ML20195E581

Forwards Draft Proposed Rule Package on Proposed Amends to 10CFR21,50 & 54 Re Use of Alternative Source Term at Operating Reactors.Rule Would Allow Holders of Operating Licenses to Revise Design Basis of Facility

ML20195E581
Person / Time
Issue date:	10/16/1998
From:	Roe J NRC (Affiliation Not Assigned)
To:	Larkins J Advisory Committee on Reactor Safeguards
References
FRN-64FR12117, RULE-PR-21-MISC, RULE-PR-50-MISC, RULE-PR-54-MISC AG12-1-041, AG12-1-41, NUDOCS 9811190034
Download: ML20195E581 (88)

Text

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October 16, 1998 -

MEMORANDUM TO: John T. Larkins, Executive Director Advisory Committee on Reactor Safeguards FROM: Jack W. Roe, Acting Director O'i9I""1 8i9""d DY '

Division of Reactor Program Management Office of Nuclear Reactor Regulation

SUBJECT:

TRANSMITTAL OF THE DRAFT PROPOSED RULE PACKAGE -

PROPOSED AMENDMENTS TO 10 CFR PARTS 21,50, AND 54; REGARDING USE OF AN ALTERNATIVE SOURCE TERM AT OPERATING REACTORS Attached is a copy of the draft proposed rule package on proposed amendments to 10 CFR Parts 21, 50, and 54. This proposed rule, if it becomes effective, would allow holders of operating licenses issued prior to January 10,1997, to revise the design basis of the facility to  ;

replace the radiological source term used in design basis accident analyses with the revised source in NUREG-1465, " Accident Source Terms for Light-Water Nuclear Power Plants."

We are providing this cooy to the Advisory Committee on Reactor Safeguards (ACRS) for their review and to support the ACRS briefing scheduled for November 4,1998. Because of tl,'e accelerated schedule imposed on this rulemaking by the Commission, the ACRS review is l

being performed in parallel with t.;e office concurrence process. We will plan to include any  ;

significant changes that were identified during concurrence in our November 4,1998 briefing. I in order to continue to meet the accelerated schedule, we need to receive notification of the acceptability of the troposed rule by close of business November 6,1998.

The Commission (SRM to SECY 98-158 dated September 4,1998) directed the staff to place a copy of this proposed rulemaking package in the PDR at the time that it is forwarded to the l ACRS.

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Octobeh 15,1998 DRAFT - PRE-DECISIONAL

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NUCLEAR REGULATORY COMMISSION 10 CFR Parts 21,50 and 54 '

RIN 3150 -XXXX Use of Altemative Source Terms at Operating Reactors AGENCY: Nuclear Regulatory Commission.

ACTION: Proposed Rule.

SUMMARY

The Nuclear Regulatory Commission (NRC) is proposing to amend its regulations to allow holders of operating licenses for nuclear power plants to voluntarily replace the traditional source term used in design basis accident analyses with an attemative source term.

This action would allow interested licensees to pursue cost beneficial licensing actions to reduce regulatory burden without compromising the margin of safety of the facility. The Commission is also proposing to amend its regulations to revise certain sections to conform

. with final 10 CFR Parts 50 and 100 rulemaking published on December 11,1996 (61 FR 65157).

DATES: Comment period expires on [ publishing +.75 days). Comments received after this date will be considered, if it is practical to do so, but the Commission is able to assure consideration only for comments received on or before this date.

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October 16, 1998 l MEMORANDUM TO: John T. Larkins, Executive Director Advisory Committee on Reactor Safeguards FROM: J W

k W. R oe, Acting Director i ision of Reactor Program Management ice of Nuclear Reactor Regulation

SUBJECT:

TRANSMITTAL OF THE DRAFT PROPOSED RULE PACKAGE -

PROPOSED AMENDMENTS TO 10 CFR PARTS 21,50, AND 54; REGARDING USE OF AN ALTERNATIVE SOURCE TERM AT OPERATING REACTORS Attached is a copy of the draft proposed rule package on proposed amendments to 10 CFR Parts 21, 50, and 54. This proposed rule, if it becomes effective, would allow holders of operating licenses issued prior to January 10,1997, to revise the design basis of the facility to replace the radiological source term used in design basis accident analyses with the revised source in NUREG-1465, " Accident Source Terms for Light-Water Nuclear Power Plants." This proposed rule would also amend Section 50.34 and Part 50, Appendix A, GDC-19 to eliminate the need for certain exemptions for applicants for construction permits, combined operating license, or design certifications docketed after January 10,1997.

We are providing this copy to the Advisory Committee on Reactor Safeguards (ACRS) for their review and to support the ACRS briefing scheduled for November 4,1998. Because of the accelerated schedule imposed on this rulemaking by the Commission, the ACRS review is being performed in parallel with the office concurrence process. We will plan to include any significant changes that were identified during concurrence in our November 4.1998 briefing.

In order to continue to meet the accelerated schedule, we need to receive notification of the acceptability of the proposed rule by close of business November 6,1998.

The Commission (SRM to SECY 98-158 dated September 4,1998) directed the staff to place a copy of this proposed rulemaking package in the PDR at the time that it is forwarded to the ACRS.

Attachment:

As stated CONTACT: Stephen F. LaVie, PERB/NRR 415-1081

October 15,1998 DRAFT - PRE DECISIONAL ADDRESSES: Mail written comments to: Secretary, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, Attention: Rulemakings and Adjudications Staff, Mail Stop 016C1.

The NRC staff specifically requests comment on whether the technical aspects of the rule should be addressed through attemative approaches other than the proposed rule, such as a simple performance-based rule with a regulatory guide endorsing industry consensus standards to permit a more rapid regulatory response by the NRC to future developments and l

changes in the consensus standards.

I Deliver comments to: One White Flint North,11555 Rockville Pike, Rockville, Maryland, l 20852, between 7:30 am and 4:15 pm on Federal workdays. i You may also submit comments via the NRC's interactive rulemaking web site, "Rulemaking Forum," through the NRC home page (http://www.nrc. gov). This site enables people to transmit comments as files (in any format, but Wordperfect version 6.1 is preferred), if your web browser supports that function. Information on the use of the Rulemaking Forum is I

available on the.website. For additional assistance on the use of the interactive rulemaking l site, contact Ms. Carol Gallagher, telephone: 301-415 5905; or by Intemet electronic mail to cag@nrc. gov.

Certain documents related to this rulemaking, including comments received and the environmental assessment and finding of no significant impact may be examined at the NRC Public Document Room,2120 L Street, NW. (Lower Level), Washington, DC. These same documents also may be viewed and downloaded electronically via the interactive rulemaking website established by NRC for this rulemaking.

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October if,1998 DRAFT - PRE-DECISIONAL FOR FURTP5R INFORMATION CONTACT: Mr. Stephen F. LaVie, Office of 19uclear Reactor Regulatio1, U.S.' Nuclear Regulatory Commission, Washington, DC 20555-0001; telephone:

301415-1081; or by intemet electronic mail to efl@nrc. gov.

SUPPLEMENTARY INFORMATION:

1. Background ll. Objectives 111. Altematives IV. Section-by-Section Analysis V. Future Regulatory Action VI. Referenced Documents Vll.

Finding of No Significant Environmentalimpact; Availability Vill. Paperwork Reduction Act Statement IX. Regulatory Analysis X. Regulatory Flexibility Certification XI. Backfit Analysis

1. Background

A holder of an operating license (i.e., the licensee) for a light-water power reactor is required by regulations issued by the Commission (or its predecessor, the U.S. Atomic Energy Commission, (AEC)) to submit a safety analysis report that contains assessments of the radiological consequences of potential accidents and an evaluation of the proposed facility site.

The Commission uses this information in its evaluation of the suitability of the reactor design FRN 3 l

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4 October 15,1998 DRAFT - PRE-DECISIONAL and the proposed site as required by its regulations contained in 10 CFR Parts 50 and 100.

4 Section 100.11, which was adopted by the AEC in 1962 (27 FR 3509, April 12,1962), requires

an applicant to assume (1) a fission product release from the reactor core, (2) the expected

! containment leak rate, and (3) the site meteorological conditions to establish an exclusion area j and a low population zone. This fission product release is based on a credible major accident that would result in substantial release of appreciable quantities of fission products from the j

! core to the containment atmosphere. A note to @ 100.11 states that Technical Information

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Document (TID) 14844, " Calculation of Distance Factors for Power and Test Reactors," may be

, used as a source of guidance in developing the exclusion area, the low population zone, and

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the population center distance.

The fission product release from the reactor core is referred to as the " source term" and 1 it is characterized by the composition and magnitude of the radioactive material, the chemical and physical properties of the material, and the timing of the release from the reactor core. The

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accident source term is used to evaluate the radiological consequences of design basis  !

l accidents (DBAs)in showing compliance with various requirements of the Commission's )

regulations. Although originally used for site suitability analyses, the accident source term is a design parameter for accident mitigation features, equipment qualification, control room operator radiation doses, and post-accident vital area access doses. The measurement range and alarm setpoints of some installed plant instrumentation and the actuation of some plant safety features are based in part on the accident source term. The TID-14844 source term was explicitly stated as a required design parameter for several Three Mile Island (TMI)-related requirements.

The Commission's methods for calculating accident doses, as described in Regulatory Guide 1.3,

• Assumptions Used for Evaluating the Potential Radiological Consequences of a FRN 4 I i

j October 15,1998 DRAFT - PRE-DECISIONAL Loss of Coolant Accident for Poiling Water Reactors"; Regulatory Guide 1.4, " Assumptions i

j Used for Evaluating the Potentif. Radiological Consequences of a Loss of Coolant Accident for Pressurized Water Reactors"; and NUREG-0800, " Standard Review Plan for the Review of i

Safety Analysis' Reports for Nuclear Power Plants," were developed to be consistent with the TID-14844 source term and the whole body and thyroid dose guidelines stated in 6100.11. In 1 this regulatory framework, the source term is assumed to be released immediately to the containment at the start of the postulated accident. The cherrdcol form of the radioiodine l

released to the containment atmosphere is assumed to be predominantly elemental, with the remainder being small fractions of particulate and organic iodine forms. Radiation doses are calculated at the exclusion area boundary (EAB) for the first 2-hours and at the low population ,

- zone (LPZ) for the assumed 30-day duration of the accident. The whole body dose comes primarily from the noble gases in the source term, and the thyroid dose is based on inhalation of ra@ iodines, in analyses performed to date, the thyroid dose has generally been limiting, and

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the deslin of some engineered safety features, such as containment spray systems and the charcoal filters in the containment, the building exhaust, and the control room ventilation i systems, are predicated on these postulated thyroid doses.- Subsequently, the Commission adopted the dose criteria in Criterion 19 of 10 CFR Part 50, Appendix A.

The source term in TID-14844 is representative of a major accident involving significant core damage, as might be postulated to occur for a large loss-of-coolant accident (LOCA).

Although the LOCA is typically the maximum credible accident, Commission experience in reviewing license applications has indicated the need to consider other accident sequences of lesser consequence but higher probability of occurrence. Some of these additional accident analyses may involve source terms that are a fraction of those specified in TID-14844. The DBAs were not intended to be actual event sequences, but rather, were intended to be FRN 5 i

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October 15,1998 DRAFT - PRE-DECISIONAL surrogates to enable deterministic evaluation of the response of the plant engineered safety features. These accident analyses are intentionally conservative in order to address known uncertainties in accident progression, fission product transport, and atmospheric dispersion.

Although probabilistic risk assessments (PRAs) can provide useful insights into system 1 performance and suggest changes in how the desired defense in depth is achieved, defense in depth continues to be an effective way to account for uncertainties in equipment and human performance. The Commission's policy statement on the use of PRA methods (60 FR 42622) calls for the use of PRA technology in all regulatory matters in a manner that complements the Commission's deterministic approach and supports the traditional defense-in-depth philosophy.

Since the publication of TID-14844, significant advances have been made in understanding the timing, magnitude, and chemical form of fission product releases from severe nuclear power plant accidents. Many of these insights developed out of the major research efforts started by the Commission and the nuclear industry after the accident at Three Mile Island (TMI). In 1995, the Commission published NUREG-1465, " Accident Source Terms for Light-Water Nuclear Power Plants," which utilized this research to provide more physically based estimates of the accident source term that could be applied to the design of future light-

water power reactors. The Commission sponsored significant review efforts by peer reviewers, foreign research partners, industry groups, and the general public (request for public comment was published in 57 FR 33374). The information in NUREG-1465 presents a representative accident source term for a boiling-water reactor (BWR) and for a pressurized-water reactor (PWR). These source terms are described in terms of radionuclide composition and magnitude, physical and chemical form, and timing of release. Where TID-14844 addressed three categories of radionuclides, the revised source terms categorize the accident release into eight groups by physical and chemical properties. Where TID-14844 assumed an immediate FRN 6

October 15,1998 ' DRAFT - PRE-DECISIONAL release of the activity, the revised source term has five release phases that are postulated to occur over several hours, with the onset of major core damage occurring after 30 minutes.

Where TID-14844 assumed radioiodine to be predominantly elemental, the revised source term assumes radioiodine to be predominantly cesium iodide (Csl), an aerosol that is more amenable to mitigation mechanisms. For DBAs, the NUREG-1465 source term is comparable to the TlD-14844 source term with regard to the magnitude of the noble gas and radiolodine release fractions. However, the revised source term offers a 'more representative description of the radionuclide composition and release timing. The Commission has determined (SECY 302, dated December 1994) that design basis analyses will ~Idress the first three release phases - coolant, gap, and in-vessel. The ex-vessel and late in-vessel phases are considered to be unduly conservative for design basis analysis purposes. These latter releases could only result from core damage accidents with vessel failure and core-concrete interactions. The estimated frequencies of such scenarios are low enough that they need not be considered credible for the purpose of meeting the requirements of 6100.11 or, as proposed herein, 6 50.67.

The objective of NUREG-1465 was to define a revised accident source term for I i

regulatory application for future light water reactors. The Commission's intent was to capture the major relevant insights available from severe accident research to provide, for regulatory purposes, a more realistic portrayal of the amount of the postulated accident source term.

These source terms were derived from examining a set of severe accident sequences for light water reactors (LWRs) of current design. Because of general similarities in plant and core I design parameters, these results are considered to be applicable to evolutionary and passive LWR designs. The revised source term has been used in evaluating the Westinghouse AP-600 FRN 7

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October'15,1998 DRAFT - PRE-DECISIONAL standard design certification application. (A draft version of NUREG-1465 was used in

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evaluating Combustion Engineering's (CE's) System 80+ design.)

The Commission considered the applicability of the revised source term to operating reactors and determined that the current analytical approach based on the TID-14844 source term would continue to be adequate to protect public health and safety, and that operating i reactors licensed under this approach would not be required to reanalyze accidents using the revised source term. The Commissien also concluded that some licensees may wish to use an i

attemative source term in analyses to support operational flexibility and cost-beneficial licensing actions. The Commission initiated several actions to provide a regulatory basis for operating l

reactors to voluntarily amend their facility design bases to enable use of the revised source in design basis analyses. First, the Commission solicited ideas on how an altemative source term i

might be implemented in November 1995, the Nuclear Energy Institute (NEI) submitted its I generic framework, Electric Power Research Institute Technical Report TR-105909, " Generic Framework for Application of Revised Accident Source Term to Operating Plants." This report and the NRC response were discussed in SECY-96-242 (November 1996). Second, the

. Commission initiated a comprehensive assessment of the overallimpact of substituting the NUREG 1465 source term for the traditionally used TlD-14844 source term at two typical facilities. This was done to evaluate the issues involved with applying the revised source term at operating plants. SECY 98-154 (June 1998) described the conclusions of this assessment.

