UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001

July 10, 2006

NRC INFORMATION NOTICE 2006-13: GROUND-WATER CONTAMINATION DUE TO

UNDETECTED LEAKAGE OF RADIOACTIVE

WATER

ADDRESSEES

All holders of operating licenses for nuclear power and research and test reactors including

those who have permanently ceased operations and have certified that fuel has been

permanently removed from the reactor and those authorized by Title 10 of the Code of Federal

Regulations (10 CFR) Part 72 licenses to store spent fuel in water-filled structures.

PURPOSE

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform

addressees of the occurrence of radioactive contamination of ground water at multiple facilities

due to undetected leakage from facility structures, systems, or components that contain or

transport radioactive fluids. It is expected that recipients will review the information for

applicability to their facilities and consider actions, as appropriate, to avoid similar problems. 

However, suggestions contained in this IN are not NRC requirements; therefore, no specific

action or written response is required.

DESCRIPTION OF CIRCUMSTANCES

Radioactive contamination of ground water has occurred at multiple facilities due to undetected

leakage from facility structures, systems, or components that contain or transport radioactive

fluids. Specific instances that have occurred recently include the following:

Braidwood Nuclear Power Plant

In March 2005, the licensee was notified by the Illinois Environmental Protection Agency (EPA)

of tritium detected in a nearby residential well. Following that notification, the licensee began

monitoring ground water between the community and the Braidwood plant. The licensee found

detectable levels of tritium in a drainage ditch near the Braidwood access road, but at that time,

no other offsite contaminated ground water was found. Based on the tritium identified in the

drainage ditch, the licensee installed additional onsite monitoring wells to identify the source of

the tritium contamination.

In November 2005, the licensee identified peak contaminated ground water levels of

58,000 picocuries per liter (pCi/L) in shallow, ground-water monitoring wells located at the edge

of the owner controlled area. The licensee notified the NRC and immediately suspended all

further liquid radioactive releases. The tritium was attributed to historical leakage from vacuum

breakers along the circulating water system blowdown line that is routinely used for radioactive

liquid releases. 

ML060540038
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Although the Braidwood piping was below ground, the vacuum breaker valve vaults

communicate with the surface. Consequently, the leaks were both above and below ground. 

The licensee subsequently determined that onsite radioactive leakage from the blowdown

system had occurred in 1996 (250,000 gallons), in 1998 (3,000,000 gallons), and in 2000

(3,000,000 gallons). Onsite tritium levels measured in a deep onsite ground-water monitoring

well measured as high as 282,000 pCi/L. Offsite tritium levels measured up to 1,600 pCi/L in a

residential well, below the Federal EPA drinking water standard of 20,000 pCi/L. The licensee

characterized the extent and magnitude of the tritium ground-water contamination as an area

that extended about 2,000 feet by 2,500 feet outside the site boundary. The licensee’s

radiological assessment for the hypothetical, maximally exposed individual indicates that the

dose consequence would be about 0.16 millirem per year (i.e., about 5 percent of the “as low as

reasonably achievable” (ALARA) criteria for nuclear plant design objectives and limiting

conditions for operation).

The NRC inspection found that the licensee did not (1) adequately evaluate the radiological

hazards associated with the leakage; (2) calculate dose to member(s) of the public; (3) revise

its environmental monitoring program to adequately measure the impact to the environment; 

(4) report aspects of the leakage in its annual effluent report; and (5) record the residual

contamination in files for decommissioning purposes (NRC Inspection Reports Nos. 50-456;

457/2006-02, Agency Wide Documents Access and Management System (ADAMS) Accession

No. ML061360416, and 50-456; 457/2006-008, ADAMS Accession No. ML 061450522).

Byron Nuclear Power Plant

Following the identification of tritium leakage at Braidwood, the licensee initiated a sampling

and analysis program along the Byron circulating water system blowdown line. Similar to the

Braidwood facility, the Byron blowdown line has six vacuum breakers located in valve vaults

located on plant property. Standing water in the vaults was sampled and analyzed, with five of

the six vaults having detectable levels of tritium up to 80,000 pCi/L. The licensee suspended all

radioactive liquid effluent releases through the blowdown line. 

