WASHINGTON, Oct 30 (Reuters) - President Donald Trump's

order for the Defense Department to start testing nuclear

weapons could lead to billions of dollars' worth of contracts

for a handful of specialized companies that dominate the United

States' nuclear weapons infrastructure.

The Trump announcement Wednesday night from South Korea ordered

the Department of Defense to "immediately" start testing nuclear

weapons, something the United States has not done since 1992.

The U.S. nuclear arsenal consists of land-launched nuclear

missiles, nuclear missile-armed submarines and aircraft with

nuclear bombs and missiles. It was unclear which portion of the

arsenal Trump wanted to test.

COMPANIES IN LINE TO BENEFIT

An investment in nuclear weapons and testing could benefit

Honeywell International ( HON ), BWX Technologies ( BWXT ),

Chugach Alaska Corp, Jacobs Solutions, Inc. ( J ), Mele

Associates, General Atomic Technologies Corporation and others

due to their specialization in nuclear test site construction,

operations, support and related engineering services, according

to Govini, a defense software company.

BWXT works with nuclear materials, while Honeywell ( HON ) runs a

key testing site, conducts tests and helps track the U.S.

nuclear stockpile.

Mele helps manage parts of the nuclear stockpile while

helping make sure nuclear material does not fall into the wrong

hands.

"Restarting nuclear weapons testing is going to reverberate

in a lot of ways, including by sending a shockwave of government

funding to companies in test site construction and engineering

support," said Tara Murphy Dougherty, CEO of Govini.

Alongside a new testing program, the U.S. is modernizing

its ground-launched intercontinental ballistic missile program,

aimed at replacing the aging Minuteman III missiles.

Northrop Grumman ( NOC ) was awarded a sole-source contract in

2020 to develop the Sentinel, with subcontractors including

Lockheed Martin ( LMT ), General Dynamics ( GD ), Bechtel,

Honeywell ( HON ), Aerojet Rocketdyne, and Textron ( TXT ).

The program, which requires extensive testing while it is

being built, represents one of the largest defense modernization

efforts in decades.

The plan includes 634 new Sentinel missiles, plus an

additional 25 missiles to support development and testing, being

procured to replace the aging Minuteman III system deployed in

1970.