ML23027A059: Difference between revisions

From kanterella
Jump to navigation Jump to search
(StriderTol Bot insert)
 
(StriderTol Bot change)
Line 16: Line 16:


=Text=
=Text=
{{#Wiki_filter:CONTROL ROOM DESIGN CRITERIA AND RADIOLOGICAL HEALTH EFFECTS June 2023 1              1 Terry Brock, John Tomon, 2                    2 David Garmon, and Elijah Dickson Division of Systems Analysis Office of Nuclear Regulatory Research United States Nuclear Regulatory Commission 1  Office of Nuclear Regulatory Research, Division of Systems Analysis, Radiation Protection Branch (RES/DSA/RPB) 2  Office of Nuclear Reactor Regulation, Division of Risk Assessment, Radiation Protection and Consequence Branch (NRR/DRA/ARCB)
{{#Wiki_filter:CONTROL ROOM DESIGN CRITERIA AND RADIOLOGICAL HEALTH EFFECTS


TABLE OF CONTENTS TABLE OF CONTENTS .............................................................................................................. iii LIST OF TABLES......................................................................................................................... v EXECUTIVE
J une 2023


==SUMMARY==
1 J ohn Tom on1 Terry Broc k,,
............................................................................................................ vii ABBREVIATIONS ....................................................................................................................... ix
2 and 2 D av id G arm on, Elijah Dickson
: 1. INTRODUCTION............................................................................................................ 1
 
D iv ision of Sy stem s Analy sis Office of N uc lear R egulatory R esearc h U nited States N uc lear R egulatory C om m ission
 
1 Office of Nuclear Regulatory Research, Division of System s Analysis, Radiation Protection Branch (RES/DSA/ RPB)
 
2 Office of Nuclear Reactor Regulation, Division of Ri s k Assessm ent, Radiation Protection and Consequence Branch (N RR/D RA /A RC B )
 
TABLE OF CONTENTS
 
T AB L E O F CO NT E NT S.............................................................................................................. iii
 
LIST O F T AB LES......................................................................................................................... v
 
EXECUT IVE SUMM ARY............................................................................................................ vii
 
A B BR E V I AT IO NS....................................................................................................................... ix
: 1. INTRODUCT ION............................................................................................................ 1
: 2. BACKGROUND............................................................................................................. 1
: 2. BACKGROUND............................................................................................................. 1
: 3. IAR TASK 1 RESULTS ................................................................................................. 4 Item 1: Identify applicable radiation dose-based regulations and their roles as operational limits or design criteria. .................................................................4 Item 2: Describe the coherent regulatory approach to radiation protection for workers under normal and emergency conditions. ..........................................7 Occupational Control Room Doses ..........................................................8 Control Room Design Criteria.................................................................12 Performance-Based Regulations, Design-Basis Accidents, and Use of Personal Protective Equipment...................................................13 Item 3: Provide an annotated bibliography of radiation protection recommendations for workers during emergency conditions from national and international organizations responsible for making recommendations for radiation protection standards. ...................................15 Item 4: Provide an assessment of the identified design criteria to contemporary radiological health effects...............................................................................16 REFERENCES............................................................................................................................ 19 iii
: 3. IAR T ASK 1 RESULT S................................................................................................. 4
 
Item 1: Identif y applic able radiation dose-based regulations and their roles as operationa l lim its or d esig n c riteria.................................................................. 4 Item 2: D esc ribe the c oherent regulatory approac h to radiation protec tion f or w ork ers under norm al and em ergenc y c onditions...........................................7 O cc upational C ontrol R oom D oses..........................................................8 C ontrol R oom D esign C riteria................................................................. 12 Perf orm anc e-Based R egulations, D esign-Basis Ac c idents, and U se of Personal Protec tiv e Equipm ent...................................................13 Item 3: Prov ide an annotated bibliography of radiation protec tion rec om m endations f or w ork ers during em ergenc y c onditions f rom national and international organizations responsible f or m ak ing rec omm endations f or radiation pro tec tion sta ndards....................................15 Item 4: Prov ide an assessm ent of the identif ied design c riteria to c ontem porary radiologic al h ealth ef f ec ts...............................................................................16 REFERENCES............................................................................................................................ 19
 
iii


LIST OF TABLES Table 1 Dose-Based Criteria and Regulations .............................................................................. 5 v
LIST OF TABLES
 
Table 1 D ose-Ba sed C riteria a nd R egulat ions.............................................................................. 5
 
v


EXECUTIVE  
EXECUTIVE  


==SUMMARY==
==SUMMARY==
With the inc reased interest in m odernized pow er reac tor f uels, inc luding ac c ident tolerant f uels and higher burnup and inc reased enric hm ent f uels, by U.S. N uc lear R egulatory C om m ission (NRC) lic ensees and industry, the N R C is c onsidering a rulem ak ing to enable the applic ation of these m odern f uel designs in an ef f ic ient m anner. To support this rulem ak ing determ ination, the Inc r eased E nr ic hm ent Wor k ing G r oup, through the O f f ic e of N uc lear R eac tor R egulation (N R R ),
sought assistanc e f rom the O f f ic e of N uc lear R egulatory R esearc h (RES) w ith inf orm al assistanc e request (IAR ) N R R-2022-019, Assessm ent of R adiation Protec tion R ec om m endations f or Em ergenc y Work ers, (August 26, 2022). The purposes of IAR N R R-2022-019 w ere to identif y N R C regulations that apply radiologic al c onsequenc es-as operational lim its or design c riteria, to desc ribe the regulatory approac hes that are applic able to w ork ers during norm al and em ergenc y c onditions, to dev elop an annotated bibliography of selec ted radiation protec tion rec om m endations that are applic able during an em ergenc y, and to prov ide an assessm ent of the identif ied design c riteria to the c ontem porary understanding of radiologic al health ef f ec ts.


With the increased interest in modernized power reactor fuels, including accident tolerant fuels and higher burnup and increased enrichment fuels, by U.S. Nuclear Regulatory Commission (NRC) licensees and industry, the NRC is considering a rulemaking to enable the application of these modern fuel designs in an efficient manner. To support this rulemaking determination, the Increased Enrichment Working Group, through the Office of Nuclear Reactor Regulation (NRR),
N R C radiologic al regulations are based to a signif ic ant ex tent on the rec om m endations of the International C om m ission on R adiologic al Protec tion (IC R P) and on the U.S. N ational C ounc il on R adiation Protec tion and M easurem ents (N C R P). M eanw hile, the Federal Em ergenc y M anagem ent Agenc y (FEM A) is the Federal agenc y of the U.S. D epartm ent of H om eland Sec urity responsible f or helping people bef ore, during, and af ter disasters. For radiologic al inc idents, the U.S. Env ironm ental Protec tion Agenc y (EPA) is the primary Federal agency that establishes protec tiv e ac tion guides and planning guidanc e f or radiologic al inc idents. These organizations establish dose-based c riteria that are deem ed suf f ic iently low to prec lude determ inistic health ef f ec ts. Theref ore, these protec tiv e dose-based c riteria prov ide an adequate m argin that w ould m aintain the operators ability to m aintain a reac tor in a saf e c ondition under ac c ident c onditions.
sought assistance from the Office of Nuclear Regulatory Research (RES) with informal assistance request (IAR) NRR-2022-019, Assessment of Radiation Protection Recommendations for Emergency Workers, (August 26, 2022). The purposes of IAR NRR-2022-019 were to identify NRC regulations that apply radiological consequences- as operational limits or design criteria, to describe the regulatory approaches that are applicable to workers during normal and emergency conditions, to develop an annotated bibliography of selected radiation protection recommendations that are applicable during an emergency, and to provide an assessment of the identified design criteria to the contemporary understanding of radiological health effects.
NRC radiological regulations are based to a significant extent on the recommendations of the International Commission on Radiological Protection (ICRP) and on the U.S. National Council on Radiation Protection and Measurements (NCRP). Meanwhile, the Federal Emergency Management Agency (FEMA) is the Federal agency of the U.S. Department of Homeland Security responsible for helping people before, during, and after disasters. For radiological incidents, the U.S. Environmental Protection Agency (EPA) is the primary Federal agency that establishes protective action guides and planning guidance for radiological incidents. These organizations establish dose-based criteria that are deemed sufficiently low to preclude deterministic health effects. Therefore, these protective dose-based criteria provide an adequate margin that would maintain the operators ability to maintain a reactor in a safe condition under accident conditions.
The RES staff found that there is ample operating and licensing experience, scientific data, and technical information; numerous recommendations from national and international organizations responsible for radiation protection standards; probabilistic risk assessment technology; and regulatory precedence that support a reevaluation of the control room design criteria of General Design Criteria (GDC) 19, Control room, in Appendix A, General Design Criteria for Nuclear Power Plants, to Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of Production and Utilization Facilities, and 10 CFR 50.67(b)(2)(iii). This review of the radiological framework for the control room design criteria provides, in part, an initial basis for NRCs realignment with the current ICRP and NCRP recommendations and the FEMA and EPA federal response guidelines.
vii


ABBREVIATIONS 10 CFR   Title 10 of the U.S. Code of Federal Regulations ADAMS    Agencywide Documents Access and Management System ALARA   as low as is reasonably achievable ATF     accident tolerant fuel DBA     design-basis accident EPA     U.S. Environmental Protection Agency FEMA    Federal Emergency Management Agency FR       Federal Register GDC     general design criterion/criteria GWd      gigawatt-day(s)
The R ES staf f f ound that there is am ple operating and lic ensing ex perienc e, sc ientif ic data, and tec hnic al inf orm ation; num erous rec om m endations f rom national and international organizations responsible f or radiation protec tion standards; probabilistic risk assessm ent tec hnology; and regulatory prec edenc e that support a reev aluation of the c ontrol room design c riteria of G eneral D esign C riteria (G D C ) 19, C ontrol room, in Appendix A, G eneral D esign C riteria f or N uc lear Pow er Plants, to Title 10 of the C ode of Federal R egulations (10 CFR) Part 50, D om estic Lic ensing of Produc tion and Utilization Fac ilities, and 10 CFR 50.67(b)(2)(iii). This rev iew of the radiologic al f ram ew ork f or the c ontrol room design c riteria prov ides, in part, an initial basis f or N R C s realignm ent w ith the c urrent IC R P and N C R P rec om m endations and the FEM A and EPA f ederal response guidelines.
Gy       gray(s)
 
IAR     informal assistance request ICRP     International Commission on Radiological Protection LD 50/60 lethal dose to 50 percent of the people within 60 days without medical treatment LPZ     low population zone LWR     light-water reactor MTU      metric ton(s) of uranium NCRP     National Council on Radiation Protection and Measurements NEIMA    Nuclear Energy Innovation and Modernization Act NRC     U.S. Nuclear Regulatory Commission NRR     Office of Nuclear Reactor Regulation rem     roentgen equivalent man RES     Office of Nuclear Regulatory Research SRM     staff requirements memorandum SSC     structure, system, and component Sv       sievert(s)
v ii
TEDE     total effective dose equivalent U       uranium ix
 
: 1.     INTRODUCTION With the increased interest in modernized power reactor fuels, including accident tolerant fuels (ATFs) and higher burnup and increased enrichment fuels, by U.S. Nuclear Regulatory Commission (NRC)-licensees and industry, the NRC is considering a rulemaking to enable the application of these modern fuel designs in an efficient manner. To support this rulemaking determination, the Increased Enrichment Working Group, through the Office of Nuclear Reactor Regulation (NRR), sought assistance from the Office of Nuclear Regulatory Research (RES) with informal assistance request (IAR) NRR-2022-019, Assessment of Radiation Protection Recommendations for Emergency Workers [Ref. 1] (August 26, 2022). The purposes of IAR NRR-2022-019 were to identify NRC regulations that apply radiological consequences as operational limits or design criteria, to describe the regulatory approaches that are applicable to workers during normal and emergency conditions, to develop an annotated bibliography of selected radiation protection recommendations that are applicable during an emergency, and to provide an assessment of the identified design criteria to contemporary understanding of radiological health effects. This IAR is expected to help inform the NRCs increased enrichment rulemaking activities and ultimately enhance the agencys ability to perform its mission when considering and licensing fuels that apply increased enrichments. This report provides the results of the IAR.
ABBREVIATIONS
: 2.     BACKGROUND ATFs are a set of new nuclear fuel technologies that have the potential to enhance safety at U.S. nuclear power plants by offering better performance during normal operation, transient conditions, and accident scenarios. On January 14, 2019, the President signed into law the Nuclear Energy Innovation and Modernization Act (NEIMA). NEIMA Section 107, Commission Report on Accident Tolerant Fuel, defines ATF as a new technology that does the following:
 
(1) makes an existing commercial nuclear reactor more resistant to a nuclear incident (as defined in section 11 of the Atomic Energy Act of 1954 (42 U.S.C. 2014)); and (2) lowers the cost of electricity over the licensed lifetime of an existing commercial nuclear reactor.
10 CFR Title 10 of the U.S. C ode of Federal R egulations ADAM S Agenc y w ide D oc um ents Ac c ess and M anagem ent Sy stem ALARA as low as is reasonably ac hiev able ATF ac c ident tolerant f uel DBA design-basis ac c ident EPA U.S. Env ironm ental Protec tion Agenc y FEM A Federal Em ergenc y M anagem ent Agenc y FR Federal R egis ter GDC general design c riterion/criteria G Wd gigaw att-day (s )
Based on stakeholder interactions, the staff is aware that industry plans to request higher fuel burnup limits (i.e., above 62 gigawatt-days per metric ton of uranium (GWd/MTU) rod average) along with the deployment of ATF concepts. To achieve higher burnup limits, industry will need to request increases in fuel enrichment from the current standard of 5.0 weight percent uranium (U)-235 up to approximately 10.0 weight percent U-235. In February 2019, industry identified potential advantages of increased enrichment fuel for light-water reactors (LWRs) in the Nuclear Energy Institute white paper The Economic Benefits and Challenges with Utilizing Increased Enrichment and Fuel Burnup for Light-Water Reactors, issued February 2019 [Ref. 2]. In September 2021, the NRC staff issued an update to the Project Plan to Prepare the U.S.
Gy gray (s)
Nuclear Regulatory Commission for Efficient Licensing of Accident Tolerant Fuels, Version 1.2
IAR inf orm al assistanc e request ICRP International C om m ission on R adiologic al Protec tion LD 50/60 lethal dose to 50 perc ent of the people w ithin 60 day s w ithout m edic al treatm ent LPZ low population zone LWR light-w ater reac tor M TU m etric ton( s) of uranium NCRP N ational C ounc il on R adiation Protec tion and M easurem ents NEIM A N uc lear Energy Innov ation and M odernization Ac t NRC U.S. N uc lear R egulatory C om m ission NRR O f f ic e of N uc lear R eac tor R egulation rem roentgen equiv alent m an RES O f f ic e of N uc lear R egulatory R esearc h SRM staf f requirem ents m em orandum SSC struc ture, sy stem, and c om ponent Sv siev er t( s)
[Ref. 3], that described the pursuit of higher burnup and increased enrichment as key components of industry ATF efforts. Industry plans to deploy batch loads of fuels enriched to levels greater than the current standard of 5.0 weight percent U-235 by the mid to late 2020s.
TEDE total ef f ec tiv e dose equiv alent U uranium
1
 
ix
: 1. INT RODUCT ION
 
With the inc reased interest in m odernized pow er reac tor f uels, inc luding ac c ident tolerant f uels (ATFs) and higher burnup and inc reased enric hm ent f uels, by U.S. N uc lear R egulatory C om m ission (NRC)-lic ensees and industry, the NRC is c onsidering a rulem ak ing to enable the applic ation of these m odern f uel designs in an ef f ic ient m anner. To support this rulem ak ing determ ination, the Inc reased Enric hm ent Work ing G roup, through the O f f ic e of N uc lear R eac tor R egulation (N R R ), sought assistanc e f rom the O f f ic e of N uc lear R egulatory R esearc h (RES) w ith inf orm al assistanc e request (IAR ) N R R-2022-019, Assessm ent of R adiation Protec tion R ec om m endations f or Em ergenc y Work ers [R ef. 1] (August 26, 2022). The purposes of IAR NRR-2022-019 were to identif y N R C regulations that apply radiologic al c onsequenc es as operational lim its or design criteria, to desc ribe the regulatory approac hes that are applic able to w ork ers during norm al and em ergenc y c onditions, to dev elop an annotated bibliography of selec ted radiation protec tion rec om m endations that are applic able during an em ergenc y, and to prov ide an assessm ent of the identif ied design c riteria to c ontem porary understanding of radiologic al health ef f ec ts. This IAR is ex pec ted to help inf orm the NRC s inc reased enric hm ent rulem ak ing ac tiv ities and ultim ately enhanc e the agenc ys ability to perf orm its m ission w hen c onsidering and lic ensing f uels that apply inc reased enric hm ents. This report prov ides the results of the IAR.
: 2. BACKGROUND
 
ATFs are a set of new nuc lear f uel tec hnologies that hav e the potential to enhanc e saf ety at U.S. nuc lear pow er plants by of f ering better perf orm anc e during norm al operation, transient c onditions, and ac c ident sc enarios. O n J anuary 14, 2019, the President signed into law the N uc lear Energy Innov ation and M odernization Ac t (N EIM A). N EIM A Sec tion 107, C om m ission R eport on Ac c ident Tolerant Fuel, def ines ATF as a new tec hnology that does the f ollow ing:
 
(1) m ak es an ex isting c om m erc ial nuc lear reac tor m ore resistant to a nuc lear inc ident (as def ined in sec tion 11 of the Atom ic Energy Ac t of 1954 (42 U.S.C. 2014)); and
 
(2) low ers the c ost of elec tric ity ov er the lic ensed lif etim e of an ex isting c om m erc ial nuc lear reac tor.
 
Based on stak eholder interac tions, the staf f is aw are that industry plans to request higher f uel burnup lim its (i.e., abov e 62 gigaw att-day s per m etric ton of uranium (G Wd/M TU) rod av erage) along w ith the deploy m ent of ATF c onc epts. To ac hiev e higher burnup lim its, industry w ill need to request inc reases in f uel enric hm ent f rom the c urrent standard of 5.0 w eight perc ent uranium (U )-235 up to approx im ately 10.0 w eight perc ent U-235. In February 2019, industry identif ied potential adv antages of inc reased enric hm ent f uel f or light-w ater reac tor s (LWR s) in the N uc lear Energy Institute w hite paper The Ec onom ic Benef its and C hallenges w ith U tilizing Inc reased Enric hm ent and Fuel Burnup f or Light-Water R eac tors, issued February 2019 [R ef. 2]. In Septem ber 2021, the NRC staf f issued an update to the Projec t Plan to Prepare the U.S.
N uc lear R egulatory C om m ission f or Ef f ic ient Lic ensing of Ac c ident Tolerant Fuels, Version 1.2
[R ef. 3], that desc ribed the pursuit of higher burnup and inc reased enric hm ent as k ey c om ponents of industry ATF ef f orts. Industry plans to deploy batc h loads of f uels enric hed to lev els greater than the c urrent standard of 5.0 w eight perc ent U-235 by the m id to late 2020s.
 
1 The dev elopm ent of the c urrent regulatory f ram ew ork did not f oresee enric hm ents greater than 5.0 w eight perc ent U-235, and thus regulations w ere generally established w ith the ex pec tation that enric hm ents w ould be below this v alue w ith reasonable bounding assum ptions c ontained w ithin the saf ety analy sis m ethodologies. H ow ev er, som e spec if ic regulations disc uss suc h enric hm ents, suc h as Title 10 of the C ode of Federal R egulations (10 CFR) 50.6 8(b)(7) [R ef. 4],
w hic h requires that U-235 enric hm ent lev els in pow er reac tor f uel be no m ore than 5.0 perc ent by w eight.
 
In response to industry interest in LWR f uels enric hed to betw een 5.0 to 10.0 w eight perc ent U-235, the NRC staf f subm itted a rulem ak ing plan in SECY-21-0109, R ulem ak ing Plan on U se of Inc reased Enric hm ent of C onv entional and Ac c ident Toleranc e Fuel D esigns f or Light-Water R eac tors, dated D ec em ber 20, 2021 [ R ef. 5], requesting C om m ission approv al to initiate rulem ak ing to am end N R C requirem ents to f ac ilitate the use of LWR f uel c ontaining uranium enric hed to greater than 5.0 w eight perc ent U-235. If lef t unc hanged, the regulatory f ram ew ork c an ac c om m odate the use of LWR f uel c ontaining enric hm ents greater than 5.0w eight perc ent U-235 using lic ensee-spec if ic ex em ptions. H ow ev er, bec ause of the w idespread interest in these new f uels, the staf f ex pec ts m any lic ensees to pursue their use, m eaning that the staf f m ay hav e to proc ess m any ex em ptions to m eet industry dem and. In SECY-21-0109, the staff rec om m ended rulem ak ing to reduc e ex em ption requests and f ac ilitate inc reased regulatory ef f ic ienc y and c onsistenc y w hile c ontinuing to ensure saf ety. R ulem ak ing on this topic w ould allow the staf f to thoroughly rev iew the potential regulatory im plic ations of f uels enric hed to greater than 5.0 w eight perc ent U-235 and identif y and assess the potential c osts and benef its of c hanging regulatory requirem ents that im pac t their use. R ulem ak ing w ould also prov ide options f or generic resolutions of these issues and inv ite stak eholder partic ipation in dec isions af f ec ting this regulatory area, rather than on a c ase-by -c ase basis, as w ould result f rom the c urrent regulatory f ram ew ork.
 
The C om m ission approv ed the staf f s proposal to initiate rulem ak ing to am end requirem ents f or the use of LWR f uel c ontaining uranium enric hed to greater than 5.0w eight perc ent U-235 in Staff Requirem ents M em orandum (SRM )-SECY-21-0109, dated M arc h 16, 2022 [ R ef. 6]. The C om m ission stated that the prov isions of the rule should only apply to high-assay low -enric hed uranium1 f uel, both f or nonprolif eration and saf eguard reasons and to f oc us the staf f s analy sis on the range of enric hm ent m ost lik ely to be c ontem plated in f uturec om m erc ial applic ations.
 
In addition, the C om m ission direc ted the staf f to tak e the f ollow ing ac tions in this rulem ak ing:
* In the regulatory basis and guidanc e, the staf f should appropriately address and analy ze f uel f ragm entation, reloc ation, and dispersal issues relev ant to f uels of high enric hm ent and burnup lev els.
* The staf f should w or k ex peditiously w ith stak eholders to identif y and dev elop nec essary regulatory guidanc e and tec hnic al bases to support the ef f ec tiv e and ef f ic ient lic ensing of inc reased enric hm ent applic ations.
 
1 Uranium f uel enriched to greater than 5.0 and less than 20.0 weight percent U -235.


The development of the current regulatory framework did not foresee enrichments greater than 5.0 weight percent U-235, and thus regulations were generally established with the expectation that enrichments would be below this value with reasonable bounding assumptions contained within the safety analysis methodologies. However, some specific regulations discuss such enrichments, such as Title 10 of the Code of Federal Regulations (10 CFR) 50.68(b)(7) [Ref. 4],
which requires that U-235 enrichment levels in power reactor fuel be no more than 5.0 percent by weight.
In response to industry interest in LWR fuels enriched to between 5.0 to 10.0 weight percent U-235, the NRC staff submitted a rulemaking plan in SECY-21-0109, Rulemaking Plan on Use of Increased Enrichment of Conventional and Accident Tolerance Fuel Designs for Light-Water Reactors, dated December 20, 2021 [Ref. 5], requesting Commission approval to initiate rulemaking to amend NRC requirements to facilitate the use of LWR fuel containing uranium enriched to greater than 5.0 weight percent U-235. If left unchanged, the regulatory framework can accommodate the use of LWR fuel containing enrichments greater than 5.0 weight percent U-235 using licensee-specific exemptions. However, because of the widespread interest in these new fuels, the staff expects many licensees to pursue their use, meaning that the staff may have to process many exemptions to meet industry demand. In SECY-21-0109, the staff recommended rulemaking to reduce exemption requests and facilitate increased regulatory efficiency and consistency while continuing to ensure safety. Rulemaking on this topic would allow the staff to thoroughly review the potential regulatory implications of fuels enriched to greater than 5.0 weight percent U-235 and identify and assess the potential costs and benefits of changing regulatory requirements that impact their use. Rulemaking would also provide options for generic resolutions of these issues and invite stakeholder participation in decisions affecting this regulatory area, rather than on a case-by-case basis, as would result from the current regulatory framework.
The Commission approved the staffs proposal to initiate rulemaking to amend requirements for the use of LWR fuel containing uranium enriched to greater than 5.0 weight percent U-235 in Staff Requirements Memorandum (SRM)-SECY-21-0109, dated March 16, 2022 [Ref. 6]. The Commission stated that the provisions of the rule should only apply to high-assay low-enriched uranium 1 fuel, both for nonproliferation and safeguard reasons and to focus the staffs analysis on the range of enrichment most likely to be contemplated in future commercial applications.
In addition, the Commission directed the staff to take the following actions in this rulemaking:
* In the regulatory basis and guidance, the staff should appropriately address and analyze fuel fragmentation, relocation, and dispersal issues relevant to fuels of high enrichment and burnup levels.
* The staff should work expeditiously with stakeholders to identify and develop necessary regulatory guidance and technical bases to support the effective and efficient licensing of increased enrichment applications.
1      Uranium fuel enriched to greater than 5.0 and less than 20.0 weight percent U-235.
2
2
* The staff should take a risk-informed approach when developing this rule and the associated regulatory basis and guidance.
* The staf f should tak e a risk-inf orm ed approac h w hen dev eloping this rule and the assoc iated regulatory basis and guidanc e.
* The staff should reexamine the schedule to determine whether key milestones can be achieved sooner than projected by leveraging ongoing regulatory innovation efforts.
* The staf f should reex am ine the sc hedule to determ ine w hether k ey m ilestones c an be ac hiev ed sooner than projec ted by lev eraging ongoing regulatory innov ation ef f orts.
Several performance-based regulations use radiological acceptance criteria. Both 10 CFR 50.67(b)(2) [Ref. 7] and General Design Criterion (GDC) 19, Control room of Appendix A, General Design Criteria for Nuclear Power Plants, to 10 CFR Part 50, Domestic Licensing of Production and Utilization Facilities [Ref. 8], provide a specific dose-based criterion of 5 rem (50 millisievert (mSv)) total effective dose equivalent (TEDE) for demonstrating the acceptability of the control room design. They represent a distinct layer of defense in depth that assumes a major accident that results in substantial meltdown of the reactor core with subsequent release of appreciable quantities of fission products. In application, they are performance based, which require that a licensee or applicant provide a control room habitability design using traditional deterministic radiological consequence analyses methods to judge the acceptability of the design.
 
