with periods of high ambient air temperatures, low winds, and high humidity. Appendix B, Section 4.1 of the LaSalle renewed facility operating licenses requires Exelon to report fish kills to the NRC as unusual or important environmental events if they are causally related to plant operation. Since 2001, Exelon has reported four fish kill events. The events occurred in July 2001, June 2005, June 2009, August 2010, and primarily affected gizzard shad. The IDNR identified other dead fish to include carp (Cyprinus carpio), smallmouth buffalo (Ictiobus bubalus), freshwater drum (Aplodinotus grunniens), channel catfish, striped bass hybrid, smallmouth bass, walleye, bluegill, white bass (Morone chrysops), yellow bullhead catfish (Ameiurus natalis), and yellow bass (M. mississippiensis). The temperature in the cooling pond during these events ranged from 93 °F (33.9 °C) to 101 °F (38.3 °C), and each event resulted in the death of approximately 1,500 to 94,500 fish. During the largest of these events, which was in July 2001, the IDNR found the maximum temperature in the cooling pond discharge canal to be 120 °F (48.9 °C) and dissolved oxygen levels to range from 6.2 to 18.8 parts per million. Section 3.7.2.2 of the LaSalle FSEIS describes these events in more detail. Since the NRC issued the FSEIS in 2016, Exelon has not reported any more recent fish kill events to the NRC. However, Exelon has observed several smaller non-reportable fish kills in the cooling pond since that time. Exelon attributes these non-reportable events to a combination of high-water temperatures, low winds, and high humidity. The most recent non-reportable fish kill occurred in July 2020.

In Section 4.7.1.3 of the LaSalle FSEIS, the NRC staff concluded that thermal impacts associated with continued operation of LaSalle during the license renewal term would be small for all aquatic resources in the cooling pond except for gizzard shad and threadfin shad, which would experience moderate thermal impacts. Moderate impacts are environmental effects that are sufficient to alter noticeably, but not destabilize, important attributes of the resource. The NRC staff determined that fish kills would have noticeable impacts on important attributes of the aquatic environment within the cooling pond (i.e., shad) based on the following:

• Exelon and IDNR noted reductions in shad population sizes following fish kills in the cooling pond.
• Exelon and IDNR attributed the decline in shad populations to fish kills causally related to plant operation.
• Based on the definition of important species in the NRC's Standard Review Plans for Environmental Reviews for Nuclear Power Plants, Supplement 1: Operating License Renewal, Revision 1 (NUREG-1555, Supplement 1, Revision 1, shad is an important aquatic attribute to the cooling pond ecosystem because it is prey for many recreationally important species.
• Fish kills are not destabilizing to shad populations because they tend to recover in about a year.
• Fish kills are expected to continue to occur in the cooling pond during the license renewal term.

For all other aquatic species, including recreationally important fish stocked by the IDNR, the NRC staff concluded in the FSEIS that thermal effects during the license renewal term would be small. Stocked species are a minor portion of affected fish during most fish kills, and the NRC staff found no evidence that fish kills noticeably altered populations of stocked species. Additionally, the staff noted that if a future fish kill negatively impacts a stocked species, the IDNR could mitigate such an effect by increasing the stocking level of that species during the following spring. At the time the NRC staff performed its license renewal review, the UHS TS temperature limits were the same as the current limits (see Table 1 and Figure 1).

The NRC staff anticipates that thermal effects under the proposed action would be qualitatively similar to those described in the FSEIS. The primary difference under the proposed action would be an incremental increase in the likelihood in the summer that fish in the thermally affected portion of the cooling pond would experience thermal effects causally related to plant operation. This is because under the proposed action, Exelon could continue to operate LaSalle during periods of higher UHS temperatures when it would currently be required to shut down. However, because the UHS is a small portion of the cooling pond, the majority of the cooling pond would be unaffected by the proposed action, and fish would be able to seek refuge in those cooler areas. Therefore, only fish within the region of the cooling pond that is thermally affected by LaSalle's effluent discharge (e.g., the discharge canal, the flow path between the discharge canal and UHS, and the UHS itself) at the time of elevated temperatures would likely be affected. Thermal effects would be most intense in or near the discharge canal and would decrease across a thermal gradient extending from the discharge canal.

