APPLICATION OF NIST ^Rn EMANATION STANDARDS FOR CALIBRATING ^Rn MONITORS

Several years of research in developing a radon emanation standard by the National Institute of Standards and Technology (NIST) has led to NIST Radon Emanation Standard SRM 4968 (Journal of Research of the MST 100:629-639; 1996). This new standard is based on a polyethylene -encapsulated ""Ra solution that has been demonstrated to emanate a well-characterized and known quantity "̂Rn when employed in "accumulation mode*. The encapsulated standard is intended to serve as a more convenient, easier-to-use, alternative to the conventionally employed "̂ Ra solution standards that have been disseminated by MIST for 5 emanation measurements for the past 40 years. The latter standards were certified only for ^Ra content only, whereas the new standards are certified in terms of two parameters, both the ""Ra content and the "̂ Rn emanation fractions. Development of this standard is considered as a land mark in the standardization of radon measurement. The ease with which the source can be used lends itself to a wide spread use by any quality conscious radon measurement laboratory. These emanation standards are already in use in the USA, Europe, Canada, and Mexico. Their use is expected to grow. Hie purpose of this presentation is to describe (1) the standard and its characteristics, (2) theoretical and practical aspects, (3) its application for routine calibration of continuous radon monitodintegrating monitors used in indoor radon measurements, and (4) the precautions needed for its use. Pennisswn for reproduction of this paper is being obtained from the publisher: Nuclear Tecfmology Publishing. 1996 International Radon Symposium UP 2.1 ~ a d i i ~ i ~relection D<Ã̂imu TECHNICAL NOTE Vol. 55. Na 3. pp. 21 1-218( 1994) Nuclear Technology Publishing APPLICATION OF NIST ^Rn EMANATION STANDARDS FOR CALIBRATING ^Rn MONITORS P. Kotrappa and L. R. Stieff Rad Elec Inc., 5714-C. Industry Lane Frederick, MD 2 170 1. USA Received January 21 1994, Amended May 4 1994. Accepted May 1