Residential wells were sampled and found not to have any detectable contamination. Additional

monitoring wells were installed near the valve vaults and detectable levels of tritium have been

found near two of the valve vaults. By April 2006, the licensee had completed repairs to the

vacuum breakers and vaults, including sealing the vault floors. After repairs were completed,

the licensee recommenced liquid effluent discharges through the circulating water system

blowdown line (NRC Preliminary Notifications Nos. PNO-III-06-004 and PNO-III-06-004B).

Dresden Nuclear Power Station

In August 2004, the licensee identified contaminated ground water in onsite monitoring wells

resulting from a leaking underground pipe connected to the condensate storage tanks. 

Subsequent, onsite sampling identified tritium levels consistent with those present in the

condensate storage tank of about 8,000,000 pCi/L. The licensee isolated the leaking pipe and

replaced the faulty section of piping. 

Following the 2004 leak, the licensee sampled the private wells of nearby residents. One of the

residents’ wells that had shown detectable tritium for a number of years had tritium levels of

approximately 1,000 pCi/L. 
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Additionally, three other residential wells were found to have measurable but lower levels of

tritium. The licensee continues to evaluate the tritium in those wells, one of which is the normal

sample point for its radiological environmental monitoring program. 

In February 2006, tritium levels of 600,000 pCi/L were detected in an onsite monitoring well

near a section of underground piping that had not been replaced in 2004. The leaking pipe was

isolated and onsite tritium levels in the two closest onsite wells subsequently stabilized at

20,000 - 50,000 pCi/L (NRC Inspection Report Nos. 50-237; 239/2006-03, ADAMS Accession

No. ML061290091).

Haddam Neck Station (Connecticut Yankee Atomic Power Plant)

The Haddam Neck Station ceased operations about 10 years ago and is being

decommissioned under an approved NRC license termination plan (LTP). The licensee’s

monitoring programs have not identified any offsite ground-water contamination associated with

plant operations. 

An onsite ground-water monitoring program has been established and is being implemented in

support of the decommissioning. The licensee initially identified tritium, cobalt-60, cesium-137

and strontium-90 in the onsite ground water and/or soil samples. The licensee has removed a

large amount of soil and some bedrock, and backfilled the excavated areas with clean soil. 

While the licensee has substantially reduced residual contamination levels, recent ground-water

sampling results have identified residual tritium up to 19,500 pCi/L, cesium-137 up to 12 pCi/L

and strontium-90 up to 4.5 pCi/L. The licensee has completed dose assessments for the

existing onsite ground-water contamination in accordance with the LTP. The dose

assessments indicate a dose contribution of less than 1 millirem per year due to the

ground-water contamination.

The NRC license termination requirement is that the all-pathways, total effective dose

equivalent to the average member of the critical group does not exceed the 10 CFR 20.1402

unrestricted release requirement of 25 millirem per year and the residual radioactivity has been

reduced to ALARA. This includes the soil exposure pathway, existing groundwater dose

contributions and future groundwater dose contributions. Additionally, the licensee must

comply with requirements by the State of Connecticut’s Department of Environmental

Protection to meet the Federal EPA Maximum Contaminant Levels. The most recent NRC

onsite inspection is documented in NRC Inspection Report No. 50-213/2005-03, ADAMS

Accession No. ML060390475.

Indian Point Nuclear Generating Station Units 1, 2, and 3

In September 2005, the licensee identified leakage of contaminated water from cracks in the

Unit 2 spent fuel pool (SFP), and subsequently discovered tritium contaminated ground water,

about 200,000 pCi/L, in a monitoring well located in the Unit 2 transformer yard. Upon

discovery of this condition, the licensee initiated extensive efforts to characterize the nature and

source of the ground-water contamination. Efforts included the installation of a series of

instrumented monitoring wells, comprehensive hydrological and geophysical assessment of the

site, engineering efforts to determine the source of contamination, and enhancements to onsite

and offsite radiological environmental monitoring. Extensive efforts were also made by the

licensee and NRC to keep members of the public and interested local, state, and federal
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stakeholders informed of progress and developments in the site characterization, and plans to

effect resolution of the ground-water contamination. 

