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Politics : Sioux Nation -- Ignore unavailable to you. Want to Upgrade?

To: stockman_scott who wrote (205472)	3/13/2011 12:26:25 PM
From: Cogito Ergo Sum	2 Recommendations Read Replies (1) \| Respond to of 361355

Some interesting discussion here: Message 27232446 From: E. Charters 3/13/2011 10:36:50 AM Read Replies (1) of 74096 Japan's meltdown. The Three Mile Chernobyl effect. Pumps that don't work, no back up, bad design, it appears that Nippon should get out of Nuclear Reactor on the Fault Zone Roulette while it still doesn't glow in the dark. Reactors that are partially melted are not fixable. That means Fukusascreamie has to be concreted in and we say bye-bye for good. If they ever do build again it should be the kind where the cooling/promoter water dumps and it shuts down with scram immediately. Candu can du that in 1/100 of a second. Exposed core has no meaning in the Candu system, as when a crisis hits you drop heavy water, which is held up by compressed air when the reactor is running. Pumps can fail. If in a Candu the pumps fail, then the core shuts down (scrams) and dumps moderator. When the power fails the reactor dumps heavy water which is the moderator inducing neutrons, and there is auto shut. Power keeps the moderator in place, so if it fails the shutdown in immediate. Scram in all reactors must take place in 4 seconds of heat rise or a runaway takes place. Emergency pumps/pipes failing is classic. Same thing that happened at Three Mile Island. Chernobyl was a shut off sensor and a wrong headed action to reduce temperature. Due to the Chernobyl situation of shut off sensors there was no way to tell if the reactor core was overheating. No one has come up with a foolproof scram that cannot be blocked by a partially damaged core. If the reactor has overheated sufficiently, most times cadmium rods will not go in the tubes because of warpage and heat expansion. A better way is needed to shut down a runaway reactor. Fukushimwhatever did scram but a weakness in this system has been exposed. The emergency coolant pumps are still critical, and they were out of action. Cracked core? They are not saying. I think they should have a side-slotted reactor with guide slots for rods entering the core from the side, not back to front. If the rods were held in by control power and naturally swung out with weights, with cadmium rods swinging in the same way, it might guarantee a faster, more assured scram. Emergency cooling water would be held back by compressed air, and enter the reactor by gravity on power failure/switch. To cause circulation for up to 4 hours, a solid water tower would siphon water in flex lines into the core and back out, with emergency diesel pumps on line to take over when siphoning ran out. Flex lines into the core would allow pumping boric acid into the core if all else failed. Better yet, take the reactor off the fault line and above Tsunami level. Looks like 25,000 dead in the Tsunami/quake and perhaps 800 billion in damage. Kobe never recovered from the 95 quake and it hurt Japan's economy severely. This does not bode well. EC<:-} siliconinvestor.com To: E. Charters who wrote (74076) 3/13/2011 10:44:02 AM From: Land Shark Read Replies (1) \| Respond to of 74097 I believe the Japanese reactor is a GE design? Pretty lousy safety systems IMO. CANDU is infinitely superior there. Makes me proud to be Canadian. The Conservatives want to sell AECL to say GE or any taker. I say keep AECL in Canadian hands. siliconinvestor.com To: Land Shark who wrote (74077) 3/13/2011 10:53:29 AM From: E. Charters Read Replies (1) \| Respond to of 74098 The design features of the AECL reactor, the Candu are not properly understood by our administration. They were developed in Canada over a 50 year period and include sensor, generator, and other rebuilds of contractor stuff that the US reactor experts have never dealt with. Most features of the Candu, even other than the core design and deuterium moderation are unique. The engineers who designed much of the unique features, some 15,000 design components, were never paid except for salary. Now Canada wants to give away their brains and hard labour to people who will look at it like a caveman would look at an Accutron wristwatch. It is a safe bet that the Politicians do not understand that a group of money mavens in a second rate electric company stateside have no clue how to run a Candu or rebuild what goes into it. They get a bunch of dry and dusty plans and ignore all the important stuff. Generator bearing metallurgy and design is as important as core design. Another case of selling our birthright for a mess of pottage. Avro Arrow, Candu good bye. It was nice to know ye. Forgive them for they know not what they do. EC<:-}

To: stockman_scott who wrote (205472)	3/13/2011 1:25:32 PM
From: Cogito Ergo Sum	Read Replies (1) \| Respond to of 361355

More here To: E. Charters who wrote (74076) 3/13/2011 1:00:08 PM From: Land Shark of 74101 All CANDU shutdown systems don't rely on the availability of power: What are the CANDU safety systems? [A. CANDU Technology] [B. The Industry] [C. Cost/Benefit] [D. Safety/Liability] [E. Waste] [F. Security/Non-Proliferation] [G. Uranium] [H. Research Reactors] [I. Other R&D] [J. Further Info] The safety philosophy of CANDU reactors [1] is based upon the principle of "Defence-in-Depth", which includes redundancy (using at least two components or systems for a given function), diversity (using two physically or functionally different means for a given function), separation (using barriers and/or distance to separate components or systems for a given function), and protection (seismically and environmentally qualifying all safety systems, equipment, and structures, including tornado protection). This philosophy is applied throughout the plant design, from the Reactor Regulation System and Special Safety Systems, to the process control systems, and the electrical power supply (including independent, separated supplies of backup power supply). The philosophy is also embodied in the Secondary Control Area (SCA) of CANDU plants, which is a backup control room capable of independently shutting down and cooling the reactor, as well as monitoring plant status. The Reactor Regulation System (RRS) is part of a fully computerized control system that is also responsible for boiler pressure and level control, unit power regulation, primary heat-transport pressure and inventory, and turbine run-up. The RRS includes two identical, independent digital computers, each capable of complete station control. The two computers run simultaneously, one acting as instantaneous back-up to the other. The Special Safety Systems, on the other hand, perform no function in the normal operation of the plant, but exist to mitigate the consequences of a serious process failure. The Special Safety Systems are fully automated and take no credit for operator intervention, although they can be initiated manually if required. They consist of: Shutdown System 1 (SDS1), Shutdown System 2 (SDS2), Emergency Core Cooling System (ECCS), and Containment System. In keeping with the Defence-in-Depth philosophy, each system is independent of the others, employing its own sensors, logic, and actuators. Each system uses triplicated logic (three sensor circuits, with two-out-of-three voting), with the ability to be tested on-line. Shutdown System 1 uses solid shutoff rods, dropping by force of gravity into the core, and is capable of shutting down the reactor for the entire spectrum of postulated initiating events. Shutdown System 2 uses high-pressure liquid poison injected into the (low-pressure) moderator, and is also capable of shutting down the reactor for the entire spectrum of postulated initiating events. The Emergency Core Cooling System (ECCS) can maintain or re-establish core cooling by supplying coolant to all reactor headers. It consists of three phases: high-pressure water injection using pressurized nitrogen (used during the early stages of an event), medium pressure water supply from the containment building's dousing tank (used during the intermediate stages), and low-pressure water supply based on recovery from the building's sump. The Containment System forms a continuous, pressure-confining envelope around the reactor core and primary heat-transport system. In the CANDU 6 design it consists of a pre-stressed, post-tensioned concrete structure, an automatically-initiated dousing system, building coolers, and a filtered air discharge system. In Ontario Power Generation's multi-reactor designs (the Ontario utility formerly known as Ontario Hydro), containment includes a vacuum building connected to all reactor vaults in the plant, with its own dousing system for reducing internal pressure. The safety systems of each CANDU plant are designed to meet international standards of reliability, and are tested routinely to ensure compliance with these standards. Message 27232693