Volume 9, Issue 4 (April 2012)

    Comparison of Regulatory Guide 1.99 Fluence Attenuation Methods

    (Received 21 May 2011; accepted 14 December 2011)

    Published Online: 2012

    CODEN: JAIOAD

      Format Pages Price  
    PDF Version 7 $25   ADD TO CART


    Abstract

    U.S. Regulatory Guide 1.99 Revision 2 (U.S. Nuclear Regulatory Commission, 1988, “Radiation Embrittlement of Reactor Vessel Materials,” Regulatory Guide 1.99, Revision 2, Washington, D.C.) provides for the use of two substantially different methods for determining through-wall fluence in nuclear reactor pressure vessels. One method is a generic attenuation curve based on a simplistic exponential decay equation. Partly due to the simplicity of its application, the generic attenuation method is predominantly used for licensing calculations. However, it has a limitation in that at increasing distances away from the core beltline, it becomes increasingly less accurate because it cannot account for neutron streaming effects in the cavity region surrounding the pressure vessel. The other attenuation method is based on a displacement per atom (dpa) calculation specific to the reactor vessel structure. The dpa method provides a more accurate representation of fluence attenuation through the reactor pressure vessel (RPV) wall at all elevations of the pressure vessel because it does account for neutron streaming in the cavity region. A requirement for using the dpa method, however, is an accurate flux solution through the RPV wall. This requirement has limited the use of traditional transport methods, such as discrete ordinates, that are limited by their treatment of cavity regions (i.e., air) outside the pressure vessel wall. TransWare Enterprises, under the sponsorship of EPRI and BWRVIP, has developed an advanced three-dimensional transport methodology capable of producing fully converged flux solutions throughout the entire reactor system, including in the cavity region and primary shield structures. This methodology provides an accurate and reliable determination of through-wall fluence in boiling water reactor (BWR) and pressurized water reactor (PWR) pressure vessels, thus allowing the dpa method to be implemented with high reliability. Using this advanced 3-D methodology, this paper presents comparisons of the generic and dpa attenuation methods at critical locations in both BWR and PWR pressure vessel walls.


    Author Information:

    Jones, Eric N.
    Consultant, TransWare Enterprises Inc., Sycamore, IL


    Stock #: JAI104028

    ISSN: 1546-962X

    DOI: 10.1520/JAI104028

    ASTM International is a member of CrossRef.

    Author
    Title Comparison of Regulatory Guide 1.99 Fluence Attenuation Methods
    Symposium , 0000-00-00
    Committee C26