Onsite ground-water tritium concentrations have been measured as high as about

600,000 pCi/L in the immediate vicinity of the Unit 2 SFP. Strontium-90 contamination has also

been identified in ground water in the vicinity of the Unit 1 decommissioned facility which has

been in SAFSTOR since 1974. The current hydrological assessment indicates that ground

water is likely migrating into the Hudson River. A conservative radiological assessment for the

maximally exposed individual indicates that the dose consequence would be about 0.01 millirem

per year (i.e., about 0.1 percent of ALARA criteria for nuclear plant design objectives and

limiting conditions for operation).

NRC Inspection Report 50-247/2005-11, dated March 16, 2006 (ADAMS Accession No.

ML060750842), documented the results of an NRC special inspection that was conducted to

review and assess the events and circumstances in this case. While the inspection reached

important safety conclusions, significant licensee performance deficiencies were not identified. 

However, NRC inspection activities are continuing to review the licensee efforts and progress to

support a final regulatory conclusion.

BACKGROUND

NRC requirements related to the radioactive liquid effluents include: 

10 CFR 20.1301(a)(1) - requires that each licensee conduct operations so that the total

effective dose equivalent to individual members of the public from the licensed operation does

not exceed 100 millirem (1 mSv) in a year.

10 CFR 20.1302 - requires licensees to perform appropriate surveys in unrestricted areas and

controlled areas to demonstrate compliance with dose limits for individual members of the

public.

10 CFR 20.1501 - requires, in part, that licensees conduct surveys that are reasonable under

the circumstances to evaluate the concentrations or quantities of radioactive material and the

potential radiological hazards.

10 CFR Part 50, Appendix I, Section II.A - establishes the design objectives and limiting

conditions for operation to meet ALARA criteria such that the calculated annual total quantity of

all radioactive material above background released to unrestricted areas will not result in an

estimated annual dose or dose commitment from liquid effluents in excess of 3 millirems to the

total body or 10 millirems to any organ. 

10 CFR Part 50, Appendix A, Criterion 64 - requires, in part, that a means be provided for

monitoring effluent discharge paths, and the plant environs for radioactivity that may be

released from normal operations. To meet this regulation, licensees implement a Radiological

Environmental Monitoring Program (REMP) which provides for ground-water monitoring. 

However, the REMP program is designed to validate the results of the licensee’s normal

radioactive gaseous and liquid effluent release programs for dose assessment in the

Unrestricted Area. Consequently, the data from the REMP program may not provide a full

understanding of the extent, types, and movement of potentially undetected radioactive

contamination in onsite ground water within the Restricted Area. NRC Regulatory Issue
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Summary 2002-02, “Lessons Learned Related to Recently Submitted Decommissioning Plans

and License Termination Plans,” dated January 16, 2002, provides additional information in this

regard (ADAMS Accession No. ML013510432).

10 CFR 50.75(g)(1) - requires, in part, that each licensee keep a record of spills or other

unusual occurrences involving the spread of contamination in and around the facility or site. 

These records must include any known information on identification of involved nuclides,

quantities, forms, and concentrations. Such documentation in a decommissioning record file is

important to provide a database for site characterization during decommissioning, as well as,

providing support for public and worker dose assessments. NUREG-1757, “Consolidated

[Office of Nuclear Material Safety and Safeguards] NMSS Decommissioning Guidance,”

provides guidance on decommissioning record keeping (ADAMS Accession No.

ML032530410).

10 CFR 50.72 - requires a four-hour report to NRC Operations Center when any event or

situation occurs, related to protection of the environment, for which a news release or

notification to other government agencies has been or will be made.

