Radiation and Environmental Protection at the CNSC

Full text

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Radiation and Environmental

Protection at the CNSC

Patsy Thompson, Director General

Rachel Lane, Radiation and Health Sciences Specialist

Directorate of Environmental and

Radiation Protection and Assessment, Canadian Nuclear Safety Commission Toronto Public Health

Toronto, Ontario

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Content

Overview of CNSC and DERPA

Radiation protection overview

CNSC Tritium Studies Project

Tritium in Lake Ontario

Tritium releases to Lake Ontario

Tritium concentration trends in drinking water

supply plants

(3)

The Canadian Nuclear Safety

Commission

Regulates the use of

nuclear energy and

materials to protect the

health, safety

and

security

of Canadians

and the environment, and

to implement Canada’s

international

commitments

on the

peaceful use of nuclear

energy

(4)

CNSC Regulates All Nuclear-Related

Facilities and Activities

• Uranium fabricators and processing

• Nuclear power plants • Radioactive waste

management facilities

• Nuclear substance processing • Industrial and medical

applications

• Nuclear research and educational

• Export/import control • Mines and mills

(5)

Independent Commission

Quasi-judicial

administrative tribunal

Reports to Parliament

through Minister of

Natural Resources

Canada

Commission proceedings

are public and webcast

Decision can only be

reviewed by Federal

Court

(6)

Organizational Chart of CNSC

President

Commission Members

Legal Services Regulatory Operations Branch Technical Support Branch Regulatory Affairs Branch Corporate Services Branch Executive Advisor Office of Audit, Evaluation & Ethics Commission Secretariat

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CNSC Structure

The CNSC is a federal regulatory agency as well as an

Independent Administrative Tribunal set up at arm’s

length from government with no ties to the nuclear

industry

The Commission consists of up to 7 permanent

members appointed by the Governor in Council

Heading the Commission is the President, who is

designated by the Governor in Council as a permanent,

full-time member

The Commission, in the discharge of its work, is

supported by over 800 scientific, technical and

professional staff

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Director General

Administrative

Assistant Planning Officer

Lead Technical Advisor

Environmental Risk Assessment Division Environmental Assessment Division Environmental

Compliance & Laboratory Services Division Radiation Protection Division Radiation and Health Sciences Division

Directorate of Environmental and Radiation Protection and Assessment (DERPA)

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DERPA Mandate

• DERPA is the CNSC’s centre of excellence for environmental assessment, geosciences, radiation protection, environmental protection and laboratory services

• DERPA’s mission is to support the CNSC in its areas of professional and technical competence by:

– providing strategic direction and leadership

– contributing to the continuous improvement of CNSC’s regulatory framework

– conducting and supporting licensing and compliance activities

– conducting public outreach activities and providing opportunity for stakeholder engagement

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International Radiation Protection

Framework

The International Atomic Energy Agency (IAEA) works

towards the safe, secure and peaceful uses of nuclear

science and technology

The International Commission on Radiological Protection

(ICRP) is an advisory body providing recommendations

and guidance on radiation protection

The United Nations Scientific Committee on the Effects of

Atomic Radiation (UNSCEAR) assesses and reports on

the levels and effects of exposure to ionizing radiation

The CNSC reviews, participates in the development of,

and follows international recommendations

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Dose-response Models

• Many models have been

proposed to explain how risk varies with radiation dose

• The CNSC applies the linear-non-threshold (LNT) model in its approach to radiation

protection, as a prudent way to protect Canadians from radiation, keeping pace with its international peers

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Dose-response and Radiation Risk

• The LNT is based on information from the strongest

epidemiological studies of exposed populations (primarily the atomic bomb survivors)

• Accurate information on the health risks for atomic bomb survivors is only available at doses greater than ~100 mSv

– radiation biology studies are used to extrapolate risk down to a dose of 0 mSv

• International studies on large cohorts of nuclear energy workers and medically exposed populations generally support the radiation risk estimates from the atomic bomb survivor studies

(13)

CNSC Radiation Protection

Framework

• LNT model

– used for radiation protection purposes to help set dose limits based on predicted risks for a given dose

– should not be used to predict cancer risk for few individuals or for low dose exposures

Dose Limits (Radiation Protection Regulations) Members of the public 1 mSv per year

Nuclear energy workers 50 mSv per year and 100 mSv per five year dosimetry period

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Tritium Overview

• Tritium is a radioactive form of hydrogen that occurs naturally and is also a by-product of nuclear reactor and tritium processing facilities’ operations

