You expect your shrimp to have a “sell by” date, not a half-life. But Walmart is warning shoppers in 13 states that they may have picked up Great Value brand frozen shrimp that was exposed to radiation in its shipping container.

The U.S. Food and Drug Administration’s recall affects a shipment of Great Value frozen shrimp that landed in the following states:

• Alabama
• Arkansas
• Florida
• Georgia
• Kentucky
• Louisiana
• Missouri
• Mississippi
• Ohio
• Oklahoma
• Pennsylvania
• Texas
• West Virginia

The story behind Walmart’s radioactive shrimp

The FDA reportedly blocked multiple shipping containers from an Indonesian supplier. Why? Because they tested positive for dangerous levels of a radioactive element called caesium-137. But some containers—such as this shipment of Walmart’s Great Value shrimp—had already gotten through.

Tiny amounts of caesium-137 are present in air and water worldwide. But large amounts are very dangerous. High levels of caesium-137 are the reason Chernobyl in Ukraine and Fukushima in Japan are still contaminated. Not an ideal surprise ingredient for your next shrimp cocktail.

Was the caesium-137 in an adjoining shipping container? Or did the Indonesian company load this seafood into an already contaminated container? We’ll have to wait for the FDA’s investigatin to find out.

Walmart admitted this is less of a shrimp-sized problem and more of a king-prawn-sized disaster. “The health and safety of our customers is always a top priority… We have issued a sales restriction and removed this product from our impacted stores. We are working with the supplier to investigate.” The company is offering a full refund for bringing radioactive shrimp back to the store.