Foreword Within weeks after the ending of World War II, plans for the first nuclear test series ‘‘Operation Crossroads*’ were underway. The purpose then, as now, was to develop new weapon systems and to study the effects of nuclear explosions on military equipment. The developmentof the nuclear testing program has been paralled by public opposition from both an arms contro] and an environmental perspective. Muchofthecriticism is due to the symbolic nature of testing nuclear weapons and from the radiation hazards associated with the early practice of testing in the atmosphere. Recently, however. specific concerns have also been raised about the current underground testing program; namely: e Are testing practices safe? e Could an accidental release of radioactive material escape undetected? e Is the public being fully informedofall the dangers emanating from the nuclear testing program? These concerns are fueled in part by the secrecy that surrounds the testing program and by publicized problemsat nuclear weapons production facilities. Atthe request of the House Committee on Interior and Insular Affairs and Senator Orrin G. Hatch, OTA undertook an assessmentof the containment and monitoring practices of the nuclear testing program. This special report reviewsthe safety of the nuclear testing program and assesses the technical procedures used to test nuclear weapons and ensure that radioactive material produced by test explosions remains contained underground. An overall evaluation considers the acceptability of the remaining risk and discusses reasonsfor the lack of public confidence. In the course of this assessment, OTA drew on the experience of many organizations and individuals. We appreciate the assistance of the U.S. Government agencies and private companies who contributed valuable information, the workshop participants who provided guidance and review,and the many additional reviewers who helped ensure the accuracy and objectivity of this report. Lin Whew. JOHN H. GIBBONS Director iti