u.s. nrc's program for keeping nuclear power plant offsite doses

RETS/REMP* NRC’s Program for Keeping Nuclear Power Plant Offsite

Doses As Low As Reasonably Achievable (ALARA)*Radiological Effluent Technical Specifications / Radiological Environmental Monitoring Program

Steven Schaffer, Ph.D. Office of Nuclear Regulatory Research

April 18, 2011

Objectives• Provide summary of regulatory framework• Describe the nuclear power plant programs

for:• Measuring radiological effluent releases • Forecasting public doses to the maximally exposed

individual near the plant• Measuring resultant radioactivity around the plant

• Identify useful references and data• Show the strengths and limitations of data

generated from these programs by using examples (breakout session)

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Some Nuclear Facts

• 104 commercial nuclear power reactors at 65 sites

• 69 Pressurized Water Reactors (PWR)

• 35 Boiling Water Reactors (BWR)

• Operate in 31 States• 4 different reactor

vendors• 26 operating companies• Supply ~ 20 percent of

the electricity in the U.S.

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PWR

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BWR

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Sources of Radiation

Radiation occurs naturally in the soil, air and water. Theaverage dose to people in the U.S. is about 620 millirem

(6.2 mSv) of radiation a year. Half of that exposure comes from natural sources (also called background radiation). The other half largely comes from nuclear

medical exams and treatments. Small amounts of radioactive material are also used in common items

such as smoke detectors, exitsigns and some watches.

Average Dose

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Dose Considerations• Pathways, receptors,

and source terms• 620 mrem/yr background• 3 mrem/yr liquid

objective• 5 mrem/yr gaseous

objective• Typically <1 mrem/yr

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Regulatory Framework

• All NRC radiation protection regulations stem from 10 CFR Part 20, “Standards for Protection Against Radiation”

• 10 CFR Part 50, “Domestic Licensing of Production and Utilization Facilities”, includes the implementation requirements for nuclear power reactors to comply with Part 20

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Salient Requirements of 10 CFR Part 20 • Public dose limits (Subpart D)

• 100 mrem/year total effective dose equivalent per reactor (1 mSv/yr)

• A total of 25 mrem/yr whole body, 75 mrem/yr thyroid, and 25 mrem/yr to critical organ from all fuel cycle facilities within 50 mile radius (EPA, 40 CFR 190)

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Salient Requirements of 10 CFR Part 20 cont. • Public exposures must be kept ALARA• Releases must be monitored to

demonstrate compliance• Release must be monitored to evaluate:

magnitude and extent, concentration and quantity, and potential radiological hazards

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Salient Requirements of 10 CFR Part 50

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• 10 CFR 50.34a – Effluent releases must be controlled

• 10 CFR 50.36a – Licensees must have an effluent release program to keep annual releases ALARA and report results

• Appendix A – General Design Criteria (GDC)– GDC 60, Each plant must have a means to

control liquid and gaseous effluent releases– GDC 64, Each plant must monitor effluent

discharge paths and plant environs for radioactivity

Salient Requirements of 10 CFR Part 50 cont.

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• Appendix I – ALARA Numerical Dose Objectives + cost-benefit analysis– Liquid pathways

• 3 mrem/yr, total body• 10 mrem/yr, critical organ

– Gaseous pathways• 5 mrem/yr, total body (noble gases)• 15 mrem/yr, critical organ (iodine and particulate

radionuclides)– Validation between RETS & REMP

Effluent Releases

• Required to monitor and report annual radiological effluent releases– Gaseous, liquid, and abnormal releases– Curies/year by radionuclide and summary role-up– Annual report for every plant

• back to year ~ 2000 in ADAMS• Prior to 2000 - reports in microfiche• NUREG/CR- 2907 14 volumes up to 1993• http://www.nrc.gov/reactors/operating/ops-

experience/tritium/plant-info.html– Electronic database on Web

• http://www.reirs.com/effluent/• 2001 – 2007 for all plants

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Public Doses• Required to calculate and report annual radiological

dose commitments to the maximally exposed individual– Calculation methods based on Regulatory Guide (RG) 1.109 and

described in each Offsite Dose Calculation Manual (ODCM)– Maximally Exposed Individual (MEI)