As described previously in this EA, the fish species most likely to experience thermal effects in the cooling pond are threadfin shad and gizzard shad. These species are the most likely to die from thermal stress. However, shad populations generally recover quickly, and shad are consistently the most abundant species in the cooling pond. Thus, fish kills and other thermal effects do not appear to significantly influence these species' populations. Stocked species generally constitute a small portion of fish affected by fish kills, and these species would continue to be assessed and stocked by the IDNR on an annual basis in accordance with the lease agreement between Exelon and IDNR. Continued stocking would mitigate any minor effects resulting from the proposed action.

In addition to the increase in allowable TS diurnal temperature limits, the proposed action would revise the TS to allow for an average, rather than absolute, UHS sediment level. This TS relates to ensuring an adequate volume of cooling water is available. This change would have no adverse effect on aquatic resources.

Based on the foregoing analysis, the NRC staff concludes that the proposed action would not result in significant impacts to aquatic resources in the cooling pond.

Some terrestrial species, such as birds or other wildlife, rely on fish or other aquatic resources from the cooling pond as a source of food. The NRC staff does not expect any significant impacts to birds or other wildlife because, if a fish kill occurs, the number of dead fish would be a small proportion of the total population of fish in the cooling pond. Furthermore, during fish kills, birds and other wildlife could consume many of the floating, dead fish.

With respect to water resources and ecological resources along and within the Illinois River, the Illinois Environmental Protection Agency (IEPA) imposes regulatory controls on LaSalle's thermal effluent through Title 35, Environmental Protection, Section 302, “Water Quality Standards,” of the Illinois Administrative Code (35 IAC 302) and through the National Pollutant Discharge Elimination System (NPDES) permitting process pursuant to the Clean Water Act. Section 302 of the Illinois Administrative Code stipulates that “[t]he maximum temperature rise shall not exceed 2.8 °C (5 °F) above natural receiving water body temperatures,” (35 IAC 302.211(d)) and that “[w]ater temperature at representative locations in the main river shall at no time exceed 33.7 °C (93 °F) from April through November and 17.7 °C (63 °F) in other months” (35 IAC 302.211(e)). Additional stipulations pertaining to the mixing zone further protect water resources and biota from thermal effluents. The LaSalle NPDES permit contains special conditions that mirror these temperature requirements and that stipulate more detailed temperature requirements at the edge of the mixing zone. Under the proposed action, LaSalle's thermal effluent would continue to be limited by the Illinois Administrative Code and the LaSalle NPDES permit to ensure that LaSalle operations do not create adverse effects on water resources or ecological resources along or within the Illinois River. Occasionally, Exelon has applied for a provisional variance to allow higher-than-permitted temperatures at the edge of the discharge mixing zone. For instance, Exelon applied for and the IEPA granted provisional variances in March, July, and August 2012, during unusual weather conditions and associated high ambient river water temperatures that impacted the ability for LaSalle's thermal discharges to meet the requirements of its NPDES permit. Exelon reported no fish kills or other events to the IEPA or the NRC that would indicate adverse environmental effects resulting from the provisional variance. The details of this provisional variance are described in Section 3.5.1.3 of the LaSalle FSEIS.

Under the proposed action, Exelon would remain subject to these Federal and State regulatory controls. The NRC staff finds it reasonable to assume that Exelon's continued compliance with, and the State's continued enforcement of, the Illinois Administrative Code and the LaSalle NPDES permit would ensure that Illinois River water and ecological resources are protected. Further, the proposed action would not alter the types or amount of effluents being discharged to the river as blowdown. Therefore, the NRC staff does not expect any significant impacts to water resources or ecological resources within and along the Illinois River as a result of the proposed action.

With respect to federally listed species, the NRC staff considered federally listed species and designated critical habitats protected under the Endangered Species Act (ESA) during its license renewal environmental review for LaSalle. Based on its review of aquatic surveys conducted in the cooling pond and Illinois River both upstream and downstream of LaSalle, the NRC staff found that no federally listed species had the potential to occur in areas that would be directly or indirectly affected by license renewal (i.e., the action area). The NRC staff also confirmed that no designated critical habitats occurred in the action area. Accordingly, the NRC staff concluded that continued operation of LaSalle during the license renewal term would have no effect on federally listed species or designated critical habitats.

