The moderator temperature coefficient of reactivity (MTC) is an important parameter in safety analyses for thermal reactors. A positive MTC can exacerbate the severity of heatup transients, while a negative MTC can worsen the severity of cooldown transients. In particular, a strongly negative MTC is the major determinate of the severity of the steamline-break accident for pressurized water reactors (PWRs). Conversely, positive and negative MTCs can mitigate the severity of cooldown and heatup transients, respectively. Consequently, the accurate measurement and prediction of MTCs is an important factor in demonstrating that power reactors can be operated safely. ANS 19.11, the standard for ''Calculation and Measurement of the Moderator Temperature Coefficient of Reactivity in Water-Moderated Power Reactors, '' recently has been approved as a national standard by the American National Standards institute (ANSI) and the American Nuclear Society (ANS). At present, the scope of the standard is limited to PWRs, because that is the only type of power reactor currently sited in the US for which measurement of the MTC is required. The standard addresses the calculation and measurement of the MTC, and it also addresses the calculation of the ITC.

The moderator temperature coefficient of reactivity (MTC) is an important parameter in safety analyses for thermal reactors. A positive MTC can exacerbate the severity of heatup transients, while a negative MTC can worsen the severity of cooldown transients. In particular, a strongly negative MTC is the major determinate of the severity of the steamline-break accident for pressurized water reactors (PWRs). Conversely, positive and negative MTCs can mitigate the severity of cooldown and heatup transients, respectively. Consequently, the accurate measurement and prediction of MTCs is an important factor in demonstrating that power reactors can be operated safely. This document discusses the development of a standard for measuring MTC.

This standard provides guidance and specifies criteria for determining the MTC in PWRs. Measurement of the isothermal temperature coefficient of reactivity (ITC) at hot-zero-power (HZP) conditions is covered in ANSI/ANS-19.6.1-2011 (R2016). This standard therefore addresses the calculation of the ITC at HZP and the calculation and measurement of the MTC at power. This standard addresses the calculation and measurement of the MTC only in PWRs because that is the only type of power reactor currently sited in the United States for which measurement of the MTC is required.

NSA is a comprehensive collection of international nuclear science and technology literature for the period 1948 through 1976, pre-dating the prestigious INIS database, which began in 1970. NSA existed as a printed product (Volumes 1-33) initially, created by DOE's predecessor, the U.S. Atomic Energy Commission (AEC). NSA includes citations to scientific and technical reports from the AEC, the U.S. Energy Research and Development Administration and its contractors, plus other agencies and international organizations, universities, and industrial and research organizations. References to books, conference proceedings, papers, patents, dissertations, engineering drawings, and journal articles from worldwide sources are also included. Abstracts and full text are provided if available.