Review of recent Canadian Standard on Controlled releases N288.1 By: T.J. Stocki G. Latouche Sept...

Review of recent Canadian Standard on Controlled releases N288.1

By: T.J. StockiG. LatoucheSept 15, 2009

Radiation Protection Bureau / Bureau de la radioprotection

Outline:

• Brief overview of CSA N288.1:• Guidelines for calculating Derived Release Limits

(DRL) for radioactive material in airborne and liquid effluents for normal operation of nuclear facilities.


N288.1 Technical Committee (TC)

• J. Ryan CANDU Owners Group Inc.,

Toronto, Ontario• R. Stepaniak AMEC NCL Canada Ltd.,

Tiverton, Ontario• P. Davis Atomic Energy of Canada Limited,

Chalk River, Ontario• A. Antoniazzi Kinectrics Inc.,

Toronto, Ontario• I. Benovich Ontario Power Generation Inc.,

Pickering, Ontario• T. Brown Bruce Power,

Tiverton, Ontario• H. Carisse Cameco Corporation,

Port Hope, Ontario• D. Chambers SENES Consultants Limited, Richmond Hill, Ontario• R. DeCaire MDS Nordion, A Division of MDS (Canada) Inc.,

Ottawa, Ontario• N. Garisto SENES Consultants Limited,

Richmond Hill, Ontario

•M. Grey Canadian Radiation Protection Association, Toronto, Ontario•M. Hamlat Canadian Nuclear Safety Commission, Ottawa, Ontario•D. Hart EcoMetrix Incorporated, Mississauga, Ontario•T. Jarv Kinectrics Inc., Toronto, Ontario•J. Lafortune International Safety Research, Ottawa, Ontario•F. Lemay International Safety Research,•J. McCulley NB Power Nuclear Corporation, Fredericton, New Brunswick•T.J. Stocki Health Canada, Ottawa, Ontario•P. Thompson Canadian Nuclear Safety Commission, Ottawa, Ontario•A. Trudel TRIUMF, Vancouver, British Columbia•D. Villeneuve Hydro-Québec Production, Trois-Rivières, Québec•L. Pelan Canadian Standards Association, Mississauga, Ontario•S. Wang Canadian Standards Association, Mississauga, Ontario

Special Acknowledgement: Ed Cooper who passed away during this work.


N288.1 Technical SubCommittee (TSC)• P. Davis Atomic Energy of Canada Limited,

Chalk River, Ontario• I. Benovich Ontario Power Generation Inc.,

Pickering, Ontario• T. Brown Bruce Power,

Tiverton, Ontario• N. Garisto SENES Consultants Limited,

Richmond Hill, Ontario• M. Hamlat Canadian Nuclear Safety Commission,

Ottawa, Ontario• D. Hart EcoMetrix Incorporated,

Mississauga, Ontario• J. McCulley NB Power Nuclear Corporation,

Fredericton, New Brunswick• T.J. Stocki Health Canada,

Ottawa, Ontario• A. Trudel TRIUMF,

Vancouver, British Columbia• L. Pelan Canadian Standards Association,

Mississauga, Ontario

•S. Wang Canadian Standards Association,Mississauga, Ontario

Valuable contributions also from:

•M. Audet Atomic Energy of Canada Limited,Chalk River, Ontario•L. Hillier MDS Nordion, A Division of MDS (Canada) Inc.,Ottawa, Ontario•M. Lupien Hydro-Québec Production,Trois-Rivières, Québec•T. Yankovich Atomic Energy of Canada


Derived Release Limit (DRL)

• DRL for a given radionuclide is release rate that would cause an individual of the most highly exposed group to receive and be committed to an annual dose equal to the regulatory annual dose limit.

• This could be from a release to air or surface water during NORMAL OPERATION of a nuclear facility.

• Uses an Environmental transfer model.


Environmental Transfer Model.


How the DRL is calculated.• DRL calculated independently for air and

water. E.g. for air:

• X9/X0 ≡ dose per unit release.


DRLs


Parameters

• The standard contains tables and tables and Tables (110 pages!) of transfer coefficients and some nominal values for some location types.

• There are also example calculations in the back:• Tritium & 137Cs released to the air.

• 14C & 131I released to the water.


Sources of parameters. (Annexes)• Annex A (Default values of transfer factors) is a set of pre-calculated parameter values for those

who will not be using a computer program to calculate from scratch. Each table follows the equations in the main body of the standard and lists its assumptions in the footnotes to the table.

Either there are references to the source of data in the footnotes or to a clause in the Standard, and then either the clause provides the source of data or the corresponding CDG section has a reference to the source of the data.

• Annex B is an example calculation using Annex A tables - no source data• Annex C (Dose Coefficients) identifies where the tables are taken from (ICRP 72, Eckerman and

Leggett, OPG study, and a few other minor references).• Annex D (Limiting radionuclides for mixed effluents) is a very abbreviated form of CDG Appendix

D - see CDG for more references.• Annex E (1/2 lives and decay constants of Radionuclides used in the Standard) says it’s form

ICRP 72• Annex F (Hydrologic and aquatic transfer models) has various references• Annex G (Parameter Values for Terrestrial pathways ) has references, but CDG is more

comprehensive (Data for intakes are from an old HC 1972 survey, but are going to be updated to new data which is from a more recent survey).

• Annex H (The finite cloud and immersion dose) has references (ref's for the 2 figures are likely in CDG) Kocher 1981 could be updated in future volume.