Related Generic Communications

NRC Information Notice 2004-05, “Spent Fuel Pool Leakage to Onsite Ground Water,” dated

March 3, 2004, (ADAMS Accession No. ML040580454) discussed SFP leakage at Salem

Station Unit 1 to the onsite ground water, including potential impact to the public and workers,

and the structural integrity of the SFP. The NRC noted that leaks can develop in SFPs and go

undetected for long periods of time absent appropriate monitoring, resulting in the

contamination of onsite ground water and the potential for undetected, unevaluated releases of

radioactivity to an unrestricted area.

DISCUSSION

NRC reviews to-date have identified the following important points associated with

ground-water contamination events: 

1. Leakage from structures, systems, or components that contain and transport radioactive

fluids can contribute, over long periods of time, to extensive ground-water

contamination. This leakage may not be easily detectable due to small leakage rates or

because the area near the point of leakage is not subject to routine radiological

monitoring. Leakage from underground piping at Braidwood released substantial

quantities of contaminated water to onsite ground water. Representative sampling and

analysis of onsite ground water may be the only viable method to detect this leakage

and the subsequent migration of the contamination, particularly for subsurface leakage

(e.g., buried pipe leakage).

2. Existing NRC regulations do not explicitly mandate routine onsite ground-water

monitoring in the Restricted Area during facility operations. If the contamination is

detected by environmental monitoring at or beyond the site boundary under the REMP,

extensive contamination may have already occurred that could have been contained if

detected sooner. Further, although licensees may be sampling onsite drinking water as
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part of its REMP, this water may originate from deeper hydro-geologic units not affected

by contamination of the shallow water table hydro-geologic unit.

3. The identification of onsite contamination may serve as an early indicator of degradation

of onsite structures, systems, or components or the need for maintenance, particularly

degradation caused by boric acid. 

4. The principal screening method of detecting leakage at reactor sites is sampling and

analyses for tritium contamination. However, other analysis methods can detect

radioactive gamma emitters, and consideration should be given to performing analyses

for typical hard-to-detect radionuclides. These nuclides can consist of both fission or

activation products that may include Nickel-63, Iron-55, Strontium-90, transuranics, and

others. While initial analyses may conclude the absence of gamma emitters and hardto-detect radionuclides, long-term migration may subsequently result in the transport of

contamination to downstream locations. Further, a working knowledge and

understanding of onsite hydrology would aid development of monitoring strategies,

sampling plans, and selection of individual sampling locations. 

 

5. Licensees typically establish onsite ground-water monitoring and sampling programs in

response to known, identified structure, system, or component leakage. Once the

source of the leakage is repaired, it is important to objectively evaluate whether it is

appropriate to terminate these supplemental onsite monitoring and sampling programs,

as the onsite monitoring and sampling programs may be the only reliable method for

detecting repeat occurrences in a timely manner, particularly for subsurface leakage. In

the case of the Dresden facility, the onsite ground-water monitoring wells that had been

installed for previous leakage incidents were instrumental in identifying the 2006

leakage, which enabled a more timely identification and limited the extent of the

contamination.

6. SFP leak detection may require special techniques since SFPs have an evaporation rate

up to several hundred gallons per day. This evaporation rate may mask small leaks in

the SFP liner and make small leakage rates difficult to detect by evaluation of make-up

rates within a water balance calculation. Consequently, licensees who are not closely

evaluating the potential for leakage, including through-wall and/or floor leakage, may not

detect such leakage. Further, the leakage may be from SFP fuel transfer tubes and

may only occur during refueling outages. Because there is considerable water transfer

activity during refueling outages, small leakage rates may not be readily apparent during

make-up or transfer operations. Other considerations include:

• Licensee experience with onsite and offsite ground-water contamination as a

result of SFP leakage varies significantly. Some licensees have identified large

areas of onsite ground-water contamination due to SFP leakage. It is important

to be aware that small, long-term, undetected leaks from SFPs can result in

extensive areas of contamination. 

• Due to the difficulty in detecting single small leaks or small leaks from different

locations, particularly those that occur over long time periods, corrective actions

may involve management of leakage (e.g., collection and treatment) rather than

leak repair.