• Tritium exposure can pose a health risk if it is ingested (drinking

water, food), inhaled or absorbed through the skin in large quantities • CNSC regulates releases of tritium to ensure the health and safety

of workers and the public, and the protection of the environment • Part of the CNSC’s mandate is to provide objective scientific,

technical and regulatory information to the public on nuclear-related health and safety

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CNSC Tritium Studies

• January 2007 the Commission directed CNSC staff to:

− initiate research studies on tritium releases in Canada

− study and evaluate tritium processing facilities against international practices

− following this request, CNSC staff launched several

research activities under the umbrella of the « Tritium Studies » project

− this study had the goal of enhancing the information available to guide regulatory oversight of tritium processing and tritium releases in

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CNSC Tritium Studies: Key Objectives

Assemble data on tritium releases in Canada

Investigate the fate of tritium releases to the atmosphere

Review engineering controls for facilities that produce or

handle tritium

Assess the health risk to workers and the public from

exposure to tritium

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Results

Adequate provision has been made through existing

regulatory mechanisms for the protection of health and safety

of Canadians related to tritium exposures

Effective controls are now uniformly in place in the Canadian

nuclear industry as a result of compliance enforcement

actions

Tritium management of routine operational releases is now

following best practices internationally

Releases are currently as low as reasonably achievable

(ALARA) and close to the minimum practically achievable

(19)

Results (cont’d)

Conservative regulatory approaches combined with strict

controls on releases are being used

Gaps do exist in tritium environmental science, but they

are not significant for people or the biosphere at current

low levels of exposure

− this has clearly been shown by a thorough assessment of the health risks of tritium

(20)

Publications

Seven CNSC public reports plus a Synthesis Report

- Journal article: Thompson et al. (2011), Radioprotection, 46(4):511-531.

1. Standards and Guidelines for Tritium in Drinking Water

2. Tritium Releases and Dose Consequences in Canada in 2006

3. Investigation of the Environmental Fate of Tritium in the Atmosphere

4. Evaluation of Facilities Handling Tritium

5. Health Effects, Dosimetry and Radiological Protection of Tritium

6. Tritium Activity in Garden Produce from Pembroke in 2007 and Dose to the Public

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Background Levels of Tritium in

Ontario Drinking Water

Location Q1 Q2 Q3 Q4

Bq/L ±2σ Bq/L ±2σ Bq/L ±2σ Bq/L ±2σ

Bancroft (Clarke Lake) <MDL <MDL <MDL No sample

Belleville (Bay of Quinte) 3.79 <MDL <MDL 3.52 2.20 No sample

Cobourg (Lake Ontario) 4.80 <MDL <MDL 5.44 2.313 No sample

Brockville (WSP) <MDL <MDL <MDL <MDL Burlington (WSP) <MDL 4.48 2.51 4.74 2.273 3.89 2.43 Goderich (WSP) <MDL <MDL 5.754 2.33 <MDL Kingston (WSP) <MDL <MDL 4.23 2.24 <MDL London (WSP) <MDL 5.34 2.58 3.84 2.22 <MDL Niagara Falls (WSP) <MDL <MDL 4.15 2.24 <MDL North Bay <MDL <MDL <MDL <MDL Orangeville <MDL <MDL <MDL <MDL Parry Sound <MDL <MDL 3.87 2.22 3.85 2.43 Sarnia <MDL 5.29 2.56 3.44 2.20 <MDL St. Catherines <MDL <MDL <MDL <MDL Sudbury <MDL <MDL <MDL <MDL Thunder Bay <MDL <MDL <MDL <MDL Windsor <MDL 4.08 2.50 <MDL <MDL

(22)

Annual Measured Tritium Concentrations from Drinking

Water Supply Plants Surrounding the Darlington and

Pickering NPPs

• Concentrations are significantly lower than Ontario DWQO • Annual averages vary from roughly 4-6 Bq/L

Annual Tritium Concentrations in from Drinking Water Supply Plants (Bq/L)

NPP Water Supply Plant 2008 2009 2010 2011 2012 O. DWQO

Darlington Bowmanville WSP 6.7 5 4.8 4.4 4.5 7000 Darlington Newcastle WSP 6.4 5 4.6 4.6 4.6 7000 Darlington Oshawa WSP 9.2 6.7 5.8 5.5 6.2 7000 Pickering Ajax WSP 7.1 6 5.5 5.8 4.4 7000 Pickering Scarborough F. J. Horgan WSP (Scarborough) 5.8 4.9 4.2 4.6 4.9 7000 Pickering Toronto R.C. Harris WSP (Toronto) 5.4 4.6 4.3 4.4 4.8 7000 Pickering Whitby WSP 8.2 6.2 5.4 5.7 5 7000

