Going green with blue blocks

Blue blocks on the Fermilab site. Each one is stamped with a unique ID number. Photo: T. Hamernik

“When I got to Fermilab 20 years ago, the NuMI project had just placed a large order for blue blocks to build the NuMI target shield pile and shielding around the hadron absorber,” said Salman Tariq, now the LBNF Beamline Project Engineer. “We cannibalized some of them to build the MiniBooNE shield pile and 50m absorber, and now they are the right thing to use for LBNF.”

What are these blue blocks?

They are ten-ton steel blocks – painted blue — that Fermilab can buy for virtually the cost of shipping from Tennessee.

The process of creating blue blocks from received steel. Before step 4, melt material is selected based on metallurgical, chemical and radiological analysis of the material. Then representative samples are taken from the molten steel, and analyzed again. Many radionuclides are removed from the melt during slagging and disposed of as process waste. Each block is inspected to meet mechanical and radiological criteria prior to painting. Image: Energy Solutions

A firm called Energy Solutions, LLC in Oak Ridge, TN collects waste steel from laboratories and nuclear power plants around the world to repurpose it. This firm treats the steel, melts it down and reforms it into blocks appropriate for use at Fermilab. Sandra Efstathiou, a senior LBNF project procurement administrator, negotiated the subcontract in 2015 to procure 700 blue blocks for the project.

“This provides a way for us and other labs to recycle this steel,” said Tariq. “Using these blocks is the most environmentally friendly way for us to build shielding for the target hall and the muon alcove. We don’t use up supplies of new steel, they don’t require any fabrication on our part, and we don’t create more waste. It’s also the most inexpensive solution.”

The Near Site conventional facilities will also use blue blocks – in fact more of them than the beamline will use – for muon shielding just downstream of the absorber complex.

“The supplier has a limited production capability, but we are buying as many as we can” said Tom Hamernik, the Near Site Conventional Facilities Project Manager. “We need eight kilotons of steel, more than the 475 blocks we’re currently planning to get will provide, so we’ll have to fill in with the next most economical option.”

The three blue arrows show the proposed locations for the blue blocks in the LBNF beamline (center and right) and conventional facilities (left). Image: LBNF

“We’ve been using blue blocks for all these years and nobody has ever showed much interest in them,” remarked Tariq. The blue blocks are now getting their 15 minutes of fame.