Third, the Commission accepted license amendment requests related to implementation of the revised source term at a small number of pilot plants. Experience has demonstrated that evaluation of a limited number of plant-specific submittals improves regulation and regulatory guidance development. The review of these pilot projects is currently in progress. Insights j from these pilot plant reviews will be incorporated into the regulatory guidance that will be FRN 8  ;

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October 15,1998 DRAFT- PRE DECISIONAL developed in conjunction with this rulemaking. Fourth, the Commission initiated,an assessment on whether rulemaking would be necessary to allow operating reactors to use an alternative source term. The proposed rule described herein, and the supporting regulatory guidance that will be developed as part of this rulemaking, have resulted from this assessment. The Commission plans to issue the supporting regulatory guidance for public comment on the same as it publishes the final rule.

This proposed rulemaking for use of an altemative source term is applicable only to those facilities for which a construction permit was issued before January 10,1997, under 10 CFR Part 50, " Domestic Licensing of Production and Utilization Facilities." The regulations of this part are supplemented by those in other parts of Chapter 1 of Title 10, including Part 100, " Reactor Fte Criteria." Part 100 contains language that qualitatively defines a required accident source term and contains a note that discusses the availability of TID-14844.

With the exception of @ 50.34(f), there are no explicit requirements in Chapter 1 of Title 10 to use the TID-14844 accident source term. Section 50.34(f), which addresses additional TMI-related requirements, is only applicable to a limited number of construction permit applications pending on February 16,1982, and to applications under Part 52.

An applicant for an operating license is required by 50.34(b) to submit a final safety analysis report (FSAR) that describes the facility and its design bas , and limits, and presents a safety analysis of the structures, systems, and components of the facility as a whole.

Guidance in performing these analyses is given in regulatory guides. In its review of the more recent applications for operating licenses, the Commission has used the review procedures in NUREG-0800," Standard Review Plan for the Review of Safety Analysis Reports for Nucle::t Power Plants"(SRP). These review procedures reference or provide acceptable assumptions and analysis methods. The facility FSAR documents the assumptions and methods actually FRN 9 l

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October 15,1998 DRAFT - PRE-DECISIONAL used by the applicant in the required safety analyses. The Commission's finding that a license may be issued is based on the review of the FSAR,- as documented in the Commission's safety evaluation report (SER). By their inclusion in the FSAR, the assumptions (including the source term) become part of the design basis

• of the facility. From a regulatory standpoint, the requirement to use the TfD-14844 source term is expressed as a licensee commitment (typically to Regulatory Guide 1.3 or 1.4) documented in the facility FSAR, and thereby subject to the requirements of $ 50.59.

L in January 1997, the Commission amended its regulations in 10 CFR Parts 21,50,52, l

54, and 100 (61 FR 65157). That regulatory action produced site criteria for future sites; presented a stable regulatory basis for seismic and geologic siting and the engineering design of future nuclear power plants to withstand seismic events; and relocated source term and dose requirements for future plants into Part 50. Since these dose requirements tend to affect reactor design rather than siting, they are more appropriately located in Part 50. This

, decoupling of siting from design is consistent with the future licensing of facilities using standardized plan designs, the design features of which will be certified in a separate design certification rulemaking. This decoupling of siting from design was directed by Congress in the 1980 Authorization Act for the NRC, Since the revised criteria would not apply to operating l

reactors, the non-seismic and seismic reactor site criteria for operating reactors were retained as Subpart A and Appendix A to Part 100, respectively. The revised reactor site criteria were

• As defined in 10 CFR Part 50.2, design bases means that information which identifies the specific functions to be performed by a structure, system, or component of a facility, and the specific values or ranges of values chosen for controlling parameters as reference bounds for design. These values may be (1) restraints derived from generally accepted " state of the art" practices for achieving functional goals, or (2) requirements derived from analysis (based on calculation and/or experiments) of the effects of a postulated accident for which a structure, system, or component must meet its functional goals. The Commission considers the accident source term to be an integral part of the design basis because it sets forth specific values (or range of values) for controlling parameters that constitute reference bounds for design.

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4 October 15,1998 DRAFT - PRE-DECISIONAL added as Subpart B in Part 100, and revised source term and dose requirements were moved to 6 50.34. The existing source term and dose reouirements of Subpart A of Part 100 will remain in place as the licensing bases for those operating reactors that do not elect to use an altemative source term.

In relocating the source term and dose requirements for future reactors to 9 50.34, the Commission retained the requirements for the exclusion area and the low population zone, but revised the associated numerical dose guidelines to replace the two different doses for the whole body and the thyroid gland with the single, total effective dose equivalent (TEDE) value.

The dose guidelines for the whole body and the thyroid, and the immediate 2-hour exposure period, were largely predicated by the assumed source term being predominantly noble gases and radioiodines instantaneously released to the containment and the assumed " single critical organ" method of modeling the intemal dose used at the time that Part 100 was originally published. However, the current dose guidelines, by focusing on doses to the thyroid and the whole body, assume that the major contributor to doses will be radioiodine. Although this may be appropriate with the TID-14844 source term, it may not be true for a source term based on a more complete understanding of accident sequences and phenomenology. The postulated chemical and physical form of radioiodine in the revised source term is more amenable to mitigation and, as such, radioiodine may not always be the predominant radionuclide in an accident release. The revised source term includes a larger number of radionuclides than did the TID-14844 source term. The whole body and thyroid dose guidelines ignore these contributors to dose. The Commission amended its radiation protection standards in Part 20 in 1991 (56 FR 23391), replacing the single, critical organ concept for asset. sing intemal exposure with the TEDE concept that assesses the impact of all relevant nuclides upon all body organs.

TEDE is defined to be the deep dose equivalent (for extemal exposure) plus the committed FRN 11

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October 15,1998 DRAFT- PRE DECISIONAL effective dose equivalent (for internal exposure). The deep dose equivalent (DDE) is comparable to the present whole body dose; the committed effective dose equivalent (CEDE) is the sum of the products of doses (integrated over a 50-year period) to selected body organs resulting from the intake of radioactive material multiplied by weighting factors for each organ that are representative of the radiation risk associated with the particular organ. The TEDE, using a risk-consistent methodology, assesses the impact of all relevant nuclides upon all body organs. Although it is expected that in many cases, the thyroid could still be the limiting organ and radiciodine the limiting radionuclide, this conclusion cannot be assured in all potential cases. The revised source term postulates that the core inventory is released in a sequence of phases over 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />, with the more significant release commencing at about 30 minutes from the start of the event. The assumption that the 2-hour exposure period starts immediately at the onset of the release is inconsistent with the phased release postulated in the revised source term. The proposed rulemaking will extend the future LWR dose guidelines to operating reactors that elect to use an altemative source term.

An accidental releas'sof radioactivity can result in radiation exposure to control room 4

operators. Normal ventilation systems may draw this activity into the controi room where it can result in extemal and intemal exposures. Control room designs differ but, in general, design features are provided to detect the accident or the activity and isolate the normal ventilation intake. Emergency ventilation systems are activated to minimize infiltration of contaminated air and to rentove activity that has entered the control room. Personnel exposures can also result from radioactivity outside of the control room. However, because of concrete shielding of the control room, these latter exposures are generally not limiting. The objective of the control room detign is to provide a location from which actions can be taken to operate the plant under normal conditions and to maintain it in a safe condition under accident conditions. General FRN 12 r

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October 15,1998 DRAFT - PRE DECISIONAL Design Criterion 19 (GDC-19)(Control Rocc. " of Appendix A to 10 CFR Part 50 (36 FR 3255),

establishes minimum requirements for the design of the contrd room, including a requirement -

for radiation protection features adequate to permit access and occupancy of the control room under accident conditions. The GDC-19 criteria were established forjudging the acceptability of the control room design for protecting control room operators under postulated design basis accidents, a significant concem being the potential increases in offsite doses that might result

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from the inability of control room personnel to adequately respond to the event.

The GDC-19 criteria are expressed in terms of whole body dose, or its equivalent to any organ. The Commission did not revise the criteria when Part 20 was amended (56 FR 23391) instead deferring such action to individual facility licensing actions (NUREG/CR-6204). This  !

l position was taken in the interest of maintaining the licensing basis for those facilities already licensed. The Commission is proposing to replace the current GDC-19 dose criteria for future reactors and for operating reactors that elect to use an altemative source term with a crite-ion expressed in terms of TEDE. The rationale for this revision is similar to the rationale, discussed earlier in this preamble, for revising the dose guidelines for offsite exposures.

On January 10,1997 (61 FR 65157), the Commission amended 10 CFR Parts 21, 50, 52,54, and 100 of its regulations to update the criteria used in decisions regarding power reactor siting for future nuclear power plants. The Commission intended that future licensing i applications in accordance with Part 52 will utilize a source term consistent with the source ter.n l information in NUREG-1465 and the accident TEDE guidelines in Parts 50 and 100. However, i 1

during the final design approval (FDA) and design certification proceeding for the Westinghouse AP-600 advanced light-water reactor design, the NRC staff and Westinghouse determined that exemptions were necessary from 99 50.34(f)(vii), -(viii), -(xxvi), and -(xxviii) and 10 CFR Part 50, Appendix A, GDC-19. This rulemaking eliminates the need for these exemptions for FRN 13

I October 15,1998 DRAFT - PRE DECISIONAL future applicants under Part 52 by making conforming changes to Part 50, Appendix A, GDC-19 and 6 50.34.

11 Objectives l

l The objectives of this proposed regulatory action are to-l 1. Provide a regulatory framework for the voluntary implementation of an attemative

( source term as a change to the design basis at currently licensed power reactors, thereby .

enabling potential cost-beneficiallicerising actions while continuing to maintain existing safety margins and defense in depth.

2. Retain the existing regulatory framework for currently licensed power reactor l

l licensees who choose not to implement an altemative source term, but continue to comply with their existing source term.

l. 3. Relocate source term and dose requirements that apply primarily to plant design into 10 CFR Part 50 for operating reactors that choose to implement an altemative source term.

4. Implement conforming changes to 9 50.34(f) and Part 50, Appendix A, GDC-19 to i

eliminate the need for exemptions for future applicants under Part 52.

l lil. Alternatives

! The first attemative consbered by the Commission was to continue using current regulations for accident dose guidelines and control room dose criteria. This is not considered to be an acceptable attemative. As discussed at 61 FR 65157, the Commission determined that dose guidelines expressed in terms of whole body and thyroid doses were inconsistent with

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October 15,1998 DRAFT - PRE-DECISIONAL i

the use of new source terms not based upon TID-14844. With regard to the exclusion area dose guideline, tha Commission had previously determined (61 FR 65157) that the dose T

guideline applies to the 2-hour period resulting in the maximum dose.

l The second attemative considered by the Commission was the replacement of the existing guidelines in 6100.11 and the existing criteria 10 CFR Part 50 Appendix A. GDC-19 with an entirely new regulation. This is not considered to be a desirable altemative because the provisions of the existing regulations form part of the licensing bases for many of the operating

reactors. Therefore, these provisions must remain in effect for operating reactors that do not

. implement an altemative source term. In addition, this altemative would also be inconsistent 4

with the Commission's philosophy of separating plant siting criteria and dose requirements.

The approach of establishing the requirements for use of an altemative source term in a new section to Part 50 while retaining the existing regulations in Part 100 Subpart A and Part 50 Appendix A GDC-19 was chosen as the best altemative.

The Commission considered altematives with regard to providing regulatory guidance to support the new section to Part 50. The first option was to issue no additional regulatory guidance. This option was not considered to be acceptable because, in the absence of clear regulatory guidance, licensee efforts in preparing applications, and the NRC staff review of submitted applications, could be hindered by differences in interpretations and technical positions. This could result in the inefficient use of licensee and staff resources, could cause licensing delays, and could lead to less uniform and less consistent regulatory implementation.

The second option was to replace the existing regulatory guides that address the radiological consequences of accidents with new revisions. This is not considered to be an acceptable choice because the provisions of the existing regulatory guides form part of the licensing bases for many of the operating reactors. Therefore, these provisions must remain in effect for those FRN 15

' October 15,1998 DRAFT - PRE-DECISIONAL operating reactors that do not implement an attemative source term. The third option was to issue a new regulatory guide on the implementation of an altemative source term that would l include, in a series of appendices, revised assumptions and acceptable analysis methods for each design basis accident. The approach of issuing a new regulatory guide was determined to i

{ be the best option. To provide review guidance for the NRC staff, a new section on design basis radiological analyses using an attemative source term would be added to the Standard Review Plan.

IV Section-by-Section Analysis A. Section 50.2 The proposed rule defines source term as it is used in 9 50.67. In NUREG-1465, the source term is defined by five projected characteristics: (1) magnitude of radioactivity release, (2) radionuclides released, (3) physical form of the radionuclides released, (4) chemical form of  ;

the radionuclides released, and (5) timing of the radioactivity release. although all five i characteristics should be addressed in applications proposing the use of an attemative source term, there may be technically justifiable applications in which all five characteristics need not i

be addressed. The Commission intends to allow licensees flexibility in implementing an l

altemative source term consistent with maintaining a conservative, clear, logical, and consistent plant design basis. The regulatory guide that supports this proposed rule will contain guidance on an acceptable analytical approach for showing compliance with this rule, l

B. Section 50.67(a)

This paragraph would define the licensees that may seek to revise their current FRN 16

October 15,1998 DRAFT- DRE-DECISIONAL radiological source term with an attemative sourw temi. The proposed rule is applicable only to holders of nuclear power plant operating licenses that were iss' ued under 10 CFR Part 50 before January 10,1997. The proposed rule would not require licensees to revise their current source term. The Commission considered the acceptability of the TID-14844 source term at current operating reactors and determined that the analytical approach based on the TID-14844 source term would continue to be adequate to protect public health and safety, and that operating reactors licensed under this approach should not be required to reanalyze design basis accidents using a new source term. The proposed rule does not explicitly define an alternative source term. In lieu of an explicit reference to NUREG-1465, Footnote 1 to the

~

proposed rule identifies the significant characteristics of an accident source term. The  !

~

regulatory guide that will be issued to support this proposed rule will identify the NUREG-1465 source term as an acceptable attemative to the source term in TfD-14844, and will provide implementation guidance. This approach provides for future revised source terms, should they i 1-be developed, and allows licensees to propose additional attematives for consideration by the Commission.

I C. Section 50.67(b)(1) 1 This paragraph of @ 50.67 would state the information that a licensee must submit as part of a license amendment to use an alternative source term. Because of the extensive use of the accident source term in the design and operation of a power r3 actor, and because of the potentialimpact on postulated accident consequences and margins of safety of a change of such a fundamental design assumption, the Commission has determined that any change to the design basis to use an altemative source term should be reviewed and approved by the Commission in the form of a license amendment. Although the source term is a fundamental FRN 17 4

e w -

4 October 15,1998 DRAFT - PRE-DECISIONAL design assumption, generic analyses performed by the NRC staff in support of this proposed rule have indicated there are potential applications that the Commission, with consideration of 2

facility-specific evaluations, would find involved no significant hazards. The procedural -

requirements for processing a license amendment are given in $$ 50.90 through 50.92.

