Vice-President & Chief Science Officer
Canadian Nuclear Safety Commission
Nov 5, 2019
University to Working in Nuclear Fuel (0:27)
(0:27-10:47) Peter describes his first job in the nuclear field.
Q. How did you first come to join the nuclear field?
A. (0:27) Peter is the Vice President and Chief Science Officer at the Canadian Nuclear Safety
Commission. Peter didn’t join the nuclear field entirely by accident. While at the University of
Toronto he took nuclear engineering courses. He then got a master’s degree in High Materials
Ceramics and learned that nuclear field is a high temperature ceramic. His first job out of
college was at Chuck River Laboratories. There he was able to use his background in physics
and material while dealing with higher temperature fuel behavior and fission power release.
Q. You were dealing mostly with ceramic uranium oxide?
A. (2:38) Peter looks into how these particles move and if they are soluble in the uranium. The
materials operate depending on the temperature of the fuel. In light water reactor fuel, the
centerline temperature is a little lower and the particles sit where they go. But in CANDU fuel,
the centerline fuel is slightly higher at 1,500-1,600 degrees, just enough for particles to migrate
out of the pellet and go into the gap between the pellet and the sheath.
Q. So atom sized bubbles find each other to great bigger ones? Or do they migrate out?
A. (4:47) Peter says they probably all migrate, similar to iodines. In CANDU fuels, because of
the changes and letting the particles back in, the fuel was developing a lot of small defects in
the sheath during operation. This was happening because some of the iodine was going into the
sheath causing stress cracking. The solution: a thin layer of carbon that acts as an iodine
scavenger. Because of fission in nuclear fuel, there are a lot of complex processes happening.
The actual composition of the fuel changes with time. The fuel starts with uranium oxide, but
with enough time you can produce plutonium and the fuel changes structure. Some of the fuel’s
behavior changes with time as well. Peter explains that the nuclear field is always working to
protect the public from iodines, that can affect thyroids. One of the most common safety
additions after Fukushima was to add passive metallic filters to catch iodines and cesium.
(10:57-40:45) Peter explains methods of safety precautions at nuclear sites from a regulatory
Q. Why are nuclear safety measures not more focused on metallic filters?
A. (10:57) From a nuclear safety perspective, Peter says there are three things that need to be
done in a nuclear reactor: 1) Control - make sure you’ve stopped the nuclear reaction in the
reactor; 2) Cool the reactor - if you don’t cool it, the entire core can melt down; 3) Containment -
keeping isotopes of iodine and cesium in mind. You always want to stop each process as early
as you can in failure. Peter explains that you want to build a robust system step by step, starting
from the beginning. Every barrier, no matter how well built, has deficiencies and in an accident,
it’s better to prepare and try to prevent as many different types of potential risks as possible.
Q. Why aren’t all reactors build underground?
A. (25:50) As a safety regulator, Peter doesn’t know what the business economics reason why
reactors aren’t built below-grade, but from a safety and security perspective it looks better.
Underground the reactor is harder to get at and removed from numerous human induced
external hazards. As a regulator, it’s important to look into design plans and point out areas for
Q. What about issues you know you can’t possibly anticipate?
A. (30:00) Peter points out that even ‘unpredictable’ events often had circumstances leading up
to them that were predictable hazards. Such as was the case with Davis-Besse. The steam leak
leading to acid was predictable due to acid leaks all over the plant. That’s why external
processes such as regulation, and regular maintenance, are so important.
Nuclear Spent Fuel
(40:50-52:48) Peter explains nuclear waste issues and public perceptions in Canada.
Q. What’s the current state of nuclear waste in Canada?
A. (40:50) There has been scientific consensus for the last 20 to 30 years that a deep geological
repository is the solution to nuclear waste.
Q. Why doesn’t dilution work with nuclear waste?
A. (41:48) Peter explains that there’s an ongoing debate about nuclear waste, asking if it is
indeed ‘waste.’ Some countries believe that spent fuel isn’t necessarily waste. But Peter agrees
with the scientists that the best way to mimic nature is to isolate the waste for a very long time.
However, the difficulties with creating repositories are often due to failure to communicate with
the public that it is a scientifically sound solution and would be monitored.
Q. Can you describe why nuclear waste poses a hazard to human health?
A. (43:48) Cesium - a very mobile particle, has high energy gamma ray and can be harmful in
small doses - is the concern for the first 500 years. Peter believes you can never fully rely on
dilution as a safety method in the nuclear field.
Q. Here’s an example, people are worried about mercury in fish. But if we replace nuclear with
alternative power sources, it would lead to a fraction of the mercury found in the ocean.
A. (48:57) Peter says that even when most scientists agree on something, getting a public
consensus on that same topic is difficult, such as repositories. Peter thinks other, more extreme
measures of waste containment, would be nearly impossible to get the public to accept.
Safety and Security and the Future of Nuclear
(52:53-1:00:20) Peter offers suggestions for improvements on the regulatory side of nuclear and
his thoughts on the future of the industry.
Q. What do you think regulators could do to improve?
A. (52:53) Peter thinks that there needs to be a better connection between nuclear safety and
security. There are some schools of thought that safety and security are all part of the same
thing, or two sides of a coin. A security threat is inherently a safety issue and vice versa. For
example, a valve needs to be replaced - a safety issue. But the new valve arrives and comes
with WIFI. Right there you’ve got a security issue. You need to be thinking about all of these
pieces as part of a larger whole, not splitting into a safety team and a security team.
Q. Are there digital controls in Canada?
A. (55:48) The Canadian nuclear industry originally proposed a digital control during the 1989s,
when Darlington was being built. As time went on, the industry became more and more
comfortable with digital controllers. In places where there isn’t this long history of familiarity,
regulators have to ask themselves ‘is this a risk or is this just a risk I’m not familiar with.’ Peter
always explains to his staff that there’s always the risk of the new, you also need to compare it
to the risk of the current.
Q. What do you see in the future of nuclear?
A. (1:00:28) Peter thinks the big nuclear reactors will undergo life-extension projects. He’s not
sure new plants will be built. He thinks instead demands for power will cause an increase in coal
and natural gas until public pressure outweighs the demand.