• Hypothetical or actual individual receiving maximum dose from site- specific exposure pathways—some use real-time met data

• Total body and critical organ (ICRP-2) for maximum age group• Age groups assessed: infant, child, teen, adult• No collective dose calculations required; few reported

– Annual report for every plant (contained in effluent report) • back to year ~ 2000 in ADAMS• Prior to 2000 - reports in microfiche• http://www.nrc.gov/reactors/operating/ops-experience/tritium/plant-

info.html– Electronic database on Web

• http://www.reirs.com/effluent/• 2001 – 2007 for all plants

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Environmental MeasurementsRequired to measure and report annual radiological levels

offsite• Radiological Environmental Monitoring Program (REMP) based on the

guidance in RG s 4.1 & 4.15, and NUREGs -1301 (PWR) & 1302 (BWR)– Typical REMPs consist of:

• Measurements of background and impacted areas– Direct exposure monitoring in every compass sector

» thermoluminscent dosimeter– Airborne iodine and particulate radionuclides focused towards areas of

prevailing winds and critical populations– Radionuclides in receiving water body– Radionuclides in site-specific food chain media

– Annual report for every plant (contained in environmental report) • back to year ~ 2000 in ADAMS• Prior to 2000 - reports in microfiche

– No electronic database available

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Reactor Oversight Process• Public Radiation Safety Cornerstone

– measures the procedures and systems designed to minimize radioactive releases from a nuclear plant during normal operations and to keep those releases within federal limits

• Each plant inspected biennially

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Quality Assurance

• Licensee follows effluent and environmental monitoring guidance in RG 4.15 & 1.21– inter-laboratory comparison– computational checks– data validation– audits– annual land-use census

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Quality Assurance

• NRC inspection procedures (71124.05, 71124.06, and 71124.07) – planning and program reviews– groundwater protection initiatives– procedures and reporting– walk-down of systems– dose calculations– inter-laboratory comparison results– land-use census

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RETS/REMP ReferencesThree most useful references for each reactor

location:1. Annual Radioactive Effluent Release Report

– Various plant-specific titles– Recent effluent release and dose data on web

2. Annual Radiological Environmental Operating /Monitoring Report

– Various plant-specific titles– More recent reports on-line

3. Offsite Dose Calculation Manual (ODCM)– Details of monitoring methods and dose calculations

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RETS/REMP References cont.

Regulatory Guides1. Regulatory Guide 1.21 - Measuring, Evaluating, and Reporting Radioactivity in Solid

Wastes and Releases of Radioactive Materials in Liquid and Gaseous Effluents from Light-Water-Cooled Nuclear Power Plants.

2. Regulatory Guide 1.109 - Calculation of Annual Doses to Man from Routine Releases of Reactor Effluents for the Purpose of Evaluating Compliance with 10 CFR Part 50, Appendix I.

3. Regulatory Guide 1.111 - Methods for Estimating Atmospheric Transport and Dispersion of Gaseous Effluents in Routine Releases from Light-Water-Cooled Reactors, Rev. 1, draft for comment, July 1977.

4. Regulatory Guide 1.113 - Estimating Aquatic Dispersion of Effluents from Accidental and Routine Reactor Releases for the Purpose of Implementing Appendix I.

5. Regulatory Guide 4.1- Programs for Monitoring Radioactivity in the Environs of Nuclear Power Plants.

6. Regulatory Guide 4.15 - Quality Assurance for Radiological Monitoring Programs (Normal Operations) - Effluent Streams and the Environment, Rev. 1.

7. Regulatory Guide 4.2 – Preparation of Environmental Reports for Nuclear Power Stations.

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RETS/REMP References cont.Supporting Documents1. NUREG-0133 - Preparation of Radiological Effluent

Technical Specifications for Nuclear Power Plants2. NUREG-1301 - Offsite Dose Calculation Manual

Guidance: Standard Radiological Effluent Controls for Pressurized Water Reactors

3. NUREG-1302 - Offsite Dose Calculation Manual Guidance: Standard Radiological Effluent Controls for Boiling Water Reactors

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Breakout Session

Site specific example

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Gaseous Effluent Data

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Nuclides Released Unit

Continuous Mode Batch ModeQ1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