4 The Commission's regulations provide a regulatory mechanism for a licensee to effect a j change in its design basis in 5 50.59. That section allows a licensee to make changes to the facility as described in the final safety evaluation report (FSAR) without prior Commission approval, unless the proposed change is deemed to involve an unreviewed safety question l (USQ), or involves a change to the technical specifications incorporated into the facility license.

If a USQ is determined to exist, or if a change to the technical specifications is involved, the licensee must request Commission approval of the change using the license amendment 4

process detailed in 6 50.90. The criteria for determining that a USQ is involved appear in 6 50.59. Significant to this proposed rule is the criterion that a USQ would exist if the proposed

change resulted in an increase in consequences of en accident or malfunction. In many applications, an attemative source term may reduce the postulated consequences of the t

accident or malfunction. For this reason, the Commission determined that the regulatory framework of 9 50.59 does not provide assurance that this change in the design basis would be r

j. recognized by the licensee as needing review by the NRC staff. Once a licensee has been 4

authorized to substitute an attemative source term in its design basis, subsequent changes to

the facility that involve an attemative source term may be processed under 9 50.59 or 9 50.90, 4

as approp6 ate. However, a sulcoquent change to the source term itself could not be implemented under @ 50.59.

The proposed rule calls for the applicant to perform analyses of the consequences of

' applicable design basis accidents previously analyzed in the safety analysis report and to FRN 18 i

t p 7 ---

g ,m g- , --%- 3 r*w - - - - . - - --- + ++ - , - - - +'-

_7 1

October 15,1998 DRAFT- PRE-DECISIONAL submit a description of the analysis inputs, assumptions, methodology, and results of these analyses for Commission review. Applicable evaluations may include, but are not limited to, those previously performed to show compliance with $ 100.11,9 50.49, Part 50 Appendix A  :

GDC-19, 9 50.34(f), and NUREG-0737 requirements ll.B.2, ll.B.3, Ill.D.3.4. The regulatory guide that supports this proposed rule will provide guidance on the scope and extent of analyses used to show compliance with this rule and on the assumptions and methods used J

therein. It is not the intent of the Commission that all of the design basis radiological analyses i for a facility be re-performed as a prerequisite for approval of the use of an attemative source term. The Commission does expect that the applicant will perform sufficient evaluations, supported by calculations as warranted, to demonstrate the acceptability of the proposed amendment.

D. Sections 50.67(b)(2)(i),-(ii), -(iii)

These subparagraphs state the three criteria for Commission approval of the license amendment to use an attemative source term. A detailed rationale for the use of 0.25 Sv (25 rem) TEDE as an accident dose guideline and the use of the 2-hour exposure period resulting in the maximum dose for future LWRs is provided at 61 FR 65157. The same considerations that formed the basis for that rationale are similarly applicable to operating reactors that elect to use an altemative source term. The Commission believes that it is technically appropriate and logical to extend the philosophy of decoupling of design and siting and the dose guidelines established for future LWRs to operating reactors that elect to use an altemative source term.

The Commission is proposing to replace the current GDC-19 dose criteria for operating reactors that elect to use an attemative source term with a criterion of 0.05 Sv (5 rem) TEDE for the duration of the accident. This criterion is included in 50.67 rather than GDC-19 in order to FRN 19 4

I l

Oc*ober 15,1998 DRAFT - PRE-DECISIONAL  !

co-locate'all of the dose requirements associated with an attemative source term. The bases 1

for the Commission's decision follow: First, the criteria in GDC-19 and that in the proposed rule l

are based on a primary occupational exposure limit. Second, The language in GDC-19: I

" . 5 rem whole body, or its equivalent to any part of the body..."is subsumed by the definition of TEDE in l 20.1003 and by the 0.05 SV (5 rem) TEDE annuallimit in 6 20.1201(a). Although the weighting factors stated in 9 20.1003 for use in determining TEDE differ in magnitude from the weighting factors implied in the 0.3 Sv (30 rem) thyroid criteria used for showing compliance with GDC-19, these differences are the result of improvement in the science of assessing intemal exposures, and do riot represent a reduction in the level of protection. Third, as l

discussed earlier in this preamble, the use of TEDE in conjunction with an attemative source term has been deemed appropriate and necessary. Fourth, the use of TEDE for the control room dose criterion is consistent with the use of TEDE in the accident dose guidelines for offsite i

exposure.

The Commission is not including a " capping" limitation, that is, an additional requirement that the dose to any individual organ not be in excess of some fraction of the total as provided for routine occupational exposures. The bases for the Commission's decision follov.: First, this decision is consistent with the recent Part 100 rulemaking (61 FR 65157) with regard to doses to persons off site. Second, the use of 0.05 Sv (5 rem) TEDE as the control room criterion does not imply that this would be an acceptable exposure during emergency conditions, or that other radiation protection standards of Part 20, including individual organ dose limits, might not apply.

This criterion is provided only to assess the acceptability of design provisions for protecting control room operators under postulated DBA conditions. The DBA conditions assumed in these analyses, although credible, generally do not represent actual accident sequences, but rather, are specified as conservative surrogates to create bounding conditions for assessing the FRN 20 l

O

m October 15,1998 DRAFT - PRE-DECISIONAL acceptability of engineered safety features. Third,9 20.1206 permits a once-in-a-lifetime planned special~ dose of five times the annual dose limits. Also, Environmental Protection Agency (EPA) guidanc'e sets a limit of five times the annual dose limits for workers performing emergency services such as lifesaving or protection of large populations. Considering the individual organ weighting factors of 9 20.1003 and assuming that only the exposure from a (

single organ contributed to TEDE, the organ dose, although exceeding the dose specified in

$ 20.1201(a), would be less than that considered acceptable as a planned special dose or as an emergency worker dose. The Commission is not suggesting that control room dose during an accident can be treated as a planned special exposure, or that the EPA emergency worker dose limits are an attemative to GDC-19 or the proposed rule. However, the Commission does believe that these provisions offer a useful perspective that supports the conclusion that the organ doses implied by the proposed 0.05 Sv (5 rem) criterion can be considered to be acceptable given the relatively low probability of the events that could result in doses of this magnitude.

Although the dose criteria in the proposed rule will supersede the dose criteria in GDC-19, the other provisions of GDC-19 remain applicable E. 10 CFR Part 50, Appendix A, GDC-19 GDC-19 would be changed to include the TEDE dose criterion for control room design for applicants for construction permits, design certifications, and combined operating licenses that submitted applications after January 10,1997, and for those licenses using an alternative l source term under 6 50.67. The proposed change to GDC-19 addresses the use of an altemative source term at operating reactors and a deficiency identified in the regulatory framework for early site permits, standard design certifications, and combined licenses under FRN 21 4

__-. , _ _. ,. _ ~ .__. ._. . __ . _. .. _.__. -. _ . ___ . . _ _

t-4.

4 October 15,1998 DRAFT - PRE-DECISIONAL Part 52. Sections 52.18,52.48, and 52.81 establish that applications filed under Part 52, Subparts A, B, and C, respectively, will be reviewed according t'o the standards given in 10 CFR

.j 4

Parts 20,50,51,55,73, and 100 to the extent that those standards are technically relevant to

. l j

the proposed design. Therefore, GDC-19 is pertinent to applications under Part 52. The recent Part 100 rulemaking (61 FR 65157) established accident TEDE guidelines (in 9 50.34) for applicants under Part 52, but did not change the existing control room whole body (or equivalent) dose criterion in GDC-19. Thus, exemptions from the dose criteris in the current i

GDC-19 were necessary in the design certification process for the Westinghouse AP-600 advanced LWR in order to use the 0.05 Sv (5 rem) TEDE criterion deemed necessary for use with an attemative source term, and exemptions would arguably be necessary for future applicants for construction permits, design certifications, and combined operating licenses.

This proposed change will eliminate the need for such exemptions.

F. Sections 21.3, 50.2, 50.49(b)(1)(i)(C), 50.65(b)(1), and 54.4(a)(1)(iii)

These sections are being revised to conform with the relocation of accident dose guidelines from $ 100.11 to $ 50.67 for operating reactors that have amended their design bases to use an attemative source term.

H. Section 50.34 A new footnote to $ 50.34 has been added to define what constitutes an accident source term. This new footnote is identical to the existing footnote 1 to 9100.11, and is being added to provide for consistency between Parts 50 and 100.

FRN 22

October 15,1998 DRAFT - PRE DECISIONAL t

1. Sections 50.34(f)(vii), -(viii), -(xxvi) and -(xxviii) .

These paragraphs are being revised to replace an explicit reference to the " TID-14844 source term" with a more general reference to " accident source term." These changes potentially affect two classes of applicants. The first affected class is facilities that obtain combined licenses under Part 52. Section 52.47(a)(ii) states that applications for combined licenses must contain, inter alia, " demonstration of compliance with any technically-relevant portions of the Three Mile Island requirements set forth in 9 50.34(f)." Section 50.34(f) contains several references to the TID-14844 source term. These references would be modified to delete the reference to TlD-14844. This will make it clear that applicants for combined licenses would not use the TID-14844 source term, but would use the source term in the design certification, if referenced, or else a source term that is justified in the combined license application.

The second affected class is the small subset of plants that had construction permits  !

pending on February 16,1982. With the proposed change, these plants could use either the TID-14844 source term or an altemative source term in their operating license applications.

V. Future Regulatory Action The NRC is developing the following regulatory guides and Standard Review Plan sections to provide prospective applicants with the necessary guidance for implementing the l proposed regulation. The draft guide and draft Standard Review Plan section will be issued to j coincide with the publication of the final regulations that would implement this proposed i

rulemaking. A notice of availability for these materials will be published in the Federal Register at a future date. l i

FRN 23 l

l l

October 15,1998 DRAFT - PRE-DECISIONAL

1. Draft Guide DG-1081, " Revised Radiological Source Term for Evaluating the Radiological Consequences of Design Basis Accidents at Boiling and Pressurized Water Reactors."

This guide is expected to present regulatory guidance on the implementation of an altemative source term at operating reactors. The guide is expected to address issues i

involving limited or selective implementation of an altemative source term and probabilistic risk assessment (PRA) issues related to plant modifications based on an attemative source term, I and to provide guidance on the scope and extent of affected DBA radiological analyses and associated acceptance criteria. The guide is expected to include, in a series of appendices, revised assumptions and methods for each affected DBA. For those facilities using an attemative source, these appendices will supersede the guidance of Regulatory Guides 1.3, 1.4,1.25, and 1.77, and will supplement guidance in Regulatory Guide 1.89. .

2. Standard Review Plan Section,15.0.1, " Radiological Consequence Analyses Using Revised Source Term."

This SRP section presents guidance to NRC staffin the review of the adequacy of licensee submittals requesting approval for use of an attemative source term.

VI. Referenced Documents Copies of NUREG-0737, NUREG-0800, NUREG-1465, and NUREG/CR-6204 may be  ;

purchased from the Superintendent of Documents, U.S. Govemment Printing Office, Mail Stop 090P, Washington, DC 20402-9328. Copies also are available from the National Technical information Service,5285 Port Royal Road, Springfield, VA 22161. A copy also is available for FRN 24

e October 15,1998 DRAFT - PRE-DECISIONAL  !

inspection and copying for a fee in the NRC Public Document Room,2120 L Street, NW. t (Lower Level), Washington, DC.

t l

4 Copies of issued regulatory guides may be purchased from the Goverr, ment Printing

{

. Office (GPO) at the current GPO price. Information on current GPO prices may be obtained by contacting _the Superintendent of Documents, U.S. Govemment Printing Office, P.O. Box

37082, Washington, DC 20402-9328. Issued guides also may be purchased from the National 4

j Technical'Information Service (NTIS) on a standing order basis. Details on this service may be obtained by writing NTIS, 5826 Port Royal Road, Springfield, VA 221'61.

Copies of SECY-94-302, SECY-96-242, SECY-98-154, TID 14' 844, and TR-105909 are f available for inspection and copying for a fee at the NRC Public Document Room,2120 L j.

j Street, NW. (Lower Level), Washington, DC. 1 b . l Vll. Draft Finding of No Significant EnvironmentalImpact: Availability The Commission has determined under the National Environmental Policy Act of 1969, as amended, and the Commission's regulations in Subpart A of 10 CFR Part 51, that this regulation is not a major Federal action significantly affecting the quality of the human environment and, therefore, an environmentalimpact statement is not required. This proposed rule would allow operating reactors to replace the traditional TID-14844 source term with a more realistic source term that is based on the insights gained from extensive accident research activities. The actual accident sequence and progression is not changed; it is the regulatory assumptions regarding the accident that will be affected by the change. The use of an attemative source term alone cannot increase the core damage frequency (CDF) or the large early release frequency (LERF) or actual offsite or onsite radiation doses. An alternative FRN 25 1

I l

i October 15,1998 DRAFT - PRE-DECISIONAL source term could be used to justify changes in the plant design that might have an impact on CDF or LERF or'that might increase offsite or onsite doses. These potential changes are subject to existing requirements in the Commission's regulations. Thus, the protection of public health and safety would not be decreased by this prcposed rulemaking. The proposed rule does not affect non-radiological plant effluents and has no significant environmental impact. l As discussed above, the determination of the environmental assessment is that there will be no significant offsite impact on the public from this action. However, the general public .

should note that the NRC welcomes public participation. Also, the Commission has committed

)

itself to complying in all its actions with President Clinton's Executive Order #12898-

• Federal Actions to Address Environmental Justice in Minority Populations and Low-income Populations," dated February 11,1994. In accordance with that executive order, the Commission has determined that there are no disproportionately high and adverse impacts on minority and low income parties. In the letter and spirit of Executive Order #12898, the .

Commission is requesting public comments on any environmentaljustice considerations or questions that the public thinks may be related to this proposed rule, but that somehow were not addressed. The Commission uses the following working definition of environmentaljustice:

Environmentaljustice means the fair treatment and meaningfulinvolvement of all people, regardless of race, ethnicity, culture, income, or educational level with respect to the development, implementation and enforcement of environmental laws, regulations, and policies.

Comments on any aspect of the environmental assessment, including environmental justice, may be submitted to the Commission as indicated under the ADDRESSES heading.

The draft environmental assessment and the draft finding of no significant impact on which this determination is based are available for inspection at the NRC Public Document Room,2120 L Street NW, (Lower Level), Washington, DC. Single copies of the environmental FRN 26

, , . - - . . .- - - - .. . - - . ~ . -

J i

1 October 15,1998 DRAFT - PRE-DECISIONAL i

assessment and finding of no significant impact are available from Mr. Stephen F. LaVie, Office '

l of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC 20555-j 0001, telephone: 301-415-1081, or by intemet electronic mail to sfl@nrc. gov. I Vill. Paperwork Reduction Act Statement i

4 This proposed rule amends information collection requirements that are subject to the l

Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et seq). This rule has been submitted to the Office of Management and Budget (OMB) for review and approval of the information collection requirements.

The public reporting burden for this information collection is estimated to average 609

' hours per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the information collection. However, because NRC expects licensees to submit an amendment

- request to use the new source term in lieu of submitting a less important amendment request, NRC does not project any change in burden for the current 10 CFR Part 50. The U.S. Nuclear Regulatory Commission is seeking public comment on the potential impact of the information collections contained in the proposed rule (or proposed policy statement) and on the following issues:

1. Is the proposed information collection necessary for the proper performance of the functions of the NRC, including whether the information will have practical utility?

