Design tips and considerations for a successful nuclear lead pour
Press releases may be edited for formatting or style | January 28, 2020
By Paul Rochus
The Nuclear industry often requires large radiation shields made primarily from lead. One common method is to pour lead into a steel fabrication. The metal shell protects the lead in a durable casing that holds up better over time. This also ensures that any risk of lead exposure is minimized as the lead is sealed in an outer casing. MarShield is a North American leader in nuclear lead pours and through this blog, we aim to highlight:
• Some of the steps we use in producing a high-quality pour
• Key considerations when designing a fabrication to be filled with lead for radiation shielding
Fabrication construction and design
To start, the fabrication needs to be designed and built to suit the shielding needs and to allow for the greatest success when filling with lead. The designing process is as follows:
• The base alloy composition: The fabrication needs to be made from a minimum of ¼” carbon steel and welded together. If the specification is for stainless steel, then we recommend a heavier gauge as it is more susceptible to deformation. Regardless, there is a risk of deformations of the materials due to the heat that is applied during the pouring process. When using stainless steel, it is likely to discolor during the pouring process. A common method to prevent deformation during the heating of the fabrication is to support it with temporary bracing or stiffening for the pour process. This will help to limit the movement of the steel.
• When pouring lead into the fabrication: Pour holes can be used, but the best method is highly recommended to leave one side completely open and then pour into the open face so that pour technicians can completely minimize lead shrink. It is best to orientate the container so that there are no areas that are hidden from the open pour face. Before the start of a lead pour, fabrications must be clean from debris, paint and other dirt.
Lead pouring process
Once the fabrication is received and inspected to make sure that it is clean and suitable for pouring, it is preheated to start to pouring process which includes the following steps:
• Step 1: Before the pouring process begins the fabrication is heated up uniformly from the bottom by using gentle-flamed, gas burners focused on the inside and outside surfaces. Preheating prevents the lead from solidifying as soon as it makes contact with the sides and bottoms of fabrication. This allows for a more solid pour and decreases the risk of porosity in the lead. The next step is to slowly start to pour the lead into the fabrication. ASTM B-29 Lead (minimum 99.94% purity) is melted and poured slowly. Temperature is constantly monitored to ensure that the temperature does get too warm at any point.
The Nuclear industry often requires large radiation shields made primarily from lead. One common method is to pour lead into a steel fabrication. The metal shell protects the lead in a durable casing that holds up better over time. This also ensures that any risk of lead exposure is minimized as the lead is sealed in an outer casing. MarShield is a North American leader in nuclear lead pours and through this blog, we aim to highlight:
• Some of the steps we use in producing a high-quality pour
• Key considerations when designing a fabrication to be filled with lead for radiation shielding
Fabrication construction and design
To start, the fabrication needs to be designed and built to suit the shielding needs and to allow for the greatest success when filling with lead. The designing process is as follows:
• The base alloy composition: The fabrication needs to be made from a minimum of ¼” carbon steel and welded together. If the specification is for stainless steel, then we recommend a heavier gauge as it is more susceptible to deformation. Regardless, there is a risk of deformations of the materials due to the heat that is applied during the pouring process. When using stainless steel, it is likely to discolor during the pouring process. A common method to prevent deformation during the heating of the fabrication is to support it with temporary bracing or stiffening for the pour process. This will help to limit the movement of the steel.
• When pouring lead into the fabrication: Pour holes can be used, but the best method is highly recommended to leave one side completely open and then pour into the open face so that pour technicians can completely minimize lead shrink. It is best to orientate the container so that there are no areas that are hidden from the open pour face. Before the start of a lead pour, fabrications must be clean from debris, paint and other dirt.
Once the fabrication is received and inspected to make sure that it is clean and suitable for pouring, it is preheated to start to pouring process which includes the following steps:
• Step 1: Before the pouring process begins the fabrication is heated up uniformly from the bottom by using gentle-flamed, gas burners focused on the inside and outside surfaces. Preheating prevents the lead from solidifying as soon as it makes contact with the sides and bottoms of fabrication. This allows for a more solid pour and decreases the risk of porosity in the lead. The next step is to slowly start to pour the lead into the fabrication. ASTM B-29 Lead (minimum 99.94% purity) is melted and poured slowly. Temperature is constantly monitored to ensure that the temperature does get too warm at any point.
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