ML050390450
| ML050390450 | |
| Person / Time | |
|---|---|
| Issue date: | 05/31/2005 |
| From: | Harry Felsher NRC/NMSS/FCSS, Office of Nuclear Regulatory Research |
| To: | |
| Felsher H, NMSS/FCSS, 301-415-5521 | |
| References | |
| DG-3023 RG-3.071, Rev 01 | |
| Download: ML050390450 (7) | |
Text
This regulatory guide is being issued in draft form to involve the public in the early stages of the development of a regulatory position in this area. It has not received staff review or approval and does not represent an official NRC staff position.
Public comments are being solicited on this draft guide (including any implementation schedule) and its associated regulatory analysis or value/impact statement. Comments should be accompanied by appropriate supporting data. Written comments may be submitted to the Rules and Directives Branch, Office of Administration, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001. Comments may be submitted electronically through the NRCs interactive rulemaking Web page at http://www.nrc.gov/what-we-do/regulatory/rulemaking.html.
Copies of comments received may be examined at the NRC Public Document Room, 11555 Rockville Pike, Rockville, MD. Comments will be most helpful if received by June 20, 2005.
Requests for single copies of draft or active regulatory guides (which may be reproduced) or for placement on an automatic distribution list for single copies of future draft guides in specific divisions should be made to the U.S. Nuclear Regulatory Commission, Washington, DC 20555, Attention: Reproduction and Distribution Services Section, or by fax to (301)415-2289; or by email to Distribution@nrc.gov. Electronic copies of this draft regulatory guide are available through the NRCs interactive rulemaking Web page (see above); the NRCs public Web site under Draft Regulatory Guides in the Regulatory Guides document collection of the NRCs Electronic Reading Room at http://www.nrc.gov/reading-rm/doc-collections/; and the NRCs Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html, under Accession No. ML050390450. Note, however, that the NRC has temporarily limited public access to ADAMS so that the agency can complete security reviews of publicly available documents and remove potentially sensitive information. Please check the NRCs Web site for updates concerning the resumption of public access to ADAMS.
U.S. NUCLEAR REGULATORY COMMISSION May 2005 OFFICE OF NUCLEAR REGULATORY RESEARCH Division 3 DRAFT REGULATORY GUIDE
Contact:
H.D. Felsher, (301) 415-5521 DRAFT REGULATORY GUIDE DG-3023 (Proposed Revision 1 of Regulatory Guide 3.71, dated August 1998)
NUCLEAR CRITICALITY SAFETY STANDARDS FOR FUELS AND MATERIAL FACILITIES A. INTRODUCTION This revised regulatory guide provides licensees and applicants with updated guidance concerning criticality safety standards that the U.S. Nuclear Regulatory Commission (NRC) has endorsed for use with nuclear fuels and material facilities. As such, this guide describes methods that the NRC staff considers acceptable for complying with the NRCs regulations in Title 10, Parts 70 and 76, of the Code of Federal Regulations (10 CFR Parts 70 and 76).
In 10 CFR Part 70, Domestic Licensing of Special Nuclear Material, Section 70.20, General License To Own Special Nuclear Material, defines a specific license to acquire, deliver, receive, possess, use, transfer, import, or export special nuclear material. According to 10 CFR 70.22, Contents of Applications, each application for such a license must contain proposed procedures to avoid nuclear criticality accidents. In 10 CFR Part 76, Certification of Gaseous Diffusion Plants, Section 76.87, Technical Safety Requirements, states that the technical safety requirements should reference procedures and equipment that are applicable to criticality prevention.
DG-3023, Page 2 The NRC staff has developed this regulatory guide to provide guidance on complying with these portions of the NRCs regulations by describing procedures for preventing nuclear criticality accidents in operations that involve handling, processing, storing, and/or transporting special nuclear material at fuel and material facilities. This regulatory guide endorses specific nuclear criticality safety standards developed by the American Nuclear Societys Standards Subcommittee 8 (ANS-8), Operations with Fissionable Materials Outside Reactors. This guide is not intended to be used by nuclear reactor licensees.
