Partly obscured behind the shock waves of President Carter's neutron "bomb" decision, a crisis on nuclear power is building in the Western alliance over the creeping U. S. embargo against export of raw material for nuclear power plants, with the Soviet Union benefiting directly.

The limit on exporting U. S. produced enriched uranium comes out of the new Nuclear Nonproliferation Act, with this unintended result: Soviet nuclear power becomes preeminent. Since breeder-reactor technology is regarded by oil-starved Europe as vital to future energy needs, our European allies may turn eastward for their enriched uranium and technology exchange.

Even without the new act, the president's abhorrence of the breeder reactor points to Soviet domination - as was pointed out in a confidential letter delivered to Carter April 4 from Rep. John W. Wydler of New York. The senior Republican on the House Science Committee, Wydler warned the president that "it is frightening to speculate on the degree of control of the world market [for breeder-produced nuclear power] that the Soviet Union might achieve by implementing" its fast-moving nuclear power program.

Economic and political stakes in the rush for nuclear energy by the Western democracies and Japan are awesome. Considering that, the Carter administration's nuclear nonpolicy could contribute to another global victory for the expansive masters of the Kremlin.

The Nuclear Nonproliferation Act, signed into law March 10 by Carter, adds to the danger. It gives the nine Western European countries who belong to EURATOM 30 days to start negotiations with the United States. The law bans U. S. exports of enriched uranium to Western Europe unless EURATOM agrees to U. S. control over spent fuel manufactured in European plants.

That is vitally important, giving Washington veto power over reprocessing spent fuel and, hence, over Europe's power to build breeder nuclear power plants. The breeder, making its own fuel as it manufactures power, is nearly indispensable to Europe's future power needs.

This unilateral change in existing agreements dating back to the mid-'60s unfuriated the European nations. Forced to play the high-stakes nuclear power game the Washington way, their first reaction was symbolic retaliation. Within the French taking the lead, they simply ignored the provision in the new U.S. law giving them 30 days to start negotiations for new licenses to import enriched uranium.

The EURATOM nations will surely agree, probably soon, to negotiate new enriched-uranium contracts. But thumbing their noses at starting the talks within the 30 days is a symbol of their anger.

Carter's deeply rooted fear is that reprocessed fuel - which is weapons-grade fuel - could be turned illegally into bombs. That is understandable when considered in a political vacuum. Unfortunately, however, the Soviet Union has no parallel concerns. The Soviets are far ahead of the breeder reactor curve today and picking up ever more speed.

Rep. Wydler drafted his warning to the president after talks with the International Atomic Energy Commission and finally with the Russians in Moscow last month. A congressional expert on nuclear power, Wydler predicted to Carter that we are "on the verge of an antomic Sputnik" - a sudden Soviet advance.

He warned the president that his opposition to the Clinch River experimental breeder reactor signals all other nations that the United States is not serious about preserving the breeder as a long-range option; that has undermined U.S. nuclear power credibility abroad "and made us an unreliable nuclear partner."

Over Carter's protest, Congress has kept the Clinch River "breeder" from dying a premature death. But that does not relieve the president from getting his act together and taking on the formidable, richly financed anti-nulcear lobby (with its equally formidable agents ensonced as officials deep inside his administration). Otherwise, the West may be doomed to fall behind the communist bloc, never to recover.

For example, the Soviets now operate a 350-megawatt experimental "breeder" on the Caspian Sea and will complete a 600-megawatt plant in 1980. Design is beginning for a 1,600-megawatt plant, which the Russians told Wydler would take only seven years to build.

No wonder, then, that the new law limiting export of U.S. enriched uranium is creating consternation. Following EURATOM's symbolic refusal to start new talks within the 30-day period, West Germany will soon increase its purchase of enriched uranium from the Russians. More attacks on the exposed flank of Prsident Carter's nuclear power policy will surely follow.