As previously described, impacts of the proposed action would be confined to the cooling pond and would not affect water resources or ecological resources along and within the Illinois River. The NRC staff's previous ESA section 7 review determined that no federally listed aquatic species or designated critical habitats occur within or near the cooling pond. The NRC staff has not identified any information indicating the presence of federally listed species in the area since that consultation concluded, and the U.S. Fish and Wildlife Service (FWS) has not listed any new aquatic species that may occur in the area since that time. The proposed action would not result in any disturbance or other impacts to terrestrial habitats, and thus, no federally listed terrestrial species would be affected. Accordingly, the NRC staff concludes that the proposed action would have no effect on federally listed species or designated critical habitats. Consultation with the FWS for the proposed action is not necessary because Federal agencies are not required to consult with the FWS if the agency determines that an action will have no effect on listed species or critical habitat.

The NRC staff has identified no foreseeable land use, visual resource, noise, or waste management impacts given that the proposed action would not result in any physical changes to LaSalle facilities or equipment or changes to any land uses on or off site. The NRC staff has identified no air quality impacts given that the proposed action would not result in air emissions beyond what would be experienced during current operations. Additionally, there would be no socioeconomic, environmental justice, or historic and cultural resource impacts associated with the proposed action since no physical changes would occur beyond the site boundaries and any impacts would be limited to the cooling pond.

Based on the foregoing analysis, the NRC staff concludes that the proposed action would have no significant environmental impacts.

Environmental Impacts of the Alternatives to the Proposed Action

As an alternative to the proposed action, the NRC staff considered the denial of the proposed action (i.e., the “no-action” alternative). Denial of the license amendment request would result in no changes to the current TS. Thus, under the no-action alternative, the licensee would continue to be required to verify that the cooling water temperature supplied to the plant from the CSCS pond is within the limits of the current TS Figure 3.7.3-1 and that the absolute sediment level in the intake flume and CSCS pond is ≤1.5 ft (18 in. or 0.5 m). If these conditions are not met, the licensee would be required to begin shutdown of LaSalle. The no-action alternative would result in no change in current environmental conditions or impacts at LaSalle. Denial of the LAR, however, could result in reduced operational flexibility and could require Exelon to derate or shutdown LaSalle if the UHS temperature approaches or exceeds the current TS temperature limit. Shutdown of operations at LaSalle due to an inability to meet current UHS temperature limit could result in various impacts, including loss of the energy and economic benefits that arise from plant operation.

Alternative Use of Resources

There are no unresolved conflicts concerning alternative uses of available resources under the proposed action.

Agencies and Persons Consulted

No additional agencies or persons were consulted regarding the environmental impact of the proposed action. However, in accordance with 10 CFR 50.91(b), the licensee provided copies of its application to the State of Illinois.

III. Finding of No Significant Impact

The NRC is considering issuing amendments for Renewed Facility Operating License Nos. NPF-11 and NPF-18, issued to Exelon for operation of LaSalle that would revise the TS for the plant to allow for an average, rather than absolute, UHS sediment level and would modify the UHS temperature curve to increase the allowable TS diurnal temperature limits of the cooling water supplied to the plant from the UHS.

Based on the EA included in Section II in this notice and incorporated by reference in this finding, the NRC staff concludes that the proposed action would not have significant effects on the quality of the human environment. The NRC staff's evaluation considered information provided in the licensee's application as well as the NRC staff's independent review of other relevant environmental documents. Section IV in this notice lists the environmental documents related to the proposed action and includes information on the availability of these documents. Based on its finding, the NRC staff has decided not to prepare an environmental impact statement for the proposed action.

This FONSI and other related environmental documents are accessible online in the ADAMS Public Documents collection at https://www.nrc.gov/reading-rm/adams.html. Persons who do not have access to ADAMS or who encounter problems in accessing the documents located in ADAMS should contact the NRC's PDR reference staff by telephone at 1-800-397-4209 or 301-415-4737, or by email to pdr.resource@nrc.gov.

IV. Availability of Documents

The documents identified in the following table are available to interested persons in ADAMS, as indicated.