2. Is the estimate of burden accurate?

FRN 27

October 15,1998 DRAFT - PRE-DECISIONAL

3. Is there a way to enhance the quality, utility, and claritp of the information to be collec ed?

- 4. How can the burden of the information collection be minimized, including the use of automated collection techniques? ,

Send comments on any aspect of this proposed information collection, including .

suggestions for reducing the burden, to the Records Management Branch (T-6F33), U.S.

Nuclear Regulatory Commission, Was'hington, DC 20555-0001, or by Intemet electronic mail at i

bjs1@nrc. gov; and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0011), Office of Management and Budget. Washington, DC 20503.

l Comments to OMB on the information collections or on the preceding issues should be submitted by (insert date 30 days after publication in the Federal Register). Comments received after this date will be considered if such consideration is practical, but assurance of consideration cannot be given to comments received after this date.-

Public Protection Notification if an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

FRN 28

October 15,1998 DRAFT- PRE-DECISIONAL IX. Regulatory Analysis .,

The Commission has prepared a regulatory analysis on this regulation. Interested persons may examine a copy of the regulatory analysis at the NRC Public Document Room, 2120 L Street NW. (Lower Level), Washington, DC. Single copies of the analysis are available from Mr. Stephen F. LaVie, Office of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, telephone: 301415-1081,' or by intemet electronic mail to sfl@nrc. gov.

X. Regulatory Flexibility Certification As required by the Regulatory Flexibility Act of 1980,5 U.S.C. 605(b), the Commission certifies that this regulation will not have a significant economic impact on a substantial number of small entities. This proposed regulation will affect only the licensing and operation of nuclear power plants. The companies that own these plants do not fall within the definition of "small entities" found in the Regulatory Flexibility Act or within the size standards established by the NRC (April 11,1995; 60 FR 18344).

XI. Backfit Analysis The NRC has determined that the backfit rule in 10 CFR 50.109, does not apply to this proposed regulation and, therefore, a backfit analysis is not required for this proposed regulation because these amendments do not involve any provisions that would impose backfits FRN 29 i

. - . , . - . - . . - - . - . . - . .~

October 15,1998 DRAFT - PRE-DECISIONAL as defined in 10 CFR 50.109(a)(1). This proposed regulation amends the Commission's regulations by se' tablishing attemate requirements that may be voluntarily adopted by licensees.

List of Subjects 10 CFR Part 21 Nuclear power plants and reactors, Penalties, Radiation protection, Reporting and recordkeeping requirements.

10 CFR Part 50 Antitrust, Classified information, Criminal penalties, Fire protection, Intergovernmental relations, Nuclear power plants and reactors, Radiation protection, Reactor siting criteria, Reporting and recordkeeping requirements.

10 CFR Part 54 Administrative practice and procedure, Age-related degradation, Backfitting, Classified information, Criminal penalties, Environmental Protection, Nuclear power plants and reactors, Reporting and recordkeeping requirements.

For the reasons noted in the preamble and under the authority of the Atomic Energy Act _

\

of 1954, as amended, the Energy Reorganization Act of 1974, as amended, and 5 U.S.C. 552 and 553, the Commission is proposing the following amendments to 10 CFR Parts 21,50, and

- _ _ _ . 54 ----- -

FRN 30

- - -+

~ . - - . - . .-... . . . - . -. - . .- ... .

{

October 15,1998 DRAFT - PRE-DECISIONAL PART 21 - REPORTING OF DEFECTS AND NONCOMPLIANCE 1

i

- 1. The authority citation for Part 21 continues to read as follows:

AUTHORITY: Sec.161,68 Stat. 948, as amended, sec. 234, 83 Stat. 444, as amended, sec.1701,106 Stat. 2951,2953 (42 U.S.C. 2201,2282,2297f); secs. 201, as amended 206, 88 Stat.1242, as amended, 1246 (42 U.S.C. 5841,5846).

Section 21.2 also issued under secs. 135,141, Pub. L. 97 - 425, 96 Stat. 2232, 2241 (42 U.S.C.10155,10161).

2. Section 21.3 is amended by revising paragraph (1)(1)(C) of the definition of Basic

. Component to read as follows:

$ 21.3 Definitions.

As used in this part Basic Component.

(1)(i)

(C) The capability to prevent or mitigate the consequences of accidents which could result in potential offsite exposures comparable to those referred to in

(( 50.34(a)(1),50.67(b)(2), or 6100.11 of this chapter, as applicable.

FRN 31

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October 15,1998 DRAFT - PRE-DECISIONAL

PART 50 - DOMESTIC LICENSING OF PRODUCTION AND, UTILIZATION FACILITIES

}

3. The authority citation for Pad 50 continues to read as follows:

AUTHORITY: Secs. 102,103,104,105,161,182,183,186,189,68 Stat. 936,937, 938,948,953,954,955,956, as amended, sec. 234, 83 Stat. 444, as amended (42 U.S.C.

4 2132, 2133, 2134, 2135, 2201. 2232, 2233, 2236, 2239, 2282); secs. 201, as amended, 202, 2

206,88 Stat.1242, as amended, 1244,1246 (42 U.S.C. 5841,5842,5846).

)

Section 50.7 also issued under Pub. L. 9509601, sec.10, 92 Stat. 2951 (42 U.S.C.

4 5851). Section 50.10 also issued under secs. 101,185,68 Stat. 955 as amended (42 U.S.C.

2131,2235), sec.102, Pub. L. 9109190,83 Stat. 853 (42 U.S.C. 4332). Sections 50.13, 50.54(dd), and 50.103 also issued under sec.108,68 Stat. 939, as amended (42 U.S.C. 2138).

Sections 50.23,50.35,50.55, and 50.56 also issued under sec.185,68 Stat. 955 (42 U.S.C.

2235). Sections 50.33a,50.55a and Appendix Q also issued under sec.102, Pub. L. 9109190, 83 Stat. 853 (42 U.S.C. 4332). Sections 50.34 and 50.54 also issued under sec. 204,88 Stat.

1245 (42 U.S.C. 5844). Sections 50.58,50.91, and 50.92 also issued under Pub. L. 9709415, 96 Stat. 2073 (42 U.S.C. 2239). Section 50.78 also issued under sec.122,68 Stat. 939 (42 U.S.C. 2152). Sections 50.80-50.81 also issued under sec.184,68 Stat. 954, as amended (42 U.S.C. 2234). Appendix F also issued under sec.187,68 Stat. 955 (42 U.S.C 2237).

4. Section 50.2 is amended by revising paragraph (1)(iii) of the definition of Basic Component and by adding in alphabetical order the definition for source term to read as follows:

FRN 32

October 15,1998

'I DRAFT - PRE-DECISIONAL 5 50.2 Definitions.

As used in this part, Basic component * *

• i (1) i (iii) The capability to prevent or mitigate the consequences of accidents which could result in potential offsite exposures comparable to those referred to in 99 50.34(a)(1),  !

50.67(b)(2), or 9100.11 of this chapter, as applicable.

i 1

Source term refers to the magnitude and mix of radionuclides released from the reactor core, their physical and chemical form, and the timing of their release.

l

5. Section 50.34 is amended by revising paragraphs (f)(vii), (f)(viii), (f)(xxvi), and (f)(xxviii), and adding new Footnote 11.to read as follows:

$ 50.34 Contents of applications; technicalinformation.

1

(,) .

(2)

(vii) Perform radiation and shielding design reviews of spaces around systems that may, as a result of an accident, contain accident source term"" radioactive materials, and FRN 33 i I

_ m ._ . _ - . _ . __ __ __. _ _ _ . _ _ _ .._. . _ _ _. _ ._ _._ _ _ . . _ _ _ _ . _ .

l l

October 15,1998 DRAFT - PRE DECISIONAL design as necessary to permit adequate access to important areas and to protect safety

~

equipment from the radiation environment. (ll.B.2)

(viii) Provide a capability to promptly obtain and analyze samples from the reactor coolant system and containment that may contain accident source term"" radioactive materials .

without radiation exposures to any individual exceeding 5 rems to the whole body or 50 rems to the extremities. Materials to be analyzed and quai Ufied include certain radionuclides that are indicators of the degree of core damage (e.g., noble gases, radiolodines and cesiums, and nonvolatile isotopes), hydrogen in the containment atmosphere, dissolved gases, chloride, and boron concentrations. (ll.B.3)

(xxvi) Provide for leakage control and detection in the design of systems outside containment that contain (or might contain) accident source term"" radioactive materials  !

following an accident. Applicants shall submit a. leakage control program, including an initial test program, a schedule for re-testing these systems, and the actions to be taken for minimizing leakage from such systems. The goalis to minimize potential exposures to workers l

and public, and to provide reasonable assurance that excessive leakage will not prevent the use of systems needed in an emergency. (Ill.D.1.1) ,

l (xxviii) Evaluate potential pathways for radioactivity and radiation that may lead to  !

control room habitability problems under accident conditions resulting in an accident source term"" release, and make necessary design provisions to preclude such problems. (lli.D.3.4)

FRN 34 4

)

October 15,1998 DRAFT - PRE-DECISIONAL

" The fission product release assumed for these calculations should be based upon a

' l 1

major accident, hypothesized for purposes of site analysis or postulated from considerations of I

l possible accidental events, that would result in potential hazards not exceeded by those from i any accident considered credible. Such accidents have generally been assumed to result in substantial meltdown of the core with subsequent release of appreciable quantities of fission products.

6. Section 50.49 is amended by revising paragraph (b)(1)(1)(C) to read as follows:

$ 50.49 Environmental qualification of electric equipment important to safety for nuclear power plants.

(b)

(1)

(i) i (C) The capability to prevent or mitigate the consequences of accidents that could result in potential offsite exposurer., comparable to the guidelines in gg 50.34(a)(1), 50.67(b)(2), or

$100,11 of this chapter, as applicable.

i 7 Section 50.65 is amended by revising paragraph (b)(1) to read as follows:

FRN 35

October 15,1998 DRAFT - PRE-DECISIONAL

$ 50.65 Requirements for monitoring the effectiveness of maintenance at nuclear power plants.

1 l

(b)

(1) Safety-related structures, systems and components that are relied upon to remain functional during and following design basis events to ensure the integrity of the reactor coolant pressure boundary, the capability to shut down the reactor and maintain it in a safe shutdown condition, or the capability to prevent or mitigate the consequences of accidents that could result in potential offsite exposure comparable to the guidelines in 69 50.34(a)(1), 50.67(b)(2),

or 100.11 of this chapter, as applicable, j

8. Part 50 is amended to add 9 50.67, a new section, to read as follows:

$ 50.67 Accident source term.

(a) Applicability. The requirements of this section apply to all holders of operating licenses issued prior to January 10,'1997, who seek to revise the current accident source term used in their design basis radiological analyses.

(b) Requirements: (1) A licensee who seeks to revise its current accident source term in design basis radiological consequence analyses shall apply for a license amendment under 6 50.90. The application shall contain an evaluation of the consequences of applicable design basis accidentsm previously analyzed in the safety analysis repot.

(2) The Commission may issue the amendment only if the applicant's analysis demonstrates with reasonable assurance that:

FRN 36

October 15,1998 DRAFT - PRE DECISIONAL (i) An individual located at any point on the boundary of the exclusion area for any 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> period following the onset of the postulated fission product release, would not receive a radiation dose in excess 'of 0.25 Sv (25 rem)W total effective dose equivalent (TEDE).

(ii) An individual located at any point on the outer boundary of the low population zone, who is exposed to the radioactive cloud resulting from the postulated fission product release (during the entire period of its passage), would not receive a radiation dose in excess of 0.25 Sv (25 rem) total effective dose equivalent (TEDE).

(iii) Adequate radiation protection is provided to permit access and occupancy of the control room under accident conditions without personnel receMng radiation exposures in excess of 0.05 Sv (5 rem) total effective dose equivalent (TEDE) for the duration of the accident.

' The fission product release assumed for these calculations should be based upon a major accident, hypothesized for purposes of design analyses or postulated from considerations of possible accidental events, that would result in potential hazards not exceeded by those from any accident considered credible. Such accidents have generally been assumed to result in substantial meltdown of the core with subsequent re' ease of appreciable quantitles of fission products.

2 The total effective dose equivalent (TEDE) of 0.25 Sv (25 rem) referred to above is i specified for use with revised source terms since it utilizes a risk-consistent methodology to assess the radiologicalimpact of all relevant nuclides upon all body organs. The latent cancer risk of a radiation dose of 0.25 Sv (25 rem) TEDE is consistent with the latent cancer risk associated with exposures of 0.25 Sv (25 rem) to the whole body and 3.0 Sv (300 rem) to the thyroid. Risk of latent cancer fatality is used as the risk measure since quantitative health FRN 37 g, -- - - - , , -- -

, a n - - - -.n - --,- .- ~ .--.------ ,.. --- ,--.-- . ---- - - - -

October 15,1998 DRAFT - PRE-DECISIONAL i objectives for it have been established in the Commission's Safety Goal Policy. .liowever, the  !

use of 0.25 Sv (25 rem) TEDE in these accident dose guidelines is not intended to imply that this value constitutes an acceptable limit for emergency doses to the public under accident conditions. Rather, this 0.25 Sv (25 rem) TEDE value has been stated in these guides as a reference value, which can be used in the evaluation of proposed design basis changes with respect to poter.tial reactor accidents of exceedingly low probability of occurrence, and low risk i of public exposure to radiation.

t

9. Part 50, Appendix A, Gene'ral Design Criterion 19, is amended to read as follows:

Appendix A to Part 50 - General Design Criteria for Nuclear Power Piants i

Criterion 19- Controt room. A control room shall be provided from which actions can be taken to operate the nuclear power unit safely under normal conditions and to maintain it in a safe condition under accident conditions, including loss-of-coolant accidents. Adequate radiation protection shall be provided to permit access and occupancy of the control room under accident conditions without personnel receiving radiation exposures in excess of 5 rem whole body, or its equivalent to any part of the body, for the duration of the accident.

Equipment at appropriate locations outside the control room shall be provided (1) with a design capability for prompt hot shutdown of the reactor, including necessary instrumentation and controls to maintain the unit in a safe conditon during hot shutdown, and (2) with a i potential capability for subsequent cold shutdown of the reactor through the use of suitable procedures.

Applicants for construction permits under this part or a design certification or combined FRN 38

~

October 15,1998 DRAFT - PRE-DECISIONAL license under Part 52 of this chapter who apply on or after January 10,1997, or holders of operating licenses using an attemative source term under 50.67, shall meet the requirements of this criterion, except that with regard to control room access and occupancy, adequate radiation protection shall be provided to ensure.that radiation exposures shall not exceed 0.05 Sv (5 rem) total effective dose equivalent (TEDE) as defined in 50.2 of this chapter for the duration of the accident.

PART 54 - REQUIREMENTS FOR RENEWAL OF OPERATING LICENSES FOR NUCLEAR POWER PLANTS

10. The authority citation for Part 54 continues to read as follows:

AUTHORITY: Sees.102,103,104,161,181,182,1.83,186,189,68 Stat. 936,937, 938,948,953,954,955, as amended, sec. 234,83 Stat.1244, as amended (42 U.S.C. 2132, 2133, 2134, 2135, 2201, 2232, 2233, 2236, 2239, 2282); secs 201, 202, 206, 88 Stat.1242, 1244, as amended (42 U.S.C. 5841,5842), E.O.12829,3 CFR,1993 Comp., p. 570; E.O.

12958, as amended,3 CFR,1995 Comp., p. 333; E.O.12968,3 CFR,1995 Comp., p. 391.

11. Section 54.4 is amended by revising paragraph (a)(1)(iii) to read as follows:

$ 54.4 Scope.