• CDG = Candu Owners Group DRL Guidance.


Radionuclides considered in Standard.• 3H, 7Be, 13N, 14C, 22,24Na, 32P, 35S, 36Cl, 41Ar, 46,47Sc,

51Cr, 54Mn, 55,59Fe, 58,60Co, 63Ni, 65Zn, 75Se, 76As, 82Br, 83m,85,85m,87,88Kr, 88Rb, 89,90Sr, 90,91Y, 94Nb, 99Mo, 99,99mTc, 103,106Ru, 103m,106Rh,110mAg, 113Sn, 113mIn, 122,124,125Sb, 125m,132Te, 125,129,131,132,133,134,135I, 125,131m,133,133m,135,135m,138Xe, 134,135,136,137,138Cs, 137m,140Ba, 140La, 141,143, 144Ce, 143, 144Pr, 147Pm, 152, 154,155Eu, 153,159Gd, 160Tb, 175,181Hf, 203Hg, 218Po, 220,222Rn, 225,226,228Ra, 225,228Ac, 228,229,230,231,234Th, 231,233, 234mPa, 232,

233,234,235,237,238U, 237, 239Np, 238, 239, 240, 241, 242Pu, 241,

243Am, and 242, 244Cm.


What types of facilities does N288.1 cover?• Old N288.1 applied primarily to CANDU

nuclear reactors in Canada. (still the focus)

• The environmental pathways make the new N288.1 applicable also to:• Research reactors

• Radioisotopes processing facilities

• Waste processing facilities (incinerators)

• Reactor types other than CANDUs.


Canada and its power reactors.


What doesn’t N288.1 cover?

• It does not cover releases from:• Uranium mine tailings

• Permanent geological disposal facilities.

• Other facilities where extensive modelling of ground water pathways is needed.

• But it can be adapted to cover parts of these such facilities.


National Organization

• Canadian Nuclear Safety Commission (CNSC) regulates the nuclear industry (nuclear energy & substances)• Regulatory control is achieved through a rigorous licensing system.

• Health Canada plays a key role in protecting all Canadians from the risk of radiation exposure. • HC gathers info on radiation exposure and sets guidelines to

protect the public.• HC provides assistance on environmental assessments.

• Natural Resources Canada (NRCan) provides information and advice on nuclear energy policy.• Provides policy advice to ensure mining is done in a sustainable &

environmentally safe manner.


National Organization.

• Atomic Energy of Canada Ltd (AECL) builds CANDU reactors. • Normally supplies medical isotopes to the world.

• Dept. of Foreign Affairs & International Trade oversees relations with IAEA. • Deals with various treaties (NPT, CTBT, etc)

• Other departments..


Industry.

• AECL builds reactors.

• MS Nordion produces medical isotopes.

• Mining.

• We have various research reactors, two large ones and a few “slow poke”.

• We have ~20 of power reactors in Canada.


Representative person

• N288.1 uses the “representative person” • “an individual who receives a dose that is

representative of the more highly exposed individuals in the population”.

• It is equivalent to, and replaces, the average member of the critical group as per ICRP 101.

• The representative person, who is almost always a hypothetical construct is used for determining compliance with dose constraints.


Example of Limits Setup for radioactive releases at a Canadian NPP• Internal Investigation Level

(IIL) are placed in that case at the high end of normal releases (97.5 percentile)

• DRLs, AL and IIL will be different from site to site

Ref: Environmental Action Levels for Bruce Powers, June 25, 2008


Example for a four reactor plant. Releases DRL AL

Air TBq/year Air TBq/year Air

HTO 4.29E+04 4.47E+03

Iodine 4.73E+00 4.94E-01

Noble Gas 3.92E+04 4.11E+03

Radioactive Particulates 2.39E+00 2.50E-01

C-14 1.80E+03 1.87E+02

Liquid TBq/year Water TBq/year Water

HTO 4.30E+06 4.20E+05

Gross Beta Gamma 7.10E+01 6.84E+00

C-14 9.72E+02 9.36E+01

Note: ILL is an internal number for the facility to use.


Regulatory limit values.(Action Levels)• The DRL is calculated and an action level is set at a

small fraction of that value (usually 10% of the DRLs at

Nuclear Power Plant). • If an action level is reached, it may indicate a loss of

control of part of a licensee’s environmental protection program & triggers a requirement for specific action (reported to CNSC).

• Action levels are an early warning system to allow the licensee to take action before the public dose limits are exceeded.


Administrative levels or Internal Investigation Level• Administrative levels or Internal Investigation Level

are based on operational experience and are lower than the Action level.

• Administrative levels or Internal Investigation Levels provide an internal warning of anomalies in monitoring data.

• They are specific to discharge points

• Exceedance of an Administrative level or Internal Investigation Level triggers an appropriate level of review and possibly action.

LatoucheG

Should not mention any specific Licensee. You Should mention only that Administrative Level or Internal Investigation level are lower than the Action Level


Specific questions:

• Use a Environmental transfer model based on transfer coefficients.

• The standard gives default values for 3 or 4 regions in Canada, but the user can use site specific and is encouraged to do so.

• Gaussian plume is used, if needed.


Specific questions: Atmospheric Transport• Uses a Gaussian plume model based on

sector averaged model (Pasquill & Smith 1962)

• Takes into account vertical dispersion and building wake effects.

• Also uses a semi-infinite cloud model or a finite cloud model for air immersion.


Conclusion.

• Gave you a brief explanation of the standard.


Questions?

• Thanks for listening!

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