MELTER NO. 1 HEATUP

UNDERSTANDING
THE STEPS
IN THE
MELTER HEATUP
PROCESS

Heatup of a melter in the Low-Activity Waste Facility consists of a series of activities to prepare for and establish a molten pool of glass inside the melter. It takes approximately 2 months to heat up one melter (approximately 22 days for the initial heatup, followed by several days of testing, followed by about 30 days of checkout).

Initial Heatup

Once the empty melter is heated to temperature using temporarily installed startup heaters, quantities of ground glass – called frit – are added until enough melted glass is present to cover the melter’s electrical heating electrodes.

Initial Heatup

 

Once the empty melter is heated to temperature using temporarily installed startup heaters, quantities of ground glass – called frit – are added until enough melted glass is present to cover the melter’s electrical heating electrodes.

Energizing the Melter

The normal melter power supplies are energized, flowing electricity through the glass pool to generate heat, like a toaster heating element, and the temporary heaters are removed.

Energizing the Melter

The normal melter power supplies are energized, flowing electricity through the glass pool to generate heat, like a toaster heating element, and the temporary heaters are removed.

Bubblers are Installed

Next, bubblers are installed to introduce air into the bottom of the melter glass pool to mix the glass.

Bubblers are Installed

Next, bubblers are installed to introduce air into the bottom of the melter glass pool to mix the glass.

More Glass Frit is Added

More glass frit is added to raise the pool to the normal operating level, and then the melter is ready to start receiving tank waste feed materials (non-hazardous simulant will be used during the testing phase).

More Glass Frit is Added

More glass frit is added to raise the pool to the normal operating level, and then the melter is ready to start receiving tank waste feed materials (non-hazardous simulant will be used during the testing phase).

Minimizing Risk

The first melter will be heated up, commissioned and verified operational before the second melter is heated and tuned. This two-phase process reduces risk and enables lessons learned from the first melter heatup to be incorporated into plans for heating up melter 2.

Minimizing Risk

The first melter will be heated up, commissioned and verified operational before the second melter is heated and tuned. This two-phase process reduces risk and enables lessons learned from the first melter heatup to be incorporated into plans for heating up melter 2.

Offgas Tuning and Testing

Upon heatup of the second melter, the melter and associated exhaust, known as offgas, and support systems will concurrently be verified operational.

Offgas Tuning and Testing

Upon heatup of the second melter, the melter and associated exhaust, known as offgas, and support systems will concurrently be verified operational.

Timing of Heatup

The melters are heated up during the commissioning phase to ensure all testing of systems feeding into and out of the melter, and the melters themselves, are verified ready to start. It also allows for the melters, which have a design life of about five years, to maximize the time expended in operations treating tank waste.

Timing of Heatup

The melters are heated up during the commissioning phase to ensure all testing of systems feeding into and out of the melter, and the melters themselves, are verified ready to start. It also allows for the melters, which have a design life of about five years, to maximize the time expended in operations treating tank waste.

MELTER HEATUP TERMINOLOGY

Cold cap

A floating mass of unmelted glass former/waste mixture during and shortly after feeding the melter. The cold cap is slowly incorporated into the glass pool. Two hours after stopping feed to the melter, the cold cap is considered fully incorporated.

Joule heating

Similar to how a toaster heating element works, heating of the glass pool by the flow of electrical current through the glass pool via electrodes on opposite ends of the pool.

Slurry

A mixture of solids and liquids forming a thick viscous mass. In the case of the LAW waste vitrification, slurry feed consists of glass forming mineral powders blended with radioactive liquid tank waste.

Frit

Ground glass, or startup material, for melters. It is a mixture of chemicals melted in a furnace, cooled to form glass, and fragmented or formed into a specified shape and particle size. Frit must be added to a certain level to ensure initiation of joule heating.

Glass formers

Chemicals, typically mineral powders including silica, which when blended and heated provide stable, resilient glass; 13 glass formers are used for LAW waste vitrification.

Bubblers

Eighteen melter agitation bubblers are used to introduce air into the bottom of the melter glass pool to mix the glass. LAW bubblers also contain thermocouple temperature sensors used to monitor the temperature of the glass pool.

Tuning feed

A special formation of feed slurry that is engineered to produce a melter “cold cap” with physical processing characteristics similar to Cold Commissioning Testing simulant (or actual waste feed) but without producing significantly hazardous offgas. It is non-hazardous (i.e., does not generate NOx/SOx in the offgas system).

Refractory conditioning

An essential part of the melter heatup process wherein the newly cast refractory lining of the melter is cured to drive off moisture and form a more resilient solid material. Refractory condition includes heating the melter at defined rates and temperature increments.

REQUIRED ACTIONS FOR MELTER HEATUP AND TUNING

Several steps are required leading to heatup of the melter. These steps are designed to provide for rigorous safety protocols and quality control associated with bringing the melters on line. Once these steps are complete, the melter is prepared for the next steps known as cold commissioning.

1. Verify Melter Configuration

Verify melter configuration for heatup, including completion of construction activities, installation of startup heaters, and verification that prerequisite interfacing systems are in service. (i.e. All supporting systems have been tested and verified)

 

 

 

 

 

 

2. Heat Meltor Refractory

Heat melter refractory from ambient to its operating temperature.

