A nuclear explosion at the Port of Long Beach could kill 60,000 people immediately, expose 150,000 more to hazardous radiation and cause 10 times the economic loss of the Sept. 11, 2001 terrorist attacks, according to a new Rand Corp. study.

The study released Tuesday by the Santa Monica-based think tank was the latest to address concerns about the possible vulnerability of the nation's ports.

It analyzed the possible effects of terrorists detonating a 10-kiloton nuclear bomb in a shipping container unloaded onto a Long Beach pier.

Get more coverage at the Homeland Security Center.

In addition to the human casualties, such a blast might destroy the infrastructure and every ship at the ports of Long Beach and Los Angeles, which together handle about one-third of the nation's imports, the study said. Damage at port-area refineries could create critical shortages.

The two ports have taken steps to tighten security.

Last September, the ports of Long Beach and Los Angeles received the second- and third-largest security grants from the U.S. Department of Homeland Security, $12.7 million and $11.4 million, respectively. The money is to go for protecting ports from small craft and underwater attacks and enhance explosive detection capabilities.

Efforts are also under way to design a facility within the Port of Los Angeles where agents could thoroughly inspect suspicious cargo.

Currently, customs officials screen cargo with radiation monitors and X-ray machines at the docks then truck suspicious containers to a warehouse six miles away for closer inspections.

Visit FOXNews.com's Homeland Security Center for complete coverage.