Overall, licensees analysis of record DBA radiological consequence analyses has a relatively small margin to the control room design criteria to generally maximize operational flexibility. This has often resulted in instances in which licensees have had to perform additional analyses to demonstrate compliance without additional safety benefit. This has become unnecessarily burdensome and has often led to a focus on safety versus compliance debates between the NRC and licensees. In addition, the relatively small margin to the control room design criteria has resulted in the submission of license amendment requests for changes with low safety significance. It has also led to the occurrence of avoidable occupational exposures controlled by 10 CFR Part 20 in cases in which licensees have increased maintenance activities to meet the 5 rem (50 mSv) TEDE criterion.
Sev eral perf orm anc e-based regulations use radiologic al ac c eptanc e c riteria. Both 10 CFR 50.67(b)(2) [R ef. 7] and G eneral D esign C riterion (GDC) 19, C ontrol room of Appendix A, G eneral D esign C riteria f or N uc lear Pow er Plants, to 10 CFR Part 50, D om estic Lic ensing of Produc tion and U tilization Fac ilities [R ef. 8], prov ide a spec if ic dose-based c riterion of 5 rem (50 m illisiev ert (m Sv )) total ef f ec tiv e dose equiv alent (TED E) f or dem onstrating the ac c eptability of the c ontrol room design. They represent a distinc t lay er of def ense in depth that assum es a m ajor ac c ident that results in substantial m eltdow n of the reac tor c ore w ith subsequent release of apprec iable quantities of f ission produc ts. In applic ation, they are perf orm anc e based, w hic h require that a lic ensee or applic ant prov ide a c ontrol room habitability design using traditional determ inistic radiologic al c onsequenc e analy ses m ethods to judge the ac c eptability of the design.
With the prospect of licensing increased enrichments greater than 5.0 and less than 20.0 weight percent U-235, the staff anticipates that, to demonstrate compliance within their safety margin, licensees would need to continue performing potentially extensive analyses to demonstrate compliance within their safety margin with no or limited additional safety benefit. Further, industry representatives for LWRs have indicated they would be seeking enrichments up to 10.0 weight percent U-235 and that meeting the criteria when transitioning to increased enrichment fuel would be challenging. Therefore, industry organizations for LWRs have conveyed plans to commit resources to develop alternative approaches to demonstrate compliance with the design criteria.
 
The impact of increased power levels, enrichment, and subsequently fuel burnup on the results of the licensees radiological consequence analysis of record for the computed DBA is multifaceted. However, a rule of thumb is that an increase in power level has a linear effect on computed radiological consequences. With an increase in U-235 enrichment necessary to reach the desired burnup level, the number of fissions within the reactor core source term also increases, which increases the resulting computed radiological consequences. The impact of 3
O v erall, lic ensees analy sis of rec ord D BA radiologic al c onsequenc e analy ses has a relativ ely sm all m argin to the c ontrol room design c riteria to generally m ax im ize operational f lex ibility. This has of ten resulted in instanc es in w hic h lic ensees hav e had to perf orm additional analy ses to dem onstrate c om plianc e w ithout additional saf ety benef it. This has bec om e unnec essarily burdensom e and has of ten led to a f oc us on saf ety v ersus c om plianc e debates betw een the N R C and lic ensees. In addition, the relativ ely sm all m argin to the c ontrol room des ign c riteria has resulted in the subm ission of lic ense am endm ent requests f or c hanges w ith low saf ety signif ic ance. It has also led to the oc c urrenc e of av oidable oc c upational ex posures c ontrolled by 10 CFR Part 20 in c ases in w hic h lic ensees hav e inc reased m aintenanc e ac tiv ities to m eet the 5 rem (50 m Sv ) TEDE c riterion.
 
With the prospec t of lic ensing inc reased enric hm ents greater than 5.0 and less than 20.0w eight perc ent U-235, the staf f antic ipates that, to dem onstrate c om plianc e w ithin their saf ety m argin, lic ensees w ould need to c ontinue perf orm ing potentially ex tensiv e analy ses to dem onstrate c om plianc e w ithin their saf ety m argin w ith no or lim ited additional saf ety benef it. Further, industry representativ es f or LWR s hav e indic ated they w ould be seek ing enric hm ents up to 10.0w eight perc ent U-235 and that m eeting the c riteria w hen transitioning to inc reased enric hm ent f uel w ould be c hallenging. Theref ore, industry organizations f or LWR s hav e c onv ey ed plans to c om m it resourc es to dev elop alternativ e approac hes to dem onstrate c om plianc e w ith the design c riteria.
 
The im pac t of inc reased pow er lev els, enric hm ent, and subsequently f uel burnup on the results of the lic ensees radiologic al c onsequenc e analy sis of rec ord f or the c om puted D BA is m ultif ac eted. H ow ev er, a rule of thum b is that an inc rease in pow er lev el has a linear ef f ec t on c om puted radiologic al c onsequenc es. With an inc rease in U-235 enric hm ent nec essary to reac h the desired burnup lev el, the num ber of f issions w ithin the reac tor c ore sourc e term also inc reases, w hic h inc reases the resulting c om puted radiologic al c onsequenc es. The im pac t of
 
3 higher burnup on radiologic al c onsequenc es is nonlinear w here the abundanc e of dif f erent radionuc lides in the f uel peak at dif f erent burnup lev els. This c ontinuously c hanging radionuc lide m ix due to burnup has a v ary ing im pac t on radiologic al c onsequenc es. Theref ore, depending on how the reac tor c ore is designed w ith inc reased U-235 enric hm ent f uel elem ents and operation at higher burnup lev els to reac h longer c y c le tim e, the im pac t on radiologic al c onsequenc es c om puted to dem onstrate c om plianc e w ith the c ontrol room des ign c riteria w ould inc rease and subsequently dec rease the retained m argin m aintained by the lic ensee to prov ide operational f lex ibility.
 
The NRC rec ognizes the c hallenges that lic ensees f ac e to retain m argin w ithin their lic ensing basis and the sm all am ount of m argin to the c ontrol room design c riteria itself. The N R C does not w ant to unnec essarily penalize lic ensees f or seek ing inc reased enric hm ents that m ay then result in m argin reduc tions and thereby requiring lic ensees to perf orm potentially ex tensiv e analy ses to dem onstrate c om plianc e w ithout a c om m ensurate inc rease in saf ety.
 
This IAR requests RES staf f to doc um ent its assessm ent f indings in a public ly av ailable m em orandum to NRR. Additionally, t he m em orandum should prov ide f or and identif y the f ollow ing task s:
: 1. Identif y applic able radiation dose-based regulations and their roles as operational lim its or design c riteria;
: 2. D esc ribe the c oherent regulatory approac h to radiation protec tion f or w ork ers under norm al and em ergenc y c onditions;
: 3. Perf orm an annotated bibliography of radiation protec tion rec om m endations f or w ork ers during em ergenc y c onditions f rom national and international organizations responsible f or m ak ing rec om m endations f or radiation protec tion standards; and
: 4. Prov ide an assessm ent of the identif ied design c riteria to c ontem porary radiologic al health ef f ec ts.
: 3. IAR T ASK 1 RESULT S
 
Item 1: Identify applicable radiation dose-based regulations and their r oles as operational limits or design criteria.
 
For this item, the RES staff researc hed the applic able regulations in v arious parts2 of 10 CFR to sum m arize the dose-based siting and design c riteria as w ell as oc c upational dose lim its.
Table 1 prov ides this sum m ar y.
 
2 Specif ically, the staf f exam ined 10 C FR Part 50, 10 C FR Part 100, Reactor Site Criteria, and 10 C FR Part 52, Licenses, Certif ications, and Approvals f or Nuclear Power Plants.
 
4 T able 1D ose-Based Criteria and Regulations
 
Operati onal Regulation Cri teri a Limit or Siting/Design Cri teri a 10 C FR 50.34(a)(ii)(D)(1) [Re f. 10] 0.25 sievert (Sv) 25 roentgen equivalent m an ( re m) total ef f ective dose equivalent Siting criteria (TED E) f or any 2-hour period f ollowing postulated f ission product release 10 C FR 50.34(a)(ii)(D)(2) 0.25 Sv (25 rem) TEDE at low population zone ( LPZ) boundary resulting f rom Siting criteria exposure to th e radioactive cloud f rom postulated f ission product release 10 C FR 50.67(b)(2)(i) 0.25 Sv (25 rem)a TEDE f or any 2-hour period f ollowing postulated f ission product Design criteria release 10 C FR 50.67(b)(2)(ii) 0.25 Sv (25 rem) TEDE at LPZ boundary resulting f rom exposure to the Design criteria radioactive cloud f rom postulated f ission product release 10 C FR 50.67(b)(2)(iii) 0.05 Sv (5 rem) Design criteria Appendix A to 10 C FR Part 50, GD C 19 0.05 Sv (5 rem) Design criteria 10 C FR 52.17(a)(1)(ix)(A) [Re f. 11] 0.25 Sv (25 rem) TED E f o r a n y 2-hour period f ollowing postulated f ission product Design criteria release 10 C FR 52.17(a)(1)(ix)(B) 0.25 Sv (25 rem) TEDE at LPZ boundary resulting f rom exposure to the Design criteria radioactive cloud f rom postulated f ission product release 10 C FR 52.47(a)(2)(iv)(A) [Re f. 12] 0.25 Sv (25 rem) TED E f o r a n y 2-hour period f ollowing postulated f ission product Design criteria release 10 C FR 52.47(a)(2)(iv)(B) 0.25 Sv (25 rem) TEDE at LPZ boundary resulting f rom exposure to the Design criteria radioactive cloud f rom postulated f ission product release 10 C FR 52.79(a)(1)(vi)(A) [Re f. 13] 0.25 Sv (25 rem) TED E f o r a n y 2-hour period f ollowing postulated f ission product Design criteria release 10 CFR 52.79(a)(1)(vi)(B) 0.25 Sv (25 rem) TEDE at LPZ boundary resulting f rom exposure to the Design criteria radioactive cloud f rom postulated f ission product release 10 C FR 52.137(a)(2)(iv)(A) [Re f. 14] 0.25 Sv (25 rem ) TEDE at any point on the exclusion area boundary f or any Design criteria 2-hour period f ollowing the onset of the postulated f ission product release 10 CFR 52.137(a)(2)(iv)(B) 0.25 Sv (25 rem) TEDE at LPZ boundary resulting f rom exposure to the Design criteria radioactive cloud f rom postulated f ission product release 10 C FR 52.157(c)(3)(d)(1) [Re f. 15] 0.25 Sv (25 rem) TED E f o r a n y 2-hour period f ollowing postulated f ission product Design criteria release 10 C FR 52.157(c)(3)(d)(2) 0.25 Sv (25 rem) TEDE at LPZ boundary resulting f rom exposure to the Design criteria radioactive cloud f rom postulated f ission product release whole body in excess of 0.25 Sv (25 rem)b or a total radiation dose in excess of 10 C FR 100.11(a)(1) [Re f. 16] 3 Sv (300 rem ) b to the thyroid f rom iodine exposure f or any 2-hour period Siting criteria f ollowing postulated f ission product release Whole body in excess of 0.25 Sv (25 rem)b or a total radiation dose in excess of 10 C FR 100.11(a)(2) 3 Sv (300 rem ) b to the thyroid f rom iodine exposure at LPZ boundary resulting Siting criteria f rom exposure to the radioactive cloud f rom postulated f ission product release Operati onal Regulation Cri teri a Limit or Siting/Design Cri teri a Additional doses f rom planned special exposures and all doses in excess of lim its shal l not exceed the num erical lim its in 10 C FR 20.1201(a) in 1 year 10 C FR 20.1206(e)(2) [Re f. 17] (i.e., individuals can receive doses equal to a total of tw i c e th e lim its in Operational lim it 10 C FR 20.1201(a) ) not to exceed f ive tim es the doses in 10 C FR 20.1201(a) during an individuals lif etim e (e.g., 0.25 Sv (25 rem))
More lim iting of (1) TED E 0.05 Sv (5 rem) or (2) the sum of the deep-dose 10 C FR 20.1201(a)(i) [Re f. 18] equivalent and com m itted dose equivalent to any organ or tissue of 0.5 Sv Operational lim it (50 rem ). Oth e r lim its apply to lens of the eye and shallow -dose equivalent to the skin.
: a. The use of 0.25 Sv (25 rem ) TEDE is not intended to im ply that this value constitutes an acceptable lim it f or em ergency doses to the public under ac cident conditions. Rather, this 0.25 Sv (25 rem ) TEDE value has been stated in this section as a ref erence value, which can be used in the evaluation of proposed design-basis changes with respect to potential reactor accidents of exceedingly low probability of occurrence and low risk of public exposure to radiation.
: b. The whole body dose of 0.25 Sv (25 rem ) ref erred to above corresponds num erically to the once in a lif etim e accidental or em ergency dose f or radiation workers that, according to recom m endations by the National Council on Radiation Protection and Measurem ents (NCRP), m ay be disregarded in the determ ination of their radiation exposure status (see National Bureau of Standards Handbook 69, Maxim um Perm issible Body Burdens and Maxim um Perm issible Concentrations of Radionuclides in Air and in Water f or Occupational Exposure, dated June 5, 1959 [Re f. 19]). However, neither its use nor that of the 3 Sv (300 rem ) value f or thyroid exposure as set f orth in these site criteria guides are intended to im ply that these num bers constitute acceptable lim its f or em ergency doses to the public under accident conditions. Rather, this 0.25 Sv (25 rem ) whole body value and the 3 Sv (300 rem ) thyroid value have been set f orth in these guides as ref erence values, which can be used in the evaluation of reactor sites with respect to potential reactor accidents of exceedingly low probability of occurrence, and low risk of public exposure to radiation.
 
Item 2: D escr ibe the coher ent regulatory approach to radiation protection for w orkers under normal and emergency conditions.
 
This sec tion prov ides bac k ground on radiation protec tion regulations and prac tic es during norm al and em ergenc y c onditions. First, oc c upational dose lim its are desc ribed bec ause they pertain prim arily to norm al operating c onditionsthe c onditions m ost prev alent during pow er plant operations. Then the c ontrol room design c riteria are desc ribed bec ause they are used to guide and assess the design of sy stem s in the c ontex t of norm al and em ergenc y c onditions.
Lastly, the applic ability of personal protec tiv e equipm ent and other m itigativ e m easures during em ergenc y c onditions is desc ribed to ex plain how the N R C has traditionally not c redited these m easures during saf ety ev aluations of c ontrol room designs; how ev er, their use c an be ex pec ted during em ergenc y c onditions.
 
R adiation protec tion c onc erns the protec tion of indiv iduals, their progeny, and hum ank ind, w hile still allow ing nec essary ac tiv ities f rom w hic h radiation ex posure m ight result. The aim of radiation protec tion is generally to prev ent detrim ental nonstoc hastic, or determ inistic, ef f ec ts (e.g., c atarac ts, sk in reddening, or ery them a) and to lim it the probability of stoc hastic ef f ec ts (i.e., c anc er) to lev els deem ed to be ac c eptable. N onstoc hastic ef f ec ts are prev ented by setting dose equiv alent lim its at suf f ic iently low v alues so that these ef f ec ts are not ex perienc ed as a result of ex posures w ithin the lim its. Stoc hastic ef f ec ts are lim ited by k eeping all justif iable ex posures as low as is reasonably ac hiev able (ALAR A), ec onom ic and soc ial f ac tors being tak en into ac c ount, subjec t alw ay s to the boundary c ondition that the applic able dose equiv alent lim its shall not be ex c eeded.
 
An additional aim of radiation protec tion is to ensure that prac tic es inv olv ing radiation ex posure are justif ied w ith regard to the benef it of the ac tiv ity c om pared to the risk s inc urred by the w ork ers w ho prov ide the benef it. Theref ore, w hen dev eloping the num eric al oc c upational dose lim it rec om m endations that apply to stoc hastic ex posure and upon w hic h the N R C regulations are based, the International C om m ission on R adiologic al Protec tion (ICRP ) ensured that the risk of f atality f rom stoc hastic ef f ec ts of radiation on the population of w ork ers w as c om parable to the risk of f atalities to w ork ers in other industries c onsidered saf e. This approac h led to c onserv ativ e dose lim itations that hav e serv ed the radiation w ork er c om m unity w ell but m ay not hav e been appropriate to apply as design c riteria that enc om pass ex pec ted sy stem perf orm anc e during highly unlik ely em ergenc y situations at pow er plants.
 
The standards set f orth in 10 CFR Part 20, Standards f or Protec tion Against R adiation
[R ef. 20], are based in part on the rec om m endations of the IC R P and its U.S. c ounterpart, the NCRP. In 1977, w ith Public ation 26, R ec om m endations of the IC R P (ICRP 26) [R ef. 21], the IC R P issued rev ised rec om m endations f or a sy stem of radiation dose lim itations. The NRC adopted this sy stem on M ay 21, 1991, in its am endm ent of 10 CFR Part 20. A s suc h, 10 CFR Part 20 puts into prac tic e rec om m endations f rom ICRP 26 and c ertain subsequent IC R P public ations. A s disc ussed in the Federal R egis ter (FR) (56 FR 23360; M ay 21, 1991)
[R ef. 22]
 
In adopting the basic tenets of the IC R P sy stem of dose lim itation, the N uc lear R egulatory C om m ission rec ognizes that, w hen applic ation of the dose lim its is c om bined w ith the princ iple of k eeping all radiation ex posures as low as is reasonably ac hiev able, the degree of protec tion c ould be signif ic antly greater
 
7 than f rom rely ing upon the dose lim its alone.
 
The regulations in 10 CFR Part 20 apply these standards to all ex posure situationsnor m al and abnorm albut an ex plic it ex em ption is also prov ided if c om plianc e w ould lim it ac tions that m ay be nec essary to protec t health and saf ety.


higher burnup on radiological consequences is nonlinear where the abundance of different radionuclides in the fuel peak at different burnup levels. This continuously changing radionuclide mix due to burnup has a varying impact on radiological consequences. Therefore, depending on how the reactor core is designed with increased U-235 enrichment fuel elements and operation at higher burnup levels to reach longer cycle time, the impact on radiological consequences computed to demonstrate compliance with the control room design criteria would increase and subsequently decrease the retained margin maintained by the licensee to provide operational flexibility.
The IC R P 26 sy stem of dose lim itation has the f ollow ing objec tiv es:
The NRC recognizes the challenges that licensees face to retain margin within their licensing basis and the small amount of margin to the control room design criteria itself. The NRC does not want to unnecessarily penalize licensees for seeking increased enrichments that may then result in margin reductions and thereby requiring licensees to perform potentially extensive analyses to demonstrate compliance without a commensurate increase in safety.
* No prac tic e shall be adopted unless its introduc tion produc es a positiv e net benef it.
This IAR requests RES staff to document its assessment findings in a publicly available memorandum to NRR. Additionally, the memorandum should provide for and identify the following tasks:
* All ex posures shall be k ept ALAR A, ec onom ic and soc ial f ac tors being tak en into ac c ount.
: 1.      Identify applicable radiation dose-based regulations and their roles as operational limits or design criteria;
* The dose equiv alent to indiv iduals shall not ex c eed the lim its rec om m ended f or the appropriate c irc um stanc es by the C om m ission.
: 2.      Describe the coherent regulatory approach to radiation protection for workers under normal and emergency conditions;
: 3.      Perform an annotated bibliography of radiation protection recommendations for workers during emergency conditions from national and international organizations responsible for making recommendations for radiation protection standards; and
: 4.      Provide an assessment of the identified design criteria to contemporary radiological health effects.
: 3.        IAR TASK 1 RESULTS Item 1:            Identify applicable radiation dose-based regulations and their roles as operational limits or design criteria.
For this item, the RES staff researched the applicable regulations in various parts 2 of 10 CFR to summarize the dose-based siting and design criteria as well as occupational dose limits.
Table 1 provides this summary.
2        Specifically, the staff examined 10 CFR Part 50, 10 CFR Part 100, Reactor Site Criteria, and 10 CFR Part 52, Licenses, Certifications, and Approvals for Nuclear Power Plants.
4


Table 1 Dose-Based Criteria and Regulations Operational Limit or Regulation                                                  Criteria Siting/Design Criteria 0.25 sievert (Sv) 25 roentgen equivalent man (rem) total effective dose equivalent 10 CFR 50.34(a)(ii)(D)(1) [Ref. 10]                                                                                                Siting criteria (TEDE) for any 2-hour period following postulated fission product release 0.25 Sv (25 rem) TEDE at low population zone (LPZ) boundary resulting from 10 CFR 50.34(a)(ii)(D)(2)                                                                                                          Siting criteria exposure to the radioactive cloud from postulated fission product release 0.25 Sv (25 rem)a TEDE for any 2-hour period following postulated fission product 10 CFR 50.67(b)(2)(i)                                                                                                              Design criteria release 0.25 Sv (25 rem) TEDE at LPZ boundary resulting from exposure to the 10 CFR 50.67(b)(2)(ii)                                                                                                            Design criteria radioactive cloud from postulated fission product release 10 CFR 50.67(b)(2)(iii)                      0.05 Sv (5 rem)                                                                      Design criteria Appendix A to 10 CFR Part 50, GDC 19          0.05 Sv (5 rem)                                                                      Design criteria 0.25 Sv (25 rem) TEDE for any 2-hour period following postulated fission product 10 CFR 52.17(a)(1)(ix)(A) [Ref. 11]                                                                                                Design criteria release 0.25 Sv (25 rem) TEDE at LPZ boundary resulting from exposure to the 10 CFR 52.17(a)(1)(ix)(B)                                                                                                          Design criteria radioactive cloud from postulated fission product release 0.25 Sv (25 rem) TEDE for any 2-hour period following postulated fission product 10 CFR 52.47(a)(2)(iv)(A) [Ref. 12]                                                                                                Design criteria 5                                                release 0.25 Sv (25 rem) TEDE at LPZ boundary resulting from exposure to the 10 CFR 52.47(a)(2)(iv)(B)                                                                                                          Design criteria radioactive cloud from postulated fission product release 0.25 Sv (25 rem) TEDE for any 2-hour period following postulated fission product 10 CFR 52.79(a)(1)(vi)(A) [Ref. 13]                                                                                                Design criteria release 0.25 Sv (25 rem) TEDE at LPZ boundary resulting from exposure to the 10 CFR 52.79(a)(1)(vi)(B)                                                                                                          Design criteria radioactive cloud from postulated fission product release 0.25 Sv (25 rem) TEDE at any point on the exclusion area boundary for any 10 CFR 52.137(a)(2)(iv)(A) [Ref. 14]                                                                                              Design criteria 2-hour period following the onset of the postulated fission product release 0.25 Sv (25 rem) TEDE at LPZ boundary resulting from exposure to the 10 CFR 52.137(a)(2)(iv)(B)                                                                                                        Design criteria radioactive cloud from postulated fission product release 0.25 Sv (25 rem) TEDE for any 2-hour period following postulated fission product 10 CFR 52.157(c)(3)(d)(1) [Ref. 15]                                                                                                Design criteria release 0.25 Sv (25 rem) TEDE at LPZ boundary resulting from exposure to the 10 CFR 52.157(c)(3)(d)(2)                                                                                                          Design criteria radioactive cloud from postulated fission product release whole body in excess of 0.25 Sv (25 rem)b or a total radiation dose in excess of 10 CFR 100.11(a)(1) [Ref. 16]                3 Sv (300 rem)b to the thyroid from iodine exposure for any 2-hour period            Siting criteria following postulated fission product release Whole body in excess of 0.25 Sv (25 rem)b or a total radiation dose in excess of 10 CFR 100.11(a)(2)                          3 Sv (300 rem)b to the thyroid from iodine exposure at LPZ boundary resulting        Siting criteria from exposure to the radioactive cloud from postulated fission product release
To ac hiev e these objec tiv es, this sy stem of dose lim itations ensures that no sourc e of ex posure is unjustif ied in relation to its benef its or those of any av ailable alternativ e, that any nec essary ex posures are k ept ALAR A, and that the dose equiv alents rec eiv ed do not ex c eed c ertain spec if ied lim its. As suc h, any nec essary ex posures are k ept ALAR A and that the dose equiv alents rec eiv ed do not ex c eed c ertain spec if ied lim its.


Operational Limit or Regulation                                                                Criteria Siting/Design Criteria Additional doses from planned special exposures and all doses in excess of limits shall not exceed the numerical limits in 10 CFR 20.1201(a) in 1 year 10 CFR 20.1206(e)(2) [Ref. 17]                          (i.e., individuals can receive doses equal to a total of twice the limits in        Operational limit 10 CFR 20.1201(a)) not to exceed five times the doses in 10 CFR 20.1201(a) during an individuals lifetime (e.g., 0.25 Sv (25 rem))
O c c upational C ontrol R oom D os es
More limiting of (1) TEDE 0.05 Sv (5 rem) or (2) the sum of the deep-dose equivalent and committed dose equivalent to any organ or tissue of 0.5 Sv 10 CFR 20.1201(a)(i) [Ref. 18]                                                                                                                Operational limit (50 rem). Other limits apply to lens of the eye and shallow-dose equivalent to the skin.
: a. The use of 0.25 Sv (25 rem) TEDE 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 this section as a reference value, which can be used in the evaluation of proposed design-basis changes with respect to potential reactor accidents of exceedingly low probability of occurrence and low risk of public exposure to radiation.
: b. The whole body dose of 0.25 Sv (25 rem) referred to above corresponds numerically to the once in a lifetime accidental or emergency dose for radiation workers that, according to recommendations by the National Council on Radiation Protection and Measurements (NCRP), may be disregarded in the determination of their radiation exposure status (see National Bureau of Standards Handbook 69, Maximum Permissible Body Burdens and Maximum Permissible Concentrations of Radionuclides in Air and in Water for Occupational Exposure, dated June 5, 1959 [Ref. 19]). However, neither its use nor 6          that of the 3 Sv (300 rem) value for thyroid exposure as set forth in these site criteria guides are intended to imply that these numbers constitute acceptable limits for emergency doses to the public under accident conditions. Rather, this 0.25 Sv (25 rem) whole body value and the 3 Sv (300 rem) thyroid value have been set forth in these guides as reference values, which can be used in the evaluation of reactor sites with respect to potential reactor accidents of exceedingly low probability of occurrence, and low risk of public exposure to radiation.


