[Federal Register: December 7, 1999 (Volume 64, Number 234)]
[Notices]               
[Page 68395-68396]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr07de99-106]                         

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NUCLEAR REGULATORY COMMISSION

Supplemental Information on the Implementation of the Final Rule 
on Radiological Criteria for License Termination

    Summary: This notice provides supplemental information regarding 
implementation of the Nuclear Regulatory Commission's (NRC) Final Rule 
on Radiological Criteria for License Termination (License Termination 
Rule (LTR)) which was issued on July 21, 1997, (62 FR 39058). This 
notice provides: (1) screening values for surface soil contamination 
release levels; and (2) information on additional NRC efforts in dose 
modeling. Supplemental information was also published in the Federal 
Register on November 18, 1998 (63 FR 64132). That notice provided 
information on: (1) The end of the ``grandfathering period;'' (2) 
issuance of draft Regulatory Guide ``Demonstrating Compliance with the 
Radiological Criteria for License Termination'' (DG-4006); (3) 
availability of DandD, version 1; (4) screening values for building 
surface contamination for beta/gamma radiation emitters (Table 1, 
Acceptable License Termination Screening Values of Common Radionuclides 
for Building Surface Contamination); (5) public workshops; (6) 
development of a decommissioning standard review plan (SRP); and (7) 
status of the NRC decommissioning guidance documents (Table 2, Existing 
Guidance Documents Applicable to Decommissioning That Will Require 
Revision or Discontinuation in Order to Implement the License 
Termination Rule).
    Supplemental Information: As discussed in the November 18, 1998, 
Federal Register notice, the DandD code provides a method for 
calculating screening concentrations for radionuclides in soil, and 
screening levels for contamination on building surfaces. NRC staff also 
stated that, during the two-year interim use period for DG-4006, it 
planned to continue to refine the screening approach and to evaluate 
the extent of conservatism in the DandD code.
    Several areas where DandD, version 1, may be overly conservative 
have been identified. One such conservatism is the methodology used for 
selection of default parameters. Selection of highly conservative 
default parameters is essentially caused by the current screening 
design of establishing a single default parameter set for all 
radionuclides listed in the DandD code. That is, if the default 
parameter set was tailored for each radionuclide, rather than using a 
common default parameter set for all radionuclides, the dose calculated 
using DandD model would, in most cases, be lower. A detailed discussion 
of the way the default parameters were selected is contained in 
``Residual Contamination from Decommissioning--Parameter Analysis--
Draft Report for Comment'' (NUREG/CR-5512, Volume 3).
    This artifact in the way the default parameters were selected has 
been discussed in several presentations at the NRC's public workshops 
(e.g., Public Workshops on Guidance for Implementing Title 10 Code of 
Federal Regulations (CFR), Subpart E, Radiological Criteria for License 
Termination) conducted in December 1998, and January, March, and June 
1999. Currently, NRC staff is developing version 2.0 of the DandD code. 
This version of the code will calculate the default parameter values 
based on the specific radionuclides that are identified by the analyst. 
In the interim, NRC staff has calculated surface soil concentrations 
for a number of common radionuclides that correspond to an annual dose 
of 0.25 mSv (25 mrem) using the default parameters that are generated 
by the approach to be used in the new version of DandD. These values 
are presented in Table 3. For mixtures of radionuclides, a screening 
dose should be calculated using the sum-of-the fractions' rule.
    The values in Table 3 (Interim Screening Values (pCi/g) of Common 
Radionuclides for Soil Surface Contamination Levels) correspond to 
surface soil (e.g., top 15-30 cm) concentrations of radionuclide 
contamination that would be deemed in compliance with the unrestricted 
use dose limit in 10 CFR 20.1402 (i.e., 0.25 mSv/yr, (25 mrem/yr)). The 
values correspond to screening ``derived concentration guidelines'' 
(DCGLs) for each specific radionuclide based on the methodology 
described in DG-4006. Sites with surface soil contamination levels 
below those listed in Table 3 would be deemed acceptable for release 
for unrestricted use provided that residual radioactivity has been 
reduced to levels that are ``as low as is reasonably achievable'' 
(ALARA). This table is not applicable to sites with subsurface and/or 
with groundwater

[[Page 68396]]