(a)

(1)

(iii) The capability to prevent or mitigate the consequences of accidents which could result in potential offsite exposures comparable to those referred to in 50.34(a)(1),

FRN-39

October 15,1998 DRAFT - PRE-DECISIONAL 50.67(b)(2), or 6100.11 of this chapter, as applicable.

Dated at Rockville, Maryland, this [****]the day of [****],1998.

l 1

For the Nuclear Regulatory Commission.

I 1

I i

John C. Hoyle, I Secretary of the Commission. l l

1 I

l I

I 1

1 1

FRN-40

Attachment 2 Draft Regulatory Analysis l

I e

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. October 15,1998 DRAFT - PRE-DECISIONAL' T

REGULATORY ANALYSIS

. REVISION OF 10 CFR PARTS 21,50, AND 54 -

'Use of an Alternative Source Term at Operating Reactors I. STATEMENT OF PROBLEM l

This regulatory analysis addresses a proposed rulemaking that will revise 10 CFR Parts 21, 50, and 54. This rulemaking was initiated to enable holders of power reactor operating licenses issued before January 10,1997, to voluntarily amend their facility design basis to replace the current accident source term in design basis radiological consequence analyses with an attemative source term. Although this proposed rulemaking is based on the accident source terms presented in NUREG-1465, Accident Source Terms forLight-WaterNuclearPower Plants, which will be endorsed by the NRC staff in a proposed regulatory guide, the rulemaking will refer to ettemative source term to enable the use of a future attemative to NUREG -1465.

(in this analysis, revised source term refers to NUREG-1465.) This rulemaking also incorporates proposed conforming revisions to 10 CFR Part 50 to eliminate the need for certain i

exemptions from Part 50 requirements for future applicants under Part 52, in addition to future j applicants under Part 52, the proposed conforming change to $50.34(f) affects the small class  !

of applicants that had a construction permit or manufacturing license pending on February 16, 1982. This proposed change would allow this small class of applicants to use an alternative to the TID-14844 source term in showing compliance with 650.34(f).

4 This regulatory analysis is presented in two parts, corresponding to the two considerations I

stated above.

RA-1

October 15,1998 .

DRAFT - PRE-DECISIONAL A. Use of an Alternative Source Term at Operating Reactors

1. Background

1

a. Accident Source Term I i

l A holder of an operating licence (licensee) for a light-water power reactor was required by l regulations issued by the NRC (or its predecessor, the U.S. Atomic Energy Commission) to  !

. submit a safety analysis report, in support of its license application, that assessed the I

)

radiological consequences of potential accidents and evaluated the proposed facility site. The NRC staff used this information in its evaluation of the suitability of the reactor design and the l

proposed site as required by its regulations contained in 10 CFR Parts 50 and 100. Section 100.11 requires an applicant to assume (1) a fission product release from the core, (2) the expected containment leak rate, and (3) the site meteorological conditions to establish an I exclusion area and a low population zone. A footnote to $100.11 provides guidance that the fission product release be based on a credible major accident that would result in substantial release of appreciable quantities of fission products from the core to the containment atmosphere. A note to $100.11 references Technical Information Document (TID) 14844, '

Calculation of Distance Factors for Power and Test Reactors, published in 1962 by the U.S.

Atomic Energy Commission, as a source of guidance and as a point of departure for addressing site-specific considerations. This fission product release, known as the TID-14844 accident source term, was used to evaluate the radiological consequences of design basis accidents (DBAs) to determine compliance with various requirements in 10 CFR Parts 50 end 100 in all of the operating reactors licensed to date. Although originally used for site suitability analyses, the accident source term is a design parameter for accident mitigation features, equipment qualification, control room operator radiation doses, and post-accident vital area access doses.

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. October 15,1998 DRAFT - PRE-DECISIONAL

i The TID-14844 source term was explicitly stated as a required design parameter for several

.l Three Mile Island (TMI)-related requirements. The NRC considers the accident source term an integral part of the design basis since it was a significant input to a large portion of the plant design.

' 1 The NRC staff's methods for calculating accident doses, as described in Regulatory Guide l 1

l 1.3, Assumptions Used for Evaluating the Potential Radiological Consequences of a Loss of Coolant Accident for Boiling Water Reactors, and Regulatory Guide 1.4, Assumptions Used for Evaluating the Potential Radiological Consequences of a Loss of Coolant Accident for Pressurized Water Reactors, and in the Standard Review Plan, were developed to be consistent with the TlD-14844 source term and the whole body and thyroid dose guidelines stated in $100.11. In that regulatory framework, the source term is assumed to be released immediately to the containment at the start of the postulated accident. The chemical form of the radioiodine released to the containment atmosphere is assumed to be predominantly elemental, with small fractions of particulate and organic iodine forms. Radiation doses are calculated at the exclusion area boundary (EAB) for the first 2-hours and at the low population  !

zone (LPZ) for the assumed 30-day duration of the accident. The whole body dose comes primarily from the noble gases in the source term, and the thyroid dose is based on inhalation of radioiodines, in analyses performed to date, the thyroid dose has generally been limiting, and the design of some engineered safety features, such as containment spray systems and containment, ventilation exhaust, and control room charcoal filters, are predicated on these postulated thyroid doses. This regulatory framework has provided a consistent analytical approach for evaluating the spectrum of potential consequences from DBAs.

Since the publication of TID-14844, significant advances have been made in understanding the timing, magnitude, and chemical form of fission product releases from severe nuclear power RA-3 4

October 15,1998 DRAFT - PRE DECISIONAL plant accidents. Many of these insights developed out of the major research effort started by the NRC and the industry after the accident at TMI. In 1995, the NRC published NUREG-1465, which utilized this research to provide more physically based estimates of the accident source term that could be applied to the design of future light-water power reactors. In NUREG 1465, the NRC staff provides a representative accident source term for a boiling-water reactor (BWR) and for a pressurized-water reactor (PWR). These source terms are described in terms of I l

radionuclide composition and magnitude, physical and chemical form, and timing of release.

Where TID-14844 addressed three categories of radionuclides, the revised source terms categorize the accident release into eight groups by physical and chemical properties. Where TID-14844 assumed an immediate release of the activity, the revised source term has five release phases that are postulated to occur over several hours, with the onset of major core i damage occurring after 30 minutes. Where TID-14844 assumed radiolodine to be predominantly elemental, the revised source term assumes radioiodine to be predominantly cesium iodide (Csi), an aerosol that is more amenable to mitigation mechanisms. For DBAs, the NUREG-1465 source term is comparable to the TID-14844 source term with regard to the magnitude of the noble gas and radiolodine release fractions. However, the revised source term presents a more representative description of the radionuclide composition and release timing. In SECY-94-302, Source Term-Related Technicaland Licensing Issues Pertaining to Evolutionary and Passive Light-Water-Reactor Designs, the NRC staff determined that the first three phases (coolant, gap, and early in-vessel) are appropriate for design basis evaluations.

The NRC staff initiated several actions to provide a regulatory basis for operating reactors to voluntarily amend their facility design bases to enable us,e of an alternative source term in design basis analyses. First, the NRC staff solicited information on how such a source term might be implemented. In November 1995, the Nuclear Energy institute (NEI) submitted its generic framework (Electric Power Research Institute Technical Report TR-105909, Generic RA-4 4

October 15,1998 DRAFT - PRE DECISIONAL Framework for Application of Revised Accident Source Term to Operating Plants). This report and the NRC response were discussed in SECY-96-242 (November 1996). Se'cond, the NRC staffinitiated a comprehensive assessment of the overallimpact of substituting the NUREG-1465 source term for the TID-14844 source term at two typical facilities. This was done to evaluate the issues involved with applying this revised source term at operating plants. SECY-98-154 (June 1998), described the conclusions of this assessment. Third, the NRC staff accepted license amendment requests related to implementation of this revised source term at a small number of pilot plants. The staff is currently reviewing these pilot projects. InsigYs t

from these pilot plant reviews will be incorporated into the regulatory guidance that wiu be developed iri conjunction with this rulemaking. Fourth, the NRC staff initiated an assessment on whether rulemaking would be necessary to allow operating reactors to use an attemative source term. The proposed rule described herein, and the supporting regulatory guidance that will be developed as part of this rulemaking, have resulted from this assessment. The NRC staff plans to issue the supporting regulatory guidance for public comment on the same date as it publishes the final rule.

b. Accident Dose Guidelines and Control Room Dose Criteria in Part 50, Appendix A, GDC-19, the NRC staff presents radiation dose criteria that are used to assess the suitability of the plant design with regard to maintaining control room habitability during DBAs. In $100.11, the NRC staff presents radiation dose guidelines that are used to assess the suitability of the plant design with regard to offsite exposures during design basis events. The dose guidelines for the who!e body and the thyroid, and the immediate 2-hour exposure period, were largely predicated by the assumed source term being predominantly noble gases and radioiodines instantaneously released to the containment and the assumed " single critical organ" method of modeling the internal dose used at the time Part RA-5 1

1 l

October 15,1998 DRAFT - PRE-DECISIONAL l

} 100 was originally published. However, the current dose guidelines, by focusing on doses to 1

the thyroid and the whole body, assume that radiolodine will be the major contributor to doses.

Although this may be appropriate with the TID-14844 source term, it may not be true for a source term based on a more complete understanding of accident sequences and

]

s phenomenology. The postulated chemical and physical form of radiolodine in the revised l

l 1

! source term is more amenable to mitigation and, as such, radioiodine may not always be the i l predominant radionuclide in an accident release. The revised source term assumes.a larger

. l number of radionuclides than did the TlD-14844 source term. The whole body and thyroid dose i

] guidelines ignored these contributors to dose.

1 i

. I in the period since these regulations were issued, there have been significant developments j in the principles and scientific knowledge underlying standards for radiation dose limitation and assessment. These developments include not only updated scientific information on l radionuclide uptake and metabolism, but also reflect changes in the basic philosophy of radiation protection. In 1991, the NRC staff revised 10 CFR Part 20, Standards for Protection Against Radiation, to reflect these developments. The accident dose guidelines in $100.11 and

' J GDC-19, were not changed when Part 20 was revised because the requisite revision to the licensing basis of each operating power reactor was not deemed warranted. The standards in I I- Part 20 include the dose quantity, total effective dose equivalent (TEDE), which is defined as the deep dose equivalent (for extemal exposure) plus the committed effective dose equivalent (for intemal exposure). The deep dose equivalent (DDE) is comparable to the present whole body dose; the committed effective dose equivalent (CEDE) is the sum of the products of doses (integrated over a 50-year period) to selected body organs resulting from the intake of

. radioactive material multiplied by weighting factors for each organ that are representative of the

} radiation risk associated with the particular organ. The TEDE, using a risk-consistent j methodology, assesses the impact of all relevant nuclides upon all body organs. It is expected RA-6 4 .

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October 15,1998 DRAFT- PRE-DECISIONAL that the thyroid could still be the limiting organ and radiolodine could still be the limiting radionuclide, and that the current whole body and thyroid guidelines could provide adequate protection; however, this conclusion cannot be assured in all potential cases. The NRC staff '

recommended in SECY-96-242 that dose guidelines expressed in terms of TEDE be required if

{

a .icensee elects to use the revised source term. In a staff requirements memorandum dated 1

February 12,1997, the Commission directed the NRC staff to incorporate TEDE in this proposed rulemaking.

i The dose guideline for the EAB in 9100.11 is specified with a 2-hour exposure period commencing immediately following the onset of the fission product release. This exposure period was predicated, in part, on the traditional source term assumption that the activity would be immediately available for release at the onset of the accident. The combination of these two assumptions resulted in the maximum postulated dose. The revised source term postulates a release that occurs in phases, with the significant release starting after about 30 minutes and continuing for about 90 minutes (through the early in-vessel phase only). Because of this, an i exposure period starting at the onset of the fission product release may not represent the i

limiting case. The NRC ' staff recommended in SECY-96-242 that dose guidelines expressed in terms of the worst 2-hour dose be considered if a licensee elects to use the revised source term. In a staff requirements memorandum dated February 12,1997, the Commission directed the NRC staff to incorporate the worst 2-hour dose in this proposed rulemaking.

2. Fricting Regulatorv Framework

a. Accident Source Term I

4 RA-7 4

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October 15,1998 DRAFT - PRE-DECISIONAL r

The proposed rulemaking for implementation of an attemative source term is applicable only to those facilities that held an operating licence before January 10,1997, under 4

10 CFR Part 50. The regulations in this part are supplemented by those in other parts of Chapter 1 of Title 10, including Part 100. Part 100 contains language that qualitatively defines

! a required accident source term and contains a note that discusses the availability of TID-14844. However, this note did not mandate the use of TID-14844. With the exception of

$50.34(f), which addresses additional TMI-related requirements, there are no explicit provisions in Title 10 requiring the use of the TID-14844 accident source term. Section 50.34(f) is only applicable to a limited number of construction permit and manufacturing license applications pending on February 16,1982, and to applications under Part 52.

Regulatory Guides 1.3 and 1.4 give the methods and assumptions acceptable to the NRC staff for assessing the consequences of design basis loss of coolant accidents (LOCAs) as required by 9100.11. These regulatory guides provide guidance involving accident source terms, much of which is derived from TID-14844. Other guides specify accident source terms either directly or by reference to Regulatory Guides 1.3 and 1.4. None of these guides, however, explicitly refers to TID-14844. The Commission publishes regulatory guides to describe methods acceptable to the NRC staff for implementing specific parts of the Commission's regulations. Compliance with these guides is not required and applicants are allowed to propose attematives for NRC staff consideration. Although NRC stafflicensing  !

reviews have been based on Regulatory Guides 1.3 and 1.4, the option for a licensee to propose attematives has been and remains a possible regulatory mechanism to implement a l source term other than the one in TID-14844.

l An applicant for an operating license is required by $50.34 to submit a final safety analysis report (FSAR) that describes the facility and its design bases and limits, and that includes a RA-8

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October 15,1998 DRAFT - PRE-DECISIONAL I 4

l safety analysis of the site and of the facility. Guidance in performing these analyses is given in i .

1 l regulatory guides, in its review of the more recent applications for operating licenses, the NRC

)

staff has used the review procedures in NUREG-0800, Standard Review Plan for the Review of i

Safety Analysis Reports forNuclearPowerPlants (SRP). These review procedures reference 1

or provide acceptable assumptions and analysis methods. Although compliance with the SRP I

is not required, in practice, many applicants adhere to the guidance in the interest of facilitating s

j NRC staff review. Operating license applications docketed after May 17,1982, are required in j $50.34(g) to contain an evaluation of the facility for conformance with the SRP. The facility a

FSAR documents the assumptions and methods actually used by the applicant in the required i

safety analyses. The NRC staff's finding that a license may be issued is based on the review of the FSAR, as documented in the staff's safety evaluation report (SER). Through inclusion in j the FSAR, these assumptions (including source term) and the licensee's methods of evaluation

]i become part of the design basis of the facility.

i

Thus, from a regulatory standpoint, the requirement to use the TID-14844 source term is a i

licensee commitment (typically expressed as a commitment to Regulatory Guide 1.3 or 1.4) i documented in the facility FSAR. The licensee may effect a change in its licensing basis, i

4 5

including the FSAR, by applying for an amendment to its license under $950.90-50.92, or on its i

own volition within the provisions of $50.59. Because of the extensive use of the accident i

source term in the design and operation of a power reactor, and because of the potentialimpact 4

l on postulated accident consequences and margins of safety of a change in such a fundamental -

t j design assumption, the NRC has concluded that an altemative source term should be

! implemented via a license amendment under 9650.90-50.92.

t i

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RA-9 i

Octob:r 15,1998 DRAFT - PRE < DECISIONAL i

j

b. ' Accident Dose Guidelines and Control Room Dose Criteria The accident dose guidelines for operating reactors licensed before January 10,1997, are i

presented in $100.11. These guidelines are expressed in terms of whole body and thyroid j dose. Two guidelines are provided. The first is for the EAB for the 2-hour period immediately 9

i following the onset of radioactivity release. The second is for the LPZ for the duration of the l event. General Design Criterion 19 (GDC-19), Contro/ Room, of Appendix A to 10 CFR Part 50, establishes minimum requirements for the design of the control room, including a requirement for radiation protection features adequate to permit access to and occupancy of

the control room under accident conditions. The GDC-19 criteria are expressed in terms of 0.05 Sv (5 rem) whole body dose, or its equivalent to any organ. SRP Section 6.4, Control

{ Room Habitability Systems, contains guidance that defines equivalent as 0.3 Sv (30 rem) to the I thyroid and 0.3 Sv (30 rem) to the skin.