Item 2:          Describe the coherent regulatory approach to radiation protection for workers under normal and emergency conditions.
The NRCs c urrent regulatory approac h to c ontrol room operator radiation ex posure c onserv ativ ely adopts the tenets of international and national radiation protec tion standards and rec om m endations. As disc ussed abov e, this approac h is prov ided in G D C 19; 10 CFR 50.67, Ac c ident sourc e term ; 10 CFR Part 20; 10 CFR 50.47(b)(11); and, by ref erenc e, the U.S. Env ironm ental Protec tion Agenc y (EPA) PAG M anual: Protec tiv e Ac tion G uides and Planning G uidanc e f or R adiologic al Inc idents, issued J anuary 2017 [ R ef. 23].
This section provides background on radiation protection regulations and practices during normal and emergency conditions. First, occupational dose limits are described because they pertain primarily to normal operating conditionsthe conditions most prevalent during power plant operations. Then the control room design criteria are described because they are used to guide and assess the design of systems in the context of normal and emergency conditions.
Lastly, the applicability of personal protective equipment and other mitigative measures during emergency conditions is described to explain how the NRC has traditionally not credited these measures during safety evaluations of control room designs; however, their use can be expected during emergency conditions.
Radiation protection concerns the protection of individuals, their progeny, and humankind, while still allowing necessary activities from which radiation exposure might result. The aim of radiation protection is generally to prevent detrimental nonstochastic, or deterministic, effects (e.g., cataracts, skin reddening, or erythema) and to limit the probability of stochastic effects (i.e., cancer) to levels deemed to be acceptable. Nonstochastic effects are prevented by setting dose equivalent limits at sufficiently low values so that these effects are not experienced as a result of exposures within the limits. Stochastic effects are limited by keeping all justifiable exposures as low as is reasonably achievable (ALARA), economic and social factors being taken into account, subject always to the boundary condition that the applicable dose equivalent limits shall not be exceeded.
An additional aim of radiation protection is to ensure that practices involving radiation exposure are justified with regard to the benefit of the activity compared to the risks incurred by the workers who provide the benefit. Therefore, when developing the numerical occupational dose limit recommendations that apply to stochastic exposure and upon which the NRC regulations are based, the International Commission on Radiological Protection (ICRP) ensured that the risk of fatality from stochastic effects of radiation on the population of workers was comparable to the risk of fatalities to workers in other industries considered safe. This approach led to conservative dose limitations that have served the radiation worker community well but may not have been appropriate to apply as design criteria that encompass expected system performance during highly unlikely emergency situations at power plants.
The standards set forth in 10 CFR Part 20, Standards for Protection Against Radiation
[Ref. 20], are based in part on the recommendations of the ICRP and its U.S. counterpart, the NCRP. In 1977, with Publication 26, Recommendations of the ICRP (ICRP 26) [Ref. 21], the ICRP issued revised recommendations for a system of radiation dose limitations. The NRC adopted this system on May 21, 1991, in its amendment of 10 CFR Part 20. As such, 10 CFR Part 20 puts into practice recommendations from ICRP 26 and certain subsequent ICRP publications. As discussed in the Federal Register (FR) (56 FR 23360; May 21, 1991)
[Ref. 22]
In adopting the basic tenets of the ICRP system of dose limitation, the Nuclear Regulatory Commission recognizes that, when application of the dose limits is combined with the principle of keeping all radiation exposures as low as is reasonably achievable, the degree of protection could be significantly greater 7


than from relying upon the dose limits alone.
ICRP 26, Sec tion G, Applic ation to the D if f erent Ty pes of Ex posure, prov ides rec om m endations f or oc c upational ex posure. These rec om m endations state in part that as f ar as is reasonably prac tic able, the m ethods f or restric ting oc c upational ex posure should be applied to the sourc e of radiation and to f eatures of the w ork plac e. The use of personal protec tiv e equipm ent should, in general, supplem ent these m ore f undam ental prov isions.
The regulations in 10 CFR Part 20 apply these standards to all exposure situationsnormal and abnormalbut an explicit exemption is also provided if compliance would limit actions that may be necessary to protect health and safety.
Theref ore, em phasis should be on intrinsic saf ety in the w ork plac e (e.g., phy sic al design and operating c harac teristic s of sy stem s) and only sec ondarily on protec tion that depends on a w ork ers ow n ac tions. H ow ev er, under abnorm al or em ergenc y situations, arrangem ents are m ade not only w ith respec t to the detec tion and assessm ent of dose or intak e, but also w ith respec t to the m itigating interv entions that m ay hav e to be applied to f urther protec t w ork ers (e.g., personal protec tiv e equipm ent, adm inistration of prophy lac tic drugs, and ev ac uation).
The ICRP 26 system of dose limitation has the following objectives:
* No practice shall be adopted unless its introduction produces a positive net benefit.
* All exposures shall be kept ALARA, economic and social factors being taken into account.
* The dose equivalent to individuals shall not exceed the limits recommended for the appropriate circumstances by the Commission.
To achieve these objectives, this system of dose limitations ensures that no source of exposure is unjustified in relation to its benefits or those of any available alternative, that any necessary exposures are kept ALARA, and that the dose equivalents received do not exceed certain specified limits. As such, any necessary exposures are kept ALARA and that the dose equivalents received do not exceed certain specified limits.
Occupational Control Room Doses The NRCs current regulatory approach to control room operator radiation exposure conservatively adopts the tenets of international and national radiation protection standards and recommendations. As discussed above, this approach is provided in GDC 19; 10 CFR 50.67, Accident source term; 10 CFR Part 20; 10 CFR 50.47(b)(11); and, by reference, the U.S. Environmental Protection Agency (EPA) PAG Manual: Protective Action Guides and Planning Guidance for Radiological Incidents, issued January 2017 [Ref. 23].
ICRP 26, Section G, Application to the Different Types of Exposure, provides recommendations for occupational exposure. These recommendations state in part that as far as is reasonably practicable, the methods for restricting occupational exposure should be applied to the source of radiation and to features of the workplace. The use of personal protective equipment should, in general, supplement these more fundamental provisions.
Therefore, emphasis should be on intrinsic safety in the workplace (e.g., physical design and operating characteristics of systems) and only secondarily on protection that depends on a workers own actions. However, under abnormal or emergency situations, arrangements are made not only with respect to the detection and assessment of dose or intake, but also with respect to the mitigating interventions that may have to be applied to further protect workers (e.g., personal protective equipment, administration of prophylactic drugs, and evacuation).
It is significant to note that the contents of Appendix A to 10 CFR Part 50 are design criteria and not operational limits. Events and situations not addressed in the facilitys design basis could in fact result in conditions for which the design might not provide the reasonable assurance sought. For example, multiple failures that are not the result of a common mode failure are not required to be addressed in the design basis of the control room. Should such multiple failures occur, the performance of the SSCs may not be adequate and compensatory plant operations 8


might be necessary. The NRCs focus on defense in depth provides assurance that even if these beyond-design-basis conditions occur, the plant design will mitigate the risk to occupational workers and public health and safety.
It is signif ic ant to note that the c ontents of Appendix A to 10 CFR Part 50 are design c riteria and not operational lim its. Ev ents and situations not addressed in the f ac ility s design basis c ould in f ac t result in c onditions f or w hic h the design m ight not prov ide the reasonable assuranc e sought. For ex am ple, m ultiple f ailures that are not the result of a c om m on m ode f ailure are not required to be addressed in the design basis of the c ontrol room. Should suc h m ultiple f ailures oc c ur, the perf orm anc e of the SSCs m ay not be adequate and c om pensatory plant operations
The standards for protection against radiation established in 10 CFR Part 20 are generally consistent with the recommendations of ICRP 26, the later ICRP recommendations from ICRP Publication 60, 1990 Recommendations of the International Commission on Radiological Protection, issued 1991 (ICRP 60) [Ref. 24], and the ICRP Publication 103, The 2007 Recommendations of the International Commission on Radiological Protection, issued 2007 (ICRP 103) [Ref. 25]. The rule applies the ICRP 26 recommendations to all exposure situationsnormal and abnormalbut also provides an explicit exemption for cases in which compliance would limit actions that may be necessary to protect health and safety. In an emergency situation, the continued actions of the control room operators are fundamental to protecting the health and safety of the public and other workers at the facility. Thus, if the event should result in conditions beyond the design basis of the control room habitability systems, thereby causing actual radiation exposures that exceed the normal occupational limits, access and occupancy of the control room may continue. There are, however, additional regulatory provisions that bear on the control of occupational exposures during emergencies.
The NRC has established emergency planning regulations in Appendix E, Emergency Planning and Preparedness for Production and Utilization Facilities, to 10 CFR Part 50, and planning standards for nuclear power reactors in 10 CFR 50.47, Emergency plans, for the purpose of providing reasonable assurance that adequate protective measures can and will be taken in the event of a radiological emergency. The regulation at 10 CFR 50.47(b)(11) addresses control of radiological exposures in an emergency and states that the means for controlling radiological exposures shall include exposure guidelines consistent with EPA Emergency Worker and Lifesaving Activity Protection Action Guides. The events that could result in control room radiation exposures comparable to the 10 CFR Part 20 normal occupational exposure limit of 0.05 Sv (5 rem) TEDE would result in the activation of the facilitys emergency response plan and the emergency response organization. Regulatory Guide 1.101, Emergency Response Planning and Preparedness for Nuclear Power Reactors, Revision 6, issued June 2021 [Ref. 26],
endorses NUREG-0654/FEMA-REP-1, Criteria for Preparation and Evaluation of Radiological Emergency Response Plans and Preparedness in Support of Nuclear Power Plants, Revision 2, issued December 2019 [Ref. 27]. NUREG-0654/FEMA-REP-1 provides specific acceptance criteria for complying with the standards set forth in 10 CFR 50.47, which designates an on-shift emergency coordinator. The on-shift emergency coordinator has the authority and responsibility to immediately and unilaterally initiate any emergency actions. These emergency actions include establishing higher exposure limits for control room operators if necessary to provide public health and safety. The emergency coordinator can also authorize issuing potassium-iodide tablets for thyroid protection or use of emergency respiratory protection equipment.
This radiation protection framework is consistent with the ICRP recommendations as follows:
ICRP 26 (paragraph 113) Situations may occur infrequently during normal operations when it may be necessary to permit a few workers to receive dose equivalents in excess of the recommended limits. In such circumstances external exposures or 9


intakes of radioactive material may be permitted provided the dose-equivalent commitment does not exceed twice the relevant annual limit in any single event, and, in a lifetime, five times this limit. The Commission wishes to emphasize that external exposures or intakes of this magnitude are only justified when alternative techniques, which do not involve such exposure of workers, are either unavailable or impracticable (see also paragraph 171).
8 m ight be nec essary. The N R C s f oc us on def ense in depth prov ides assuranc e that ev en if these bey ond-design-basis c onditions oc c ur, the plant design w ill m itigate the risk to occupational w ork ers and public health and saf ety.
(paragraph 114) Planned special exposures should not be permitted if the worker has previously received abnormal exposures resulting in dose equivalents in excess of five times the relevant annual limit. Planned special exposures should not be permitted for women of reproductive capacity. Dose equivalents resulting from planned special exposures should be recorded with those from usual exposures, but any excess over the limits recommended in paragraphs 103 et seq. should not by itself constitute a reason for excluding a worker from his usual occupation. (Accidental and emergency exposures are discussed in section G, paragraph 160).
(paragraph 167) As far as is reasonably practicable, the arrangements for restricting occupational exposure should be those applied to the source of radiation and to features of the workplace. The use of personal protective equipment should in general be supplementary to these more fundamental provisions. The emphasis should thus be on intrinsic safety in the workplace and only secondarily on protection that depends on the workers own actions.
(paragraph 169) External exposure may be restricted by the use of shielding, distance and limitation of time of exposure. Shielding produces intrinsically safe conditions in the workplace. Distance and limitation of time of exposure require the careful training and supervision of workers. Complete protection is afforded by the use of closed installations providing virtually complete shielding for the radiation source and effectively preventing access. However, the failure of such equipment as interlock systems may cause excessive exposure. Operating procedures should therefore include routine checks of such systems.
(paragraph 189) The emergency plans (which should, as far as practicable, be drawn up in advance) should have three clearly distinguished objectives. The first is to restrict exposures as far as reasonably achievable and, in particular, to attempt to avoid exposures above the dose-equivalent limits. The second is to bring the situation back under control, and the third is to obtain information for assessing the causes and consequences of the event.
(paragraph 191) During the immediate course of a serious incident, urgent action to save life, to prevent injuries, or to prevent a substantial increase in the scale of the incident, may require that some workers be exposed in excess of the limits.
(paragraph 192) Once the initial event has been brought under control, there remains the problem of remedial work. It will usually be appropriate to carry this out while maintaining compliance with the Commissions [i.e., the ICRPs]
recommended limits but, exceptionally, there may be situations which the use of 10


the limits would involve excessive expense or an excessive involvement of people and time. Consideration should then be given to the appropriateness of authorizing a planned special exposure for a limited number of individuals to carry out various essential operations, leaving the remainder to be done in compliance with the limits.
The standards f or protec tion against radiation established in 10 CFR Part 20 are generally c onsistent w ith the rec om m endations of IC R P 26, the later IC R P rec om m endations f rom ICRP Public ation 60, 1990 R ec om m endations of the International C om m ission on R adiologic al Protec tion, issued 1991 (ICRP 60) [R ef. 24], and the ICRP Public ation 103, The 2007 R ec om m endations of the International C om m ission on R adiologic al Protec tion, issued 2007 (ICRP 103) [R ef. 25]. The rule applies the ICRP 26 rec om m endations to all ex posure situationsnorm al and abnorm al but also prov ides an ex plic it ex em ption f or c ases in w hic h c om plianc e w ould lim it ac tions that m ay be nec essary to protec t health and saf ety. In an em ergenc y situation, the c ontinued ac tions of the c ontrol room operators are f undam ental to protec ting the health and saf ety of the public and other w ork ers at the f ac ility. Thus, if the ev ent should result in c onditions bey ond the design basis of the c ontrol room habitability sy stem s, thereby c ausing ac tual radiation ex posures that ex c eed the norm al oc c upational lim its, acc ess and oc c upanc y of the c ontrol room m ay c ontinue. There are, how ev er, additional regulatory prov isions that bear on the c ontrol of oc c upational ex posures during em ergenc ies.
ICRP 60 (paragraph 195) The initial treatment of potential exposures should form part of the system of protection applied to practices, but it should be recognised that the exposures, if they occur, may lead to intervention. At this stage, there should be two objectives, prevention and mitigation. Prevention is the reduction of the probability of the sequences of events that may cause or increase radiation exposures. It involves maintaining the reliability of all the operating and safety systems and of the associated working procedures. Mitigation is the limitation and reduction of the exposures if any of these sequences do occur. It involves the use of engineered safety features and operational procedures to control each sequence of events with the aim of limiting its consequences, should it occur.
The arrangements for mitigation should not be restricted to plans for intervention.
A great deal can be accomplished at the stages of design and operation to reduce the consequences of accident sequences so that intervention may not become necessary. It is difficult to compare, and to combine, the benefit of a reduction in probability (prevention) with that of a reduction in dose (mitigation) because a reduction in probability by a factor is not usually seen as equivalent to a reduction in dose by the same factor.
(paragraph S49) The benefit of a particular protective action within a programme of intervention should be judged on the basis of the reduction in dose achieved or expected by that specific protective action, i.e. the dose averted. Thus, each protective action has to be considered on its own merits. In addition, however, the doses that would be incurred via all the relevant pathways of exposure, some subject to protective actions and some not, should be assessed. If the total dose in some individuals is so high as to be unacceptable even in an emergency, the feasibility of additional protective actions influencing the major contributions to the total dose should be urgently reviewed. Doses causing serious deterministic effects, or a high probability of stochastic effects would call for such a review.
(paragraph S50) Occupational exposures of emergency teams during emergency and remedial action can be limited by operational controls. Some relaxation of the controls for normal situations can be permitted in serious accidents without lowering the long-term level of protection. This relaxation should not permit the exposures in the control of the accident and in the immediate and urgent remedial work to give effective doses of more than about 0.5 Sv [50 rem] except for life-saving actions, which can rarely be limited by dosimetric assessments.
The equivalent dose to skin should not be allowed to exceed about 5 Sv
[500 rem]. Once the immediate emergency is under control, remedial work should be treated as part of the occupational exposure incurred in a practice.
11


ICRP 103 (paragraph u) Emergency exposure situations include consideration of emergency preparedness and emergency response. Emergency preparedness should include planning for the implementation of optimised protection strategies which have the purpose of reducing exposures, should the emergency occur, to below the selected value of the reference level. During emergency response, the reference level would act as a benchmark for evaluating the effectiveness of protective actions and as one input into the need for establishing further actions.
The N R C has established em ergenc y planning regulations in Appendix E, Em ergenc y Planning and Preparedness f or Produc tion and U tilization Fac ilities, to 10 CFR Part 50, and planning standards f or nuc lear pow er reac tors in 10 CFR 50.47, Em ergenc y p lans, f or the purpose of prov iding reasonable assuranc e that adequate protec tiv e m easures c an and w ill be tak en in the ev ent of a radiologic al em ergenc y. The regulation at 10 CFR 50.47(b)(11) addresses c ontrol of radiologic al ex posures in an em ergenc y and states that the m eans f or c ontrolling radiologic al ex posures shall inc lude ex posure guidelines c onsistent w ith EPA Em ergenc y Work er and Lif esav ing Ac tiv ity Protec tion Ac tion G uides. The ev ents that c ould result inc ontrol room radiation ex posures c om parable to the 10 CFR Part 20 norm al oc c upational ex posure lim it of 0.05 Sv (5 rem ) TE D E w ould r esult in the ac tiv ation of the f ac ility s em er genc y r esponse plan and the em ergenc y response organization. R egulatory G uide 1.101, Em ergenc y R esponse Planning and Preparedness f or N uc lear Pow er R eac tors, R ev ision 6, issued J une 2021 [ R ef. 26],
Control Room Design Criteria The control room design criteria, as described in GDC 19, call for the plant design to incorporate radiation protection features that, in the event of an emergency, would maintain the radiation exposure of control room personnel to a level equal to their normal occupational exposure limits.
endorses N U R EG-0654/FEM A -REP-1, C riteria f or Preparation and Ev aluation of R adiologic al Em ergenc y R esponse Plans and Preparedness in Support of N uc lear Pow er Plants, R ev ision 2, issued D ec em ber 2019 [ R ef. 27]. NUREG -0654/FEM A -REP-1 prov ides spec if ic ac c eptanc e c riteria f or c om ply ing w ith the standards set f orth in 10 CFR 50.47, w hic h designates an on-shif t em ergenc y c oordinator. The on-shif t em ergenc y c oordinator has the authority and responsibility to im m ediately and unilaterally initiate any em ergenc y ac tions. These em ergenc y ac tions inc lude establishing higher ex posure lim its f or c ontrol room operators if nec essary to prov ide public health and saf ety. The e m ergenc y c oordinator c an also authorize issuing potassium-iodide tablets f or thy roid protec tion or use of em ergenc y respiratory protec tion equipm ent.
It is generally understood that an objective of the criteria is to ensure that the design of the control room and its habitability systems was such that a shirt-sleeved environment was provided for the control room operators. Exceeding the control room design criteria numerical value of 0.05 Sv (5 rem) TEDE would not impose an immediate health effect or even require an evacuation requirement on the control room operators. However, having a numerical criterion for designers to reference when accounting for accidents in their designs is necessary and consistent with the ICRP. Though setting the criteria to the normal occupational dose limits to assess plant performance during emergency conditions may mask its intended purposes when also assessing other regulations. To provide context, we highlight a parallel between the control room design criteria and the occupational dose limits in 10 CFR 20.1206, Planned special exposures. As long as licensees meet certain criteria, 10 CFR Part 20 allows planned special exposures up to twice the annual occupational dose limits provided that lifetime exposure of 0.25 Sv (25 rem) TEDE is not exceeded. As discussed in 56 FR 23372, planned special exposures were retained in the amended 10 CFR Part 20 in part to address the fact that under the new system of dose limitation workers would no longer have a lifetime dose limit, or dose bank, equaling five times the quantity of the age of the worker minus 18, or 5(N18). While the use of planned special exposures was predicted to be infrequent, it was expected that they would be used if the elimination of the lifetime dose limits might create a severe handicap to the licensees operations. Therefore, the Commission concluded that an infrequent exposure of workers up to twice the occupational dose limit was adequately protective of radiation workers.
Now, the control room design criteria are applicable to a lowfrequency event, whereas the planned special exposure is designed for a more likely routine radiological exposure event.
Based on a potential radiological risk each rule is intending to protect against, the applicable dose constraints for less likely emergency events should be aligned (higher) than the dose constraints for the lower frequency events (planned special exposures) at 0.10 sievert (Sv)
(10 roentgen equivalent man (rem)) as well as routine occupational exposures 0.05 Sv (5 rem).
ICRP 26 (paragraph 190) Although, by their nature, accidental exposures are not subject to control, their magnitude can to some extent be limited by intervention, especially if attention has been paid to this possibility during the design of installations and equipment and the preparation of operating instructions.
12


ICRP 60 (paragraph 224) Occupational exposures directly due to an accident can be limited only by the design of the plant and its protective features and by the provision of emergency procedures. Ideally, the aim should be to keep the doses within those permitted in normal conditions, but, while this is usually possible, it may not always be so in serious accidents.
This radiation protec tion f ram ew ork is c onsistent w ith the IC R P rec om m endations as f ollow s:
ICRP 103 (paragraph r) The process of planning protection in planned exposure situations should include consideration of deviations from normal operating procedures including accidents and malicious events. ... Potential exposures are not planned but they can be anticipated. The designer and the user of a source must therefore take actions to reduce the likelihood of a potential exposure happening, such as assessing the probability of an event and introducing engineering safeguards commensurate to this probability.
Performance-Based Regulations, Design-Basis Accidents, and Use of Personal Protective Equipment The control room design criteria regulations are performance based, requiring a licensee or applicant to provide a control room habitability design that meets a specified dose-based criterion. Specifically, they establish performance requirements for control room habitability systems that would be called upon in a DBA. This is directly responsive to the ICRP recommendations to emphasize intrinsic safety features. These systems serve the function of mitigation, thereby minimizing the need for intervention, which might involve evacuation, administration of prophylactic drugs, or use of personal protective equipment that could impair the operators ability to perform the actions necessary to provide adequate public health and safety. 3 To demonstrate compliance, licensees perform traditional deterministic DBA radiological consequence analyses using regulatory source terms which are reviewed and approved by the staff. Performance-based regulations, such as 10 CFR 50.67(b)(2)(iii) and GDC 19, do not provide prescriptive methodologies to determine the regulations are met and therefore do not require licensees to use specific designs or methodologies to comply with the regulations. As such, NRC RGs and standard review plans provide acceptable methodologies that licensees can use to perform the analyses, which are then incorporated, as appropriate, into the licensing basis for the licensees facility. In general, the staff has generally not accepted, except in interim situations, personal protective measures such as respiratory protection or prophylactic drugs which is consistent with the ICRP recommendations.
The licensing process is based on the concept of defense in depth, in which power plant design, operation, siting, and emergency planning comprise independent layers of nuclear safety. This approach encourages nuclear plant designers to incorporate several lines of defense in order to maintain the effectiveness of physical barriers between radiation sources and materials from workers, members of the public, and the environment in operational states and, for some 3        This is also consistent with 10 CFR 20.1701, Use of process or other engineering controls" [Ref. 28], which requires the licensee to use, to the extent practical, process or other engineering controls (e.g., containment, decontamination, or ventilation) to control the concentrations of radioactive materials in air.
13


barriers, in accident conditions. The approach uses DBAs with regulatory source terms to compute radiological consequences when assessing the effectiveness of each line of defense.
ICRP 26
As such, the DBAs establish and confirm the design basis of the nuclear facility, including its safety-related SSCs and items important to safety, ensuring that the plant design meets the safety and numerical radiological criteria set forth in regulations and subsequent guidance. Due to the conservative, deterministic nature of the DBA analyses, there is a margin of safety such that control room design may be adequate for many events beyond the design basis. However, it remains possible that actual radiation exposures from beyond-design-basis events, or those resulting from multiple failures of the control room habitability systems coincident with a DBA, could exceed the design criteria. In such an event, the radiation exposures are still subject to 10 CFR Part 20 first and then the facilitys emergency plan, which would use personal protective equipment, if necessary, supplementary to these more fundamental design provisions. Under emergency conditions, both maintain radiation exposures to be ALARA and, to the extent practicable, limited to normal occupational levels. This is consistent with the ICRP 26, ICRP 60, and ICRP 103 recommendations.
 
ICRP 26 (paragraph 167) As far as is reasonably practicable, the arrangements for restricting occupational exposure should be applied to the source of radiation and to features of the workplace. The use of personal protective equipment should in general be supplementary to these more fundamental provisions. The emphasis should thus be on intrinsic safety in the workplace and only secondarily on protection that depends on the workers own actions.
(paragraph 113) Situations m ay oc c ur inf requently during norm al operations w hen it m ay be nec essary to perm it a f ew w ork ers to rec eiv e dose equiv alents in ex c ess of the rec om m ended lim its. In suc h c irc um stanc es ex ternal ex posures or
ICRP 60 (paragraph 195) The initial treatment of potential exposures should form part of the system of protection applied to practices, but it should be recognized that the exposures, if they occur, may lead to intervention. At this stage there should be two objectives, prevention and mitigation. Prevention is the reduction of the probability of the sequences of events that may cause or increase radiation exposures. It involves maintaining the reliability of all of the operating and safety systems and of the associated working procedures. Mitigation is the limitation and reduction of the exposures if any of these sequences do occur. It involves the use of engineered safety features and operational procedures to control each sequence of events with the aim of limiting its consequences, should it occur.
 