Regulatory guides are issued to describe to the public methods that the NRC staff considers acceptable for use in implementing specific parts of the agencys regulations, to explain techniques that the staff uses in evaluating specific problems or postulated accidents, and to provide guidance to applicants. Regulatory guides are not substitutes for regulations, and compliance with regulatory guides is not required. Regulatory guides are issued in draft form to solicit public comment and involve the public in developing the agencys regulatory positions.
Draft regulatory guides have not received complete staff review; therefore, they do not represent official NRC staff positions.
This draft regulatory guide contains information collections that are covered by the requirements of 10 CFR Part 70, which the Office of Management and Budget (OMB) approved under OMB control number 3150-0009. The NRC may neither conduct nor sponsor, and a person is not required to respond to, an information collection request or requirement unless the requesting document displays a currently valid OMB control number. However, this draft regulatory guide contains additional information collections that are covered by the requirements of 10 CFR 76.8, which apply to a wholly-owned instrumentality of the United States and affect fewer than ten respondents. As a result, OMB clearance is not required pursuant to the Paperwork Reduction Act (44 U.S.C. 3501, et seq.).
DG-3023, Page 3 B. DISCUSSION The NRC initially issued Regulatory Guide 3.71 in 1998 to provide guidance concerning procedures that the staff considered acceptable for complying with the agencys regulatory requirements in 10 CFR 70.20, 70.22 and 76.87. Toward that end, the original guide endorsed specific safety standards that ANS-8 developed to provide guidance, criteria, and best practices for use in preventing and mitigating criticality accidents during operations that involve handling, processing, storing, and/or transporting special nuclear material at fuel and material facilities. The original guide also took exceptions to certain portions of individual ANSI/ANS-8 standards. In addition, the original guide consolidated and replaced a number of earlier NRC regulatory guides, thereby providing all of the relevant guidance in a single document.
The ANS-8 standards endorsed in Regulatory Guide 3.71 were approved by the American Nuclear Societys Consensus Committee N16 on Nuclear Criticality Safety, as well as the American National Standards Institute (ANSI). Nonetheless, each ANSI/ANS-8 standard is reviewed every 5 years by a working group of expert practitioners in the area so that it can be revised, reaffirmed, or withdrawn, as appropriate to reflect the current state of the art. (This time can be extended to as long as 10 years or more under special circumstances.) New standards are also added when the need arises. Since the timing and issuance of individual standards is independent of the other standards, the list of current standards and their respective dates of issuance is constantly changing.
As a result, since the NRC published Regulatory Guide 3.71 in 1998, several ANSI/ANS-8 nuclear criticality safety standards have been added, reaffirmed, revised, or withdrawn.
Consequently, the NRC staff has decided to update this guide to clarify which standards the agency endorses and to clearly state exceptions to individual standards. This proposed revision does not change any of the guidance provided in Regulatory Guide 3.71; rather, it provides guidance concerning changes that have occurred since the NRC published the original guide in 1998. For completeness, this guide restates the endorsements and exceptions stated in Regulatory Guide 3.71, as applicable, while identifying endorsements of or exceptions to new or modified standards. Since the ANSI/ANS-8 standards are constantly being issued, revised, reaffirmed, or withdrawn, the NRC staff plans to revise this guide on a regular basis.
DG-3023, Page 4 C. REGULATORY POSITION The ANSI/ANS-8 nuclear criticality safety standards provide procedures and methodologies that the NRC staff considers generally acceptable for use in preventing and mitigating nuclear criticality accidents. However, use of the ANSI/ANS-8 nuclear criticality safety standards is not a substitute for detailed nuclear criticality safety analyses for specific operations.
In addition, inclusion of a reference to another standard in an endorsed standard does not imply NRC endorsement of the referenced standard.
The NRC staff will follow the requirements denoted in the ANSI/ANS-8 standards. The word shall in an ANSI/ANS-8 standard denotes a requirement; the word should denotes a recommendation; and the word may denotes permission (neither a requirement nor a recommendation). When a licensee or applicant commits to an ANSI/ANS-8 standard cited in this regulatory guide, the licensee or applicant must perform all operations in accordance with the requirements stated in that standard, but not necessarily with its recommendations.
Licensees or applicants may follow the recommendations given in the ANSI/ANS-8 standards, unless an exception is stated in this regulatory guide, otherwise specified in 10 CFR Parts 70 or 76, or addressed by other acceptable methods.