contamination and a more comprehensive dose impact analysis would be 
required. The table is intended for use as screening criteria to 
facilitate license termination for many simple routine decommissioning 
cases that do not require a site-specific dose assessment. For 
facilities with contamination levels above those in Table 3, additional 
site-specific dose assessments may be necessary, and licensees should 
refer to DG-4006 regarding acceptable methods for conducting the 
appropriate dose assessment.
    NRC staff has also prepared ``Preliminary Guidelines for Evaluating 
Dose Assessments in Support of Decommissioning.'' The purpose of these 
guidelines is to provide a consistent approach for NRC staff to 
evaluate dose assessments conducted to demonstrate compliance with the 
LTR. This interim guidance was developed by NRC staff for reviewing 
dose assessments and may be useful to licensees preparing dose 
assessment during both screening and site-specific analyses. A copy of 
the guidance is available on the web site ``http://
techconf.llnl.gov/.''
    During our analysis of the basis for selecting the default 
parameter set for the DandD code, we discovered a transcription error 
in the soil-to-plant transfer factor for S-35. This error substantially 
overestimates the allowable DCGL for this radionuclide. The soil-to-
plant transfer factor has been revised in DandD version 1 and posted on 
the above referenced web site. In addition, a ``patch'' to correct this 
problem for users that already have the code installed is also 
available from this web site.
    The staff intends to consider placing Tables 1 and 3, revised as 
necessary, to reflect improvement in the DandD code in the Standard 
Review Plan for decommissioning, and/or in the next revision of the 
Regulatory Guide DG-4006. Comments on these Tables may be submitted 
within 30 days from the date of this notice to the Rules and Directives 
Branch, Division of Administrative Services, Office of Administration, 
U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001.
    For Further Information Contact: For more information, contact Dr. 
Boby Abu-Eid, High-Level Waste and Performance Assessment Branch, 
Division of Waste Management, Office of Nuclear Material Safety and 
Safeguards, U.S. Nuclear Regulatory Commission, Washington, DC 20555-
0001. Telephone: (301) 415-5811; fax: (301) 415-5398; or email: 
bae@nrc.gov.

    Dated at Rockville, Maryland, this 29th day of November 1999.

    For the Nuclear Regulatory Commission.
Larry W. Camper,
Chief, Decommissioning Branch Division of Waste Management, Office of 
Nuclear Material Safety and Safeguards.

       Table 3.\1\--Interim Screening Values \2\ (pCi/g) of Common
           Radionuclides for Soil Surface Contamination Levels
------------------------------------------------------------------------
                                               Surface soil screening
               Radionuclide                          values \3\
------------------------------------------------------------------------
H-3.......................................  1.1 E+02
C-14......................................  1.2 E+01
Na-22.....................................  4.3 E+00
S-35......................................  2.7 E+02
Cl-36.....................................  3.6 E-01
Ca-45.....................................  5.7 E+01
Sc-46.....................................  1.5 E+01
Mn-54.....................................  1.5 E+01
Fe-55.....................................  1.0 E+04
Co-57.....................................  1.5 E+02
Co-60.....................................  3.8 E+00
Ni-59.....................................  5.5 E+03
Ni-63.....................................  2.1 E+03
Sr-90.....................................  1.7 E+00
Nb-94.....................................  5.8 E+00
Tc-99.....................................  1.9 E+01
I-129.....................................  5.0 E-01
Cs-134....................................  5.7 E+00
Cs-137....................................  1.1 E+01
Eu-152....................................  8.7 E+00
Eu-154....................................  8.0 E+00
Ir-192....................................  4.1 E+01
Pb-210....................................  9.0 E-01
Ra-226....................................  7.0 E-01
Ra-226+C \4\..............................  6.0 E-01
Ac-227....................................  5.0 E-01
Ac-227+C..................................  5.0 E-01
Th-228....................................  4.7 E+00
Th-228+C..................................  4.7 E+00
Th-230....................................  1.8 E+00
Th-230+C..................................  6.0 E-01
Th-232....................................  1.1 E+00
Th-232+C..................................  1.1 E+00
Pa-231....................................  3.0 E-01
Pa-231+C..................................  3.0 E-01
U-234.....................................  1.3 E+01
U-235.....................................  8.0 E+00
U-235+C...................................  2.9 E-01
U-238.....................................  1.4 E+01
U-238+C...................................  5.0 E-01
Pu-238....................................  2.5 E+00
Pu-239....................................  2.3 E+00
Pu-241....................................  7.2 E+01
Am-241....................................  2.1 E+00
Cm-242....................................  1.6 E+02
Cm-243....................................  3.2 E+00
------------------------------------------------------------------------
\1\ Tables 1 and 2 were published in the Federal Register on November
  18, 1998, (63 FR 64132)
\2\ These values represent superficial surface soil concentrations of
  individual radionuclides that would be deemed in compliance with the
  25 mrem/y (0.25 mSv) unrestricted release dose limit in 10 CFR
  20.1402. For radionuclides in a mixture, the ``sum of fractions'' rule
  applies; see Part 20, Appendix B, Note 4. Refer to NRC Draft Guidance
  DG-4006 for further information on application of the values in this
  table.
\3\ Screening values (pCi/g) equivalent to 25 mrem/y derived using DandD
  screening methodology (SNL Letter Report for NRC Project JCN W6227,
  January 30, 1998). These values were derived based on selection of the
  90th Percentile of the output dose distribution for each specific
  radionuclide (or radionuclide with the specific decay chain).
  Behavioral parameters are set at the mean of the distribution of the
  assumed critical group. The Metabolic parameters are set at Standard
  Man or at the mean of the distribution for an average man.
\4\ ``+C'' indicates a value for a radionuclide with its decay progeny
  present in equilibrium. The values are concentrations of the parent
  radionuclide, but account for contributions from the complete chain of
  progeny in equilibrium with the parent radionuclide.

[FR Doc. 99-31508 Filed 12-6-99; 8:45 am]
BILLING CODE 7590-01-P

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