Atomic Insights

Atomic energy technology, politics, and perceptions from a nuclear energy insider who served as a US nuclear submarine engineer officer

Atomic Insights June 1996

In the News June 1996

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Power Cutoffs Ordered in Northeast

(May 22, 1996) – Unusually hot weather forced several electric utilities in the Northeast United States to cut power to customers who had agreed to power interruptions in return for lower rates and to reduce voltage by 5 to 8 percent in order to protect reserve margins.

Affected utilities included Con Edison, PP&L, Northeast Utilities, Public Service Enterprise Group and the New England Power Pool.

The early season heat wave caught the utilities by surprise. Several large generating stations were off-line for planned maintenance. The situation was made worse by the recent forced idling of the Millstone nuclear plants after allegations of violations of license conditions in relation to refueling operations.

SMUD Cancels Energy Projects

(May 15, 1996) – The Sacramento Municipal Utility District announced the cancellation of a cogeneration project and a wind power project involving construction of 150 wind turbines. SMUD has filed a lawsuit with the developer of the cogeneration project.

The wind power project was cancelled after concerns surfaced regarding the reliability of the Kenetech Windpower 33 M wind turbines. Questions about the financial condition of the supplier also surfaced after a California Public Utilities Commission decision that some observers report cost the company as much as $500 million in new business.

SMUD has a history of strong support for alternative energy sources.

Iraq Agrees to UN Oil Deal

(May 20, 1996) – With its economy in tatters, Iraq finally agreed to the conditions imposed by the UN on the sale of $2 billion dollars worth of oil every six months. At current prices, reaching that sales level would require the production of approximately 600,000 barrels of oil per day.

Industry experts predict that it will take Iraq less than two months to reach this level of production for export, despite a continuing embargo on certain technical assistance.

There is some concern in oil markets that this additional supply will have a negative effect on world oil prices, but traders shrugged off the announcement of the deal and bid oil prices higher the next trading day. Some analysts report that the pending sale of Iraqi oil had already been figured into the market price.

PHWR Historical Problem Areas: Sources of Incidents

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The pressure tubes of a CANDU® are in a hostile environment that includes a high neutron flux, hot, high temperature water, and a certain amount of hydrogen and oxygen released by the decomposition of water by radiation.Though the CANDU® has proven itself to be a reliable, cost effective and safe power generation system, there are some known weaknesses considered to be class problems requiring corrective action.

In some cases, the solution has been improved materials, in others it has been increased monitoring and planned replacement before failure. Often a combination of the two techniques has been used. None of the problems are particularly unusual in a complex industrial machine.

Pressure Tubes

The pressure tubes of a CANDU are in a hostile environment that includes a high neutron flux, hot, high temperature water, and a certain amount of hydrogen and oxygen released by the decomposition of water by radiation.

It is not surprising that these tubes suffer degradation over time that has occasionally resulted in a tube breech. As a result of this known problem, the pressure tubes are normally scheduled for replacement at the mid-point of a CANDUs operating life. There has also been a large amount of research and development aimed at developing improved alloys. The Canadians have had to fully support the costs of this research, since the pressure tubes are unique to their reactor design.

Relief Valves

Like all high pressure fluid systems, CANDUs depend on pressure relief valves to protect the piping from excessive pressure. Because relief valves must, by nature, balance the need for sensitive response to inputs with the fact that a false alarm could cause a dramatic and dangerous loss of pressure, their design is a challenge.

For example, a failed relief valve was the root cause of the loss of primary coolant pressure and subsequent damage caused during the Three-Mile Island accident.

Although the consequences were far less severe due to better operator and system response, several relief valve problems combined to cause a significant loss of coolant incident at Unit 2 of the Pickering station in 1994.

Improvements have been made to prevent the same failures from recurring, however, relief valves remain an item that requires operator and maintenance action. This is a problem whose solution is sought by a huge number of other interested industries both inside and outside of the power generation field.

Steam Generators

The steam generators used for CANDU reactor plants are very similar to the U-tube design used in many pressurized water reactors. They require a good deal of care in construction and operation to allow them to withstand the difficult environment caused by boiling water, corrosion deposits and chemical attack.

So far, however, the operating record of the CANDU steam generators is better than that of many pressurized water generators. The need for replacement before the end of the design life has been rare.

Letter from the Editor: Reactors With a Can-Do Attitude

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Canada decided that it would be prudent to develop a reactor design that could operate on natural uranium. This decision was consciously aimed at making the Canadian nuclear industry independent of American political decision making.One of the highest compliments that you can pay to a submariner is to describe him as someone with a “can-do” […]

Some Reactors CANDU®: What Others Cannot

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CANDU® reactors are designed to operate with fuel that is composed of natural uranium dioxide formed into cylindrical pellets and inserted into zirconium alloy tubes. No enrichment is necessary. An understanding of some of the features of the CANDU® reactor design makes it obvious that many of the negative perceptions about nuclear power are, in […]