Are Canada's nuclear power plants ready in case of disaster?

Are Canada's nuclear power plants ready in case of disaster?

Postby Oscar » Sun Jul 19, 2015 5:48 pm

Are Canada's nuclear power plants ready in case of disaster? (Article is below . . . )

BACKGROUND:

From: Gordon Edwards
Sent: Sunday, July 19, 2015 4:36 PM

Background: July 19, 2015

It is becoming increasingly clear that the Canadian nuclear establishment is turning a blind eye to serious unresolved safety issues. If uncorrected, these defects will affect adversely affect the behaviour of Ontario's CANDU reactors under severe accident conditions, likely leading to far greater radioactivity releases than those currently anticipated.

According to testimony given at the recent Bruce licensing hearings by a nuclear engineer well-versed in CANDU technology, Sunil Nijhawan, there are about forty serious safety problems that are unacknowledged by OPG experts or by CNSC staff.

Example: Hydrogen Gas Explosions

One particular problem has to do with the generation of explosive hydrogen gas if there is a loss of regular cooling and emergency cooling to the reactor core. Even if the reactor is totally shut down, the intense radioactivity in the irradiated fuel will drive the temperature upwards beyond 1000 degrees C in the absence of cooling.

At such temperatures, the hot steam (H2O) reacts very rapidly with zirconium metal (Zr) to produce zirconium oxide (ZrO) and hydrogen gas (H2). Since all nuclear power reactors use zirconium metal as a "cladding" for the uranium fuel, there is a rapid buildup of hydrogen gas mixed with radioactive gases and vapours from the damaged fuel (because the cladding is shot).

Many readers will recall the three violent explosions that occurred at the Fukushima Dai-ichi nuclear reactors in 2011, blowing the outer shells of three of the six nuclear reactors to kingdom come, and releasing radioactive gases and vapours into the atmosphere. If such violent explosions were to occur in an Ontario CANDU reactor, causing similar damage to the outer containment structures, the radioactive releases offsite will be considerably greater than those from Fukushima because of the fact that the CANDUs do not possess an inner pressure-resistant containment structure such as the Fukushima reactors had.

Accordingly, CANDU reactors have "hydrogen gas recombiners" inside the reactor buildings. These devices are supposed to reduce the explosion potential by recombining hydrogen gas (H2) with oxygen gas (O2) to produce non-explosive water (H2O). If these devices work as intended, the explosion potential should be averted and the reactor structure should be safe.

But CANDU reactors have far more zirconium in the core of the reactor than other reactor types, so the hydrogen gas generation will be correspondingly greater. Not only is the fuel cladding made of zirconium metal, but also the hundreds of pressure tubes and the thousands of fuel bundles inside the core. The pressure tubes are connected to "feeder pipes" made of carbon steel, and at high temperatures there is even more hydrogen gas generated by the oxidation of the carbon steel feeders than there is by oxidization of the zirconium metal in the core.

Mr. Nijhawan has performed these calculations and has demonstrated that Canada's nuclear experts have not provided adequate protection against the enormous quantity of hydrogen gas that can be generated under severe accident conditions -- a situation far worse than that at Fukushima. The existing hydrogen recombiners are not only inadequate to the task, but they become so hot in the course of operation that they may well provide the spark that will trigger the very hydrogen gas explosion that they are supposed to prevent.

Such a situation must never be allowed to develop, because there is no adequate recovery strategy after such a massive explosion. Mr. Nijhawan has pointed out the need for more and larger hydrogen recombiners, much better positioning of the recombiners to prevent the accumulation of hydrogen gas near the roof of the plant, and a reliable external cooling system to prevent the recombiners themselves from overheating.

So far, Ontario Power Generation (OPG) and the Canadian Nuclear Safety Commission (CNSC) has refused to take these concerns into account. They stubbornly insist that they have done enough to make the plant safe and will go no further.

This is only one item in a list of dozens of other equally serious safety concerns that Mr. Nijhawan has identified. Instead of treating him as a welcome contributor, the industry seems determined to ignore his concerns because, in their opinion, the reactors are already safe enough and need not be made any safer.

Gordon Edwards, President
Canadian Coalition for Nuclear Responsibility
http://www.ccnr.org

= = = = = =

Are Canada's nuclear power plants ready in case of disaster?

[ http://www.thestar.com/news/canada/2015 ... aster.html ]

Meltdown at Fukushima forced nuclear facilities across the country to review their fail-safe measures, but the modifications being put in place might still be inadequate.

By Kevin Bissett, Canadian Press via Toronto Star, Jul 18 2015 [ http://tinyurl.com/qzep4se ]

The meltdown of three nuclear reactors at the Fukushima facility in Japan following an earthquake and tsunami in 2011 should be a warning to power plant operators that "new, more extreme weather events" must be a part of their disaster-mitigation capabilities. PHOTO

FREDERICTON - More than four years after an earthquake and tsunami triggered a meltdown of three nuclear reactors in Japan, [ http://www.thestar.com/news/world/2011/ ... hreat.html ] lessons learned are still being put into place at nuclear power plants in Canada.

But one critic is questioning whether the industry and the Canadian Nuclear Safety Commission [ http://nuclearsafety.gc.ca/eng/ ] have gone far enough in preparing for potential disasters, particularly in light of climate change.

Shawn-Patrick Stensil, a nuclear industry observer with Greenpeace, [ http://www.greenpeace.org/international ... s/nuclear/ ] said that, while the technical changes mandated by the commission are good, there also needs to be a new mindset in the nuclear industry after what happened at the Fukushima Dai-ichi facility.

Using a recent licence-renewal hearing for the Bruce nuclear plants in Ontario as an example, he said discussions on tornado strengths were inadequate and more severe weather must be considered as a result of climate change.

"Fukushima should be a warning that we should be looking at these new, more extreme weather events in the risk assessments of all plants globally, and we haven't done that yet," Stensil added.

MORE:

[ http://www.thestar.com/news/canada/2015 ... aster.html ]
Oscar
Site Admin
 
Posts: 9079
Joined: Wed May 03, 2006 3:23 pm

Return to Uranium/Nuclear/Waste

Who is online

Users browsing this forum: No registered users and 6 guests

cron