1.
ANSI/ANS-8 Nuclear Criticality Standards Endorsed by the NRC The NRC endorses the following ANSI/ANS-8 nuclear criticality safety standards:
ANSI/ANS-8.5-1996 (Reaffirmed in 2002), Use of Borosilicate-Glass Raschig Rings as a Neutron Absorber in Solutions of Fissile Material ANSI/ANS-8.6-1983 (Reaffirmed in 2001), Safety in Conducting Subcritical Neutron-Multiplication Measurements In Situ ANSI/ANS-8.7-1998, Nuclear Criticality Safety in the Storage of Fissile Materials ANSI/ANS-8.12-1987 (Reaffirmed in 2002), Nuclear Criticality Control and Safety of Plutonium-Uranium Fuel Mixtures Outside Reactors ANSI/ANS-8.14-2004, Use of Soluble Neutron Absorbers in Nuclear Facilities Outside Reactors ANSI/ANS-8.15-1981 (Reaffirmed in 1995), Nuclear Criticality Control of Special Actinide Elements ANSI/ANS-8.19-1996, Administrative Practices for Nuclear Criticality Safety ANSI/ANS-8.20-1991 (Reaffirmed in 1999), Nuclear Criticality Safety Training ANSI/ANS-8.21-1995 (Reaffirmed in 2001), Use of Fixed Neutron Absorbers in Nuclear Facilities Outside Reactors ANSI/ANS-8.22-1997, Nuclear Criticality Safety Based on Limiting and Controlling Moderators ANSI/ANS-8.23-1997, Nuclear Criticality Accident Emergency Planning and Response
DG-3023, Page 5 2.
ANSI/ANS-8 Nuclear Criticality Standards Endorsed by the NRC with Exceptions The NRC endorses the following ANSI/ANS-8 nuclear criticality safety standards, but takes exception to certain sections, as follows:
ANSI/ANS-8.1-1998, Nuclear Criticality Safety in Operations with Fissionable Materials Outside Reactors The guidance on validating calculational methods for nuclear criticality safety, as specified in ANSI/ANS-8.1-1998, provides a procedure that is acceptable to the NRC staff for establishing the validity and applicability of calculational methods used in assessing nuclear criticality safety. However, it is not sufficient to merely refer to this standard in describing the validation of a method. Rather, a licensee or applicant should provide the details of validation (as stated in Section 4.3.6 of the standard) to (1) demonstrate the adequacy of the margins of subcriticality relative to the bias and criticality parameters, (2) demonstrate that the calculations embrace the range of variables to which the method will be applied, and (3) demonstrate the trends in the bias upon which the licensee or applicant will base the extension of the area of applicability. In addition, the details of validation should state computer codes used, operations, recipes for choosing code options (where applicable), cross-section sets, and any numerical parameters necessary to describe the input.
ANSI/ANS-8.3-1997 (Reaffirmed in 2003), Criticality Accident Alarm System The guidance on criticality accident alarm systems, as specified in ANSI/ANS-8.3-1997 (reaffirmed in 2003), is generally acceptable to the NRC staff. An exception is that 10 CFR 70.24, Criticality Accident Requirements, requires criticality alarm systems in each area in which special nuclear material is handled, used, or stored, whereas Section 4.2.1 of the standard merely requires an evaluation for such areas.
Another exception is that 10 CFR 70.24 and 10 CFR 76.89, Criticality Accident Requirements, require that each area must be covered by two detectors, whereas Section 4.5.1 of the standard permits coverage by a single reliable detector.
Finally, 10 CFR 70.24 and 10 CFR 76.89 require a monitoring system capable of detecting a nuclear criticality that produces an absorbed dose in soft tissue of 20 rads of combined neutron and gamma radiation at an unshielded distance of 2 meters from the reacting material within 1 minute.
