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CAC Meeting May 20, 2008 Transportation of Tritiated Heavy Water to Darlington.

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Presentation on theme: "CAC Meeting May 20, 2008 Transportation of Tritiated Heavy Water to Darlington."— Presentation transcript:

1 CAC Meeting May 20, 2008 Transportation of Tritiated Heavy Water to Darlington

2 Presentation Plan Issue raised by Community Working Group Why do we have tritium? Why is tritiated heavy water shipped to Darlington? How is tritiated heavy water shipped to Darlington? Have there ever been public exposures as a result of shipment? Issue resolution

3 Issue #122 Biophysical effects of tritiated water from Pickering NGS sent to the Darlington Tritium Removal Facility Why and how does PNGS ship tritiated water to Darlington Tritium Removal Facility (Darlington)? At any time during its shipment, are members of the public exposed to unsafe radiation levels?

4 Why do we use Heavy Water? Both the moderator system and the primary heat transport systems are filled with heavy water It is used to slow fast neutrons down It is used because the heavy hydrogen (deuterium) atoms in heavy water dont tend to absorb neutrons like light hydrogen atoms

5 Fission Process Begins Incoming thermal (slow) Neutron U-235 atom

6 To Fission or Not to Fission 82 % of the excited form of U-236 created by neutron absorption fissions quickly 18 % emit a gamma ray and remain as U-236 U-236 (excited after neutron absorption)

7 Fission Process Emitted Neutron Fission Product Emitted Neutron Emitted Neutron Gamma rays

8 Heavy water slows neutrons Incoming fast Neutron Heavy Water Molecule Deuterium atoms (hydrogen atom with 1 proton and 1 neutron in its nucleus) Oxygen atom Deflected slower Neutron

9 Tritium Formation Process Incoming Neutron Heavy Water Molecule Deuterium atoms (hydrogen atom with 1 proton and 1 neutron in its nucleus)

10 Tritiated Heavy Water Deuterium atom Tritium atom Half-life 12.3 yrs Oxygen atom

11 Why do we want to get rid of tritium? It is radioactive. In the form of tritiated heavy water it is taken into the body both through the skin and via respiration. It builds up in the moderator and heat transport systems with continued operation Workers are exposed to tritiated heavy water that escapes station systems Higher worker dose More protective equipment must be worn Public is exposed via air and waterborne emissions from the station

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13 Why do we ship it to Darlington Station? The Darlington tritium removal facility partially removes the tritium from tritiated heavy water Tritium gas produced there is stored in special containers De-tritiated Heavy Water is returned to Pickering for re-use

14 How do we ship it to Darlington Station? Inside specially designed transportation packages intended only for that usage Sealed Impact, fire and leak resistant The detritiated heavy water is returned using the same transport packages

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16 TDO Packages on Trailer

17 How do we know shipping is safe? The design is verified as meeting CNSC (IAEA) requirements Impact test to simulate a vehicular accident 9 metre drop onto a solid target onto its weakest point Fire test to simulate a post vehicular accident fire 30 Minutes in 800 Degree Centigrade fire Leakage test 8 hour immersion at 15 metre depth or equivalent All three tests conducted in series

18 TDO Package Cross-section Volume: 5000 L Weight Dry: 11,000 kg Filled: 16,300 kg Diameter: 2.4 m Height: 2.7 m

19 Has there ever been an unsafe exposure from transportation of tritiated heavy water to and from Darlington? No ! The TDO package is monitored before departure and on arrival to make sure all applicable limits have been met There has never been event that involved a release during transit

20 Issue #122 Biophysical effects of tritiated water from Pickering NGS sent to the Darlington Tritium Removal Facility Why and how does PNGS ship tritiated water to Darlington Tritium Removal Facility (Darlington)? At any time during its shipment, are members of the public exposed to unsafe radiation levels?

21 Suggested Disposition Category 1 No further action required, the issue has been dealt with to the extent required or the extent possible. or The issue is being managed satisfactorily and would be brought back to the CAC only if an unusual result or event arose calling into question the managed process for the issue.


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