The arrangement for mitigation should not be restricted to plans of intervention. A great deal can be accomplished at the stages of design and operation to reduce the consequences of accident sequences so that intervention may not become necessary.
9 intak es of radioac tiv e m aterial m ay be perm itted prov ided the dose-equiv alent c om m itm ent does not ex c eed tw ic e the relev ant annual lim it in any single ev ent, and, in a lif etim e, f iv e tim es this lim it. The C om m ission w ishes to em phasize that ex ternal ex posures or intak es of this m agnitude are only justif ied w hen alternativ e tec hniques, w hic h do not inv olv e suc h ex posure of w ork ers, are either unav ailable or im prac tic able (see also paragraph 171).
ICRP 103 (paragraph t) Emphasis on optimisation using reference levels in emergency and existing exposure situations focuses attention on the residual level of dose remaining after implementation of protection strategies. This residual dose should be below the reference level, which represents the total residual dose as 14
 
(paragraph 114) Planned spec ial ex posures should not be perm itted if the w ork er has prev iously rec eiv ed abnorm al ex posures resulting in dose equiv alents in ex c ess of f iv e tim es the relev ant annual lim it. Planned spec ial ex posures should not be perm itted f or w om en of reproduc tiv e c apac ity. D ose equiv alents resulting f rom planned spec ial ex posures should be rec orded w ith those f rom usual ex posures, but any ex c ess ov er the lim its rec om m ended in paragraphs 103 et s eq. should not by itself c onstitute a reason f or ex c luding a w ork er f rom his usual oc c upation. (Ac c idental and em ergenc y ex posures are disc ussed in sec tion G, paragraph 160).
 
(paragraph 167) As f ar as is reasonably prac tic able, the arrangem ents f or restric ting oc c upational ex posure should be those applied to the sourc e of radiation and to f eatures of the w ork plac e. The use of personal protec tiv e equipm ent should in general be supplem entary to these m ore f undam ental prov isions. The em phasis should thus be on intrinsic saf ety in the w ork plac e and only sec ondarily on protec tion that depends on the w ork ers ow n ac tions.
 
(paragraph 169) Ex ternal ex posure m ay be restric ted by the use of shielding, distanc e and lim itation of tim e of ex posure. Shielding produc es intrinsic ally saf e c onditions in the w ork plac e. D istanc e and lim itation of tim e of ex posure require the c aref ul training and superv ision of w ork ers. C om plete protec tion is af f orded by the use of c losed installations prov iding v irtually c om plete shielding f or the radiation sourc e and ef f ec tiv ely prev enting ac c ess. H ow ev er, the f ailure of suc h equipm ent as interloc k sy stem s m ay c ause ex c essiv e ex posure. O perating proc edures should theref ore inc lude routine c hec k s of suc h sy stem s.
 
(paragraph 189) The em ergenc y plans (w hic h should, as f ar as prac tic able, be draw n up in adv anc e) should hav e three c learly distinguished objectiv es. The f irst is to restric t ex posures as f ar as reasonably ac hiev able and, in partic ular, to attem pt to av oid ex posures abov e the dose-equiv alent lim its. The sec ond is to bring the situation bac k under c ontrol, and the third is to obtain inf orm ation f or assessing the c auses and c onsequenc es of the ev ent.
 
(paragraph 191) D uring the im m ediate c ourse of a serious inc ident, urgent ac tion to sav e lif e, to prev ent injuries, or to prev ent a substantial inc rease in the sc ale of the inc ident, m ay require that som e w ork ers be ex posed in ex c ess of the lim its.
 
(paragraph 192) O nc e the initial ev ent has been brought under c ontrol, there rem ains the problem of rem edial w ork. It w ill usually be appropriate to c arry this out w hile m aintaining c om plianc e w ith the C om m issions [i.e., the IC R Ps]
rec om m ended lim its but, ex c eptionally, there m ay be situations w hic h the use of
 
10 the lim its w ould inv olv e ex c essiv e ex pense or an ex c essiv e inv olv em ent of people and tim e. C onsideration should then be giv en to the appropriateness of authorizing a planned spec ial ex posure f or a lim ited num ber of indiv iduals to c arry out v arious essential operations, leav ing the rem ainder to be done in c om plianc e w ith the lim its.
 
ICRP 60
 
(paragraph 195) The initial treatm ent of potential ex posur es should f orm part of the sy stem of protec tion applied to prac tic es, but it should be rec ognised that the ex posures, if they oc c ur, m ay lead to interv ention. At this stage, there should be tw o objec tiv es, prev ention and m itigation. Prev ention is the reduc tion of the probability of the sequenc es of ev ents that m ay c ause or inc rease radiation ex posures. It inv olv es m aintaining the reliability of all the operating and saf ety sy stem s and of the assoc iated w ork ing proc edures. M itigation is the lim itation and reduc tion of the ex posures if any of these sequenc es do oc c ur. It inv olv es the use of engineered saf ety f eatures and operational proc edures to c ontrol eac h sequenc e of ev ents w ith the aim of lim iting its c onsequenc es, should it oc c ur.
The arrangem ents f or m itigation should not be restric ted to plans f or interv ention.
A great deal c an be ac c om plished at the stages of design and operation to reduc e the c onsequenc es of ac c ident sequenc es so that interv ention m ay not bec om e nec essary. It is dif f ic ult to c om pare, and to c om bine, the benef it of a reduc tion in probability (prev ention) w ith that of a reduc tion in dose (m itigation) bec ause a reduc tion in probability by a f ac tor is not usually seen as equiv alent to a reduc tion in dose by the sam e f ac tor.
 
(paragraph S49) The benef it of a partic ular protec tiv e ac tion w ithin a program m e of interv ention should be judged on the basis of the reduc tion in dose ac hiev ed or ex pec ted by that spec if ic protec tiv e ac tion, i.e. the dose av erted. Thus, eac h protec tiv e ac tion has to be c onsidered on its ow n m erits. In addition, how ev er, the doses that w ould be inc urred v ia all the relev ant pathw ay s of ex posure, som e subjec t to protec tiv e ac tions and som e not, should be assessed. If the total dose in som e indiv iduals is so high as to be unac c eptable ev en in an em ergenc y, the f easibility of additional protec tiv e ac tions inf luenc ing the m ajor c ontributions to the total dose should be urgently rev iew ed. D oses c ausing serious determ inistic ef f ec ts, or a high probability of stoc hastic ef f ec ts w ould c all f or suc h a rev iew.
 
(paragraph S50) O c c upational ex posures of em ergenc y team s during em ergenc y and rem edial ac tion c an be lim ited by operational c ontrols. Som e relax ation of the c ontrols f or norm al situations c an be perm itted in serious ac c idents w ithout low ering the long-term lev el of protec tion. This relax ation should not perm it the ex posures in the c ontrol of the ac c ident and in the im m ediate and urgent rem edial w ork to giv e ef f ec tiv e doses of m ore than about 0.5Sv [50 rem ] ex c ept f or lif e-sav i ng ac tions, w hic h c an rarely be lim ited by dosim etric assessm ents.
The equiv alent dose to sk in should not be allow ed to ex c eed about 5 Sv
[500 rem ]. O nc e the im m ediate em ergenc y is under c ontrol, rem edial w ork should be treated as part of the oc c upational ex posure inc urred in a prac tic e.
 
11 ICRP 103
 
(paragraph u) Em ergenc y ex posure situations inc lude c onsideration of em ergenc y preparedness and em ergenc y response. Em ergenc y preparedness should inc lude planning f or the im plem entation of optim ised protec tion strategies w hic h hav e the purpose of reduc ing ex posures, should the em ergenc y oc c ur, to below the selec ted v alue of the ref erenc e lev el. D uring em ergenc y response, the ref erenc e lev el w ould ac t as a benc hm ark f or ev aluating the ef f ec tiv eness of protec tiv e ac tions and as one input into the need f or establishing f urther ac tions.
 
C ontrol R oom D es ign C riteria
 
The c ontrol room design c riteria, as desc ribed in G D C 19, c all f or the plant design to inc orporate radiation protec tion f eatures that, in the ev ent of an em er genc y, w ould m aintain the radiation ex posure of c ontrol room personnel to a lev el equal to their norm al oc c upational ex posure lim its.
It is generally understood that an objec tiv e of the c riteria is to ensure that the design of the c ontrol room and its habitability sy stem s w as suc h that a shirt-sleev ed env ironm ent w as prov ided f or the c ontrol room operators. Ex c eeding the c ontrol room d esign c riteria num eric al v alue of 0.05 Sv (5 rem ) TED E w ould not im pose an im m ediate health ef f ec t or ev en requirean ev ac uation requirem ent on the c ontrol room operators. H ow ev er, hav ing a num eric al c riterion f or designers to ref erenc e w hen ac c ounting f or ac c idents in their designs is nec essary and c onsistent w ith the IC R P. Though setting the c riteria to the norm al oc c upationa l dose lim its to assess plant perf orm anc e during em ergenc y c onditions m ay m ask its intended purposes w hen also assessing other regulations. To prov ide c ontex t, w e highlight a parallel betw een the c ontrol room design c riteria and the oc c upational dose lim its in 10 CFR 20.1206, Planned spec ial ex posures. As long as lic ensees m eet c ertain c riteria, 10 CFR Part 20 allow s planned spec ial ex posures up to tw ic e the annual oc c upational dose lim its prov ided that lif etim e ex posure of 0.25 Sv (25 rem ) TED E is not ex c eeded. As disc ussed in 56 FR 23372, planned spec ial ex posures w ere retained in the am ended 10 CFR Part 20 in part to address the f ac t that under the new sy stem of dose lim itation w ork ers w ould no longer hav e a lif etim e dose lim it, or dose bank, equaling f iv e tim es the quantity of the age of the w ork er m inus 18, or 5(N 18). While the use of planned spec ial ex posures w as predic ted to be inf requent, it w as ex pec ted that they w ould be used if the elim ination of the lif etim e dose lim its m ight c reate a sev ere handic ap to the lic ensees operations. Theref ore, the C om m ission c onc luded that an inf requent ex posure of w ork ers up to tw ic e the oc c upational dose lim it w as adequately protec tiv e of radiation w ork ers.
Now, the c ontrol room design c riteria are applic able to a low f requenc y ev ent, w hereas the planned spec ial ex posure is designed f or a m ore lik ely routine radiologic al ex posure ev ent.
Based on a potential radiologic al risk eac h rule is intending to protec t against, the applic able dose c onstraints f or less lik ely em ergenc y ev ents should be aligned (higher) than the dose c onstraints f or the low er f requenc y ev ents (planned spec ial ex posures) at 0.10 siev ert (Sv )
(10 roentgen equiv alent m an (rem )) as w ell as routine oc c upational ex posures 0.05 Sv (5 rem ).
 
ICRP 26
 
(paragraph 190) Although, by their nature, ac c idental ex posures are not subjec t to c ontrol, their m agnitude c an to som e ex tent be lim ited by interv ention, espec ially if attention has been paid to this possibility during the design of installations and equipm ent and the preparation of operating instruc tions.
 
12 ICRP 60
 
(paragraph 224) O c c upational ex posures direc tly due to an ac c ident c an be lim ited only by the design of the plant and its protec tiv e f eatures and by the prov ision of em ergenc y proc edures. Ideally, the aim should be to k eep the doses w ithin those perm itted in norm al c onditions, but, w hile this is usually possible, it m ay not alw ay s be so in serious ac c idents.
 
ICRP 103
 
(paragraph r) The proc ess of planning protec tion in planned ex posure situations should inc lude c onsideration of dev iations f rom norm al operating proc edures inc luding ac c idents and m alic ious ev ents.... Potential ex posures are not planned but they c an be antic ipated. The designer and the user of a sourc e m ust theref ore tak e ac tions to reduc e the lik elihood of a potential ex posure happening, suc h as assessing the probability of an ev ent and introduc ing engineering saf eguards c om m ensurate to this probability.
 
Performanc e-Bas ed R egulations, D es ign-Basis Ac c ident s, and U s e of Pers onal Protec tiv e Equipment
 
The c ontrol room design c riteria regulations are perf orm anc e based, requiring a lic ensee or applic ant to prov ide a c ontrol room habitability design that m eets a spec if ied dose-based c riterion. Spec if ic ally, they establish perf orm anc e requirem ents f or c ontrol room habitability sy stem s that w ould be c alled upon in a DBA. This is direc tly responsiv e to the ICRP rec om m endations to em phasize intrinsic saf ety f eatures. These sy stem s serv e the f unc tion of m itigation, thereby m inim izing the need f or interv ention, w hic h m ight inv olv e ev ac uation, adm inistration of prophy lac tic drugs, or use of personal protec tiv e equipm ent that c ould im pair the operators ability to perf orm the ac tions nec essary to prov ide adequate public health and saf ety. 3 To dem onstrate c om plianc e, lic ensees perf orm traditional determ inistic DBA radiologic al c onsequenc e analy ses using regulatory sourc e term s w hic h are rev iew ed and approv ed by the staf f. Perf orm anc e-based regulations, suc h as 10 CFR 50.67(b)(2)(iii) and GDC 19, do not prov ide presc riptiv e m ethodologies to determ ine the regulations are m et and theref ore do not require lic ensees to use spec if ic designs or m ethodologies to c om ply w ith the regulations. As suc h, N R C RG s and standard rev iew plans prov ide ac c eptable m ethodologies that lic ensees c an use to perf orm the analy ses, w hic h are then inc orporated, as appropriate, into the lic ensing basis f or the lic ensee s f ac ility. In general, the staf f has generally not ac c epted, ex c ept in interim situations, personal protec tiv e m easures suc h as respiratory protec tion or prophy lac tic drugs w hic h is c onsistent w ith the IC R P rec om m endations.
 
The lic ensing proc ess is based on the c onc ept of def ensein depth, in w hic h pow er plant design, operation, siting, and em ergenc y planning c om prise independent lay ers of nuc lear saf ety. This approac h enc ourages nuc lear plant designers to inc orporate sev eral lines of def ense in order to m aintain the ef f ec tiv eness of phy sic al barriers betw een radiation sourc es and m aterials f rom w ork ers, m em bers of the public, and the env ironm ent in operational states and, f or som e
 
3 This is also consistent with 10 C FR 20.1701, U se of process or other engineering controls" [Re f. 28], w h i c h requires the licensee to use, to the extent practical, process or other engineering controls (e.g., containm ent, decontam ination, or ventilation) to control the concentrations of radioactive m aterials in air.
 
13 barriers, in ac c ident c onditions. The approac h uses DBAs w ith regulatory sourc e term s to c om pute radiologic al c onsequenc es w hen assessing the ef f ec tiv eness of eac h line of def ense.
A s suc h, the DBAs establish and c onf irm the design basis of the nuc lear f ac ility, inc luding its saf ety-related SSCs and item s im portant to saf ety, ensuring that the plant design m eets the saf ety and num eric al radiologic al c riteria set f orth in regulations and subsequent guidanc e. D ue to the c onserv ativ e, determ inistic nature of the DBA analy ses, there is a m argin of saf ety suc h that c ontrol room design m ay be adequate f or m any ev ents bey ond the design basis. H ow ev er, it rem ains possible that ac tual radiation ex posures f rom bey ond-design-basis ev ents, or those resulting f rom m ultiple f ailures of the c ontrol room habitability sy stem s c oinc ident w ith a DBA, c ould ex c eed the design c riteria. In suc h an ev ent, the radiation ex posures are still subjec t to 10 CFR Part 20 f irst and then the f ac ility s em ergenc y plan, w hic h w ould us e personal protec tiv e equipm ent, if nec essary, supplem entary to these m ore f undam ental design prov isions. U nder em ergenc y c onditions, both m aintain radiation ex posures to be ALARA and, to the ex tent prac tic able, lim ited to norm al oc c upational lev els. This is c onsistent w ith the ICRP 26, I CRP 60, and IC R P 103 rec om m endations.
 
ICRP 26
 
(paragraph 167) As f ar as is reasonably prac tic able, the arrangem ents f or restric ting oc c upational ex posure should be applied to the sourc e of radiation and to f eatures of the w ork plac e. The use of personal protec tiv e equipm ent should in general be supplem entary to these m ore f undam ental prov isions. The em phasis should thus be on intrinsic saf ety in the w ork plac e and only sec ondarily on protec tion that depends on the w ork ers ow n ac tions.
 
ICRP 60
 
(paragraph 195) The initial treatm ent of potential ex posures should f orm part of the sy stem of protec tion applied to prac tic es, but it should be rec ognized that the ex posures, if they oc c ur, m ay lead to interv ention. At this stage there should be tw o objec tiv es, prev ention and m itigation. Prev ention is the reduc tion of the probability of the sequenc es of ev ents that m ay c ause or inc rease radiation ex posures. It inv olv es m aintaining the reliability of all of the operating and saf ety sy stem s and of the assoc iated w ork ing proc edures. M itigation is the lim itation and reduc tion of the ex posures if any of these sequenc es do oc c ur. It inv olv es the use of engineered saf ety f eatures and operational proc edures to c ontrol eac h sequenc e of ev ents w ith the aim of lim iting its c onsequenc es, should it oc c ur.
The arrangem ent f or m itigation should not be restric ted to plans of interv ention. A great deal c an be ac c om plished at the stages of design and operation to reduc e the c onsequenc es of ac c ident sequenc es so that interv ention m ay not bec om e nec essary.
 
ICRP 103
 
(paragraph t) Em phasis on optim isation using ref erenc e lev els in em ergenc y and ex isting ex posure situations f oc uses attention on the residual lev el of dose rem aining af ter im plem entation of protec tion strategies. This residual dose should be below the ref erenc e lev el, w hic h represents the total residual dose as
 
14 a result of an em ergenc y, or in an ex isting situation, that the regulator w ould plan not to ex c eed. These ex posure situations of ten inv olv e m ultiple ex posure pathw ay s w hic h m eans that protec tion strategies inv olv ing a num ber of dif f erent protec tiv e ac tions w ill hav e to be c onsidered. The proc ess of optim isation w ill how ev er c ontinue to use the dose av erted by spec if ic c ounterm easures as an im portant input into the dev elopm ent of optim ized strategies.
 
Item 3: Provide an annotated bibliography of radiation protection r ecommendations for w or ker s during emergency conditions from national and international organiz ations responsible for making recommendations for radiation protection standards.
 
The staf f rev iew ed a num ber of sourc e m aterials to understand the c urrent state of k now ledge and organizations rec om m endations f or protec ting radiation w ork ers f rom radiation under ac c ident c onditions. The purpose of this rev iew w as to determ ine w hether reex am ining the tec hnic al basis f or the c ontrol room design c riteria w ould be w arranted in light of this inc reased enric hm ent rulem ak ing. The staf f also rev iew ed other N R C regulations and national and international organizations responsible f or m ak ing rec om m endations f or radiation protec tion standards. The purpose w as to understand w hether the c urrently selec ted num eric al v alue of 0.05 Sv (5 rem ) TED E f its w ithin the range of v alues used f or w ork er protec tion during em ergenc y c onditions:
* At the tim e that G D C 19 w as published in 1971, 10 CFR Part 20 lim ited oc c upational radiation ex posure to 0.03 Sv (3 rem ) w hole body dose per c alendar quarter, prov ided the total lif etim e dose w as v erif ied not to ex c eed 0.05 Sv (5 rem ) tim es the indiv iduals age in y ears m inus 18 (i.e., 5(N18)). It w as possible to rec eiv e a radiation ex posure of up to 0.12 Sv (12 rem ) in a giv en y ear.
* The c urrent annual lim it on oc c upational radiation dose ex posurein 10 CFR 20.1201, O c c upational D ose Lim its f or adults, is 0.05 Sv (5 rem ) TEDE. U nder 10 CFR 20.1201, it is possible to rec eiv e oc c upational radiation ex posure of up to 0.10 Sv (10 rem ) TEDE ov er a 12-m onth period straddling tw o c alendar y ears.
* The c urrent 10 CFR 20.1206 on planned spec ial ex posures also perm its an adult w ork er to rec eiv e doses in addition to and ac c ounted f or separately f rom the doses rec eiv ed under the lim its spec if ied in 10 CFR 20.1201 of f iv e tim es the annual dose lim its during the indiv iduals lif etim e, not to ac c um ulate f aster than 0.05 Sv (5 rem ) TED E in any one y ear. It is possible to rec eiv e radiation ex posure of up to 0. 10 Sv (10 rem ) TED E w ithin a single c alendar y ear period.
* The EPA ex posure guidelines f ound in the PAG M anual rec om m end that doses rec eiv ed under em ergenc y c onditions should be m aintained ALARA and, to the ex tent prac tic able, lim ited to 0.05 Sv (5 rem ). The guideline f or ac tions to pr otec t v aluable pr oper ty is 0.10 Sv (10 rem ) w here a low er dose is not prac tic able, the guideline f or ac tions to sav e a lif e or to protec t large populations is 0.25 Sv (25 rem ) w here a low er dose is not prac tic able, and ex posures greater than 0.25 Sv (25 rem ) m ay be appropriate f or lif esav ing or protec ting large populations if the w ork ers are v olunteers w ho are f ully aw are of the risk s inv olv ed.


a result of an emergency, or in an existing situation, that the regulator would plan not to exceed. These exposure situations often involve multiple exposure pathways which means that protection strategies involving a number of different protective actions will have to be considered. The process of optimisation will however continue to use the dose averted by specific countermeasures as an important input into the development of optimized strategies.
Item 3:          Provide an annotated bibliography of radiation protection recommendations for workers during emergency conditions from national and international organizations responsible for making recommendations for radiation protection standards.
The staff reviewed a number of source materials to understand the current state of knowledge and organizations recommendations for protecting radiation workers from radiation under accident conditions. The purpose of this review was to determine whether reexamining the technical basis for the control room design criteria would be warranted in light of this increased enrichment rulemaking. The staff also reviewed other NRC regulations and national and international organizations responsible for making recommendations for radiation protection standards. The purpose was to understand whether the currently selected numerical value of 0.05 Sv (5 rem) TEDE fits within the range of values used for worker protection during emergency conditions:
* At the time that GDC 19 was published in 1971, 10 CFR Part 20 limited occupational radiation exposure to 0.03 Sv (3 rem) whole body dose per calendar quarter, provided the total lifetime dose was verified not to exceed 0.05 Sv (5 rem) times the individuals age in years minus 18 (i.e., 5(N18)). It was possible to receive a radiation exposure of up to 0.12 Sv (12 rem) in a given year.
* The current annual limit on occupational radiation dose exposure in 10 CFR 20.1201, Occupational Dose Limits for adults, is 0.05 Sv (5 rem) TEDE. Under 10 CFR 20.1201, it is possible to receive occupational radiation exposure of up to 0.10 Sv (10 rem) TEDE over a 12-month period straddling two calendar years.
* The current 10 CFR 20.1206 on planned special exposures also permits an adult worker to receive doses in addition to and accounted for separately from the doses received under the limits specified in 10 CFR 20.1201 of five times the annual dose limits during the individuals lifetime, not to accumulate faster than 0.05 Sv (5 rem) TEDE in any one year. It is possible to receive radiation exposure of up to 0.10 Sv (10 rem) TEDE within a single calendar year period.
* The EPA exposure guidelines found in the PAG Manual recommend that doses received under emergency conditions should be maintained ALARA and, to the extent practicable, limited to 0.05 Sv (5 rem). The guideline for actions to protect valuable property is 0.10 Sv (10 rem) where a lower dose is not practicable, the guideline for actions to save a life or to protect large populations is 0.25 Sv (25 rem) where a lower dose is not practicable, and exposures greater than 0.25 Sv (25 rem) may be appropriate for lifesaving or protecting large populations if the workers are volunteers who are fully aware of the risks involved.
15
15
* Health Physics Society Position Statement PS010-4, Radiation Risk in Perspective, issued January 2020 [Ref. 29], states that substantial and convincing scientific data show evidence of health effects following high-dose exposures (i.e., many multiples of natural background). However, below levels of about 100 mSv (10 rem) above background from all sources combined, the observed radiation effects in people are not statistically different from zero.
* H ealth Phy sic s Soc iety Position Statem ent PS010-4, R adiation R isk in Perspec tiv e, issued J anuary 2020 [R ef. 29], states that substantial and c onv inc ing sc ientif ic data show ev idenc e of health ef f ec ts f ollow ing high-dose ex posures ( i.e., m any m ultiples of natural bac k ground). H ow ev er, below lev els of about 100 m Sv (10 rem ) abov e bac k ground f rom all sourc es c om bined, the observ ed radiation ef f ec ts in people are not statistic ally dif f erent f rom zero.
* ICRP Publication 109, Application of the Commissions Recommendations for the Protection of People in Emergency Exposure Situations, issued 2009 [Ref. 30], specifies a range of 0.02-0.10 Sv (2-10 rem) acute for emergency exposure situations. For doses above 0.10 Sv (10 rem), protective measures should be justified.
* ICRP Public ation 109, Applic ation of the C om m issions R ec om m endations f or the Protec tion of People in Em ergenc y Ex posure Situations, issued 2009 [R ef. 30], spec if ies a range of 0.02- 0.10 Sv (2 - 10 rem ) ac ute f or em ergenc y ex posure situations. For doses abov e 0.10 Sv (10 rem ), protec tiv e m easures should be justif ied.
* International Atomic Energy Agency guidance [Ref. 31] for emergency workers specify a range of 0.05-1 Sv (5-100 rem), depending on the severity of the actions needed.
* Inter national A tom ic E ner gy A genc y guidanc e [ R ef. 31] f or em ergenc y w ork ers spec if y a range of 0.05-1 Sv (5 -100 rem ), depending on the sev erity of the ac tions needed.
* NCRP Report No. 180, Management of Exposure to Ionizing Radiation: Radiation Protection Guidance for the United States, issued 2018 [Ref. 32], specifies that (1) during lifesaving activities or actions to prevent a catastrophic situation, which includes other urgent rescue activities, 0.5 gray (Gy) cumulative whole-body absorbed dose (50 rad) should be implemented at the command level, and (2) for other emergency activities, including extended activities following initial lifesaving, rescue, and damage control response, an effective dose to emergency workers should not exceed 0.10 Sv (10 rem).
* NCRP R eport N o. 180, M anagem ent of Ex posure to Ionizing R adiation: R adiation Protec tion G uidanc e f or the U nited States, issued 2018 [R ef. 32], spec if ies that (1) during lif esav ing ac tiv ities or ac tions to prev ent a c atastrophic situation, w hic h inc ludes other urgent resc ue ac tiv ities, 0.5 gray (Gy ) c um ulativ e w hole-body absorbed dose (50 rad) should be im plem ented at the c om m and lev el, and (2) f or other em ergenc y ac tiv ities, inc luding ex tended ac tiv ities f ollow ing initial lif esav ing, resc ue, and dam age c ontrol response, an ef f ec tiv e dose to em ergenc y w ork ers should not ex c eed 0. 10 Sv (10 rem ).
In summary, there is a range of regulatory-based and international and national organization-based recommendations for radiation exposures for radiation workers under normal and emergency conditions. According to the regulations, occupational workers can receive up to 0.10 Sv (10 rem) occupationally during a 12-month period under a special circumstance within a calendar year. Intergovernmental and national and international organizations recommend emergency exposure dose limitations up to 0.25 Sv (25 rem) TEDE or 0.5 Gy (50 rad) whole body and up to 1 Gy (100 rad) for emergency responders. As such, the control room design criteria intended to assess the acceptability of a given control room design is on the lower end of a range of recommended values for emergency response planning to protect against actual incurred radiation exposure during an event.
 
