Importing uranium - including some from communist countries - is hurting U.S.uranium producers and threatens national security, according to Rep. Howard C. Nielson, R-Utah.

He wrote Commerce Secretary Robert Mosbacher, whose department is investigating the effect of uranium imports, on Thursday. Nielson questioned the wisdom of importing more than 50 percent of uranium used in America, and buying increasing amounts from the Soviet Union and China."It is incredible to me that U.S. utilities are apparently willing to buy uranium from communist countries to generate nuclear power for their ratepayers. Clearly, these two communist countries are not reliable suppliers during times of national emergency," he wrote.

"There can be no doubt that uranium is vital to national security. The basic question which the department's investigation must consider is whether it is in the national interest to sacrifice the domestic uranium industry to subsidize imports."

Nielson has long called for more protection of the domestic uranium industry, which is floundering. He said if current trends continue, nearly 75 percent of U.S. uranium needs will be filled in the 1990s by imports.

Nielson also criticized the Free Trade Agreement with Canada and its effect on uranium imports.

He said it places no restrictions on the import of Canadian uranium to the United States, but Canadian law prohibits the sale of its uranium to America for military use - so no assurance is made of shipments during times of national emergency.