The (blank) led to the demise of new nuclear power plants planned for washington. 1. Accident at Three Mile Island 2. Construction of the Grand Coulee Dam 3. Creation of the WPPSS 4. Cleanup of the hanford project site

The correct answer is 1. Accident at Three Mile Island.

The incident at Three Mile Island, a partial nuclear meltdown in a reactor near Harrisburg, Pennsylvania, in 1979, had a significant impact on the nuclear power industry in the United States. While the question specifically mentions Washington, the Three Mile Island accident had repercussions nationwide, affecting public perception safety concerns, and regulatory scrutiny of nuclear power plants.

Following the accident, public confidence in nuclear power diminished, leading to increased safety regulations, higher construction costs for new plants and a more stringent licensing process. This shift in public opinion and increased regulatory hurdles contributed to the demise of planned nuclear power plants not only in Washington but across the country. Investors and utilities became more cautious about investing in new nuclear projects due to financial uncertainties and concerns about safety and public acceptance.