Item 4:         Provide an assessment of the identified design criteria to contemporary radiological health effects.
In sum m ary, there is a range of regulatory-based and international and national organization-based rec om m endations f or radiation ex posures f or radiation w ork ers under norm al and em ergenc y c onditions. Ac c ording to the regulations, oc c upational w ork ers c an rec eiv e up to 0. 10 Sv (10 rem ) oc c upationally during a 12-m onth period under a spec ial circumstanc e w ithin a c alendar y ear. Intergov ernm ental and national and international organizations rec om m end em ergenc y ex posure dos e lim itations up to 0.25 Sv (25 rem ) TEDE or 0.5 Gy (50 rad) w hole body and up to 1 Gy (100 rad) f or em ergenc y responders. As suc h, the c ontrol room design c riteria intended to assess the ac c eptability of a giv en c ontrol room design is on the low er end of a range of rec om m ended v alues f or em ergenc y response planning to protec t against ac tual inc urred radiation ex posure during an ev ent.
This section provides the staffs assessment of the control room design criteria, with a numerical value of 0.05 Sv (5 rem), as compared to information found in professional literature, as well as recommendations regarding modern health physics knowledge, radiation protection standards, and radiation epidemiology knowledge.
 
As discussed above, the control room design criteria were developed and issued to establish minimum necessary design, fabrication, construction, testing, and performance requirements for SSCs that provide reasonable assurance that a facility can be operated without undue risk to the health and safety of the occupational workers and of the public. The design criteria are not operational limits, and they do not represent actual exposures received during normal operation 16
Item 4: Provide an assessment of the identified design criteria to contemporary radiological health effects.
 
This sec tion prov ides the staf f s assessm ent of the c ontrol room design c riteria, w ith a num eric al v alue of 0. 05 Sv (5 rem ), as c om pared to inf orm ation f ound in prof essional literature, as w ell as rec om m endations regarding m odern health phy sic s k now ledge, radiation protec tion standards, and radiation epidem iology k now ledge.
 
As disc ussed abov e, the c ontrol room design c riteria w ere dev eloped and issued to establish m inim um nec essary design, f abric ation, c onstruc tion, testing, and perf orm anc e requirem ents f or SSCs that prov ide reasonable assuranc e that a f ac ility c an be operated w ithout undue risk to the health and saf ety of the oc c upational w ork ers and of the public. The design c riteria are not operational lim its, and they do not represent ac tual ex posures rec eiv ed during norm al operation
 
16 or an em ergenc y c ondition. Instead, these c riteria are f igures-of -m erit that are c om pared against the results of traditional determ inistic radiologic al c onsequenc e analy ses using a DBA sourc e term to judge the ac c eptability of the c ontrol room design.
 
In the c ontex t of the inc reased enric hm ent rulem ak ing, the question arises as to w hether the c urrent c ontrol room design c riteria c ould be i nc reased to a higher, y et still saf e, perf orm anc e lev el w hen c onsidering c ontem porary understandings of radiologic al health ef f ec ts.
 
With suf f ic ient dose, the biologic al health ef f ec ts of radiation ex posure m anif est in one of tw o w ay s: stoc hastic or determ inistic. Stoc hastic health ef f ec ts oc c ur random ly, and the probability of the ef f ec ts oc c urring, rather than their sev erity, is assum ed to be a linear f unc tion of dose w ithout threshold. D oses that c ontribute to stoc hastic ef f ec ts c an be ac c um ulated ov er long periods of tim e, f rom y ears to dec ades. Canc er inc idenc e is an ex am ple of a stoc hastic ef f ec t.
C onv ersely, f or determ inistic health ef f ec t s, the sev erity v aries w ith the dose f or w hic h an em piric ally deriv ed threshold is established. Ac ute radiation sy ndrom e is a signif ic ant determ inistic ef f ec t that c an pose signif ic ant saf ety issues during em ergenc y responsebec ause it c an signif ic antly ham per the ef f ec tiv eness of c ontrol room operators. D ata on the v arious f orm s of ac ute radiation sy ndrom e hav e been c ollec ted f rom m any sourc es. Anim al ex perienc es prov ide the bulk of the data and results. At the hum an lev el, data hav e been draw n f rom ex perienc es in radiation therapy and studies f rom a num ber of nuc lear-related ac c idents.
 
There are tw o radiation units that assess either stoc hastic ef f ec ts or determ inistic radiation health ef f ec ts. The f irst is the Sv (or rem ) TEDE, w hic h is the sum of the ef f ec tiv e dose equiv alent f or ex ternal ex posures and the c om m itted ef f ec tiv e dose equiv alent f or internal ex posures. The Sv (rem ) TEDE adjusts the dose equiv alent radiation ex posure using a tissue w eighting f ac tor that represents the proportion of the risk of stoc hastic ef f ec ts resulting f rom irradiation of an organ, or tissue, to the total risk of stoc hastic ef f ec ts w hen the w hole body is irradiated unif orm ly. The c om m itted ef f ec tiv e dose equiv alent is a 50-y ear c om m itted dose based on an initial intak e of radioac tiv e m aterial used to estim ate the stoc hastic health ef f ec t of c anc er m ortality. In other w ords, the dose is assigned to the f irst y ear of intak e to estim ate the inc reased probability of c anc er induc ed f atality af ter 50 y ears. The sec ond radiation unit is the Gy, or rad, w hic h is used to m easure the am ount of energy deposited in tissue. Ty pic ally,
radiation ex posures that c ause determ inistic health ef f ec ts are m easured in Gy ( rad).
 
Ex posure of the w hole body to a large dose ov er a short period of tim e (< 1 hour) m ay c ause ef f ec ts due to the sensitiv ity of c ells in the body. Ac ute radiation sy ndrom e c an result f ollow ing signif ic ant w hole-body ex posures in a short tim e. Ef f ec ts m ay inc lude blood c hanges, nausea, v om iting, diarrhea, and c entral nerv ous sy stem dam age. H em atopoietic sy ndrom e is observ ed by a dec rease in blood c ell c ount at doses of about 1 Gy (100 rad). G astrointestinal sy ndrom e f rom a dose of about 5 Gy (500 rad) w ill result in nausea, v om iting, and diarrhea. C entral nerv ous sy stem sy ndrom e, observ ed at about a dose of 20 Gy (2,000 rad), w ill af f ec t the m usc le and brain f unc tion of the c entral nerv ous sy stem. The dose w hic h is lethal to 50 perc ent of the people w ithin 60 day s if m edic al treatm ent is not prov ided is c alled the LD 50/60. The LD 50/60 dose is approx im ately 3-5 Gy (300- 500 rads; ~90 tim es the annual dose lim it f or routine oc c upational ex posure) in an hour to an av erage adult. If rec eiv ed w ithin a short tim e period (e.g., a f ew hours), an LD 5-/60 dose w ill c ause v om iting and diarrhea w ithin a f ew hours and loss of hair, f ev er, and w eight loss w ithin a f ew w eek s. These ef f ec ts w ould not oc c ur if the
 
17 sam e dose w ere ac c um ulated gradually ov er m any w eek s or m onths, suc h as during radiation therapy treatm ents.
 
The radiation risk of c anc er m ortality is assessed by f ir st quantif y ing the baseline risk of c anc er death w ithin a giv en population. For the U nited States, this is approx im ately 20 perc ent.
Therefore, a population of 10,000 people w ould dev elop approx im ately 2,000 (20 perc ent of 10,000) f atal c anc ers due to the natural inc idenc e of c anc er. Ex posure to radiation dose of up to 0.01 Sv (1 rem ) m ay inc rease the ov erall risk to 20 perc ent + 0.05 perc ent = 20.05 perc ent.
C ollec tiv e dose to a population of 10,000 person-rem (0.01 Sv (1 rem ) to eac h person in a population of 10,000) m ay result in f iv e additional c anc er f atalities, besides the 2,000 that w ill oc c ur naturally. That is, there w ould be 2, 005 f atal c anc ers, rather than 2, 000. H ow ev er, the natural inc idenc e of f atal c anc ers is not prec isely 2,000, and it is not possible to unequiv oc ally distinguish these additional c ases f rom those oc c urring naturally. As a c onsequenc e of c ollec tiv e dose in a lif etim e, approx im ately 42 out of 100 people w ill be diagnosed w ith c anc er f rom c auses unrelated to radiation. As prev iously m entioned, about 20 perc ent of the population dies f rom som e f orm of c anc er. So, of the 42 perc ent of people w ho dev elop c anc er, half w ill surv iv e. If 100 people rec eiv ed a dose of 0.1 Sv (10 rem ), it is estim ated that there w ill be one additional c anc er inc idenc e in this group f or a total of 43 c anc er inc idents. M ore inf orm ation c onc erning risk f rom ionizing radiation is av ailable in Regulatory Guide 8.29, Instruc tion C onc erning R isk s f rom O c c upational R adiation Ex posure, R ev ision 1, issued February 1996
[R ef. 33].
 
In sum m ary, ionizing radiation c an c ause biologic al ef f ec ts. While the biologic al ef f ec ts f rom ionizing radiation are not unique to radiation, it is im portant to limit the am ount of radiation dose rec eiv ed by an indiv idual. The probability of stoc hastic ef f ec ts of radiation, suc h as c ausing c anc er, inc rease w ith radiation dose. The lim itation of stoc hastic ef f ec ts is ac hiev ed by k eeping all justif iable ex posures ALAR A, giv en ec onom ic and soc ial f ac tors being c onsidered, subjec t alw ay s to the boundary c ondition that the appropriate dose lim it is not ex c eeded. D eterm inistic ef f ec ts hav e a threshold dose that m ust be ex c eeded f or the ef f ec ts to oc c ur, and the sev erity of these ef f ec ts also inc reases w ith dose. The prev ention of determ inistic ef f ec ts is ac hiev ed by setting dose equiv alent lim its at suf f ic iently low v alues so that no threshold dose w ould be reac hed, ev en f ollow ing ex posure f or the w hole of a lif etim e or f or the total period of an indiv iduals w ork ing lif e. As disc ussed abov e, the N R C has set dose lim its to m inim ize stoc hastic ef f ec ts and to av oid determ inistic ef f ec ts. Theref ore, the aim of the NRCs radiation protec tion standards is to prev ent detrim ental determ inistic ef f ec ts and to lim it the probability of stoc hastic ef f ec ts to lev els deem ed to be ac c eptable.
 
The c ontrol room design c riteria radiation unit of rem TED E does not tec hnic ally m atc h the ex pec ted m easured determ inistic health ef f ec ts ex pec ted f rom a reac tor ac c ident. H ow ev er, the 10 CFR Part 20 annual oc c upational ex posure lim it of 0.05 Sv (5 rem ) TE D E is set suf f ic iently low that no determ inistic threshold dose w ould be reac hed. This oc c upational ex po sure lim it is applic able to both norm al and em ergenc y c onditions. The rev iew of regulations pertaining to oc c upational w ork ers and radiation protec tion rec om m endations f or w ork ers during em ergenc y c onditions identif ied a range of rec om m ended ac c eptable c riteria. These c riteria w ould c ontinue to prov ide reasonable assuranc e that the f ac ility c an be operated during an em ergenc y w ithout undue risk to public health and saf ety as they are set suf f ic iently low to protec t against determ inistic health ef f ec ts that w ould cause operator im partm ent.


or an emergency condition. Instead, these criteria are figures-of-merit that are compared against the results of traditional deterministic radiological consequence analyses using a DBA source term to judge the acceptability of the control room design.
18 REFERENCES
In the context of the increased enrichment rulemaking, the question arises as to whether the current control room design criteria could be increased to a higher, yet still safe, performance level when considering contemporary understandings of radiological health effects.
: 1. U.S. Nuc lear Regulatory Com m ission (NRC), Assessm ent of R adiation Protec tion R ec om m endations f or Em ergenc y Work ers, Form 843, Inf orm al Assistanc e R equest NRR-2022-019, August 26, 2022, Agenc y w ide D oc um ents Ac c ess and M anagem ent Sy stem (ADAM S) Ac c ession N o. M L22259A017.
With sufficient dose, the biological health effects of radiation exposure manifest in one of two ways: stochastic or deterministic. Stochastic health effects occur randomly, and the probability of the effects occurring, rather than their severity, is assumed to be a linear function of dose without threshold. Doses that contribute to stochastic effects can be accumulated over long periods of time, from years to decades. Cancer incidence is an example of a stochastic effect.
: 2. N uc lear Energy Institute, The Ec onom ic Benef its and C hallenges w ith U tilizing Inc reased Enric hm ent and Fuel Burnup f or Light-Water R eac tors, February 2019, M L21259A191.
Conversely, for deterministic health effects, the severity varies with the dose for which an empirically derived threshold is established. Acute radiation syndrome is a significant deterministic effect that can pose significant safety issues during emergency response because it can significantly hamper the effectiveness of control room operators. Data on the various forms of acute radiation syndrome have been collected from many sources. Animal experiences provide the bulk of the data and results. At the human level, data have been drawn from experiences in radiation therapy and studies from a number of nuclear-related accidents.
: 3. NRC, Projec t Plan to Prepare the U.S. N uc lear R egulatory C om m ission f or Ef f ic ient Lic ensing of Ac c ident Tolerant Fuels, Version 1.2, Septem ber 2021, M L21243A298.
There are two radiation units that assess either stochastic effects or deterministic radiation health effects. The first is the Sv (or rem) TEDE, which is the sum of the effective dose equivalent for external exposures and the committed effective dose equivalent for internal exposures. The Sv (rem) TEDE adjusts the dose equivalent radiation exposure using a tissue weighting factor that represents the proportion of the risk of stochastic effects resulting from irradiation of an organ, or tissue, to the total risk of stochastic effects when the whole body is irradiated uniformly. The committed effective dose equivalent is a 50-year committed dose based on an initial intake of radioactive material used to estimate the stochastic health effect of cancer mortality. In other words, the dose is assigned to the first year of intake to estimate the increased probability of cancer induced fatality after 50 years. The second radiation unit is the Gy, or rad, which is used to measure the amount of energy deposited in tissue. Typically, radiation exposures that cause deterministic health effects are measured in Gy (rad).
: 4. U.S. Code of Federal R egulations, C ritic ality ac c ident requirem ents, Sec tion 50.68, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc -
Exposure of the whole body to a large dose over a short period of time (<1 hour) may cause effects due to the sensitivity of cells in the body. Acute radiation syndrome can result following significant whole-body exposures in a short time. Effects may include blood changes, nausea, vomiting, diarrhea, and central nervous system damage. Hematopoietic syndrome is observed by a decrease in blood cell count at doses of about 1 Gy (100 rad). Gastrointestinal syndrome from a dose of about 5 Gy (500 rad) will result in nausea, vomiting, and diarrhea. Central nervous system syndrome, observed at about a dose of 20 Gy (2,000 rad), will affect the muscle and brain function of the central nervous system. The dose which is lethal to 50 percent of the people within 60 days if medical treatment is not provided is called the LD 50/60. The LD 50/60 dose is approximately 3-5 Gy (300-500 rads; ~90 times the annual dose limit for routine occupational exposure) in an hour to an average adult. If received within a short time period (e.g., a few hours), an LD 5-/60 dose will cause vomiting and diarrhea within a few hours and loss of hair, fever, and weight loss within a few weeks. These effects would not occur if the 17
c ollec tions/c f r/part050/part050-0068.htm l )
: 5. NRC, R ulem ak ing Plan on U se of Inc reased Enric hm ent of C onv entional and Ac c ident Tolerant Fuel D esigns f or Light-Water R eac tors, SECY-21-0109, D ec em ber 20, 2021, M L21232A237.
: 6. NRC, Staf f R equirem ents SECY-21-0109R ulem ak ing Plan on U se of Inc reased Enric hm ent of C onv entional and Ac c ident Tolerant Fuel D esigns f or Light-Water R eac tors, SRM -SECY-21-0109, M arc h 16, 2022, M L22075A103.
: 7. U.S. C ode of Federal R egulations, Ac c ident sourc e ter m, Sec tion 50.67, C hapter I,
Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc -
c ollec tions/c f r/part050/part050-0067.htm l )
: 8. U.S. C ode of Federal R egulations, C ontrol room, G eneral D esign C riterion 19, G eneral D esign C riteria f or N uc lear Pow er Plants, Appendix A, Part 50, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc -
c ollec tions/c f r/part050/part050-appa.htm l#4_appa )
: 9. U.S. N uc lear R egulatory C om m ission, Be risk SM ART G uidanc e f or Integrating R isk Insights into N R C D ec isions, NUREG/KM -0016, M arc h 20 21, M L21071A238.
: 10. U.S. C ode of Federal R egulations, C ontents of applic ations; tec hnic al inf orm ation, Sec tion 50.34, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc-c ollec tions/c f r/part050/part050-0034.htm l )
: 11. U.S. C ode of Federal R egulations, C ontents of applic ations; tec hnic al inf orm ation, Sec tion 52.17, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc-c ollec tions/c f r/part052/part052-0017.htm l )
: 12. U.S. C ode of Federal R egulations, C ontents of applic ations; tec hnic al inf orm ation, Sec tion 5 2.47, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc-c ollec tions/c f r/part052/part052-0047.htm l )


same dose were accumulated gradually over many weeks or months, such as during radiation therapy treatments.
19
The radiation risk of cancer mortality is assessed by first quantifying the baseline risk of cancer death within a given population. For the United States, this is approximately 20 percent.
: 13. U.S. C ode of Federal R egulations, C ontents of applic ations; tec hnic al inf orm ation, Sec tion 5 2.79, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc-c ollec tions/c f r/part052/part052-0079.htm l )
Therefore, a population of 10,000 people would develop approximately 2,000 (20 percent of 10,000) fatal cancers due to the natural incidence of cancer. Exposure to radiation dose of up to 0.01 Sv (1 rem) may increase the overall risk to 20 percent + 0.05 percent = 20.05 percent.
: 14. U.S. C ode of Federal R egulations, C ontents of applic ations; tec hnic al inf orm ation, Sec tion 5 2.137, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc-c ollec tions/c f r/part052/part052-0137.htm l )
Collective dose to a population of 10,000 person-rem (0.01 Sv (1 rem) to each person in a population of 10,000) may result in five additional cancer fatalities, besides the 2,000 that will occur naturally. That is, there would be 2,005 fatal cancers, rather than 2,000. However, the natural incidence of fatal cancers is not precisely 2,000, and it is not possible to unequivocally distinguish these additional cases from those occurring naturally. As a consequence of collective dose in a lifetime, approximately 42 out of 100 people will be diagnosed with cancer from causes unrelated to radiation. As previously mentioned, about 20 percent of the population dies from some form of cancer. So, of the 42 percent of people who develop cancer, half will survive. If 100 people received a dose of 0.1 Sv (10 rem), it is estimated that there will be one additional cancer incidence in this group for a total of 43 cancer incidents. More information concerning risk from ionizing radiation is available in Regulatory Guide 8.29, Instruction Concerning Risks from Occupational Radiation Exposure, Revision 1, issued February 1996
: 15. U.S. C ode of Federal R egulations, C ontents of applic ations; tec hnic al inf orm ation in f inal saf ety analy sis report, Sec tion 5 2.157, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc -c ollec tions/c f r/part052/part052-0157.htm l )
[Ref. 33].
: 16. U.S. C ode of Federal R egulations, D eterm ination of ex c lusion area, low population zone, and population c enter distanc e, Sec tion 100.11, C hapter I, Title 10, Energy.
In summary, ionizing radiation can cause biological effects. While the biological effects from ionizing radiation are not unique to radiation, it is important to limit the amount of radiation dose received by an individual. The probability of stochastic effects of radiation, such as causing cancer, increase with radiation dose. The limitation of stochastic effects is achieved by keeping all justifiable exposures ALARA, given economic and social factors being considered, subject always to the boundary condition that the appropriate dose limit is not exceeded. Deterministic effects have a threshold dose that must be exceeded for the effects to occur, and the severity of these effects also increases with dose. The prevention of deterministic effects is achieved by setting dose equivalent limits at sufficiently low values so that no threshold dose would be reached, even following exposure for the whole of a lifetime or for the total period of an individuals working life. As discussed above, the NRC has set dose limits to minimize stochastic effects and to avoid deterministic effects. Therefore, the aim of the NRCs radiation protection standards is to prevent detrimental deterministic effects and to limit the probability of stochastic effects to levels deemed to be acceptable.
(av ailable at https://w w w.nrc.gov /reading-rm /doc -c ollec tions/c f r/part100/part100-0011.htm l)
The control room design criteria radiation unit of rem TEDE does not technically match the expected measured deterministic health effects expected from a reactor accident. However, the 10 CFR Part 20 annual occupational exposure limit of 0.05 Sv (5 rem) TEDE is set sufficiently low that no deterministic threshold dose would be reached. This occupational exposure limit is applicable to both normal and emergency conditions. The review of regulations pertaining to occupational workers and radiation protection recommendations for workers during emergency conditions identified a range of recommended acceptable criteria. These criteria would continue to provide reasonable assurance that the facility can be operated during an emergency without undue risk to public health and safety as they are set sufficiently low to protect against deterministic health effects that would cause operator impartment.
: 17. U.S. C ode of Federal R egulations, Planned spec ial ex posures, Sec tion 20.1206, O c c upational D ose Lim its, Subpart C, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc -c ollec tions/c f r/part020/part020-1206.htm l )
18
: 18. U.S. C ode of Federal R egulations, O c c upational dose lim its f or adults, Sec tion 20.1201, O c c upational D ose Lim its, Subpart C, C hapter I, Title 10, Energy.
(av ailable at https://w w w.nrc.gov /reading-rm /doc -c ollec tions/c f r/part020/part020-1201.htm l)
: 19. U.S. N ational Bureau of S tandar ds, Maximum Permi ssible Body Burdens and M ax im um Perm issible C onc entrations of R adionuc lides in Air and in Water f or O c c upational Ex posure, H andbook 69, J une 5, 1959 (av ailable at https://nv lpubs.nist.gov /nistpubs/Legac y /hb/nbshandbo ok 69.pdf).
: 20. U.S. C ode of Federal R egulations, Standards f or Protec tion Against R adiation, Part 20, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc -
c ollec tions/c f r/part020/index.htm l)
: 21. International C om m ission on R adiologic al Protec tion (ICRP), Re c om m endations of the ICRP, Annals of the ICRP 1(3), ICRP Public ation 26, 1977 (av ailable at https://w w w.ic rp.org/public ation.asp?id= IC R P%20Public ation%2026).
: 22. N R C, Standards f or Protec tion against R adiation, Federal R egis ter, Vol. 56, N o. 98, pp. 23360- 23401, M ay 21, 1991. (av ailable at https://arc hiv es.f ederalregister.gov /issue_slic e/1991/5/21/23349-2 3474.pdf #page= 12 )
: 23. U.S. Env ironm ental Protec tion Agenc y, PAG M anual: Protec tiv e Ac tion G uides and Planning G uidanc e f or R adiologic al Inc idents, EPA-400/R -17/001, J anuary 2017 (av ailable at https://w w w.epa.gov /radiation/protec tiv e-ac tion-guides -pags#pagm anual).
: 24. ICRP, 1990 R ec om m endations of the International C om m ission on R adiologic al Protec tion, Annals of the ICRP 21(1-3), ICRP Public ation 60 (U sers Edition), 1991