?

e 4

i in January 1997, the NRC amended its regulations in 10 CFR Parts 21,50,52,54, and 100 4

to (1) provide site criteria for future sites and (2) relocate source term and dose requirements

i. for future plants into 950.34. The guidelines of $100.11 mmain in place as the licensing basis

, for operating reactors licensed before January 10,1997. In relocating the source term and s

dose requirements for future reactors to 50.34, the NRC retained it'e requirements for the

{ EAB and the LPZ, but revised the associated numerical dose guidelines to replace the two i

different doses for the whole body and the thyroid gland with the single, total effective dose equivalent (TEDE) value. The dose guideline for the EAB was expressed in terms of the 2-hour period that yielded the maximum dose. The NRC did not, at that time, amend the control room dose criterion in GDC-19.

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. October 15,1998 DRAFT - PRE-DECISIONAL ,

l In a staff requirements memorandum dated February 12,1997, the Commission' directed that the amended dose guidelines be made applicable to operating plants choosing to use the revised source term. Therefore, an attemative source term cannot be implemented without a modification of the accident dose guidelines and the GDC-19 criteria. It is this needed modification that makes the proposed rule necessary.

B. Conforming Changes for Part 52 Part 52 govems the issuance of early site permits, standard design certifications, and combined

, licenses for nuclear power facilities. Part 52 is used in conjunction with applicable requirements of Part 50. The TMI-related requirements in $50.34(f) were specifically incorporated by reference in $52.47(a)(ii). This incorporation by reference is necessary because 950.34(f) limits applicability to specifically identified facilities for which an application for a construction permit was pending on February 16,1982. The NRC staff expects that future plants will use the revised source term, or an approved altemative, in supporting safety analyses. Since

$$50.34(f)(vil), -(viii), -(xxvi), and -(xxviii) contain specific references to the TID-14844 source term, these sections need to be revised. The control room habitability criteria in GDC-19 were incorporated by reference in $52.47(a)(i). This criterion is expressed in terms of whole body dose or its equivalent to any part of the body rather than in terms of TEDE. Exemptions from these requirements were necessary for the Westinghouse AP-600 final design approval and design certification. The proposed rulemaking will address changes to these affected sections in order to avoid the need for exemptions for subsequent applicants under Part 52. l l

I The conforming changes to $50.34(f) would also be applicable to the small subset of specifically listed applicants that had a construction permit application pending on February 16, 1982. The NRC does not expect these applications to be pursued further. However, should RA - 11 4

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a o October 15,1998 DRAFT- PRE DECISIONAL one of these applications be reactivated, the applicant would, in effect, be given the option of using an approved alternative to the TID-14844 source term.

II. OBJECTIVE OF PROPOSED RULE A. Use of an Alternative Source Term at Operating Reactors The objective of this proposed regulatory action is to set up a regulatory framework for the voluntary implementation of an attemative source term as a change to the design basis at currently licensed power reactors, there. enabling potential cost-beneficial licensing actions while continuing to maintain existing safety margins and defense in depth.

This will be accomplished by e

providing revised accident dose guidelines and control room habitability dose criteria -

that are consistent with the characteristics of the revised source term and that reflect updated scientific information on radionuclide uptake and metabolism, and also reflect current radiation protection standards, and e

requiring submittal for a license amendment that contains an evaluation of the consequences of applicable design basis accidents previously analyzed in the safety analysis report.

Sirce conformance to the proposed rule is voluntary and since the proposed rule will not constitute a backfit, the licensing bases for operating reactors that do not adopt an attemative source term must remain in the regulation. Therefore, the proposed rule is designated as a

( RA - 12

October 15,1998 DRAFT - PRE-DECISIONAL new section, $50.67, applicable to operat;ng reactors licensed before January 10,1997, that are proposing to use an alternative source term. The existing requirements in Part 100 and GDC-19 are maintained for operating reactors that continue to use the TID-14844 source term.

The NRC staff will prepare a regulatory guide and an SRP section in support of this rule.

The drafts of these guidance documents will be issued for public comment at the time the final rule is published (September 1999). >

B. Conforming Changes for Part 52 The objective of this proposed regulatory action is to eliminate the need for applicants under Part 52 to request exemptions from certain of the NRC's regulations. The need for these exemptions was identified during the Westinghouse AP-600 advanced reactor design certification proceeding.

This will be accomplished by e Explicit references to the T/D-14844 source term-in 550.34(f) will be revised to read accident source term. A footnote will be added to define an accident source term in 9eneric terminology (similar language to the corresponding footnote in Part 100).

GDC-19 will be revised to incorporate a revised dose criterion that is applicable only to applicants for construction permits under this part, or a design certification or combined license under 10 CFR Part 52 who apply on or after January 10,1997. The current dose criterion will remain in effect for those operating reactors that continue to use the TID-14844 source term.

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October 15,1998 DRAFT - PRE-DECISIONAL lit. ALTERNATIVE APPROACHES A. Use of an Alternative Source Term at Operating Reactors I

1 The no-action altemative of retaining the existing accident source term was not considered in the development of the proposed rulemaking. In SECY-96-242, the staff made recommendations to the Commission on how the revised source term could be implemented at operating reactors. The staff requirements memorandum on SECY-96-242 directed the staff to (1) complete the re-baselining study, (2) complete pilot plant evaluations, (3) commence rulemaking, and (4) include the TEDE terminology and the worst 2-hour methodology.

The first attemative considered by the NRC was to continue using current regulations for accident dose guidelines and control room dose criteria. This is not considered to be an acceptable attemative. The NRC had previously determined in the January 1997 Part 50 and Part 100 final rulemaking that dose guidelines expressed in terms of whole body and thyroid doses were inconsistent with the use of the revised source term. With regard to the EAB dose guideline, the NRC also determined that the dose guideline applies to that 2-hour period resulting in the maximum dose.

The second attemative considered by the NRC was to replace the existing guidelines in

$100.11 and the existing criteria GDC-19 with an entirely new regulation. This is not considered to be an acceptable altemative because the provisions of the existing regulations form part of the licensing bases for rnany of the operating reactors. Therefore, these provisions must remain in effect for operating reactors that do not implement an attemative source term.

In addition, this rulemaking altemative would also be inconsistent with the Commission's RA - 14

, 7 October 15,1998 ,y  ; DRAFT- PRE-DECISIONAL philosophy of separating plant sit'ing criteria and dose requirements. The approach of i

astablishing the requirements for use of an altemative source term in a new section to Part 50 i

while retaining the existing ' regulations in Part 100 Subpart A and GDC-19 was chosen as the

best rulemaking altemative.

l The NRC considered attematives with regard to providing regulatory guidance to support l

the new section to Part 50.RThe first attemative was to issue no additional regulatory guidance, j This was not considered to be acceptable attemative because, in the absence of clear

.t regulatory guidance, licensee efforts in preparing applications, and the NRC staff review of

submitted applications, could be hindered by differences in interpretations and technical positions. This could result in the inefficient use of licensee and staff resources, could cause licensing delays, and could lead to less uniform and less consistent regulatory implementation.

The second altemative was to replace the existing regulatory guides that address accident radiological consequences with new revisions. This was not considered to be an acceptable attemative because the provisions of the existing regulatory guides form part of the licensing bases for many of the operating reactors. Therefore, these provisions must remain in effect for operating reactors that do not implement an altemative source term. The third rulemaking altemative was to issue a new regulatory guide on the implementation of a revised source tarm that would include, in a series of appendices, revised assumptions and acceptable analysis methods for each design basis accident. The approach of issuing a new regulatory guide was chosen as the best altemative. To provide review guidance for the NRC staff, a new section on design basis radiological analyses using an altemative source term would be added to the Standard Review Plan.

i RA - 15 l

l Octob;r 15,1998 DRAFT - PRE-DECISIONAL l

B. Conforming Changes for Part 52 1

Since these revisions are conforming changes for a rulemaking issued earlier, the no-action attemative was not considered to be acceptable. No reasonable attemative was identified for the necessary $50.34(f) revisions. The reference to TID-14844 needs to be removed.

With regard to a revised control room dose criterion, the revised criterion could have been implemented by changing Part 52 (that cross-references Part 50, by a changing $50.34(a), or i by changing GDC-19. A change to GDC-19 was deemed to be the simplest and clearest I

approach and, therefore, was considered to be the acceptable altemative.  ;

IV. EVALUATION OF VALUES AND IMPACTS The NRC has determined that the public health and safety and the common defense and security would continue to be adequately protected if the proposed rulemaking were implemented. The NRC has qualitatively determined that the potential values associated with the revised source term are substantial enough to justify the rulemaking, and clearly outweigh any reductions in values associated with the current accident source term. This proposed rulemaking is voluntary for operating reactors. (The conforming changes for Part 52 will be mandatory for future applicants.) The basis for these conclusions is discussed in the sections to follow.

A. Use of an Alternative Source Term at Operating Reactors

1. Values RA - 16

~. - - . - . . - - - - - - . - - -.= .-- ._ _ - _ . . . . . - .

1 j October 15,1998 DRAFT - PRE-DECISIONAL j This proposed rule would allow operating reactors to voluntarily replace the traditional TID-

~

14844 source term with a source term that is based on the insights gained from extensive accident research activities. The accident source term is a design parameter for accident mitigation features, equipment qualification, control room operator radiation doses, and post-accident vital area access doses. The design of some engineered safety features, such as containment spray systems and containment, ventilation exhaust, and control room charcoal filters, is largely predicated on the radiation doses postulated using these source terms. It is l

expected that an attemative source term, with its improvements in the understanding of chemical / physical form and release timing, could be used to effect reductions in operational and  !

maintenance requirements associated with some of these systems. These reductions would have economic benefit.

The implementation of an attemative source term does not, in itself, have economic value.

It is the modifications to the facility structures, systems, components, and procedures, enabled i

by an altemative source term that give rise to the associated values and impacts. Since this is I a voluntarily action on the part of the licensee, it is expected that licensees will not pursue applications of an attemative source term unless it is perceived to be in their benefit to do so.

Given this conclusion, and given the large number of possible applications varying in scope and extent, the NRC has not performed quantitative value-impact analyses. In 1996, NEl informally polled the industry to determine how often and for what uses licensees might apply the NUREG-1465 source term. Although the poll was informal and does not constitute any commitment to act, the results of the poll indicate the level of interest in the proposed  ;

rulemaking. The responses received represented 43 operating power reactors. Of these,41 reactors plan to use the revised source term to pursue plant modifications. Anticipated applications includes the following:

RA - 17

.3-_.___.,_._

October 15,1998.

DRAFT - PRE-DECISIONAL e change in allowable leak rate (24 plants) l_ .

e .

change in isolation valve actuation timing (31 plants)

L  ;

e simplification of filtration units (27 plants) e _ change in mitigation sysicm actuation timing (22 plants)

L i

^

L .e change in equipment qualification (2 plants) l 1

There is an expectation that many of the attemative source term applications may provide .

concomitant improvements in overall safety and in reduced occupational exposure, as well as l t

economic benefits. Because of the wide range of possible applications and the voluntary

. nature of this rulemaking, it is not reasonable to quantify possible outcomes. Reductions in occupational exposures may be realized through reductions in maintenance efforts associated with maintaining unnecessarily limiting leakage, timing, or filtration requirements. Improvements in overall safety may be realized through reduced emergency diesel generator loadirW improved containment ventilation system performance due to lessened filter flow resistance, and closer synchronization of mitigation feature actuation with the onset of major fission product I

release, to provide just three examples. There may be improvements in safety margins realized i i

due to the upgrading of analysis assumptions, methods, and acceptance criteria.

l It is believed that the proposed rulemaking will result in an improvernent in the allocation of resources both for the NRC and for industry.- The industry will be allowed to propose applications of an altemative source term that could reduce unnecessary or ineffective l

l RA - 18

a s

. October 15,1998 DRAFT - PRE-DECISIONAL requirerpents in the facility design basis. Limited resources could be diverted to safety issues of i.

greatsr significance. -

2. Costa

! l Si the implementation of an attemative source term is a voluntarily action on the part of the licensee, licensees are not expected to pursue applications of an altemative source term i-unless. it is perceived to be in their benefit to do so.- Given this conclusion, and given the large number of possible applications varying in scope and extent, the NRC has not performed quantitative value-impact analyses.  !

4

3. Impacts i

The implementation of the NUREG-1465 source term at an operating power reactor would replace the traditional TID-14844 source term with a source term that is based on the insights i

j gained from extensive accident research activities. The actual accident sequence and 4 - .

progression are not changed; it is the regulatory assumptions regarding the accident that will be i

affected by substituting the revised source term. Use of an attemative source term alone cannot increase the core damage frequency (CDF) or the large early release frequency (LERF) or actual offsite or onsite radiation doses. (Although actualdoses would not increase, analysis i

results may show an increase in some postulated doses because additional radionuclides will 5

be considered and dose modeling will be more comprehensive.) The accident source term is j used in analyses performed to assess the adequacy of the plant design to contend with a DBA in order to ensure adequate defense in depth and adequate safety margins. An alternative c

source term c:)uld be used to justify changes in the plant design that could have an impact on CDF or LERF or that could increase offsite or onsite doses. These potential changes are RA - 19

d i

October 15,1998 DRAFT - PRE-DECISIONAL subject to existing requirements in the Commission's regulations. The supporting regulatory 9uide for this rulemaking will discuss the need for an evaluation of the impacts of an attemative source term implementation, including consideration of reductions in defense in depth, safety margins, or both. Consistent with Regulatory Guide 1.174, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Current Licensing Basis, the draft guide will indicate that PRA insights may have to be considered if the proposed changes to the design basis are not addressed in currently approved NRC staff positions.

The Commission directed the NRC staff to assess the impacts ofimplementing the NUREG-1465 source term at operating reactors. The results of this study were presented to the Commission in SECY-98-154, Results of the Revised (NUREG-1465) Source Term Re-Baselining for Operating Reactors. The major areas examined were the effect on individual offsite and control room dose, the effect on doses used in equipment environmental qualification, and the effect of potential modifications that might be enabled by the revised source term. The study also assessed the margin afforded by the revised source term in comparison to assessments performed using the integrated severe accident assessment code, MELCOR. The study indicated that the impact of implementing the revised source term at operating reactors will produce lower postulated doses in the majority of cases. The Commission intends to address the exceptions in the regulatory guidance that will be developed

, l to support the proposed rule and in the processing of the individuallicense amendments. The MELCOR analyses indicated that the design basis dose calculations still have a substantial margin (a factor of two or greater) even though the postulated dose may be less than that indicated by calculations using the current source term. The study also indicated that many of the plant systems that are likely to be considered for modification are not involved in risk 1

significant sequences and are, therefore, not likely to have a substantial offsite risk impact using RA - 20 4

l l

October 15,1998 DRAFT - PRE-DECISIONAL l a measure such as LERF. At the present time, the only approved altemative to the TID-14844 l

source term is that in NUREG-1465. The Commission expects that any future proposed i

attemative source term will be subjected to the same level of scrutiny as was used in approving l

NUREG-1465.