Fission gasesAr-41 Ci ND 1.17E+00 ND ND 5.72E-02 5.31E-02 6.05E-02 6.26E-02Kr-85 Ci ND ND NR NR 1.28E+00 ND NR NRXe-133 Ci ND 5.07E+00 ND 3.89E+00 1.03E-02 4.02E-03 5.87E-03 2.16E-01Xe-135 Ci ND 2.34E-01 ND ND 4.12E-04 ND ND 2.01E-05Total for Period 6.47E+00 3.89E+00 1.35E+00 5.71E-02 6.64E-02 2.79E-01

IodinesI-131 Ci 1.24E-06 ND 3.68E-06 1.83E-06 ND ND ND NDI-133 Ci NR NR 4.24E-05 9.42E-06 NR NR ND NDTotal for Period 1.24E-06 4.61E-05 1.13E-05

ParticulatesBe-7 Ci 2.51E-06 ND 1.59E-06 ND ND ND ND NDCo-60 Ci NR NR ND 1.14E-06 NR NR ND NDSr-89 Ci 7.99E-08 2.14E-07 2.05E-07 1.73E-07 ND ND ND NDTotal for Period 2.59E-06 2.14E-07 1.80E-06 1.31E-06

TritiumH-3 Ci 1.66E+01 4.53E+01 5.82E+01 3.61E+01 2.10E-02 6.01E-03 1.38E-02 3.29E-02

Liquid Effluent DataNuclides Released Unit

Continuous Mode Batch ModeQ1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

Fission and activation productsCo-57 Ci ND ND ND ND 2.46E-06 1.57E-06 ND 1.48E-06Co-58 Ci ND ND ND ND 1.72E-03 7.60E-04 5.09E-07 2.00E-04Co-60 Ci ND ND ND ND 1.47E-02 6.64E-03 5.11E-03 3.71E-03Cr-51 Ci ND ND ND ND 1.30E-04 1.85E-04 ND NDCs-134 Ci ND ND ND ND 3.53E-04 1.05E-05 7.90E-05 NDCs-137 Ci ND ND ND ND 5.23E-04 4.90E-05 2.01E-04 2.76E-06Fe-55 Ci ND ND ND ND 1.46E-02 5.72E-03 9.87E-03 3.02E-03Fe-59 Ci ND ND ND ND ND 1.71E-05 3.74E-06 NDMn-54 Ci ND ND ND ND 8.78E-04 3.32E-04 3.55E-04 3.53E-04Nb-95 Ci ND ND ND ND 2.19E-04 3.05E-05 ND 4.52E-05Nb-97 Ci ND ND ND ND 9.12E-05 1.92E-05 2.16E-05 NDSr-89 Ci ND ND ND ND 3.24E-05 3.24E-05 ND 5.88E-06Sr-90 Ci ND ND ND ND 4.59E-05 ND ND NDZr-95 Ci ND ND ND ND 5.78E-05 ND ND NDTotal for Period 4.16E-02 1.63E-02 1.71E-02 9.87E-03

TritiumH-3 Ci ND ND ND ND 2.46E-06 1.57E-06 1.69E+02 9.68E+01

Total for Period 2.46E-06 1.57E-06 1.69E+02 9.68E+01

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Site-Specific MEI

• Dose from liquid effluent– MEI obtains all dietary fish from fishing in the

local river adjacent to the plant– MEI obtains all drinking water from closest

downstream public supply using local water– MEI is an adult

– Other sites it could be other age groups

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Site-Specific MEI (cont.)

• Dose from gaseous effluent– Total body dose

• Only from submersion in a noble gas cloud at the site boundary

• Assume ground level release– Organ dose

• Exposure from iodine and particulate radionuclides• Individual lives at the maximum off-site location• Exposure pathways include inhalation, ground plane,

cow meat and garden vegetable ingestion• Assume ground level releases• Child maximum exposure age

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Annual MEI Dose Data Liquid Releases example

Liquid Releases

Quarterly Objective

Maximum Dose

Yearly Objective

Annual Dose % of LimitPathway Unit Q1 Q2 Q3 Q4

Bone mrem 5.00E+00 3.79E-04 3.00E-03 1.43E-03 2.00E-03 1.00E+01 6.82E-03 6.82E-02