REFERENCES
20 (av ailable at https://w w w.ic rp.org/public ation.asp?id= IC R P%20Public ation%2060%20(U sers%20Editi on)).
: 1. U.S. Nuclear Regulatory Commission (NRC), Assessment of Radiation Protection Recommendations for Emergency Workers, Form 843, Informal Assistance Request NRR-2022-019, August 26, 2022, Agencywide Documents Access and Management System (ADAMS) Accession No. ML22259A017.
: 25. ICRP, The 2007 R ec om m endations of the International C om m ission on R adiologic al Protec tion, Annals of the ICRP 37(2-4), ICRP Public ation 103, 2007 (av ailable at https://www.ic rp.org/public ation.asp?id= IC R P%20Public ation%20103).
: 2. Nuclear Energy Institute, The Economic Benefits and Challenges with Utilizing Increased Enrichment and Fuel Burnup for Light-Water Reactors, February 2019, ML21259A191.
: 26. NRC, Em ergenc y R esponse Planning and Preparedness f or N uc lear Pow er R eac tors,
: 3. NRC, Project Plan to Prepare the U.S. Nuclear Regulatory Commission for Efficient Licensing of Accident Tolerant Fuels, Version 1.2, September 2021, ML21243A298.
R egulatory G uide 1.101, R ev ision 6, J une 2021, M L21111A090.
: 4. U.S. Code of Federal Regulations, Criticality accident requirements, Section 50.68, Chapter I, Title 10, Energy. (available at https://www.nrc.gov/reading-rm/doc-collections/cfr/part050/part050-0068.html)
: 27. NRC and Federal Em ergenc y M anagem ent Agenc y, C riteria f or Preparation and Ev aluation of R adiologic al Em ergenc y R esponse Plans and Preparednessin Support of N uc lear Pow er Plants: Final R eport, NUREG -0654/ FEM A-REP-1, R ev. 2, D ec em ber 2019, M L19347D 139.
: 5. NRC, Rulemaking Plan on Use of Increased Enrichment of Conventional and Accident Tolerant Fuel Designs for Light-Water Reactors, SECY-21-0109, December 20, 2021, ML21232A237.
: 28. U.S. C ode of Federal R egulations, U se of proc ess or other engineering c ontrols, Sec tion 20.1701, R espiratory Protec tion and C ontrols to R estric t Internal Ex posure in R estric ted Areas, Subpart H, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc -c ollec tions/c f r/part020/part020-1701.htm l )
: 6. NRC, Staff RequirementsSECY-21-0109Rulemaking Plan on Use of Increased Enrichment of Conventional and Accident Tolerant Fuel Designs for Light-Water Reactors, SRM-SECY-21-0109, March 16, 2022, ML22075A103.
: 29. H ealth Phy sic s Soc iety, Position Statem ent of the H ealth Phy sic s Soc iety PS010-4:
: 7. U.S. Code of Federal Regulations, Accident source term, Section 50.67, Chapter I, Title 10, Energy. (available at https://www.nrc.gov/reading-rm/doc-collections/cfr/part050/part050-0067.html)
R adiation R isk in Perspec tiv e, H ealth Phy s ic s 118(1), pp. 79-80, J anuary 2020.
: 8. U.S. Code of Federal Regulations, Control room, General Design Criterion 19, General Design Criteria for Nuclear Power Plants, Appendix A, Part 50, Chapter I, Title 10, Energy. (available at https://www.nrc.gov/reading-rm/doc-collections/cfr/part050/part050-appa.html#4_appa)
(av ailable at https://journals.lw w.c om /health-phy sic s/f ulltex t/2020/01000/position_statem ent_of _the_health_phy sic s_soc iety.8.aspx)
: 9. U.S. Nuclear Regulatory Commission, Be riskSMARTGuidance for Integrating Risk Insights into NRC Decisions, NUREG/KM-0016, March 2021, ML21071A238.
: 30. ICRP, Applic ation of the C om m ission s R ec om m endations f or the Protec tion of People in Em ergenc y Ex posure Situations, Annals of the ICRP 39(1), ICRP Public ation 109, 2009 (av ailable at https://w w w.ic rp.org/public ation.asp?id= ic rp%20public ation%20109).
: 10. U.S. Code of Federal Regulations, Contents of applications; technical information, Section 50.34, Chapter I, Title 10, Energy. (available at https://www.nrc.gov/reading-rm/doc-collections/cfr/part050/part050-0034.html)
: 31. International Atom ic Energy Agenc y, Portable D igital Assistant f or First R esponders to a R adiologic al Em ergenc y: Em ergenc y w ork er turn-bac k dose guidanc e, n.d. (av ailable at https://www-pub.iaea.org/m tc d/public ations/pdf /epr-f irst_res -pda/htm l/ti2-turn-bac k -
: 11. U.S. Code of Federal Regulations, Contents of applications; technical information, Section 52.17, Chapter I, Title 10, Energy. (available at https://www.nrc.gov/reading-rm/doc-collections/cfr/part052/part052-0017.html)
dose.htm #f tn.10).
: 12. U.S. Code of Federal Regulations, Contents of applications; technical information, Section 52.47, Chapter I, Title 10, Energy. (available at https://www.nrc.gov/reading-rm/doc-collections/cfr/part052/part052-0047.html) 19
: 32. N ational C ounc il on R adiation Protec tion and M easurem ents (NCRP), M anagem ent of Ex posure to Ionizing R adiation: R adiation Protec tion G uidanc e f or the U nited States, NCRP R eport N o. 180, 2018 (av ailable at https://nc rponline.org/shop/reports/report-no-180-m anagem ent -of -ex posure-to -ionizing-radiation-radiation-protec tion-guidanc e-f or -
: 13. U.S. Code of Federal Regulations, Contents of applications; technical information, Section 52.79, Chapter I, Title 10, Energy. (available at https://www.nrc.gov/reading-rm/doc-collections/cfr/part052/part052-0079.html)
the-united-states -2018-2018/ ).
: 14. U.S. Code of Federal Regulations, Contents of applications; technical information, Section 52.137, Chapter I, Title 10, Energy. (available at https://www.nrc.gov/reading-rm/doc-collections/cfr/part052/part052-0137.html)
: 33. NRC, I nstruc tion Conc erning Risk s f r om O c c upational Radiation Ex posure, R egulatory G uide 8. 29, R ev. 1, February 1996, ML003739438.
: 15. U.S. Code of Federal Regulations, Contents of applications; technical information in final safety analysis report, Section 52.157, Chapter I, Title 10, Energy. (available at https://www.nrc.gov/reading-rm/doc-collections/cfr/part052/part052-0157.html)
: 16. U.S. Code of Federal Regulations, Determination of exclusion area, low population zone, and population center distance, Section 100.11, Chapter I, Title 10, Energy.
(available at https://www.nrc.gov/reading-rm/doc-collections/cfr/part100/part100-0011.html)
: 17. U.S. Code of Federal Regulations, Planned special exposures, Section 20.1206, Occupational Dose Limits, Subpart C, Chapter I, Title 10, Energy. (available at https://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1206.html)
: 18. U.S. Code of Federal Regulations, Occupational dose limits for adults, Section 20.1201, Occupational Dose Limits, Subpart C, Chapter I, Title 10, Energy.
(available at https://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1201.html)
: 19. U.S. National Bureau of Standards, Maximum Permissible Body Burdens and Maximum Permissible Concentrations of Radionuclides in Air and in Water for Occupational Exposure, Handbook 69, June 5, 1959 (available at https://nvlpubs.nist.gov/nistpubs/Legacy/hb/nbshandbook69.pdf).
: 20. U.S. Code of Federal Regulations, Standards for Protection Against Radiation, Part 20, Chapter I, Title 10, Energy. (available at https://www.nrc.gov/reading-rm/doc-collections/cfr/part020/index.html)
: 21. International Commission on Radiological Protection (ICRP), Recommendations of the ICRP, Annals of the ICRP 1(3), ICRP Publication 26, 1977 (available at https://www.icrp.org/publication.asp?id=ICRP%20Publication%2026).
: 22. NRC, Standards for Protection against Radiation, Federal Register, Vol. 56, No. 98, pp. 23360-23401, May 21, 1991. (available at https://archives.federalregister.gov/issue_slice/1991/5/21/23349-23474.pdf#page=12)
: 23. U.S. Environmental Protection Agency, PAG Manual: Protective Action Guides and Planning Guidance for Radiological Incidents, EPA-400/R-17/001, January 2017 (available at https://www.epa.gov/radiation/protective-action-guides-pags#pagmanual).
: 24. ICRP, 1990 Recommendations of the International Commission on Radiological Protection, Annals of the ICRP 21(1-3), ICRP Publication 60 (Users Edition), 1991 20


(available at https://www.icrp.org/publication.asp?id=ICRP%20Publication%2060%20(Users%20Editi on)).
: 25. ICRP, The 2007 Recommendations of the International Commission on Radiological Protection, Annals of the ICRP 37(2-4), ICRP Publication 103, 2007 (available at https://www.icrp.org/publication.asp?id=ICRP%20Publication%20103).
: 26. NRC, Emergency Response Planning and Preparedness for Nuclear Power Reactors, Regulatory Guide 1.101, Revision 6, June 2021, ML21111A090.
: 27. NRC and Federal Emergency Management Agency, Criteria for Preparation and Evaluation of Radiological Emergency Response Plans and Preparedness in Support of Nuclear Power Plants: Final Report, NUREG-0654/FEMA-REP-1, Rev. 2, December 2019, ML19347D139.
: 28. U.S. Code of Federal Regulations, Use of process or other engineering controls, Section 20.1701, Respiratory Protection and Controls to Restrict Internal Exposure in Restricted Areas, Subpart H, Chapter I, Title 10, Energy. (available at https://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1701.html)
: 29. Health Physics Society, Position Statement of the Health Physics Society PS010-4:
Radiation Risk in Perspective, Health Physics 118(1), pp. 79-80, January 2020.
(available at https://journals.lww.com/health-physics/fulltext/2020/01000/position_statement_of_the_health_physics_society.8.aspx)
: 30. ICRP, Application of the Commissions Recommendations for the Protection of People in Emergency Exposure Situations, Annals of the ICRP 39(1), ICRP Publication 109, 2009 (available at https://www.icrp.org/publication.asp?id=icrp%20publication%20109).
: 31. International Atomic Energy Agency, Portable Digital Assistant for First Responders to a Radiological Emergency: Emergency worker turn-back dose guidance, n.d. (available at https://www-pub.iaea.org/mtcd/publications/pdf/epr-first_res-pda/html/ti2-turn-back-dose.htm#ftn.10).
: 32. National Council on Radiation Protection and Measurements (NCRP), Management of Exposure to Ionizing Radiation: Radiation Protection Guidance for the United States, NCRP Report No. 180, 2018 (available at https://ncrponline.org/shop/reports/report-no-180-management-of-exposure-to-ionizing-radiation-radiation-protection-guidance-for-the-united-states-2018-2018/).
: 33. NRC, Instruction Concerning Risks from Occupational Radiation Exposure, Regulatory Guide 8.29, Rev. 1, February 1996, ML003739438.
21}}
21}}

Revision as of 10:24, 15 November 2024

Control Room Design Criteria and Radiological Health Effects, Iar NRR-2022-019 Report
ML23027A059
Person / Time
Issue date: 06/30/2023
From: Terry Brock, John Tomon
NRC/RES/DSA
To:
Shared Package
ML23027A058 List:
References
Download: ML23027A059 (1)
v • d • e


Text

CONTROL ROOM DESIGN CRITERIA AND RADIOLOGICAL HEALTH EFFECTS

J une 2023

1 J ohn Tom on1 Terry Broc k,,

2 and 2 D av id G arm on, Elijah Dickson

D iv ision of Sy stem s Analy sis Office of N uc lear R egulatory R esearc h U nited States N uc lear R egulatory C om m ission

1 Office of Nuclear Regulatory Research, Division of System s Analysis, Radiation Protection Branch (RES/DSA/ RPB)

2 Office of Nuclear Reactor Regulation, Division of Ri s k Assessm ent, Radiation Protection and Consequence Branch (N RR/D RA /A RC B )

TABLE OF CONTENTS

T AB L E O F CO NT E NT S.............................................................................................................. iii

LIST O F T AB LES......................................................................................................................... v

EXECUT IVE SUMM ARY............................................................................................................ vii

A B BR E V I AT IO NS....................................................................................................................... ix

1. INTRODUCT ION............................................................................................................ 1
2. BACKGROUND............................................................................................................. 1
3. IAR T ASK 1 RESULT S................................................................................................. 4

Item 1: Identif y applic able radiation dose-based regulations and their roles as operationa l lim its or d esig n c riteria.................................................................. 4 Item 2: D esc ribe the c oherent regulatory approac h to radiation protec tion f or w ork ers under norm al and em ergenc y c onditions...........................................7 O cc upational C ontrol R oom D oses..........................................................8 C ontrol R oom D esign C riteria................................................................. 12 Perf orm anc e-Based R egulations, D esign-Basis Ac c idents, and U se of Personal Protec tiv e Equipm ent...................................................13 Item 3: Prov ide an annotated bibliography of radiation protec tion rec om m endations f or w ork ers during em ergenc y c onditions f rom national and international organizations responsible f or m ak ing rec omm endations f or radiation pro tec tion sta ndards....................................15 Item 4: Prov ide an assessm ent of the identif ied design c riteria to c ontem porary radiologic al h ealth ef f ec ts...............................................................................16 REFERENCES............................................................................................................................ 19

iii

LIST OF TABLES

Table 1 D ose-Ba sed C riteria a nd R egulat ions.............................................................................. 5

v

EXECUTIVE

SUMMARY

With the inc reased interest in m odernized pow er reac tor f uels, inc luding ac c ident tolerant f uels and higher burnup and inc reased enric hm ent f uels, by U.S. N uc lear R egulatory C om m ission (NRC) lic ensees and industry, the N R C is c onsidering a rulem ak ing to enable the applic ation of these m odern f uel designs in an ef f ic ient m anner. To support this rulem ak ing determ ination, the Inc r eased E nr ic hm ent Wor k ing G r oup, through the O f f ic e of N uc lear R eac tor R egulation (N R R ),

sought assistanc e f rom the O f f ic e of N uc lear R egulatory R esearc h (RES) w ith inf orm al assistanc e request (IAR ) N R R-2022-019, Assessm ent of R adiation Protec tion R ec om m endations f or Em ergenc y Work ers, (August 26, 2022). The purposes of IAR N R R-2022-019 w ere to identif y N R C regulations that apply radiologic al c onsequenc es-as operational lim its or design c riteria, to desc ribe the regulatory approac hes that are applic able to w ork ers during norm al and em ergenc y c onditions, to dev elop an annotated bibliography of selec ted radiation protec tion rec om m endations that are applic able during an em ergenc y, and to prov ide an assessm ent of the identif ied design c riteria to the c ontem porary understanding of radiologic al health ef f ec ts.

N R C radiologic al regulations are based to a signif ic ant ex tent on the rec om m endations of the International C om m ission on R adiologic al Protec tion (IC R P) and on the U.S. N ational C ounc il on R adiation Protec tion and M easurem ents (N C R P). M eanw hile, the Federal Em ergenc y M anagem ent Agenc y (FEM A) is the Federal agenc y of the U.S. D epartm ent of H om eland Sec urity responsible f or helping people bef ore, during, and af ter disasters. For radiologic al inc idents, the U.S. Env ironm ental Protec tion Agenc y (EPA) is the primary Federal agency that establishes protec tiv e ac tion guides and planning guidanc e f or radiologic al inc idents. These organizations establish dose-based c riteria that are deem ed suf f ic iently low to prec lude determ inistic health ef f ec ts. Theref ore, these protec tiv e dose-based c riteria prov ide an adequate m argin that w ould m aintain the operators ability to m aintain a reac tor in a saf e c ondition under ac c ident c onditions.

The R ES staf f f ound that there is am ple operating and lic ensing ex perienc e, sc ientif ic data, and tec hnic al inf orm ation; num erous rec om m endations f rom national and international organizations responsible f or radiation protec tion standards; probabilistic risk assessm ent tec hnology; and regulatory prec edenc e that support a reev aluation of the c ontrol room design c riteria of G eneral D esign C riteria (G D C ) 19, C ontrol room, in Appendix A, G eneral D esign C riteria f or N uc lear Pow er Plants, to Title 10 of the C ode of Federal R egulations (10 CFR) Part 50, D om estic Lic ensing of Produc tion and Utilization Fac ilities, and 10 CFR 50.67(b)(2)(iii). This rev iew of the radiologic al f ram ew ork f or the c ontrol room design c riteria prov ides, in part, an initial basis f or N R C s realignm ent w ith the c urrent IC R P and N C R P rec om m endations and the FEM A and EPA f ederal response guidelines.

v ii

ABBREVIATIONS

10 CFR Title 10 of the U.S. C ode of Federal R egulations ADAM S Agenc y w ide D oc um ents Ac c ess and M anagem ent Sy stem ALARA as low as is reasonably ac hiev able ATF ac c ident tolerant f uel DBA design-basis ac c ident EPA U.S. Env ironm ental Protec tion Agenc y FEM A Federal Em ergenc y M anagem ent Agenc y FR Federal R egis ter GDC general design c riterion/criteria G Wd gigaw att-day (s )

Gy gray (s)

IAR inf orm al assistanc e request ICRP International C om m ission on R adiologic al Protec tion LD 50/60 lethal dose to 50 perc ent of the people w ithin 60 day s w ithout m edic al treatm ent LPZ low population zone LWR light-w ater reac tor M TU m etric ton( s) of uranium NCRP N ational C ounc il on R adiation Protec tion and M easurem ents NEIM A N uc lear Energy Innov ation and M odernization Ac t NRC U.S. N uc lear R egulatory C om m ission NRR O f f ic e of N uc lear R eac tor R egulation rem roentgen equiv alent m an RES O f f ic e of N uc lear R egulatory R esearc h SRM staf f requirem ents m em orandum SSC struc ture, sy stem, and c om ponent Sv siev er t( s)

TEDE total ef f ec tiv e dose equiv alent U uranium

ix

1. INT RODUCT ION

With the inc reased interest in m odernized pow er reac tor f uels, inc luding ac c ident tolerant f uels (ATFs) and higher burnup and inc reased enric hm ent f uels, by U.S. N uc lear R egulatory C om m ission (NRC)-lic ensees and industry, the NRC is c onsidering a rulem ak ing to enable the applic ation of these m odern f uel designs in an ef f ic ient m anner. To support this rulem ak ing determ ination, the Inc reased Enric hm ent Work ing G roup, through the O f f ic e of N uc lear R eac tor R egulation (N R R ), sought assistanc e f rom the O f f ic e of N uc lear R egulatory R esearc h (RES) w ith inf orm al assistanc e request (IAR ) N R R-2022-019, Assessm ent of R adiation Protec tion R ec om m endations f or Em ergenc y Work ers [R ef. 1] (August 26, 2022). The purposes of IAR NRR-2022-019 were to identif y N R C regulations that apply radiologic al c onsequenc es as operational lim its or design criteria, to desc ribe the regulatory approac hes that are applic able to w ork ers during norm al and em ergenc y c onditions, to dev elop an annotated bibliography of selec ted radiation protec tion rec om m endations that are applic able during an em ergenc y, and to prov ide an assessm ent of the identif ied design c riteria to c ontem porary understanding of radiologic al health ef f ec ts. This IAR is ex pec ted to help inf orm the NRC s inc reased enric hm ent rulem ak ing ac tiv ities and ultim ately enhanc e the agenc ys ability to perf orm its m ission w hen c onsidering and lic ensing f uels that apply inc reased enric hm ents. This report prov ides the results of the IAR.

2. BACKGROUND

ATFs are a set of new nuc lear f uel tec hnologies that hav e the potential to enhanc e saf ety at U.S. nuc lear pow er plants by of f ering better perf orm anc e during norm al operation, transient c onditions, and ac c ident sc enarios. O n J anuary 14, 2019, the President signed into law the N uc lear Energy Innov ation and M odernization Ac t (N EIM A). N EIM A Sec tion 107, C om m ission R eport on Ac c ident Tolerant Fuel, def ines ATF as a new tec hnology that does the f ollow ing:

(1) m ak es an ex isting c om m erc ial nuc lear reac tor m ore resistant to a nuc lear inc ident (as def ined in sec tion 11 of the Atom ic Energy Ac t of 1954 (42 U.S.C. 2014)); and

(2) low ers the c ost of elec tric ity ov er the lic ensed lif etim e of an ex isting c om m erc ial nuc lear reac tor.

Based on stak eholder interac tions, the staf f is aw are that industry plans to request higher f uel burnup lim its (i.e., abov e 62 gigaw att-day s per m etric ton of uranium (G Wd/M TU) rod av erage) along w ith the deploy m ent of ATF c onc epts. To ac hiev e higher burnup lim its, industry w ill need to request inc reases in f uel enric hm ent f rom the c urrent standard of 5.0 w eight perc ent uranium (U )-235 up to approx im ately 10.0 w eight perc ent U-235. In February 2019, industry identif ied potential adv antages of inc reased enric hm ent f uel f or light-w ater reac tor s (LWR s) in the N uc lear Energy Institute w hite paper The Ec onom ic Benef its and C hallenges w ith U tilizing Inc reased Enric hm ent and Fuel Burnup f or Light-Water R eac tors, issued February 2019 [R ef. 2]. In Septem ber 2021, the NRC staf f issued an update to the Projec t Plan to Prepare the U.S.

N uc lear R egulatory C om m ission f or Ef f ic ient Lic ensing of Ac c ident Tolerant Fuels, Version 1.2

[R ef. 3], that desc ribed the pursuit of higher burnup and inc reased enric hm ent as k ey c om ponents of industry ATF ef f orts. Industry plans to deploy batc h loads of f uels enric hed to lev els greater than the c urrent standard of 5.0 w eight perc ent U-235 by the m id to late 2020s.

1 The dev elopm ent of the c urrent regulatory f ram ew ork did not f oresee enric hm ents greater than 5.0 w eight perc ent U-235, and thus regulations w ere generally established w ith the ex pec tation that enric hm ents w ould be below this v alue w ith reasonable bounding assum ptions c ontained w ithin the saf ety analy sis m ethodologies. H ow ev er, som e spec if ic regulations disc uss suc h enric hm ents, suc h as Title 10 of the C ode of Federal R egulations (10 CFR) 50.6 8(b)(7) [R ef. 4],

w hic h requires that U-235 enric hm ent lev els in pow er reac tor f uel be no m ore than 5.0 perc ent by w eight.

In response to industry interest in LWR f uels enric hed to betw een 5.0 to 10.0 w eight perc ent U-235, the NRC staf f subm itted a rulem ak ing plan in SECY-21-0109, R ulem ak ing Plan on U se of Inc reased Enric hm ent of C onv entional and Ac c ident Toleranc e Fuel D esigns f or Light-Water R eac tors, dated D ec em ber 20, 2021 [ R ef. 5], requesting C om m ission approv al to initiate rulem ak ing to am end N R C requirem ents to f ac ilitate the use of LWR f uel c ontaining uranium enric hed to greater than 5.0 w eight perc ent U-235. If lef t unc hanged, the regulatory f ram ew ork c an ac c om m odate the use of LWR f uel c ontaining enric hm ents greater than 5.0w eight perc ent U-235 using lic ensee-spec if ic ex em ptions. H ow ev er, bec ause of the w idespread interest in these new f uels, the staf f ex pec ts m any lic ensees to pursue their use, m eaning that the staf f m ay hav e to proc ess m any ex em ptions to m eet industry dem and. In SECY-21-0109, the staff rec om m ended rulem ak ing to reduc e ex em ption requests and f ac ilitate inc reased regulatory ef f ic ienc y and c onsistenc y w hile c ontinuing to ensure saf ety. R ulem ak ing on this topic w ould allow the staf f to thoroughly rev iew the potential regulatory im plic ations of f uels enric hed to greater than 5.0 w eight perc ent U-235 and identif y and assess the potential c osts and benef its of c hanging regulatory requirem ents that im pac t their use. R ulem ak ing w ould also prov ide options f or generic resolutions of these issues and inv ite stak eholder partic ipation in dec isions af f ec ting this regulatory area, rather than on a c ase-by -c ase basis, as w ould result f rom the c urrent regulatory f ram ew ork.

The C om m ission approv ed the staf f s proposal to initiate rulem ak ing to am end requirem ents f or the use of LWR f uel c ontaining uranium enric hed to greater than 5.0w eight perc ent U-235 in Staff Requirem ents M em orandum (SRM )-SECY-21-0109, dated M arc h 16, 2022 [ R ef. 6]. The C om m ission stated that the prov isions of the rule should only apply to high-assay low -enric hed uranium1 f uel, both f or nonprolif eration and saf eguard reasons and to f oc us the staf f s analy sis on the range of enric hm ent m ost lik ely to be c ontem plated in f uturec om m erc ial applic ations.

In addition, the C om m ission direc ted the staf f to tak e the f ollow ing ac tions in this rulem ak ing:

  • In the regulatory basis and guidanc e, the staf f should appropriately address and analy ze f uel f ragm entation, reloc ation, and dispersal issues relev ant to f uels of high enric hm ent and burnup lev els.
  • The staf f should w or k ex peditiously w ith stak eholders to identif y and dev elop nec essary regulatory guidanc e and tec hnic al bases to support the ef f ec tiv e and ef f ic ient lic ensing of inc reased enric hm ent applic ations.

1 Uranium f uel enriched to greater than 5.0 and less than 20.0 weight percent U -235.

2

  • The staf f should tak e a risk-inf orm ed approac h w hen dev eloping this rule and the assoc iated regulatory basis and guidanc e.
  • The staf f should reex am ine the sc hedule to determ ine w hether k ey m ilestones c an be ac hiev ed sooner than projec ted by lev eraging ongoing regulatory innov ation ef f orts.

Sev eral perf orm anc e-based regulations use radiologic al ac c eptanc e c riteria. Both 10 CFR 50.67(b)(2) [R ef. 7] and G eneral D esign C riterion (GDC) 19, C ontrol room of Appendix A, G eneral D esign C riteria f or N uc lear Pow er Plants, to 10 CFR Part 50, D om estic Lic ensing of Produc tion and U tilization Fac ilities [R ef. 8], prov ide a spec if ic dose-based c riterion of 5 rem (50 m illisiev ert (m Sv )) total ef f ec tiv e dose equiv alent (TED E) f or dem onstrating the ac c eptability of the c ontrol room design. They represent a distinc t lay er of def ense in depth that assum es a m ajor ac c ident that results in substantial m eltdow n of the reac tor c ore w ith subsequent release of apprec iable quantities of f ission produc ts. In applic ation, they are perf orm anc e based, w hic h require that a lic ensee or applic ant prov ide a c ontrol room habitability design using traditional determ inistic radiologic al c onsequenc e analy ses m ethods to judge the ac c eptability of the design.

O v erall, lic ensees analy sis of rec ord D BA radiologic al c onsequenc e analy ses has a relativ ely sm all m argin to the c ontrol room design c riteria to generally m ax im ize operational f lex ibility. This has of ten resulted in instanc es in w hic h lic ensees hav e had to perf orm additional analy ses to dem onstrate c om plianc e w ithout additional saf ety benef it. This has bec om e unnec essarily burdensom e and has of ten led to a f oc us on saf ety v ersus c om plianc e debates betw een the N R C and lic ensees. In addition, the relativ ely sm all m argin to the c ontrol room des ign c riteria has resulted in the subm ission of lic ense am endm ent requests f or c hanges w ith low saf ety signif ic ance. It has also led to the oc c urrenc e of av oidable oc c upational ex posures c ontrolled by 10 CFR Part 20 in c ases in w hic h lic ensees hav e inc reased m aintenanc e ac tiv ities to m eet the 5 rem (50 m Sv ) TEDE c riterion.

With the prospec t of lic ensing inc reased enric hm ents greater than 5.0 and less than 20.0w eight perc ent U-235, the staf f antic ipates that, to dem onstrate c om plianc e w ithin their saf ety m argin, lic ensees w ould need to c ontinue perf orm ing potentially ex tensiv e analy ses to dem onstrate c om plianc e w ithin their saf ety m argin w ith no or lim ited additional saf ety benef it. Further, industry representativ es f or LWR s hav e indic ated they w ould be seek ing enric hm ents up to 10.0w eight perc ent U-235 and that m eeting the c riteria w hen transitioning to inc reased enric hm ent f uel w ould be c hallenging. Theref ore, industry organizations f or LWR s hav e c onv ey ed plans to c om m it resourc es to dev elop alternativ e approac hes to dem onstrate c om plianc e w ith the design c riteria.