On the basis of these considerations, the NRC staff does not believe that the proposed rulemaking will involve a significant increase in the probability or consequences of accidents previously analyzed, nor will it create a new or different type of accident or result in a significant reduction in safety margin.

4. Backfit ConsidAratiOQS The NRC has determined that the backfit rule,10 CFR 50.109, does not apply to this proposed regulation, and, therefore, a backfit analysis is not required for this proposed rulemaking because these amendments do not involve any provisions that would impose backfits as defined in 10 CFR 50.109(a)(1). The proposed $50.67 amends the Commission's regulations by establishing altemate requirements that may be voluntarily adopted by operating reactors licensed before January 1997 that have adopted, or are proposing to adopt, an attemative source term.

5. J.monets on Other Procrams. Other Acencies The proposed rulemaking does not affect Federal, State, or local govemment agencies, or Agreement State licensees because the rulemaking affects only the licensing and operation of nuclear power plants that are regulated by the NRC under Part 50. Within the NRC, the t-l RA - 21

, _7 -.,___ __ ,_ .. . . . . . _ . _ _ . .~ _ . _ _ . _ _ _ _ _ . . _

October 15,1998 DRAFT - PRE-DECISIONAL cognizant office is Nuclear Reactor Regulation, which is sponsoring this proposed rulemaking.

No other NRC office is affected by this proposed rulemaking. .

B. Conforming Changes for Part 52

1. Values The proposed conforming changes will eliminate the need for future applicants under Part 52 to apply for exemptions from certain paragraphs in 50.34(f) and GDC-19. This will eliminate the costs associated with preparing and processing an exemption request. By eliminating the need for exemptions, the integrity of the regulations is maintained.

2. Costs Since the conforming changes will eliminate the need for future applicants under Part 52 to apply for exemptions from certain paragraphs in $50.34(f) and GDC-19, it is expected that costs will be reduced, not increased.

3. Impacts Since these are conforming changes for regulations already promulgated, there can be no significant increase in the probability or consequences of accidents previously analyzed, nor will a new or different type of accident be created, nor will there be a significant reduction in safety margins.

RA - 22

- ,.4- -

, mW i s}TV October 15,1998.- hp DRAFT - PRE-DECISIONAL x,ygg The proposed conf 6nhi changes to $50.34(f) would also be applicable to the small subset

- of specifically listed applicants that had a construction permit application pending on F'ebruary 16,1982. The NRC does nht' expect these applications to be pursued further. However' should ,

a',

one of these applications bkrp-activated, the applicant would be given the option of using an l gw .

approved attemative to the TID-14844 source term. Should an affected applicant choose to use

. w!@ l an attemative source term [tS impact discussion and conclusions above for the proposed W y; i

$50.67 would apply. mty 1

I 4, Backfit Coneidaratinns.

,.I- [

The NRC has determined that the backfit rule,10 CFR 50.109, does not apply to this proposed regulation and, tibrefore, a backfit analysis is not required for this proposed 1

regulation because these afnendments do not involve any provisions that would impose backfits

--: '7 j as defined in 10 CFR 50:l109(a)(1).

3 y

• The proposed cNnges to $50.34(f), by removing the explicit reference to TID-14844, ,

gy ,

allow future applicianis under Part 52 to use an attemative source term without the need for seeking exemptions, and will allow the small class of applicants for which a

} construction permit or manufacturing license was pending on February 16,1982, to use 5

l' s

an approved attemative to the TID-14844 source term in showing compliance with

j. 950.34(f). With the exception of the Westinghouse AP-600 final design approval process, there are no pending Part 52 applications. (Westinghouse requested an l exemption from the affected paragraphs in $50.34(f) to use the revised source term.)

l

,

• The proposed change to GDC-19, will require future applicants under Part 50 or Part 52 i

1

after January 10,1997, to show compliance with the 0.05 Sv (5 rem) TEDE dose i

RA - 23 3 f.

• n r a

\ e P

October 15,1998 DRAFT - PRE-DECISIONAL criterion. There are no applicants in this status at the present time.

i j 5. Imonete on NRC Staff. Other Proarams. and Other Agencies 1

a b

The proposed rulemaking does not affect Federal, State, or local govemment agencies, or i

Agreement State licensees, because the rulemaking affects only the licensing and operation of nuclear power plants that are regulated by the NRC under Part 50. Within the NRC, the l

I cognizant office is Nuclear Reactor Regulation, which is sponsoring this proposed rulemaking.

l No other NRC office is affected by this proposed rulemaking.

l l V. DECISION RATIONALE 1

A. Use of an Alternative Source Term at Operating Reactors The decision to create a new section in Part 50, i.e.,650.67, and to include the following provisions: the need for a license amendment, the accident dose guidelines $50.34(a)(1)(ii),

and the 0.05 Sv (5 rem) TEDE dose criterion for the control room, was based on the following j rationale:

4

a. The objective of providing a regulatory framework for the voluntary implementation of an attemative source term as a change to the design basis at currently licensed power reactors, thereby enabling potential cost-beneficial licensing actions while continuing to maintain existing safety margins and defense in depth.

b. The need for accident dose guidelines and control room habitability dose criteria that are consistent with the characteristics of the revised source term, and that reflect updated RA - 24

October 15,1998 DRAFT - PRE-DECISIONAL scientific information on radionuclide uptake and metabolism and current radiation

^

protection standards. -

c. The provision that an attemative source term be implemented in a facility's design basis via a license amendment, which addresses NRC staff concem that the current language i of 650.59 could be interpreted as allowing this change without prior staff approval. (The NRC is currently considering changes to 50.59. The approach taken in 650.67 is not inconsistent with the proposed language in 950.59.)

d. The results of the NRC staff re-baselining study that did not identify any significant concems related to implementation of the revised source term.

4

! i s

e. The Commission philosophy of separating plant siting from plant design, as evidenced by the January 1997 Part 50 and Part 100 final rule.

f. The need to maintain the existing licensing basis for the operating reactors that continue i

to use the TID-14844 source term.

B. Conforming Changes for Part 52 The decision to address needed conforming changes to Part 50, and to include the 0.05 Sv i

(5 rem) TED dose criterion for the control room, was based on the following rationale:

a. The desire to eliminate the need for exemptions from compliance with the affected j sections.

4 i

RA - 25 3

_ _ , _ ___. _ _ _ _, - _ _ . _ _ _ _ _ - . _ - -~

Octob:r 15,1998 DRAFT - PRE-DECISIONAL

b. The need for control room habitability dose criteria that are consistent with the characteristics of the revised source term, and that reflect updated scientific information on radionuclide uptake and metabolism and current radiation protection standards VI. IMPLEMENTATION in the interest of facilitating stakeholder pnticipation in this rulemaking and in the interest of allowing interested licensees to proceed with the development of applications, the Commission decided to separate development of the proposed rule from the proposed draft guide and draft SRP section. This regulatory analysis addresses only the proposed rule. The following are the major milestones: 1 Proposed rule to Commission 12/15/98 Final rule, draft guide, draft SRP section to 7/30/99 Commission Final guide, SRP section to Commission 1/24/00 As this is a voluntary rulemaking for operating reactors, there is no effective date or required schedule for implementation on the part of licensees. No backfit is involved.

l l

The proposed rule language is provided in the Federa/ Register entry for which this' regulatory analysis applies. The accident dose guidelines and the control room dose criteria in the proposed rule are readily quantifiable and enforceable. These guidelines and criteria are performance based, i.e., the proposed rule does not prescribe how to meet the requirement.

RA - 26 4

October 15,1998 DRAFT - PRE-DECISIONAL Vll. REFERENCES .

1. Accident Source Terms forUght-WaterNuclearPowerPlants, NUREG-1465, February 1995

2. Calculation of Distance Factors for Power and test Reactor Sites, Technical information Document (TID) 14844, March 1962

3. Results of the Revised (NUREG-1465) Source Term Re-Baselining for Operating Reactors, SECY-98-154, June 1998

4. Amendments to 10 CFR Parts 50, 52, and 100, and Issuance of New Appendix S to Part 50, SECY-96-118, May 1996

5. Use of the NUREG-1465 Source Term at Operating Reactors, SECY-96-242, November

~1 996 RA - 27

4 d

4 I

4 1

i Attachment 3 i

i 1

i i

1 3

i 4

i Draft 3

Environmental Assessment i

s

)

}

1 J

i l l

i 3

i 4

)

i I

I

. . . -. . - - - - - - - - - . - . . , - .. . -. . . ~ .- - -

October _15,1998 DRAFT - PRE-DECISIONAL DRAFT ENVIRONMENTAL ASSESSMENT d

REVISION OF 10 CFR PARTS 21,50, AND 54 t

The Nuclear Regulatory Commission is proposing to amend its regulations to allow the holders of operating licenses at currently operating reactors to voluntarily amend their design bases to replace the current accident source term with the revised source term in NUREG-1465 Accident Source Terms forLight-WaterNuclearPowerPlants; identification of Action The Commission is proposing to amend 10 CFR Part 50 by adding a new section,650.67, to address the use of an attemative accident source term. Section 50.67 will apply to all holders of operating licenses issued before January 10,1997, that seek to amend their facility design basis to replace the current accident source term with an attemative source term on or after the effective date of the final regulation. These licensees will be required by $50.67 to evaluate the radiological consequences of the design basis accidents previously analyzed in the safety analysis report, and to request a license amendment under 650.90. Acceptance criteria for the accident radiological consequence analyses appear in $50.67. These criteria are accident dose guidelines for evaluation of releases of radioactivity to the environment and the resulting exposures to persons offsite, and dose criteria for plant personnel occupying the control room during postulated accidents.

The proposed rule amends a current regulation by establishing attemate requirements that licensees may voluntarily adopt. The Commission concluded that the existing analytical approach based on the current source term continues to be adequate to protect public health and safety; therefore, the Commission does not intend to backfit the revised source term or the changes in accident dose guidelines and control room habitability criteria on operating power reactors. Since the proposed revision to the regulation will not constitute a backfit, the bases for existing nuclear power plants must be preserved. For this reason, the current accident dose guidelines in 9100.11 and the current control room habitability criteria of Appendix A to 10 CFR Part 50 will remain in effect for those licensees that do not apply for the use os an altemate source term.

EA-1 e

1 October 15,1998-DRAFT - PRE-DECISIONAL The Commission is also proposing to amend 10 CFR Part 50 by revising 10 CFR Part 50,

' Appendix A, GDC-19 to use a' dose criterion based on total effective dose equivalent. The .

revised criterion, which will be in addition to the current dose criterion in GDC-19, is applicable only to applicants for construction permits under this part, or applicants for a design certification i

or combined license under 10 CFR Part 52, that apply on or after January 10,1997, or holders of operating licenses using an attemative source term.

Need for the Action Une of an Altemative hurm Term Current operating light-water reactors were licensed, in part, on the basis of safety analyses that used fission product release assumptions presented in the Technical information Documont (TID) 14844, Calculation of Distance Factors for Power and Test Reactor Sites (1962). Although initially applied to the evaluation of proposed reactor sites, these fission product release assumptions, known collectively as the " source term," have been used in .

{

soveral regulatory applications related to light-water reactors. This source term was a key input to many of the design analyses associated with currently operating reactors and is a significant

, component of the design basis for these facilities. - During the period since the publication of -  !

TID-14844, significant advances have been made in understanding the timing, magnitude, physical form, and chemical form of fission product releases from severe nuclear power plant accidents. in 1995, the NRC published NUREG-1465, Accident Source Terms forLight-Water Nuclear Power Plants, which utilized these source term insights to produce revised estimates of the accident source term. These source terms are described in terms of radionuclide composition and magnitude, physical and chemical form, and timing of release. For design i basis accident assessments, the NUREG-1465 source term is comparable to the TID-14844 l

source term with regard to the magnitude of the noble gas and radioiodine release fractions.

However, the revised source term provides a more representative description of the radionuclide composition and release timing.

{

l The objective of NUREG-1465 was to define a revised accident source term for regulatory application for future light water reactors. The Commission's intent was to capture the major '

relevant insights available from severe accident research to provide, for regulatory purposes, a more realistic portrayal of the amount of the postulated accident source term. These source '

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l October 15,1998 DRAFT - PRE-DECISIONAL l

terms were derived from examination of a set of severe accident sequences for light water reactors of current design. Because of general similarities in plant and core design parameters, '

these results are considered to be applicable to evolutionary and passive LWR designs. The Commission considered the applicability of the revised source term to operating reactors and determined that the current analytical approach based on the TID-14844 source term would continue to be adequate to protect public health and safety and that operating reactors licensed under this approach would not be required to reanalyze design basis accidents using the revised source term. The Commission also concluded that some licensees may wish to use an attemative source term in analyses to support operational flexibility and cost-beneficial licensing actions. These actions could reduce regulatory burden.

i in January 1997, the Commission amended its regulations in 10 CFR Parts 21,50,52,54, and 100 (61 FR 65157). That regulatory action provided site criteria for future sites and relocated i

t source term and dose requirements for future plants into Part 50. Since these dose

) requirements tend to affect reactor design rather than siting, they are more appropriately

, located in Part 50. Since the revised criteria would not apply to operating reactors, the non-(

seismic and seismic reactor site criteria for operating reactors was retained as Subpart A and

Appendix A to Part 100, respectively. The revised reactor site criteria were added as Subpart B

] in Part 100, and revised source term and dose requirements were relocated to $50.34. The existing source term and dose requirements of Subpart A of Part 100 will remain in place as the licensing bases for those operating reactors that do not elect to use the revised source term.

j The Commission retained the requirements for the exclusion area and the low population zone, l but revised the associated numerical dose guidelines to replace the two different doses for the i

whole body and the thyroid gland with the single, total effective dose equivalent (TEDE) value. '

I The dose guidelines for the whole body and thyroid, and for the immediate 2-hour exposure period, were largely predicated by the assumed source term being predominantly noble gases ,  ;

and radioiodines instantaneously released to the containment and the assumed " single critical organ" method of modeling the intemal dose used at the time that Part 100 was originally put,lished. However, the current dose guidelines, by focusing on doses to the thyroid and I whole body, assume that the major contributor to doses will be radiolodine. Although this may be appropriate with the TID-14844 source term, it may not be true for a source term based on a more complete understanding of accident sequences and phenomenology. The postulated chemical and physical forms of radioiodine in the revised source term are more amenable to mitigation and, as such, radiciodine may not always be the predominant radionuclide in an accident release. The revised source term includes a larger number of radionuclides than did EA-3 4

October 15,1998 DRAFT - PRE-DECISIONAL' i

the TID-14844 source term. The whole body and thyroid dose guidelines ignore these l

contributors to dose. The TEDE, using a risk-consistent methodology, assesses the impact of  !

all relevant 'nuclides upon all body organs. Although it is expected that, in many cases, the thyroid could still be the limiting organ and radioiodine the limiting radionuclide, this conclusion

(

I cannot be assured in all potential cases. The revised source term postulates that the core  !

