Neutron quality factors being doubled for U.S.

[Janzow1@aol.com]

    Neutron quality factors for at least one U.S. use will be doubled in the 
near future unless regulatory changes currently being considered are 
successfully opposed.
    Specifically, the U.S. Department of Transportation (DOT) is considering 
revising its transport regulations to make them compatible with IAEA 
recommendations as stated in IAEA "Safety  Standards Series No. ST-1", 
published in 1996.  ST-1 includes a reduction by a factor of two of the 
quantity of certain neutron-emitters (including Cf-252) which may be shipped 
as Special Form material in a Type A package (the A-sub-1 limit).  That 
reduction is based on a factor-of-two increase in the "weighting factor" 
(Q-value, RBE, etc.) for neutrons recommended in ICRP Publication 60, 
published in 1991.
    Formal implementation of ST-1 limits by the DOT may be construed as 
suggesting or requiring the adoption of the higher "weighting factor" by 
other U.S. agencies such as the NRC and DOE, thereby effectively halving 
neutron exposure limits and doubling reported neutron exposures.
    My understanding is that the higher value in ICRP 60 lacks scientific 
explanation, and is opposed by many U.S. experts (NCRP, NAS, CIRRPC).  The 
Health Physics and Radiological Health Handbook, Revised Edition, dated 1992, 
 states on page 543 that the ICRP issued a statement (ICRP Publication 45 
1985b) from its meeting in Paris during March 1985. "The information now 
available on the relative biological effectiveness (RBE) for neutrons for a 
variety of cellular effects in vitro, and for life shortening in the mouse, 
is being reviewed by the Commission. The implications of this information 
will be considered as part of a larger review of recommendations to be 
undertaken by the Comission over the  next four years or so.  Meanwhile, in 
the case of neutrons, the Commission  recommends an increase in Q by a factor 
of 2.  The permitted approximation for Q for fast neutrons thus changes from 
10 to 20."  The same book contains a table referenced to ICRP Publication 60, 
1991, which gives "weighting factors" for various energy ranges of neutrons.  
The factor is 20 for neutrons in the 10 keV to 2 MeV range.  No supporting 
data is given.  ISO 8529, ("Neutron reference radiations for calibrating 
neutron-measuring devices used for radiation protection purposes and for 
determining their response as a function of neutron energy", International 
Standard ISO 8529: 1989, Annex B) published in 1989, recommends values for 
neutron fluence-to-dose conversions consistent with the lower Q values.
    I am seeking comments, references, etc. relating to the origin or 
validity of the neutron "weighting factors" in ICRP 60 which either support 
or refute the data.
    Should any of you wish to comment directly to DOT:
    The adoption of ST-1 into U.S. regulations is being considered under DOT 
Docket No. RSPA-99-6283 (HM-230); the text of the original proposal is 
available at http;//hazmat.dot.gov/99_6283.htm.  A revision extending the 
comment period to June 29, 2000 is available at 
http://hazmat.dot.gov/99_6283_ext.htm.  Written comments should refer to 
Docket No. RSPA-99-6283 and be sent in duplicate to:
    Dockets Management System
    US Department of Transportation, PL-401
    400 Seventh Street, SW
    Washington, D.C. 20590-0001
    
    ST-1 itself is being considered for revision.  The comment period for the 
U.S. ends May 1, 2000. A draft of IAEA ST-2 (the "explanatory material" for 
ST-1) contains the higher "weighting factors" in its Appendix 1, and is being 
considered for acceptance by the U.S.  Comments on either may be sent to : 
    Richard W. Boyle, Chief
    Radioactive Materials Branch (DHM-23)
    Office of Hazardous Materials Technology
    Research and Special Programs Administrations
    U.S. Department of Transportation
    400 Seventh Street, SW
    Washington, D.C. 20590


Respectfully,
Ed

Edward F. Janzow
Frontier Technology Corporation
janzow1@aol.com
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