The im pac t of inc reased pow er lev els, enric hm ent, and subsequently f uel burnup on the results of the lic ensees radiologic al c onsequenc e analy sis of rec ord f or the c om puted D BA is m ultif ac eted. H ow ev er, a rule of thum b is that an inc rease in pow er lev el has a linear ef f ec t on c om puted radiologic al c onsequenc es. With an inc rease in U-235 enric hm ent nec essary to reac h the desired burnup lev el, the num ber of f issions w ithin the reac tor c ore sourc e term also inc reases, w hic h inc reases the resulting c om puted radiologic al c onsequenc es. The im pac t of

3 higher burnup on radiologic al c onsequenc es is nonlinear w here the abundanc e of dif f erent radionuc lides in the f uel peak at dif f erent burnup lev els. This c ontinuously c hanging radionuc lide m ix due to burnup has a v ary ing im pac t on radiologic al c onsequenc es. Theref ore, depending on how the reac tor c ore is designed w ith inc reased U-235 enric hm ent f uel elem ents and operation at higher burnup lev els to reac h longer c y c le tim e, the im pac t on radiologic al c onsequenc es c om puted to dem onstrate c om plianc e w ith the c ontrol room des ign c riteria w ould inc rease and subsequently dec rease the retained m argin m aintained by the lic ensee to prov ide operational f lex ibility.

The NRC rec ognizes the c hallenges that lic ensees f ac e to retain m argin w ithin their lic ensing basis and the sm all am ount of m argin to the c ontrol room design c riteria itself. The N R C does not w ant to unnec essarily penalize lic ensees f or seek ing inc reased enric hm ents that m ay then result in m argin reduc tions and thereby requiring lic ensees to perf orm potentially ex tensiv e analy ses to dem onstrate c om plianc e w ithout a c om m ensurate inc rease in saf ety.

This IAR requests RES staf f to doc um ent its assessm ent f indings in a public ly av ailable m em orandum to NRR. Additionally, t he m em orandum should prov ide f or and identif y the f ollow ing task s:

1. Identif y applic able radiation dose-based regulations and their roles as operational lim its or design c riteria;
2. D esc ribe the c oherent regulatory approac h to radiation protec tion f or w ork ers under norm al and em ergenc y c onditions;
3. Perf orm an annotated bibliography of radiation protec tion rec om m endations f or w ork ers during em ergenc y c onditions f rom national and international organizations responsible f or m ak ing rec om m endations f or radiation protec tion standards; and
4. Prov ide an assessm ent of the identif ied design c riteria to c ontem porary radiologic al health ef f ec ts.
3. IAR T ASK 1 RESULT S

Item 1: Identify applicable radiation dose-based regulations and their r oles as operational limits or design criteria.

For this item, the RES staff researc hed the applic able regulations in v arious parts2 of 10 CFR to sum m arize the dose-based siting and design c riteria as w ell as oc c upational dose lim its.

Table 1 prov ides this sum m ar y.

2 Specif ically, the staf f exam ined 10 C FR Part 50, 10 C FR Part 100, Reactor Site Criteria, and 10 C FR Part 52, Licenses, Certif ications, and Approvals f or Nuclear Power Plants.

4 T able 1D ose-Based Criteria and Regulations

Operati onal Regulation Cri teri a Limit or Siting/Design Cri teri a 10 C FR 50.34(a)(ii)(D)(1) [Re f. 10] 0.25 sievert (Sv) 25 roentgen equivalent m an ( re m) total ef f ective dose equivalent Siting criteria (TED E) f or any 2-hour period f ollowing postulated f ission product release 10 C FR 50.34(a)(ii)(D)(2) 0.25 Sv (25 rem) TEDE at low population zone ( LPZ) boundary resulting f rom Siting criteria exposure to th e radioactive cloud f rom postulated f ission product release 10 C FR 50.67(b)(2)(i) 0.25 Sv (25 rem)a TEDE f or any 2-hour period f ollowing postulated f ission product Design criteria release 10 C FR 50.67(b)(2)(ii) 0.25 Sv (25 rem) TEDE at LPZ boundary resulting f rom exposure to the Design criteria radioactive cloud f rom postulated f ission product release 10 C FR 50.67(b)(2)(iii) 0.05 Sv (5 rem) Design criteria Appendix A to 10 C FR Part 50, GD C 19 0.05 Sv (5 rem) Design criteria 10 C FR 52.17(a)(1)(ix)(A) [Re f. 11] 0.25 Sv (25 rem) TED E f o r a n y 2-hour period f ollowing postulated f ission product Design criteria release 10 C FR 52.17(a)(1)(ix)(B) 0.25 Sv (25 rem) TEDE at LPZ boundary resulting f rom exposure to the Design criteria radioactive cloud f rom postulated f ission product release 10 C FR 52.47(a)(2)(iv)(A) [Re f. 12] 0.25 Sv (25 rem) TED E f o r a n y 2-hour period f ollowing postulated f ission product Design criteria release 10 C FR 52.47(a)(2)(iv)(B) 0.25 Sv (25 rem) TEDE at LPZ boundary resulting f rom exposure to the Design criteria radioactive cloud f rom postulated f ission product release 10 C FR 52.79(a)(1)(vi)(A) [Re f. 13] 0.25 Sv (25 rem) TED E f o r a n y 2-hour period f ollowing postulated f ission product Design criteria release 10 CFR 52.79(a)(1)(vi)(B) 0.25 Sv (25 rem) TEDE at LPZ boundary resulting f rom exposure to the Design criteria radioactive cloud f rom postulated f ission product release 10 C FR 52.137(a)(2)(iv)(A) [Re f. 14] 0.25 Sv (25 rem ) TEDE at any point on the exclusion area boundary f or any Design criteria 2-hour period f ollowing the onset of the postulated f ission product release 10 CFR 52.137(a)(2)(iv)(B) 0.25 Sv (25 rem) TEDE at LPZ boundary resulting f rom exposure to the Design criteria radioactive cloud f rom postulated f ission product release 10 C FR 52.157(c)(3)(d)(1) [Re f. 15] 0.25 Sv (25 rem) TED E f o r a n y 2-hour period f ollowing postulated f ission product Design criteria release 10 C FR 52.157(c)(3)(d)(2) 0.25 Sv (25 rem) TEDE at LPZ boundary resulting f rom exposure to the Design criteria radioactive cloud f rom postulated f ission product release whole body in excess of 0.25 Sv (25 rem)b or a total radiation dose in excess of 10 C FR 100.11(a)(1) [Re f. 16] 3 Sv (300 rem ) b to the thyroid f rom iodine exposure f or any 2-hour period Siting criteria f ollowing postulated f ission product release Whole body in excess of 0.25 Sv (25 rem)b or a total radiation dose in excess of 10 C FR 100.11(a)(2) 3 Sv (300 rem ) b to the thyroid f rom iodine exposure at LPZ boundary resulting Siting criteria f rom exposure to the radioactive cloud f rom postulated f ission product release Operati onal Regulation Cri teri a Limit or Siting/Design Cri teri a Additional doses f rom planned special exposures and all doses in excess of lim its shal l not exceed the num erical lim its in 10 C FR 20.1201(a) in 1 year 10 C FR 20.1206(e)(2) [Re f. 17] (i.e., individuals can receive doses equal to a total of tw i c e th e lim its in Operational lim it 10 C FR 20.1201(a) ) not to exceed f ive tim es the doses in 10 C FR 20.1201(a) during an individuals lif etim e (e.g., 0.25 Sv (25 rem))

More lim iting of (1) TED E 0.05 Sv (5 rem) or (2) the sum of the deep-dose 10 C FR 20.1201(a)(i) [Re f. 18] equivalent and com m itted dose equivalent to any organ or tissue of 0.5 Sv Operational lim it (50 rem ). Oth e r lim its apply to lens of the eye and shallow -dose equivalent to the skin.

a. The use of 0.25 Sv (25 rem ) TEDE is not intended to im ply that this value constitutes an acceptable lim it f or em ergency doses to the public under ac cident conditions. Rather, this 0.25 Sv (25 rem ) TEDE value has been stated in this section as a ref erence value, which can be used in the evaluation of proposed design-basis changes with respect to potential reactor accidents of exceedingly low probability of occurrence and low risk of public exposure to radiation.
b. The whole body dose of 0.25 Sv (25 rem ) ref erred to above corresponds num erically to the once in a lif etim e accidental or em ergency dose f or radiation workers that, according to recom m endations by the National Council on Radiation Protection and Measurem ents (NCRP), m ay be disregarded in the determ ination of their radiation exposure status (see National Bureau of Standards Handbook 69, Maxim um Perm issible Body Burdens and Maxim um Perm issible Concentrations of Radionuclides in Air and in Water f or Occupational Exposure, dated June 5, 1959 [Re f. 19]). However, neither its use nor that of the 3 Sv (300 rem ) value f or thyroid exposure as set f orth in these site criteria guides are intended to im ply that these num bers constitute acceptable lim its f or em ergency doses to the public under accident conditions. Rather, this 0.25 Sv (25 rem ) whole body value and the 3 Sv (300 rem ) thyroid value have been set f orth in these guides as ref erence values, which can be used in the evaluation of reactor sites with respect to potential reactor accidents of exceedingly low probability of occurrence, and low risk of public exposure to radiation.

Item 2: D escr ibe the coher ent regulatory approach to radiation protection for w orkers under normal and emergency conditions.

This sec tion prov ides bac k ground on radiation protec tion regulations and prac tic es during norm al and em ergenc y c onditions. First, oc c upational dose lim its are desc ribed bec ause they pertain prim arily to norm al operating c onditionsthe c onditions m ost prev alent during pow er plant operations. Then the c ontrol room design c riteria are desc ribed bec ause they are used to guide and assess the design of sy stem s in the c ontex t of norm al and em ergenc y c onditions.

Lastly, the applic ability of personal protec tiv e equipm ent and other m itigativ e m easures during em ergenc y c onditions is desc ribed to ex plain how the N R C has traditionally not c redited these m easures during saf ety ev aluations of c ontrol room designs; how ev er, their use c an be ex pec ted during em ergenc y c onditions.

R adiation protec tion c onc erns the protec tion of indiv iduals, their progeny, and hum ank ind, w hile still allow ing nec essary ac tiv ities f rom w hic h radiation ex posure m ight result. The aim of radiation protec tion is generally to prev ent detrim ental nonstoc hastic, or determ inistic, ef f ec ts (e.g., c atarac ts, sk in reddening, or ery them a) and to lim it the probability of stoc hastic ef f ec ts (i.e., c anc er) to lev els deem ed to be ac c eptable. N onstoc hastic ef f ec ts are prev ented by setting dose equiv alent lim its at suf f ic iently low v alues so that these ef f ec ts are not ex perienc ed as a result of ex posures w ithin the lim its. Stoc hastic ef f ec ts are lim ited by k eeping all justif iable ex posures as low as is reasonably ac hiev able (ALAR A), ec onom ic and soc ial f ac tors being tak en into ac c ount, subjec t alw ay s to the boundary c ondition that the applic able dose equiv alent lim its shall not be ex c eeded.

An additional aim of radiation protec tion is to ensure that prac tic es inv olv ing radiation ex posure are justif ied w ith regard to the benef it of the ac tiv ity c om pared to the risk s inc urred by the w ork ers w ho prov ide the benef it. Theref ore, w hen dev eloping the num eric al oc c upational dose lim it rec om m endations that apply to stoc hastic ex posure and upon w hic h the N R C regulations are based, the International C om m ission on R adiologic al Protec tion (ICRP ) ensured that the risk of f atality f rom stoc hastic ef f ec ts of radiation on the population of w ork ers w as c om parable to the risk of f atalities to w ork ers in other industries c onsidered saf e. This approac h led to c onserv ativ e dose lim itations that hav e serv ed the radiation w ork er c om m unity w ell but m ay not hav e been appropriate to apply as design c riteria that enc om pass ex pec ted sy stem perf orm anc e during highly unlik ely em ergenc y situations at pow er plants.

The standards set f orth in 10 CFR Part 20, Standards f or Protec tion Against R adiation

[R ef. 20], are based in part on the rec om m endations of the IC R P and its U.S. c ounterpart, the NCRP. In 1977, w ith Public ation 26, R ec om m endations of the IC R P (ICRP 26) [R ef. 21], the IC R P issued rev ised rec om m endations f or a sy stem of radiation dose lim itations. The NRC adopted this sy stem on M ay 21, 1991, in its am endm ent of 10 CFR Part 20. A s suc h, 10 CFR Part 20 puts into prac tic e rec om m endations f rom ICRP 26 and c ertain subsequent IC R P public ations. A s disc ussed in the Federal R egis ter (FR) (56 FR 23360; M ay 21, 1991)

[R ef. 22]

In adopting the basic tenets of the IC R P sy stem of dose lim itation, the N uc lear R egulatory C om m ission rec ognizes that, w hen applic ation of the dose lim its is c om bined w ith the princ iple of k eeping all radiation ex posures as low as is reasonably ac hiev able, the degree of protec tion c ould be signif ic antly greater

7 than f rom rely ing upon the dose lim its alone.

The regulations in 10 CFR Part 20 apply these standards to all ex posure situationsnor m al and abnorm albut an ex plic it ex em ption is also prov ided if c om plianc e w ould lim it ac tions that m ay be nec essary to protec t health and saf ety.

The IC R P 26 sy stem of dose lim itation has the f ollow ing objec tiv es:

  • No prac tic e shall be adopted unless its introduc tion produc es a positiv e net benef it.
  • All ex posures shall be k ept ALAR A, ec onom ic and soc ial f ac tors being tak en into ac c ount.
  • The dose equiv alent to indiv iduals shall not ex c eed the lim its rec om m ended f or the appropriate c irc um stanc es by the C om m ission.

To ac hiev e these objec tiv es, this sy stem of dose lim itations ensures that no sourc e of ex posure is unjustif ied in relation to its benef its or those of any av ailable alternativ e, that any nec essary ex posures are k ept ALAR A, and that the dose equiv alents rec eiv ed do not ex c eed c ertain spec if ied lim its. As suc h, any nec essary ex posures are k ept ALAR A and that the dose equiv alents rec eiv ed do not ex c eed c ertain spec if ied lim its.

O c c upational C ontrol R oom D os es

The NRCs c urrent regulatory approac h to c ontrol room operator radiation ex posure c onserv ativ ely adopts the tenets of international and national radiation protec tion standards and rec om m endations. As disc ussed abov e, this approac h is prov ided in G D C 19; 10 CFR 50.67, Ac c ident sourc e term ; 10 CFR Part 20; 10 CFR 50.47(b)(11); and, by ref erenc e, the U.S. Env ironm ental Protec tion Agenc y (EPA) PAG M anual: Protec tiv e Ac tion G uides and Planning G uidanc e f or R adiologic al Inc idents, issued J anuary 2017 [ R ef. 23].

ICRP 26, Sec tion G, Applic ation to the D if f erent Ty pes of Ex posure, prov ides rec om m endations f or oc c upational ex posure. These rec om m endations state in part that as f ar as is reasonably prac tic able, the m ethods f or restric ting oc c upational ex posure should be applied to the sourc e of radiation and to f eatures of the w ork plac e. The use of personal protec tiv e equipm ent should, in general, supplem ent these m ore f undam ental prov isions.

Theref ore, em phasis should be on intrinsic saf ety in the w ork plac e (e.g., phy sic al design and operating c harac teristic s of sy stem s) and only sec ondarily on protec tion that depends on a w ork ers ow n ac tions. H ow ev er, under abnorm al or em ergenc y situations, arrangem ents are m ade not only w ith respec t to the detec tion and assessm ent of dose or intak e, but also w ith respec t to the m itigating interv entions that m ay hav e to be applied to f urther protec t w ork ers (e.g., personal protec tiv e equipm ent, adm inistration of prophy lac tic drugs, and ev ac uation).

It is signif ic ant to note that the c ontents of Appendix A to 10 CFR Part 50 are design c riteria and not operational lim its. Ev ents and situations not addressed in the f ac ility s design basis c ould in f ac t result in c onditions f or w hic h the design m ight not prov ide the reasonable assuranc e sought. For ex am ple, m ultiple f ailures that are not the result of a c om m on m ode f ailure are not required to be addressed in the design basis of the c ontrol room. Should suc h m ultiple f ailures oc c ur, the perf orm anc e of the SSCs m ay not be adequate and c om pensatory plant operations

8 m ight be nec essary. The N R C s f oc us on def ense in depth prov ides assuranc e that ev en if these bey ond-design-basis c onditions oc c ur, the plant design w ill m itigate the risk to occupational w ork ers and public health and saf ety.

The standards f or protec tion against radiation established in 10 CFR Part 20 are generally c onsistent w ith the rec om m endations of IC R P 26, the later IC R P rec om m endations f rom ICRP Public ation 60, 1990 R ec om m endations of the International C om m ission on R adiologic al Protec tion, issued 1991 (ICRP 60) [R ef. 24], and the ICRP Public ation 103, The 2007 R ec om m endations of the International C om m ission on R adiologic al Protec tion, issued 2007 (ICRP 103) [R ef. 25]. The rule applies the ICRP 26 rec om m endations to all ex posure situationsnorm al and abnorm al but also prov ides an ex plic it ex em ption f or c ases in w hic h c om plianc e w ould lim it ac tions that m ay be nec essary to protec t health and saf ety. In an em ergenc y situation, the c ontinued ac tions of the c ontrol room operators are f undam ental to protec ting the health and saf ety of the public and other w ork ers at the f ac ility. Thus, if the ev ent should result in c onditions bey ond the design basis of the c ontrol room habitability sy stem s, thereby c ausing ac tual radiation ex posures that ex c eed the norm al oc c upational lim its, acc ess and oc c upanc y of the c ontrol room m ay c ontinue. There are, how ev er, additional regulatory prov isions that bear on the c ontrol of oc c upational ex posures during em ergenc ies.

The N R C has established em ergenc y planning regulations in Appendix E, Em ergenc y Planning and Preparedness f or Produc tion and U tilization Fac ilities, to 10 CFR Part 50, and planning standards f or nuc lear pow er reac tors in 10 CFR 50.47, Em ergenc y p lans, f or the purpose of prov iding reasonable assuranc e that adequate protec tiv e m easures c an and w ill be tak en in the ev ent of a radiologic al em ergenc y. The regulation at 10 CFR 50.47(b)(11) addresses c ontrol of radiologic al ex posures in an em ergenc y and states that the m eans f or c ontrolling radiologic al ex posures shall inc lude ex posure guidelines c onsistent w ith EPA Em ergenc y Work er and Lif esav ing Ac tiv ity Protec tion Ac tion G uides. The ev ents that c ould result inc ontrol room radiation ex posures c om parable to the 10 CFR Part 20 norm al oc c upational ex posure lim it of 0.05 Sv (5 rem ) TE D E w ould r esult in the ac tiv ation of the f ac ility s em er genc y r esponse plan and the em ergenc y response organization. R egulatory G uide 1.101, Em ergenc y R esponse Planning and Preparedness f or N uc lear Pow er R eac tors, R ev ision 6, issued J une 2021 [ R ef. 26],

endorses N U R EG-0654/FEM A -REP-1, C riteria f or Preparation and Ev aluation of R adiologic al Em ergenc y R esponse Plans and Preparedness in Support of N uc lear Pow er Plants, R ev ision 2, issued D ec em ber 2019 [ R ef. 27]. NUREG -0654/FEM A -REP-1 prov ides spec if ic ac c eptanc e c riteria f or c om ply ing w ith the standards set f orth in 10 CFR 50.47, w hic h designates an on-shif t em ergenc y c oordinator. The on-shif t em ergenc y c oordinator has the authority and responsibility to im m ediately and unilaterally initiate any em ergenc y ac tions. These em ergenc y ac tions inc lude establishing higher ex posure lim its f or c ontrol room operators if nec essary to prov ide public health and saf ety. The e m ergenc y c oordinator c an also authorize issuing potassium-iodide tablets f or thy roid protec tion or use of em ergenc y respiratory protec tion equipm ent.

This radiation protec tion f ram ew ork is c onsistent w ith the IC R P rec om m endations as f ollow s:

ICRP 26

(paragraph 113) Situations m ay oc c ur inf requently during norm al operations w hen it m ay be nec essary to perm it a f ew w ork ers to rec eiv e dose equiv alents in ex c ess of the rec om m ended lim its. In suc h c irc um stanc es ex ternal ex posures or

9 intak es of radioac tiv e m aterial m ay be perm itted prov ided the dose-equiv alent c om m itm ent does not ex c eed tw ic e the relev ant annual lim it in any single ev ent, and, in a lif etim e, f iv e tim es this lim it. The C om m ission w ishes to em phasize that ex ternal ex posures or intak es of this m agnitude are only justif ied w hen alternativ e tec hniques, w hic h do not inv olv e suc h ex posure of w ork ers, are either unav ailable or im prac tic able (see also paragraph 171).

(paragraph 114) Planned spec ial ex posures should not be perm itted if the w ork er has prev iously rec eiv ed abnorm al ex posures resulting in dose equiv alents in ex c ess of f iv e tim es the relev ant annual lim it. Planned spec ial ex posures should not be perm itted f or w om en of reproduc tiv e c apac ity. D ose equiv alents resulting f rom planned spec ial ex posures should be rec orded w ith those f rom usual ex posures, but any ex c ess ov er the lim its rec om m ended in paragraphs 103 et s eq. should not by itself c onstitute a reason f or ex c luding a w ork er f rom his usual oc c upation. (Ac c idental and em ergenc y ex posures are disc ussed in sec tion G, paragraph 160).

(paragraph 167) As f ar as is reasonably prac tic able, the arrangem ents f or restric ting oc c upational ex posure should be those applied to the sourc e of radiation and to f eatures of the w ork plac e. The use of personal protec tiv e equipm ent should in general be supplem entary to these m ore f undam ental prov isions. The em phasis should thus be on intrinsic saf ety in the w ork plac e and only sec ondarily on protec tion that depends on the w ork ers ow n ac tions.

(paragraph 169) Ex ternal ex posure m ay be restric ted by the use of shielding, distanc e and lim itation of tim e of ex posure. Shielding produc es intrinsic ally saf e c onditions in the w ork plac e. D istanc e and lim itation of tim e of ex posure require the c aref ul training and superv ision of w ork ers. C om plete protec tion is af f orded by the use of c losed installations prov iding v irtually c om plete shielding f or the radiation sourc e and ef f ec tiv ely prev enting ac c ess. H ow ev er, the f ailure of suc h equipm ent as interloc k sy stem s m ay c ause ex c essiv e ex posure. O perating proc edures should theref ore inc lude routine c hec k s of suc h sy stem s.

(paragraph 189) The em ergenc y plans (w hic h should, as f ar as prac tic able, be draw n up in adv anc e) should hav e three c learly distinguished objectiv es. The f irst is to restric t ex posures as f ar as reasonably ac hiev able and, in partic ular, to attem pt to av oid ex posures abov e the dose-equiv alent lim its. The sec ond is to bring the situation bac k under c ontrol, and the third is to obtain inf orm ation f or assessing the c auses and c onsequenc es of the ev ent.

(paragraph 191) D uring the im m ediate c ourse of a serious inc ident, urgent ac tion to sav e lif e, to prev ent injuries, or to prev ent a substantial inc rease in the sc ale of the inc ident, m ay require that som e w ork ers be ex posed in ex c ess of the lim its.

(paragraph 192) O nc e the initial ev ent has been brought under c ontrol, there rem ains the problem of rem edial w ork. It w ill usually be appropriate to c arry this out w hile m aintaining c om plianc e w ith the C om m issions [i.e., the IC R Ps]

rec om m ended lim its but, ex c eptionally, there m ay be situations w hic h the use of

10 the lim its w ould inv olv e ex c essiv e ex pense or an ex c essiv e inv olv em ent of people and tim e. C onsideration should then be giv en to the appropriateness of authorizing a planned spec ial ex posure f or a lim ited num ber of indiv iduals to c arry out v arious essential operations, leav ing the rem ainder to be done in c om plianc e w ith the lim its.

ICRP 60

(paragraph 195) The initial treatm ent of potential ex posur es should f orm part of the sy stem of protec tion applied to prac tic es, but it should be rec ognised that the ex posures, if they oc c ur, m ay lead to interv ention. At this stage, there should be tw o objec tiv es, prev ention and m itigation. Prev ention is the reduc tion of the probability of the sequenc es of ev ents that m ay c ause or inc rease radiation ex posures. It inv olv es m aintaining the reliability of all the operating and saf ety sy stem s and of the assoc iated w ork ing proc edures. M itigation is the lim itation and reduc tion of the ex posures if any of these sequenc es do oc c ur. It inv olv es the use of engineered saf ety f eatures and operational proc edures to c ontrol eac h sequenc e of ev ents w ith the aim of lim iting its c onsequenc es, should it oc c ur.

The arrangem ents f or m itigation should not be restric ted to plans f or interv ention.

A great deal c an be ac c om plished at the stages of design and operation to reduc e the c onsequenc es of ac c ident sequenc es so that interv ention m ay not bec om e nec essary. It is dif f ic ult to c om pare, and to c om bine, the benef it of a reduc tion in probability (prev ention) w ith that of a reduc tion in dose (m itigation) bec ause a reduc tion in probability by a f ac tor is not usually seen as equiv alent to a reduc tion in dose by the sam e f ac tor.

(paragraph S49) The benef it of a partic ular protec tiv e ac tion w ithin a program m e of interv ention should be judged on the basis of the reduc tion in dose ac hiev ed or ex pec ted by that spec if ic protec tiv e ac tion, i.e. the dose av erted. Thus, eac h protec tiv e ac tion has to be c onsidered on its ow n m erits. In addition, how ev er, the doses that w ould be inc urred v ia all the relev ant pathw ay s of ex posure, som e subjec t to protec tiv e ac tions and som e not, should be assessed. If the total dose in som e indiv iduals is so high as to be unac c eptable ev en in an em ergenc y, the f easibility of additional protec tiv e ac tions inf luenc ing the m ajor c ontributions to the total dose should be urgently rev iew ed. D oses c ausing serious determ inistic ef f ec ts, or a high probability of stoc hastic ef f ec ts w ould c all f or suc h a rev iew.

(paragraph S50) O c c upational ex posures of em ergenc y team s during em ergenc y and rem edial ac tion c an be lim ited by operational c ontrols. Som e relax ation of the c ontrols f or norm al situations c an be perm itted in serious ac c idents w ithout low ering the long-term lev el of protec tion. This relax ation should not perm it the ex posures in the c ontrol of the ac c ident and in the im m ediate and urgent rem edial w ork to giv e ef f ec tiv e doses of m ore than about 0.5Sv [50 rem ] ex c ept f or lif e-sav i ng ac tions, w hic h c an rarely be lim ited by dosim etric assessm ents.

