Market Need - Nuclear Waste Storage:

Overall Market Summary:

In 1998, The Office of Civilian Radioactive Waste Management of the U.S. Department Of Energy (DOE) estimated that over the next 100 years, a total of $20.6 billion, will be spent on development and evaluation, licensing, pre-emplacement construction, emplacement operations, monitoring, and closure and decommissioning of the permanent waste disposal site.

Proposed designs for storing nuclear waste, involve burying steel canisters containing spent fuel 300 m below the earth’s surface. Premature corrosion of these canisters presents the largest threat to the success of this proposed storage design. ElectraWatch CHM technology could be used to effectively measure the corrosive state of the storage containers to ensure safe storage of the nuclear waste. Each year $42.2 million is spent on detecting and repairing corrosion damage to these buried steel canisters. Employing ElectraWatch CHM technology could help significantly reduce this cost while improving overall safety.

CHM Application Example:

Many of the coating systems inside reactor containment facilities are over 30 years old. The most common means of inspection is visual inspection performed in accordance with ASTM D5163. Flaking paint is a concern due to the clogging of drains that could impede recirculation of coolant in the event of a Design Basis Accidents (DBA). A better inspection tool is needed in order to predict incipient coating failure so that paint touchup and repairs can be undertaken during normal plant shutdowns. This would enhance the safety posture of the facility.

The containment facility consists of a steel vessel, steel structural components, a concrete deck and concrete internal structures with a total surface area of about 350,000 square feet. Most of the facilities were built in the 1970’s and are 30-35 years old. The steel vessel is a ¼ inch thick sheet inside a concrete containment that is 3 to 4 feet thick. The steel is attached to the concrete with studs. A common coating system is a zinc-rich primer with an epoxy topcoat. The internal steel structures consist of beams and columns and a large crane that are coated with either an epoxy or zinc-rich primer with an epoxy topcoat A typical concrete deck is approx. 8 inches thick on top of a metal surface and is reinforced with #6 uncoated rebar about 1.5 inches deep. The deck is subject to mechanical abrasion and impact due to falling tools. The concrete internal structural walls range in thickness from 8 inches to over 4 feet and would be much more heavily reinforced. Concrete surfaces are often covered with a thin concrete curing compound during construction. A concrete surface up to 120 mils is then applied in some facilities. Then a final coat of a 6 mil epoxy topcoat is applied.

The worst coating problems are found on the steel substrates, where it is believed that there were quality assurance problems with the original coating application. The failure mode is called zinc splitting, in which the topcoat delaminates from the primer. The containment vessel has a normal temperature of about 110 degrees Fahrenheit, a humidity of 80 to 90 percent and a radiation level of 100mrem per hour during reactor operation. The operating profile of the typical electrical utility commercial reactor is 18 months of generating followed by 3 to 4 weeks of refueling and maintenance. The coating was qualified to receive a lifetime dose of 100 million Rad over 40 years and then survive a DBA where temperature peaks at 270 degrees Fahrenheit and the pressure peaks at 40 to 50 psig in one second. ANSI Standard N101.2 describes the method for the original qualifying tests. The original coating systems are no longer available, as they have high levels of volatile organic compounds (VOCs). The coatings used for touch up are low in VOC. Some of The current coating systems used are Amerlok 400, Carboline 801, or Carboguard 890.

A Coating Health Monitor (CHM) using Electrochemical Impedance Spectroscopy (EIS) was developed by ElectraWatch, Inc. as a deliverable from a Small Business Innovative Research (SBIR) program. EIS measures the coating impedance at three discrete frequencies (0.2, 0.5 and 0.9 Hz). A good coating has an impedance of 109 ohms. A degraded coating has an impedance of 107 ohms and a coating that will imminently fail has an impedance of 105 ohms. A portable EIS device has been designed and prototyped to accurately measure the level of coating degradation of the coating systems inside reactor containment facilities.