DG-3023, Page 6 ANSI/ANS-8.10-1983 (Reaffirmed in 1999), Criteria for Nuclear Criticality Safety Controls in Operations With Shielding and Confinement The guidance on using shielding and confinement as a nuclear criticality safety control, as specified in ANSI/ANS-8.10-1983 (reaffirmed in 1999), is generally accepted by the NRC staff. An exception to Section 4.2.1 of the standard is the assumption that the radiation source strengths and releases from a nuclear criticality accident arise from an excursion occurring in an unfavorable geometry containing a solution of 400 g/L of uranium enriched in U-235. The excursion produces an initial burst of 1x1018 fissions in 0.5 second, followed successively at 10-minute intervals by 47 bursts of 1.9x1017 fissions, for a total of 1x1019 fissions in 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. The excursion is assumed to be terminated by evaporation of 100 liters of the solution. Licensees and applicants may use a less-conservative nuclear criticality accident condition if detailed analyses of credible nuclear criticality accidents are performed and shown to be applicable to the conditions being evaluated.
ANSI/ANS-8.17-1984 (Reaffirmed in 1997), Criticality Safety Criteria for the Handling, Storage, and Transportation of LWR Fuel Outside Reactors The general safety criteria and criteria to establish subcriticality, as specified in ANSI/ANS-8.17-1984 (reaffirmed in 1997), provide guidance that is acceptable to the NRC staff for preventing nuclear criticality accidents in handling, storing, and transporting fuel assemblies at fuel and material facilities. The only exception is that licensees and applicants may take credit for fuel burnup only when the amount of burnup is confirmed by physical measurements that are appropriate for each type of fuel assembly in the environment in which it is to be stored.
3.
ANSI/ANS-8 Nuclear Criticality Standards Withdrawn by the NRC The NRC has withdrawn its endorsement of ANSI/ANS-8.9-1987 (Reaffirmed in 1995),
Nuclear Criticality Safety Criteria for Steel-Pipe Intersections Containing Aqueous Solutions of Fissile Materials. This standard, which was listed in Regulatory Guide 3.71-1998, has subsequently been withdrawn by ANS (i.e., it is a historical standard). Although the NRC has withdrawn its endorsement of the standard, there is nothing technically wrong with this standard and it would be acceptable for licensees and applicants to use it.
DG-3023, Page 7 D. IMPLEMENTATION The purpose of this section is to provide information to applicants and licensees regarding the NRC staffs plans for using this draft regulatory guide. No backfitting is intended or approved in connection with the issuance of this guide.
The NRC has issued this draft guide to encourage public participation in its development.
Except when an applicant or licensee proposes or has previously established an acceptable alternative method for complying with specified portions of the NRCs regulations, the methods to be described in the active guide will reflect public comments and will be used in evaluating submittals in connection with license applications submitted under 10 CFR Part 70, Domestic Licensing of Special Nuclear Material, and 10 CFR Part 76, Certification of Gaseous Diffusion Plants.
REGULATORY ANALYSIS The NRC published a draft regulatory analysis when the agency issued the original draft of this guide (as DG-3013) for public comment in January 1998. Since that time, several ANSI/ANS-8 nuclear criticality safety standards have been added, reaffirmed, revised, or withdrawn. Consequently, the NRC staff has decided to update this guide to clarify which standards the agency endorses and to clearly state exceptions to individual standards. However, this proposed revision does not change any of the guidance provided in Regulatory Guide 3.71; rather, it provides guidance concerning changes that have occurred since the NRC published the original guide 1998. Consequently, the NRC staff has not prepared a separate regulatory analysis for this revised regulatory guide. The original regulatory analysis for DG-3013 is available for inspection or copying (for a fee) in the NRCs Public Document Room (PDR),
which is located at 11555 Rockville Pike, Rockville, Maryland. The PDRs mailing address is USNRC PDR, Washington, DC 20555-0001. The PDR can also be reached by telephone at (301) 415-4737 or (800) 397-4205, by fax at (301) 415-3548; and by email to PDR@nrc.gov.
BACKFIT ANALYSIS This proposed revision of Regulatory Guide 3.71 does not require a backfit analysis, as described in 10 CFR 70.76(b) and 10 CFR 76.76(b), because it does not impose a new or amended provision in the Commissions rules or a regulatory staff position interpreting the Commissions rules that is either new or different from a previous applicable staff position. In addition, this regulatory guide does not require modification or addition to structures, systems, components, or design of a facility or the procedures or organization required to design, construct, or operate a facility. Rather, a licensee or applicant is free to select a preferred method for achieving compliance with a license or the rules or orders of the Commission, as described in 10 CFR Parts 70 and 76.