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Historical Tritium

For Lake Ontario

background from

“lake model”

is

1.6 Bq/L

(24)

Annual Tritium Releases to

Lake Ontario

Orders of magnitude lower than the derived release

limits

Decreasing trends have been observed since 2008

Annual Tritium Oxide Released to Lake Ontario (Bq/year)

NPP 2008 2009 2010 2011 2012 DRL

Darlington NPP 3.90E+14 1.90E+14 1.40E+14 1.10E+14 1.40E+14 5.3E+18

(25)

Health Effects, Dosimetry and

Radiological Protection of Tritium

The study’s objectives were to:

Conduct an independent review of scientific literature to

assess the health risks to workers and the public from

exposures to tritium

Assess Canadian and international dosimetry practices

for tritium intakes

Review the current approaches for limiting exposure to

tritium

(26)

Health Effects, Dosimetry and

Radiological Protection of Tritium

Tritium beta radiation is about 1.4 times more effective in

causing biological effects than x-rays and 2.2 times more

effective than gamma rays

The radiation weighting factor of 1 in the current ICRP

radiation protection framework has not decreased the

level of protection afforded to workers or members of the

public

– tritium exposures very low and well below doses at which an increased risk of cancer has been observed

(27)

Health Effects, Dosimetry and

Radiological Protection of Tritium

Current dosimetry and biokinetic models for assessing

dose are acceptable for radiation protection purposes

Studies have shown that tritium exposures at current

levels in Canada are highly unlikely to cause adverse

health effects

Canada’s current regulatory framework has effectively

controlled tritium exposures

(28)

Canadian Nuclear Energy Workers

• In 2005, a 15-country study of nuclear workers reported significantly increased radiation-related risks of all cancers excluding leukemia, with Canadian data a major factor behind the pooled results

• An earlier Canadian study, based on the same data, found very different results

• This apparent discrepancy in the results between the Canadian and the 15-country studies attracted considerable attention and

questions

• A review of the Canadian data and a reanalysis of the revised cohort helped to explain the unexpected findings and provided revised risk estimates

(29)

Canadian Nuclear Energy Workers

• There was no evidence of radiation risk for 42, 228 workers employed by the NPPs and post-1964 AECL workers

• A significant dose-response for solid cancer was identified with 3,088 early (1956–1964) AECL workers having a significant increase in risk

• There was no evidence of increased risk from tritium exposure

• All workers had mortality lower than the general population

• The significantly increased risks for early AECL workers are most likely due to the incomplete transfer of historical dose data to the National Dose

Registry (NDR)

• Further investigation of this group of early AECL workers is necessary to ensure accuracy and completeness of radiation dose records in the NDR

(30)

RADICON

Radiation and Incidence of Cancer Around Ontario

Nuclear Power Plants from 1990 to 2008 study (the

"RADICON" study)

Determine the radiation doses to members of the public

living within 25 km of the Pickering, Darlington and Bruce

NPPs from 1985 to 2008

Compare cancer rates among these populations with the

general Ontario population from 1990 to 2008

(31)

RADICON

• Public radiation doses resulting from the operation of the NPPs are 100 to 1,000 times lower than natural background radiation • No evidence of childhood leukemia clusters around the three

Ontario NPPs

• All cancers for all age groups are well within the natural variation of the disease in Ontario

• Thus, radiation is not a plausible explanation for any excess cancers observed within 25 km of any Ontario NPP

(32)

Recent Third Party Research

Leukemia in young children in the vicinity of British

nuclear power plants: a case-control study

(Bithell et al.,

2013)

A recent British case-control study found that young

children who were born or live near a NPP from 1962 to

2007 do not have a greater risk of developing childhood

leukemia or non-Hodgkin lymphoma

The results draw the same conclusions as those in the

RADICON Study

(33)

Recent Third Party Research

Estimating cancer risk in relation to tritium exposure from

routine operation of a nuclear-generating station in

Pickering, Ontario

(Wanigaratne

et al., 2013)

A recent study by Cancer Care Ontario found that tritium

was not associated with an increased risk of

radiation-sensitive cancers in Pickering, Ontario

It is important because it isolates tritium-specific dose

data

It increases our understanding of cancer risks and

low-level tritium exposure

(34)

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