I inventory is released in a sequence of phases over 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />, with the more significant release <

commencing at about 30 minutes from the start of the event. The assumption that the 2-hour exposure period starts immediately at the onset of the release is inconsistent with the phased release postulated in the revised source term. A detailed rationale for the use of 0.25 Sv (25 rem) TEDE as an accident dose guideline and 'the use of the 2-hour exposure period resulting in the maximum dose for future light wMer reactors (LWRs)is provided at 61 FR 65157. The considerations that formed the basis for that rationale are also applicable to operating reactors that elect to use the revised source term. The Commission believes that it is technically appropriate and logical to extend the dose guidelines, established for future LWRs using the 3

revised source term to operating reactors that elect to use the same revised source term.

l The Commission determined that, for use with the revised source term, accident dose guidelines and control room habitability should be expressed in terms of TEDE, and that the 2-hour exposure period should be based on the 2-hour period that yields the maximum dose.

The proposed $50.67 incorporates these acceptance criteria.

1 Conforming Change to GDC-19 The proposed change to GDC-19 is not related to the use of an altemative source term at operating reactors, but is included here to address a deficiency identified in the regulatory framework for early site permits, standard design certifications, and combined licenses under Part 52. Sections 52.18,52.48, and 52.81 establish that applications filed under Part 52 Subparts A, B, and C, respectively, will be reviewed according to the standards given in 10 CFR Parts 20, 50, 51, 55, 73, and 100 to the extent that those standards are technically relevant to the proposed design. Therefore, GDC-19 is pertinent to applications under Part 52. The recent Part 100 rulemaking (61 FR 65157) established accident TEDE guidelines (in 650.34) for applicants under Part 52, but did not establish a revised control room dose criterion. Therefore, exemptions from the dose criterion in the current GDC-19 were necessary in the design certification process for the Westinghouse AP-600 advanced light water reactor in order to use the 0.05 Sv (5 rem) TEDE criterion deemed necessary for use with the revised source term.

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i -

j October 15,1998 DRAFT - PRE-DECISIONAL f The proposed change will eliminate the need for exemptions by future applicants under Part 52.

The proposed change is also applicable to future applications under Part 50 that are filed on or e

j - after January 10,1997. -

1

Environmentalimpacts of the Action

, The implementation of an altemative source term at an operating power reactor would replace 2

the traditional TID-14844 source term with a source term that would be based on the insights l gained from extensive accident research activities. The actual accident sequence and f progression are not changed; it is the regulatory assumptions regarding the accident that will be l affected by substituting an attemative source term. Use of an attemative source term alone

}

j cannot increase the core damage frequency (CDF) or the large early release frequency (LERF) j or actual offsite or onsite radiation doses. (Although actualdoses would not increase, analysis i

results may show an increase in some postulated doses because additional radionuclides will be considered and dose modeling will be more comprehensive.) The source term is used in

[

i analyses performed to assess the adequacy of the plant design to contend with a design basis

accident (DBA)in order to ensure adequate defense in depth and adequate safety margins.

The attemative source term could be used to justify changes in the plant design that could have l .

j an impact on CDF or LERF or that could increase offsite or onsite doses. These potential 1 {

[ changes are subject to existing requirements in the Commission's regulations. Thus, the i protection of public health and safety would not be decreased by this proposed rulemaking, 4 l f- The Commission directed the NRC staff to assess the impacts ofimplementing the revised l source term at operating reactors. The results of this study were presented to the Commission l

in SECY-98-154, Results of the Revised (NUREG-1465) Source Term Re-Baselining for j Operating Reactors. The major areas examined included the effect on individual offsite and

, control room dose, the effect on doses used in equipment environmental qualification, and the i

s effect of potential modifications that might be enabled by the revised source term. The study i also assessed the margin afforded by the revised source term in comparison to assessments performed using the integrated severe accident assessment code, MELCOR. The study i indicated that the impact of implementing the revised source term at operating reactors will j produce lower postulated doses in the majority of cases. The Commission intends to address I

the exceptions in the regulatory guidance that will be developed to support the proposed rule and in the processing of the individuallicense amendments. The MELCOR analyses indicated

] that the design basis dose calculations still have a substantial margin (a factor of two or greater) 1

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1 i l o .

i

- Octob*r 15,1998 DRAFT - PRE-DECISIONAL even though the postulated dose may be less than that indicated by calculations using the j

current source term. The study also indicated that many of the plant systems that are likely to

( be considered for modification are not involved in risk significant sequences and are, therefore,

not likely to have a substantial offsite risk impact using a measure such as LERF.

h There is an expectation that many of the attemative source term applications may provide concomitant improvements in overall safety and in reduced occupational exposure, as well as i

4 economic benefits. In light of the wide range of possible applications and the voluntary nature j of this proposed rulemaking, it is not reasonable to quantify possible outcomes. Occupational j exposures may be reduced through reductions in maintenance efforts associated with

maintaining unnecessarily limiting leakage, timing, or filtration requirements. Overall safety may le be improved through (1) reduced emergency diesel generator loading, (2) improved i

containment ventilation system performance due to lessened filter flow resistance, and (3) closer synchronization of accident mitigation feature actuation with the onset of major fission product release. There may be improvements in safety margins realized due to the upgrading I

of analysis assumptions, methods, and acceptance criteria.

j The radiological consequences of DBAs will not be increased by the use of the revised source j term. The proposed dose guidelines are comparable, in level of protection, to the existing j guidelines. The proposed rule does not affect non-radiological plant effluents and has no other

] environmental impact. Therefore, the Commission concludes that there are no significant non-j radiological environmental impacts associated with the amendments to the regulations.

,t i

h Alternatives to the Action

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I j As required by Section 102(2)(E) of National Environmental Policy Act (NEPA) (42 U.S.C.A.

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4332(2)(E)), the staff has considered possible attematives to the proposed action. Most of the

} attematives considered were related to administrative details such as location of the proposed f rule and the means of providing regulatory guidance. These attematives are neutral with regard to environmental impact and will not be considered further. With regard to environmental

. impacts, the altematives can be reduced to (1) retain the existing accident source term, i.e., the no-action alternative, and (2) allow the use of the revised source term.

' The first altemative considered by the Commission was to retain the existing accident source term, i.e., the no-action alternative. This was not considered to be an acceptable altemative, as I l

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8 October 15,1998 DRAFT - PRE-DECISIONAL it would preclude the use of an attemative source term by operating reactors and the potential reductions in regulatory burden. This rulemaking attemative wou'd also preclude potential concomitant improvements in overall safety and in reduced occupational exposure. ~ The enviromentalimpact of a postulated DBA would be unchanged. The foreclosure of potential concomitant improvements could prevent some actions that could reduce the risk and/or consequences of accidents. Since it is not possible to predict the source term applications that

- may voluntarily be proposed by license with any degree of certainty, this aspect is not evaluated further.

The second altemative considered by the Commission was to allow the voluntary use of the revised source term at operating plants, including the use of dose guidelines and dose criteria consistent with the characteristics of the revised source term. This attemative would establish the requirements for use of an attemative source term in a new section to Part 50 while retaining the existing regulations in 10 CFR Part 100 Subpart A and GDC-19. The proposed approach was chosen as the best rulemaking altemative. It is believed that the proposed rulemaking will result in an improvement in the allocation of resources both for the NRC and for industry. The industry will be allowed to propose applications of an altemative source term that could reduce unnecessary or ineffective requirements in the facility design basis. The NRC and the industry stand to gain from having appropriate regulatory requirements and guidance needed to facilitate preparation and NRC staff review of licensee submittals. Limited resources 1

could be diverted to safety issues of greater significance. The environmentalimpacts of the  ;

proposed use of the revised source term were addressed earlierin tNs assessment and it was l concluded that there would be no signifi:: ant environmentalimpact. Given the conclusion of no significant impact and the economic benefits that could be achieved, this altemative is clearly superior to the no-action attemative.

Alternative Use of Resources No attemative use of resources was considered. The proposed rule applies only to existing operating reactors and the use of an attemative source term for analysis purposes has no impact on the use of resources. Although this rule also makes conforming changes related to future pirat R::ensing, the environmental impact of the future plant licensing would, by regulation. be assessed as part of the plant licensing.

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DRAFT - PRE-DECISIONAL Agencies and Persons Consulted i The NRC staff developed the proposed rulemaking. No outside agencies or consultants were used in developing this proposed rulemaking package. The NRC staff also obtained advice from the NRC Advisory Committee on Reactor Safeguards.

Conclusion The Commission has made a draft determination under the National Environmental Policy Act

- of 1969, as amended, that the proposed amendments to 10 CFR Parts 21, 50, and 54 to allow the holders of operating licenses at currently operating reactors to voluntarily amend their design bases to replace the current accident source term with an attemative source tenn, do not have a significant effect on the quality of the human environment and that an environmental

!.mpact statement is not required.

- This draft determination is based on the following:

1. The foregoing environmental assessment.

2. The proposed accident revised source term and the proposed accident dose guidelines were incorporated into the Commission's regulations in Parts 50 and 100 for future plant licensing by a final rulemaking on January 10,1997. The environmental assessment for that final rule made a finding of no significant impact. The proposed rule is a logical extension of these provisions to operating reactors, and a similar finding is appropriate.

3. The revised source term reflects the significant advances that have been made in understanding the timing, magnitude, and chemical form of fission product releases from severe nuclear power plant accidents. This altemative source term provides more physically based estimates of the accident source term. The Commission sponsored significant review efforts by peer reviewe... , ,'oreign research partners, industry groups, and the general public (57 FR 33374).

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October 15,1998 DRAFT - PREDECISIONAL References

1. Accident Source Terms forLight-WaterNuclearPowerPlants, NUREG-1465, February 1995

2. Calculation of Distance Factors for Power and Test Reactor Sites, Technical Information Document (TID) 14844, March 1962

3. Results of the Revised (NUREG-1465) Source Term Re-Baselining for Operating Reactors, i

SECY-98-154, June 1998

4. Amendments to 10 CFR Parts 50, 52, and 100, and issuance ofNew Appendix S to Part \

50, SECY-96-118, May 1996 1

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Attachment 4 i

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Congressional Letters 4

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The Honorable Dan Schaefer, Chairman Subcommittee on Energy and Power i

Committee on Commerce )

United States House of Representatives Washington, DC 20515 )

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Dear Mr. Chairman:

Enclosed for the information of the Subcommittee are copies of a public announcement and a

• - proposed amendment to 10 CFR Parts 21, 50, and 54. The proposed rule would allow holders of operating licenses at currently operating reactors to voluntarily amend the!r design bases to replace the current accident source term with the revised source term in NUREG-1465, i

Accident Source Terms forLight-Water NuclearPower Plants. The Commission is also

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proposing some changes to various sections of its regulations to conform with revisions implemented earlier.

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Since the publication of the current accident source term in 1962, significant advances have been made in understanding the timing, magnitude, and chemical form of fission product

! releases from severe nuclear power plant accidents. Many of these insights developed out of the major research effort started by the NRC and the industry after the accident at Three Mile Island (TM1). The proposed rule would enable currently licensed power reactors to propose j

applications of the revised source term that could reduce unnecessary or ineffective j-requirements in the facility design basis, thereby reducing the regulatory burden. It is believed that the proposed rulemaking will result in an improvement in the allocation of resources both j

for the NRC ~and for industry. Also, there is an expectation that many of the revised source

! term applications may provide concomitant improvements in overall safety and in reduced i occupational exposure, as well as economic benefits.

The NRC staff has determined that the public health and safety and the common defense and j.

security would continue to be adequately protected if the proposed rulemaking were implemented.

i' Sincerely, Dennis K. Rathbun, Director Office of Congressional Affairs i

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Enclosure:

Public Announcement 1

Federal Register Notice i

cc

Representative Ralph Hall 4

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The Honorable James N. Inhofe, Chairman Subcommittee on Clean Air, Wetlands, Private Property and Nuclear Safety Committee on Environment and Public Works United States Senate Washington, DC 20510

Dear Mr. Chairman:

Enclosed for the information of the SubcGrinittee are copies of a Public Announcement and a proposed amendment to 10 CFR Parts 21,50, and 54. The proposed rule would allow holders of operating licenses at currently operating reactors to voluntarily amend their design bases to replace the current accident source term with the revised source term in NUREG-1465, Accident Source Terms for Light-WaterNuclear Powerplants. The Commission is also proposing some changss to various sections of its regulations to conform with revisions implemented earlier.

Since the publication of the current accident source term in 1962, significant advances have been made in understanding the timing, magnitude, and chemical form of fission product releases from severe nuclear power plant accidents. Many of these insights developed out of the major research effort started by the NRC and the industry after the accident at Three Mile Island (TMI). The proposed rule would enable currently licensed power reactors to propose applications of the revised source term that could reduce unnecessary or ineffective requirements in the facility design basis, thereby reducing the regulatory burden. It is believed that the proposed rulemaking will result in an improvement in the allocation of resources both for the NRC and for industry. Also, there is an expectation that many of the revised source term applications may provide concomitant improvements in overall safety and in reduced occupational exposure, as well as economic benefits.

The NRC staff has determined that the public health and safety and the common defense and security would continue to be adequately protected if the proposed rulemaking were implemented.

Sincerely, Dennis K. Rathbun, Director Office of Congressional Affairs l

Enclosure:

Public Announcement  !

Federal Register Notice j i

cc; Senator Bob Graham l

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Attachment 5 4

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i Draft

,4 Public Announcement i

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DRAFT PUBUC ANNOUNCEMENT NRC PROPOSES CHANGES TO ALLOW USE OF REVISED SOURCE. TERM AT OPERATING REACTORS 1 i The Nuclear Regulatory Commission is proposing to amend its regulations to allow holders of operating licenses for nuclear power plants to voluntarily replace the traditional i

source term used in design basis accident analyses with a revised source term. This revised i

source term was developed from the results of a major research effort to obtain a better j

understanding of fission-product transport and release mechanisms in light water reactors I under severe accident conditions. This action would allow interested licensees to pursue cat-beneficial licensing actions to reduce regulatory burden without compromising the margin of safety of the facility. In addition, the Commission is also proposing to amend its regulations to revise certain sections to conform with final 10 CFR Parts 50 and 100 rulomaking published on January 10,1997.

Since the publication of the current accident source term in 1962, significant advances have been made in understanding the timing, magnitude, and chemical form of fission product releases from severe nuclear power plant accidents. Many of these insights developed out of the major research effort started by the NRC and the industry after the accident at Three Mile Island (TMI). The proposed rule would enable currently licensed power reactors to propose applications of the revised source term that could reduce unnecessary or ineffective requirements in the facility design basis, ti?ereby reducing the regulatory burden. It is believed that the proposed rulemaking will result in at. !mprovement in the allocation of resources both for the NRC and for industry. Also, there is an expectation that many of the revised source term applications may provide concomitant improvements in overall safety and in reduced occupational exposure, as well as economic benefits.

The NRC staff has determined that the public health and safety and the common defense and security would continue to be adequately protected if the proposed rulemaking were implemented.

' Interested persons are invited to submit comments on the proposed changes within 75 days after publication of a Federal Register notice on this subject, expected shortly Written comments shouid be malled to the Secretary, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, Attention: Rulemaking and Adjudications Staff. Comments may also be submitted via the NRC's interactive rulemaking web site at http://www.nrc. gov /NRC/ rule.html.

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