GI-LLI mrem 5.00E+00 4.49E-03 1.03E-03 3.50E-03 2.95E-03 1.00E+01 1.20E-02 1.20E-01

Kidney mrem 5.00E+00 4.17E-03 2.03E-03 3.49E-03 3.41E-03 1.00E+01 1.31E-02 1.31E-01

Liver mrem 5.00E+00 4.00E-03 4.86E-03 4.76E-03 5.27E-03 1.00E+01 1.89E-02 1.89E-01

Lung mrem 5.00E+00 6.26E-03 2.62E-03 6.37E-03 7.33E-03 1.00E+01 2.26E-02 2.26E-01

Thyroid mrem 5.00E+00 3.66E-03 6.11E-04 2.87E-03 2.46E-03 1.00E+01 9.60E-03 9.60E-02

Total Body mrem 1.50E+00 3.86E-03 3.46E-03 4.11E-03 4.36E-03 3.00E+00 1.58E-02 5.26E-01

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Annual MEI Dose Data Gaseous Releases example

Airborne Releases

Quarterly Objective

Maximum Dose

Yearly Objective

Annual Dose % of LimitPathway Unit Q1 Q2 Q3 Q4

Beta mrad 1.00E+01 7.64E-06 2.60E-06 2.61E-06 3.27E-06 2.00E+01 1.61E-05 8.06E-05

Bone mrem 7.50E+00 5.86E-08 9.10E-08 1.03E-09 5.66E-15 1.50E+01 1.51E-07 1.00E-06

Gamma mrad 5.00E+00 2.16E-05 7.30E-06 7.29E-06 9.00E-06 1.00E+01 4.52E-05 4.52E-04

GI-LLI mrem 7.50E+00 1.59E-04 1.55E-04 5.28E-05 2.63E-05 1.50E+01 3.93E-04 2.62E-03

Kidney mrem 7.50E+00 1.59E-04 1.55E-04 5.28E-05 2.63E-05 1.50E+01 3.93E-04 2.62E-03

Liver mrem 7.50E+00 1.59E-04 1.55E-04 5.28E-05 2.63E-05 1.50E+01 3.93E-04 2.62E-03

Lung mrem 7.50E+00 1.59E-04 1.55E-04 5.28E-05 2.63E-05 1.50E+01 3.93E-04 2.62E-03

Thyroid mrem 7.50E+00 1.59E-04 1.55E-04 5.28E-05 2.63E-05 1.50E+01 3.93E-04 2.62E-03

Total Body mrem 7.50E+00 1.59E-04 1.55E-04 5.28E-05 2.63E-05 1.50E+01 3.93E-04 2.62E-03

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Example REMP

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Example REMP (cont.)

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Example REMP (cont.)

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Example REMP (cont.)

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Example REMP (cont.)

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Example REMP (cont.)

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Example Results - Air

• No manmade radionuclides detected since the 1980s or the Chernobyl incident– Fukushima ? - TBD

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Example Results - Direct Radiation • Control (background)

standard deviation = 2.2 mrem per quarter

• is 140x > annual liquid pathway total body dose

• is 5600x > annual gaseous pathway total body dose to the MEI

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Example Results – Water

• Annual H-3 releases have increased since 1996 due to power up-rate—still below objectives and limits

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Example Results – Sediment

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Note that preoperational concentrations show that the indicator location is higher than control

Example Results - Fish

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Preoperational concentrations higher than all operational years except 1999

Example Results – Vegetation

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Only measurements above MDC are at control locations

MEI Dose Summary

• Gaseous effluent – 0.0004 mrem/yr• Liquid effluent – 0.016 mrem/yr

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Usefulness of RETS/REMP Data• Environmental measurement data

represent very good characterizations of background radiation from direct exposure sources

• Demonstrates compliance with the ALARA objectives and dose limits

• REMP validates RETS program

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Usefulness of RETS/REMP Data cont.• Data limitations

– Site-specific dose estimates are for a hypothetical individual and represent a conservative upper bound. Typical exposures are less

– Dose estimates from power plant effluents are well within the variability of site-specific background radiation

– Environmental monitoring data confirm that radioactivity from nuclear power plant effluents is extremely low and difficult to distinguish from background radiation

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