• Some licensees have not evaluated the capability of their SFP leak detection

systems to detect small leaks. Leakage trending and tracking programs can
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supplement leakage detection systems and provide an indication of changes in

apparent leakage rates. Any unexplained change in leakage rates, including a

reduction in leakage rates, should prompt further evaluation.

• Clogging of SFP telltale drain systems could result in undetected SFP leakage. 

Maintenance and cleaning programs for SFP telltale drain systems ensure viable

drain paths remain open. Alternate methods to look for leakage are available for

facilities without SFP telltale drain systems. 

7. Leakage from facility structures to the environment can itself become a source of

contaminated in-leakage (back into the facility) at another location. Because stations

have facilities and rooms below grade level, it is not uncommon for ground water to leak

into the facilities. It is important to evaluate unexpected in-leakage to determine if it is

contaminated ground water using radio-analytical and chemical analysis (e.g., boron).

8. Radioactive contamination of subsurface rock, soil, or ground-water contamination can

impact decommissioning decisions. Remediation at the time of discovery in some

instances could prevent significant migration to large subsurface areas that could

complicate and increase the cost of decommissioning. Hydrogeology studies and the

addition of onsite monitoring wells should be considered to identify ground-water flow

patterns, support knowledge of the location and extent of contamination, to quantify

contaminant migration, and to support decision-making for potential remediation

measures. These studies can also support an estimation of future decommissioning

costs. 

9. NRC’s inspection program identified that there is an apparent wide variation in licensee

knowledge in the requirement to document the ground-water contamination issues

consistent with all parts of 10 CFR 50.75(g)(1) for the decommissioning record file. 

Such documentation is important to provide a database for site characterization during

decommissioning, as well as, providing support for public and worker dose

assessments. 

CONCLUSION

Although NRC regulations require licensees to make surveys, as necessary, to evaluate the

potential hazard of radioactive material released in order to assess doses to members of the

public and workers, the above examples indicate that undetected leakage to ground water from

facility structures, systems, or components can occur; resulting in unmonitored and unassessed

exposure pathways to members of the public.

GENERIC IMPLICATIONS

This information notice provides a timely means of communicating to licensee senior

management information regarding ground-water contamination. To address this important

issue, NRC is actively pursuing rulemaking to revise 10 CFR 20.1406, “minimization of

contamination,” and its supporting guidance, as well as changes to NRC inspection and

enforcement guidance. These ongoing NRC efforts are part of the NRC’s Integrated

Decommissioning Improvements Plan (ADAMS Accession No. ML050890059) to resolve issues

described in SECY-03-0069, “Results of the License Termination Rule Analysis” and its staff
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requirements (ADAMS Accession Nos. ML030840302 and ML033210595). A publically

available NRC memorandum dated September 23, 2005, provides the results of an initial NRC

study of ground-water contamination at decommissioning sites (ADAMS Accession No.

ML052630421).

CONTACT

This information notice requires no specific action or written response. If there are any

questions about this notice, contact one of the persons listed below or the appropriate project

manager in the Office of Nuclear Reactor Regulation (NRR) or Office of Nuclear Material Safety

and Safeguards.

/RA/ /RA/

Charles L. Miller, Director Ho K. Nieh, Acting Director

Division of Industrial and Medical Nuclear Safety Division of Policy and Rulemaking

Office of Nuclear Material Safety Office of Nuclear Reactor Regulation

 and Safeguards

Technical Contacts: 

Timothy Frye, NRR Marvin Mendonca, NRR

301-415-9676 301-415-2191

E-mail: tjf@nrc.gov E-mail: mmm@nrc.gov

John White , RI James Shepherd, NMSS

610-337-5114 301-415-6712

E-mail: jrw1@nrc.gov E-mail: jcs2@nrc.gov

Steve Orth, RIII Thomas Nicholson, RES

630-829-9827 301-415-6268

E-mail: sko@nrc.gov E-mail: tjn@nrc.gov

Ronald Nimitz, RI

610-337-5267

E-mail: rln@nrc.gov