3. Frit Addition and Joule Heating

Perform frit addition and joule heating – Add glass frit to the melter until joule heating is initiated. Continue frit addition under joule heating until melter is full of molten glass to within normal operating range.

 

 

 

 

 

 

4. Reconfigure Melter

Reconfigure the melter to normal operating configuration (remove startup heaters and install bubblers).

5. Complete Frit Addition

Complete frit addition to the maximum level

 

 

 

 

 

 

6. Power Supply and Offgas Tuning

Perform initial melter power supply and offgas tuning. 

7. Perform Initial Glass Pours

Perform initial glass pours using glass from frit.

 

 

 

 

 

 

8. Melter Tuning

Melter Tuning – Set and refine control loops for dynamic response demonstrating system requirements are met while operating on tuning feed.

9. Melter Control

a.) Maintain glass pool temperature at 2,102 °F ± 77 °F using joule heating control loop.

b.) Demonstrate ability of melter feed systems to provide the desired recipe of tuning feed at the rates required.

c.) Form, control, and maintain a cold cap on the glass pool by varying feed rate and bubbler rate.

 

 

 

 

 

 

10. Perform Glass Pours

Perform glass pours.

11. Demonstrate Safety Confinement

Demonstrate safety confinement functions.

 

 

 

 

 

 

12. Prepare System for Testing

Prepare system for cold commissioning testing.

REQUIRED ACTIONS FOR MELTER HEATUP AND TUNING

Several steps are required leading to heatup of the melter. These steps are designed to provide for rigorous safety protocols and quality control associated with bringing the melters on line. Once these steps are complete, the melter is prepared for the next steps known as cold commissioning.

1. Verify Melter Configuration

Verify melter configuration for heatup, including completion of construction activities, installation of startup heaters, and verification that prerequisite interfacing systems are in service. (i.e. All supporting systems have been tested and verified)

2. Heat Meltor Refractory

Heat melter refractory from ambient to its operating temperature.

3. Frit Addition and Joule Heating

Perform frit addition and joule heating – Add glass frit to the melter until joule heating is initiated. Continue frit addition under joule heating until melter is full of molten glass to within normal operating range.

4. Reconfigure Melter

Reconfigure the melter to normal operating configuration (remove startup heaters and install bubblers).

5. Complete Frit Addition

Complete frit addition to the maximum level

6. Power Supply and Offgas Tuning

Perform initial melter power supply and offgas tuning.

7. Perform Initial Glass Pours

Perform initial glass pours using glass from frit.

8. Melter Tuning

Melter Tuning – Set and refine control loops for dynamic response demonstrating system requirements are met while operating on tuning feed.

9. Melter Control

a.) Maintain glass pool temperature at 2,102 °F ± 77 °F using joule heating control loop.
b.) Demonstrate ability of melter feed systems to provide the desired recipe of tuning feed at the rates required.
c.) Form, control, and maintain a cold cap on the glass pool by varying feed rate and bubbler rate.

10. Perform Glass Pours

Perform glass pours.

11. Demonstrate Safety Confinement

Demonstrate safety confinement functions.

12. Prepare System for Testing

Prepare system for fold commissioning testing.

MELTER HEATUP FAQs

When were first melters installed?

Assembly of the first melter was completed in June 2017. Melters were delivered to the Vit Plant in parts and assembled/fabricated on-site.

Will we “see” anything coming from the DFLAW facility after the melter is heated up and running? (exhaust, steam, plumes from a stack, etc.)

The rigorous offgas and charcoal filter system collects most discharge from the LAW facility. Because the discharge from the melters is high humidity, you may possibly see a steam/condensation plume from the offgas stack on a cold day.

How long after Melter Heatup until start of operations (treating waste)?

In the current schedule, the Operational Readiness Review for start of operations is 14 months after Melter 1 Heatup is completed. The Commissioning Test Planning Schedule lists 40 activities that must be completed from Melter 1 Heatup to initiation of tank waste into the facility. This important commissioning work takes approximately one year to complete.

What is the plan to replace a melter if one goes bad during operations or testing?

Melters have a limited lifetime and are designed to be replaced approximately every 5 years. A third melter is being fabricated now and is substantially complete. If one melter goes down, the replacement melter would be installed while the second melter continues operations.

How long does it take to heat up a melter?

It takes approximately 2 months. It takes about 22 days for the initial heatup, followed by several days of testing with frit addition through the melter head, followed by about 30 days of checkout with slurry feed from the feed system.

Will the melters stay on once they are heated up?

Yes. Melters have a life span of approximately five years; once they are heated up they will remain on and maintain a pool of molten glass until replacement.

Is there anything in the melters when they are heated up?

Melters are empty during the initial heating period. Melters are then loaded with frit to establish the initial glass pool.

Are you heating up just one melter or both?

Initially, a single melter is heated up and tested. This creates an opportunity to incorporate lessons learned into the design or heatup procedures for the second melter. Melter Heatup is deferred to the end of commissioning phase to reduce melter idle time prior to hot commissioning. The shorter amount of time melters are active during testing will allow for a longer life span during vitrification operations.

How have personnel trained and prepared to heat up the melter, do it safely, and to meet quality standards?

Training for operators includes classroom training, on the job training, simulator training, qualifications, drills, and proficiency demonstrations.