The equiv alent dose to sk in should not be allow ed to ex c eed about 5 Sv

[500 rem ]. O nc e the im m ediate em ergenc y is under c ontrol, rem edial w ork should be treated as part of the oc c upational ex posure inc urred in a prac tic e.

11 ICRP 103

(paragraph u) Em ergenc y ex posure situations inc lude c onsideration of em ergenc y preparedness and em ergenc y response. Em ergenc y preparedness should inc lude planning f or the im plem entation of optim ised protec tion strategies w hic h hav e the purpose of reduc ing ex posures, should the em ergenc y oc c ur, to below the selec ted v alue of the ref erenc e lev el. D uring em ergenc y response, the ref erenc e lev el w ould ac t as a benc hm ark f or ev aluating the ef f ec tiv eness of protec tiv e ac tions and as one input into the need f or establishing f urther ac tions.

C ontrol R oom D es ign C riteria

The c ontrol room design c riteria, as desc ribed in G D C 19, c all f or the plant design to inc orporate radiation protec tion f eatures that, in the ev ent of an em er genc y, w ould m aintain the radiation ex posure of c ontrol room personnel to a lev el equal to their norm al oc c upational ex posure lim its.

It is generally understood that an objec tiv e of the c riteria is to ensure that the design of the c ontrol room and its habitability sy stem s w as suc h that a shirt-sleev ed env ironm ent w as prov ided f or the c ontrol room operators. Ex c eeding the c ontrol room d esign c riteria num eric al v alue of 0.05 Sv (5 rem ) TED E w ould not im pose an im m ediate health ef f ec t or ev en requirean ev ac uation requirem ent on the c ontrol room operators. H ow ev er, hav ing a num eric al c riterion f or designers to ref erenc e w hen ac c ounting f or ac c idents in their designs is nec essary and c onsistent w ith the IC R P. Though setting the c riteria to the norm al oc c upationa l dose lim its to assess plant perf orm anc e during em ergenc y c onditions m ay m ask its intended purposes w hen also assessing other regulations. To prov ide c ontex t, w e highlight a parallel betw een the c ontrol room design c riteria and the oc c upational dose lim its in 10 CFR 20.1206, Planned spec ial ex posures. As long as lic ensees m eet c ertain c riteria, 10 CFR Part 20 allow s planned spec ial ex posures up to tw ic e the annual oc c upational dose lim its prov ided that lif etim e ex posure of 0.25 Sv (25 rem ) TED E is not ex c eeded. As disc ussed in 56 FR 23372, planned spec ial ex posures w ere retained in the am ended 10 CFR Part 20 in part to address the f ac t that under the new sy stem of dose lim itation w ork ers w ould no longer hav e a lif etim e dose lim it, or dose bank, equaling f iv e tim es the quantity of the age of the w ork er m inus 18, or 5(N 18). While the use of planned spec ial ex posures w as predic ted to be inf requent, it w as ex pec ted that they w ould be used if the elim ination of the lif etim e dose lim its m ight c reate a sev ere handic ap to the lic ensees operations. Theref ore, the C om m ission c onc luded that an inf requent ex posure of w ork ers up to tw ic e the oc c upational dose lim it w as adequately protec tiv e of radiation w ork ers.

Now, the c ontrol room design c riteria are applic able to a low f requenc y ev ent, w hereas the planned spec ial ex posure is designed f or a m ore lik ely routine radiologic al ex posure ev ent.

Based on a potential radiologic al risk eac h rule is intending to protec t against, the applic able dose c onstraints f or less lik ely em ergenc y ev ents should be aligned (higher) than the dose c onstraints f or the low er f requenc y ev ents (planned spec ial ex posures) at 0.10 siev ert (Sv )

(10 roentgen equiv alent m an (rem )) as w ell as routine oc c upational ex posures 0.05 Sv (5 rem ).

ICRP 26

(paragraph 190) Although, by their nature, ac c idental ex posures are not subjec t to c ontrol, their m agnitude c an to som e ex tent be lim ited by interv ention, espec ially if attention has been paid to this possibility during the design of installations and equipm ent and the preparation of operating instruc tions.

12 ICRP 60

(paragraph 224) O c c upational ex posures direc tly due to an ac c ident c an be lim ited only by the design of the plant and its protec tiv e f eatures and by the prov ision of em ergenc y proc edures. Ideally, the aim should be to k eep the doses w ithin those perm itted in norm al c onditions, but, w hile this is usually possible, it m ay not alw ay s be so in serious ac c idents.

ICRP 103

(paragraph r) The proc ess of planning protec tion in planned ex posure situations should inc lude c onsideration of dev iations f rom norm al operating proc edures inc luding ac c idents and m alic ious ev ents.... Potential ex posures are not planned but they c an be antic ipated. The designer and the user of a sourc e m ust theref ore tak e ac tions to reduc e the lik elihood of a potential ex posure happening, suc h as assessing the probability of an ev ent and introduc ing engineering saf eguards c om m ensurate to this probability.

Performanc e-Bas ed R egulations, D es ign-Basis Ac c ident s, and U s e of Pers onal Protec tiv e Equipment

The c ontrol room design c riteria regulations are perf orm anc e based, requiring a lic ensee or applic ant to prov ide a c ontrol room habitability design that m eets a spec if ied dose-based c riterion. Spec if ic ally, they establish perf orm anc e requirem ents f or c ontrol room habitability sy stem s that w ould be c alled upon in a DBA. This is direc tly responsiv e to the ICRP rec om m endations to em phasize intrinsic saf ety f eatures. These sy stem s serv e the f unc tion of m itigation, thereby m inim izing the need f or interv ention, w hic h m ight inv olv e ev ac uation, adm inistration of prophy lac tic drugs, or use of personal protec tiv e equipm ent that c ould im pair the operators ability to perf orm the ac tions nec essary to prov ide adequate public health and saf ety. 3 To dem onstrate c om plianc e, lic ensees perf orm traditional determ inistic DBA radiologic al c onsequenc e analy ses using regulatory sourc e term s w hic h are rev iew ed and approv ed by the staf f. Perf orm anc e-based regulations, suc h as 10 CFR 50.67(b)(2)(iii) and GDC 19, do not prov ide presc riptiv e m ethodologies to determ ine the regulations are m et and theref ore do not require lic ensees to use spec if ic designs or m ethodologies to c om ply w ith the regulations. As suc h, N R C RG s and standard rev iew plans prov ide ac c eptable m ethodologies that lic ensees c an use to perf orm the analy ses, w hic h are then inc orporated, as appropriate, into the lic ensing basis f or the lic ensee s f ac ility. In general, the staf f has generally not ac c epted, ex c ept in interim situations, personal protec tiv e m easures suc h as respiratory protec tion or prophy lac tic drugs w hic h is c onsistent w ith the IC R P rec om m endations.

The lic ensing proc ess is based on the c onc ept of def ensein depth, in w hic h pow er plant design, operation, siting, and em ergenc y planning c om prise independent lay ers of nuc lear saf ety. This approac h enc ourages nuc lear plant designers to inc orporate sev eral lines of def ense in order to m aintain the ef f ec tiv eness of phy sic al barriers betw een radiation sourc es and m aterials f rom w ork ers, m em bers of the public, and the env ironm ent in operational states and, f or som e

3 This is also consistent with 10 C FR 20.1701, U se of process or other engineering controls" [Re f. 28], w h i c h requires the licensee to use, to the extent practical, process or other engineering controls (e.g., containm ent, decontam ination, or ventilation) to control the concentrations of radioactive m aterials in air.

13 barriers, in ac c ident c onditions. The approac h uses DBAs w ith regulatory sourc e term s to c om pute radiologic al c onsequenc es w hen assessing the ef f ec tiv eness of eac h line of def ense.

A s suc h, the DBAs establish and c onf irm the design basis of the nuc lear f ac ility, inc luding its saf ety-related SSCs and item s im portant to saf ety, ensuring that the plant design m eets the saf ety and num eric al radiologic al c riteria set f orth in regulations and subsequent guidanc e. D ue to the c onserv ativ e, determ inistic nature of the DBA analy ses, there is a m argin of saf ety suc h that c ontrol room design m ay be adequate f or m any ev ents bey ond the design basis. H ow ev er, it rem ains possible that ac tual radiation ex posures f rom bey ond-design-basis ev ents, or those resulting f rom m ultiple f ailures of the c ontrol room habitability sy stem s c oinc ident w ith a DBA, c ould ex c eed the design c riteria. In suc h an ev ent, the radiation ex posures are still subjec t to 10 CFR Part 20 f irst and then the f ac ility s em ergenc y plan, w hic h w ould us e personal protec tiv e equipm ent, if nec essary, supplem entary to these m ore f undam ental design prov isions. U nder em ergenc y c onditions, both m aintain radiation ex posures to be ALARA and, to the ex tent prac tic able, lim ited to norm al oc c upational lev els. This is c onsistent w ith the ICRP 26, I CRP 60, and IC R P 103 rec om m endations.

ICRP 26

(paragraph 167) As f ar as is reasonably prac tic able, the arrangem ents f or restric ting oc c upational ex posure should be applied to the sourc e of radiation and to f eatures of the w ork plac e. The use of personal protec tiv e equipm ent should in general be supplem entary to these m ore f undam ental prov isions. The em phasis should thus be on intrinsic saf ety in the w ork plac e and only sec ondarily on protec tion that depends on the w ork ers ow n ac tions.

ICRP 60

(paragraph 195) The initial treatm ent of potential ex posures should f orm part of the sy stem of protec tion applied to prac tic es, but it should be rec ognized that the ex posures, if they oc c ur, m ay lead to interv ention. At this stage there should be tw o objec tiv es, prev ention and m itigation. Prev ention is the reduc tion of the probability of the sequenc es of ev ents that m ay c ause or inc rease radiation ex posures. It inv olv es m aintaining the reliability of all of the operating and saf ety sy stem s and of the assoc iated w ork ing proc edures. M itigation is the lim itation and reduc tion of the ex posures if any of these sequenc es do oc c ur. It inv olv es the use of engineered saf ety f eatures and operational proc edures to c ontrol eac h sequenc e of ev ents w ith the aim of lim iting its c onsequenc es, should it oc c ur.

The arrangem ent f or m itigation should not be restric ted to plans of interv ention. A great deal c an be ac c om plished at the stages of design and operation to reduc e the c onsequenc es of ac c ident sequenc es so that interv ention m ay not bec om e nec essary.

ICRP 103

(paragraph t) Em phasis on optim isation using ref erenc e lev els in em ergenc y and ex isting ex posure situations f oc uses attention on the residual lev el of dose rem aining af ter im plem entation of protec tion strategies. This residual dose should be below the ref erenc e lev el, w hic h represents the total residual dose as

14 a result of an em ergenc y, or in an ex isting situation, that the regulator w ould plan not to ex c eed. These ex posure situations of ten inv olv e m ultiple ex posure pathw ay s w hic h m eans that protec tion strategies inv olv ing a num ber of dif f erent protec tiv e ac tions w ill hav e to be c onsidered. The proc ess of optim isation w ill how ev er c ontinue to use the dose av erted by spec if ic c ounterm easures as an im portant input into the dev elopm ent of optim ized strategies.

Item 3: Provide an annotated bibliography of radiation protection r ecommendations for w or ker s during emergency conditions from national and international organiz ations responsible for making recommendations for radiation protection standards.

The staf f rev iew ed a num ber of sourc e m aterials to understand the c urrent state of k now ledge and organizations rec om m endations f or protec ting radiation w ork ers f rom radiation under ac c ident c onditions. The purpose of this rev iew w as to determ ine w hether reex am ining the tec hnic al basis f or the c ontrol room design c riteria w ould be w arranted in light of this inc reased enric hm ent rulem ak ing. The staf f also rev iew ed other N R C regulations and national and international organizations responsible f or m ak ing rec om m endations f or radiation protec tion standards. The purpose w as to understand w hether the c urrently selec ted num eric al v alue of 0.05 Sv (5 rem ) TED E f its w ithin the range of v alues used f or w ork er protec tion during em ergenc y c onditions:

  • At the tim e that G D C 19 w as published in 1971, 10 CFR Part 20 lim ited oc c upational radiation ex posure to 0.03 Sv (3 rem ) w hole body dose per c alendar quarter, prov ided the total lif etim e dose w as v erif ied not to ex c eed 0.05 Sv (5 rem ) tim es the indiv iduals age in y ears m inus 18 (i.e., 5(N18)). It w as possible to rec eiv e a radiation ex posure of up to 0.12 Sv (12 rem ) in a giv en y ear.
  • The c urrent annual lim it on oc c upational radiation dose ex posurein 10 CFR 20.1201, O c c upational D ose Lim its f or adults, is 0.05 Sv (5 rem ) TEDE. U nder 10 CFR 20.1201, it is possible to rec eiv e oc c upational radiation ex posure of up to 0.10 Sv (10 rem ) TEDE ov er a 12-m onth period straddling tw o c alendar y ears.
  • The c urrent 10 CFR 20.1206 on planned spec ial ex posures also perm its an adult w ork er to rec eiv e doses in addition to and ac c ounted f or separately f rom the doses rec eiv ed under the lim its spec if ied in 10 CFR 20.1201 of f iv e tim es the annual dose lim its during the indiv iduals lif etim e, not to ac c um ulate f aster than 0.05 Sv (5 rem ) TED E in any one y ear. It is possible to rec eiv e radiation ex posure of up to 0. 10 Sv (10 rem ) TED E w ithin a single c alendar y ear period.
  • The EPA ex posure guidelines f ound in the PAG M anual rec om m end that doses rec eiv ed under em ergenc y c onditions should be m aintained ALARA and, to the ex tent prac tic able, lim ited to 0.05 Sv (5 rem ). The guideline f or ac tions to pr otec t v aluable pr oper ty is 0.10 Sv (10 rem ) w here a low er dose is not prac tic able, the guideline f or ac tions to sav e a lif e or to protec t large populations is 0.25 Sv (25 rem ) w here a low er dose is not prac tic able, and ex posures greater than 0.25 Sv (25 rem ) m ay be appropriate f or lif esav ing or protec ting large populations if the w ork ers are v olunteers w ho are f ully aw are of the risk s inv olv ed.

15

  • H ealth Phy sic s Soc iety Position Statem ent PS010-4, R adiation R isk in Perspec tiv e, issued J anuary 2020 [R ef. 29], states that substantial and c onv inc ing sc ientif ic data show ev idenc e of health ef f ec ts f ollow ing high-dose ex posures ( i.e., m any m ultiples of natural bac k ground). H ow ev er, below lev els of about 100 m Sv (10 rem ) abov e bac k ground f rom all sourc es c om bined, the observ ed radiation ef f ec ts in people are not statistic ally dif f erent f rom zero.
  • ICRP Public ation 109, Applic ation of the C om m issions R ec om m endations f or the Protec tion of People in Em ergenc y Ex posure Situations, issued 2009 [R ef. 30], spec if ies a range of 0.02- 0.10 Sv (2 - 10 rem ) ac ute f or em ergenc y ex posure situations. For doses abov e 0.10 Sv (10 rem ), protec tiv e m easures should be justif ied.
  • Inter national A tom ic E ner gy A genc y guidanc e [ R ef. 31] f or em ergenc y w ork ers spec if y a range of 0.05-1 Sv (5 -100 rem ), depending on the sev erity of the ac tions needed.
  • NCRP R eport N o. 180, M anagem ent of Ex posure to Ionizing R adiation: R adiation Protec tion G uidanc e f or the U nited States, issued 2018 [R ef. 32], spec if ies that (1) during lif esav ing ac tiv ities or ac tions to prev ent a c atastrophic situation, w hic h inc ludes other urgent resc ue ac tiv ities, 0.5 gray (Gy ) c um ulativ e w hole-body absorbed dose (50 rad) should be im plem ented at the c om m and lev el, and (2) f or other em ergenc y ac tiv ities, inc luding ex tended ac tiv ities f ollow ing initial lif esav ing, resc ue, and dam age c ontrol response, an ef f ec tiv e dose to em ergenc y w ork ers should not ex c eed 0. 10 Sv (10 rem ).

In sum m ary, there is a range of regulatory-based and international and national organization-based rec om m endations f or radiation ex posures f or radiation w ork ers under norm al and em ergenc y c onditions. Ac c ording to the regulations, oc c upational w ork ers c an rec eiv e up to 0. 10 Sv (10 rem ) oc c upationally during a 12-m onth period under a spec ial circumstanc e w ithin a c alendar y ear. Intergov ernm ental and national and international organizations rec om m end em ergenc y ex posure dos e lim itations up to 0.25 Sv (25 rem ) TEDE or 0.5 Gy (50 rad) w hole body and up to 1 Gy (100 rad) f or em ergenc y responders. As suc h, the c ontrol room design c riteria intended to assess the ac c eptability of a giv en c ontrol room design is on the low er end of a range of rec om m ended v alues f or em ergenc y response planning to protec t against ac tual inc urred radiation ex posure during an ev ent.

Item 4: Provide an assessment of the identified design criteria to contemporary radiological health effects.

This sec tion prov ides the staf f s assessm ent of the c ontrol room design c riteria, w ith a num eric al v alue of 0. 05 Sv (5 rem ), as c om pared to inf orm ation f ound in prof essional literature, as w ell as rec om m endations regarding m odern health phy sic s k now ledge, radiation protec tion standards, and radiation epidem iology k now ledge.

As disc ussed abov e, the c ontrol room design c riteria w ere dev eloped and issued to establish m inim um nec essary design, f abric ation, c onstruc tion, testing, and perf orm anc e requirem ents f or SSCs that prov ide reasonable assuranc e that a f ac ility c an be operated w ithout undue risk to the health and saf ety of the oc c upational w ork ers and of the public. The design c riteria are not operational lim its, and they do not represent ac tual ex posures rec eiv ed during norm al operation

16 or an em ergenc y c ondition. Instead, these c riteria are f igures-of -m erit that are c om pared against the results of traditional determ inistic radiologic al c onsequenc e analy ses using a DBA sourc e term to judge the ac c eptability of the c ontrol room design.

In the c ontex t of the inc reased enric hm ent rulem ak ing, the question arises as to w hether the c urrent c ontrol room design c riteria c ould be i nc reased to a higher, y et still saf e, perf orm anc e lev el w hen c onsidering c ontem porary understandings of radiologic al health ef f ec ts.

With suf f ic ient dose, the biologic al health ef f ec ts of radiation ex posure m anif est in one of tw o w ay s: stoc hastic or determ inistic. Stoc hastic health ef f ec ts oc c ur random ly, and the probability of the ef f ec ts oc c urring, rather than their sev erity, is assum ed to be a linear f unc tion of dose w ithout threshold. D oses that c ontribute to stoc hastic ef f ec ts c an be ac c um ulated ov er long periods of tim e, f rom y ears to dec ades. Canc er inc idenc e is an ex am ple of a stoc hastic ef f ec t.

C onv ersely, f or determ inistic health ef f ec t s, the sev erity v aries w ith the dose f or w hic h an em piric ally deriv ed threshold is established. Ac ute radiation sy ndrom e is a signif ic ant determ inistic ef f ec t that c an pose signif ic ant saf ety issues during em ergenc y responsebec ause it c an signif ic antly ham per the ef f ec tiv eness of c ontrol room operators. D ata on the v arious f orm s of ac ute radiation sy ndrom e hav e been c ollec ted f rom m any sourc es. Anim al ex perienc es prov ide the bulk of the data and results. At the hum an lev el, data hav e been draw n f rom ex perienc es in radiation therapy and studies f rom a num ber of nuc lear-related ac c idents.

There are tw o radiation units that assess either stoc hastic ef f ec ts or determ inistic radiation health ef f ec ts. The f irst is the Sv (or rem ) TEDE, w hic h is the sum of the ef f ec tiv e dose equiv alent f or ex ternal ex posures and the c om m itted ef f ec tiv e dose equiv alent f or internal ex posures. The Sv (rem ) TEDE adjusts the dose equiv alent radiation ex posure using a tissue w eighting f ac tor that represents the proportion of the risk of stoc hastic ef f ec ts resulting f rom irradiation of an organ, or tissue, to the total risk of stoc hastic ef f ec ts w hen the w hole body is irradiated unif orm ly. The c om m itted ef f ec tiv e dose equiv alent is a 50-y ear c om m itted dose based on an initial intak e of radioac tiv e m aterial used to estim ate the stoc hastic health ef f ec t of c anc er m ortality. In other w ords, the dose is assigned to the f irst y ear of intak e to estim ate the inc reased probability of c anc er induc ed f atality af ter 50 y ears. The sec ond radiation unit is the Gy, or rad, w hic h is used to m easure the am ount of energy deposited in tissue. Ty pic ally,

radiation ex posures that c ause determ inistic health ef f ec ts are m easured in Gy ( rad).

Ex posure of the w hole body to a large dose ov er a short period of tim e (< 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />) m ay c ause ef f ec ts due to the sensitiv ity of c ells in the body. Ac ute radiation sy ndrom e c an result f ollow ing signif ic ant w hole-body ex posures in a short tim e. Ef f ec ts m ay inc lude blood c hanges, nausea, v om iting, diarrhea, and c entral nerv ous sy stem dam age. H em atopoietic sy ndrom e is observ ed by a dec rease in blood c ell c ount at doses of about 1 Gy (100 rad). G astrointestinal sy ndrom e f rom a dose of about 5 Gy (500 rad) w ill result in nausea, v om iting, and diarrhea. C entral nerv ous sy stem sy ndrom e, observ ed at about a dose of 20 Gy (2,000 rad), w ill af f ec t the m usc le and brain f unc tion of the c entral nerv ous sy stem. The dose w hic h is lethal to 50 perc ent of the people w ithin 60 day s if m edic al treatm ent is not prov ided is c alled the LD 50/60. The LD 50/60 dose is approx im ately 3-5 Gy (300- 500 rads; ~90 tim es the annual dose lim it f or routine oc c upational ex posure) in an hour to an av erage adult. If rec eiv ed w ithin a short tim e period (e.g., a f ew hours), an LD 5-/60 dose w ill c ause v om iting and diarrhea w ithin a f ew hours and loss of hair, f ev er, and w eight loss w ithin a f ew w eek s. These ef f ec ts w ould not oc c ur if the

17 sam e dose w ere ac c um ulated gradually ov er m any w eek s or m onths, suc h as during radiation therapy treatm ents.

The radiation risk of c anc er m ortality is assessed by f ir st quantif y ing the baseline risk of c anc er death w ithin a giv en population. For the U nited States, this is approx im ately 20 perc ent.

Therefore, a population of 10,000 people w ould dev elop approx im ately 2,000 (20 perc ent of 10,000) f atal c anc ers due to the natural inc idenc e of c anc er. Ex posure to radiation dose of up to 0.01 Sv (1 rem ) m ay inc rease the ov erall risk to 20 perc ent + 0.05 perc ent = 20.05 perc ent.

C ollec tiv e dose to a population of 10,000 person-rem (0.01 Sv (1 rem ) to eac h person in a population of 10,000) m ay result in f iv e additional c anc er f atalities, besides the 2,000 that w ill oc c ur naturally. That is, there w ould be 2, 005 f atal c anc ers, rather than 2, 000. H ow ev er, the natural inc idenc e of f atal c anc ers is not prec isely 2,000, and it is not possible to unequiv oc ally distinguish these additional c ases f rom those oc c urring naturally. As a c onsequenc e of c ollec tiv e dose in a lif etim e, approx im ately 42 out of 100 people w ill be diagnosed w ith c anc er f rom c auses unrelated to radiation. As prev iously m entioned, about 20 perc ent of the population dies f rom som e f orm of c anc er. So, of the 42 perc ent of people w ho dev elop c anc er, half w ill surv iv e. If 100 people rec eiv ed a dose of 0.1 Sv (10 rem ), it is estim ated that there w ill be one additional c anc er inc idenc e in this group f or a total of 43 c anc er inc idents. M ore inf orm ation c onc erning risk f rom ionizing radiation is av ailable in Regulatory Guide 8.29, Instruc tion C onc erning R isk s f rom O c c upational R adiation Ex posure, R ev ision 1, issued February 1996

[R ef. 33].

In sum m ary, ionizing radiation c an c ause biologic al ef f ec ts. While the biologic al ef f ec ts f rom ionizing radiation are not unique to radiation, it is im portant to limit the am ount of radiation dose rec eiv ed by an indiv idual. The probability of stoc hastic ef f ec ts of radiation, suc h as c ausing c anc er, inc rease w ith radiation dose. The lim itation of stoc hastic ef f ec ts is ac hiev ed by k eeping all justif iable ex posures ALAR A, giv en ec onom ic and soc ial f ac tors being c onsidered, subjec t alw ay s to the boundary c ondition that the appropriate dose lim it is not ex c eeded. D eterm inistic ef f ec ts hav e a threshold dose that m ust be ex c eeded f or the ef f ec ts to oc c ur, and the sev erity of these ef f ec ts also inc reases w ith dose. The prev ention of determ inistic ef f ec ts is ac hiev ed by setting dose equiv alent lim its at suf f ic iently low v alues so that no threshold dose w ould be reac hed, ev en f ollow ing ex posure f or the w hole of a lif etim e or f or the total period of an indiv iduals w ork ing lif e. As disc ussed abov e, the N R C has set dose lim its to m inim ize stoc hastic ef f ec ts and to av oid determ inistic ef f ec ts. Theref ore, the aim of the NRCs radiation protec tion standards is to prev ent detrim ental determ inistic ef f ec ts and to lim it the probability of stoc hastic ef f ec ts to lev els deem ed to be ac c eptable.

The c ontrol room design c riteria radiation unit of rem TED E does not tec hnic ally m atc h the ex pec ted m easured determ inistic health ef f ec ts ex pec ted f rom a reac tor ac c ident. H ow ev er, the 10 CFR Part 20 annual oc c upational ex posure lim it of 0.05 Sv (5 rem ) TE D E is set suf f ic iently low that no determ inistic threshold dose w ould be reac hed. This oc c upational ex po sure lim it is applic able to both norm al and em ergenc y c onditions. The rev iew of regulations pertaining to oc c upational w ork ers and radiation protec tion rec om m endations f or w ork ers during em ergenc y c onditions identif ied a range of rec om m ended ac c eptable c riteria. These c riteria w ould c ontinue to prov ide reasonable assuranc e that the f ac ility c an be operated during an em ergenc y w ithout undue risk to public health and saf ety as they are set suf f ic iently low to protec t against determ inistic health ef f ec ts that w ould cause operator im partm ent.

18 REFERENCES

1. U.S. Nuc lear Regulatory Com m ission (NRC), Assessm ent of R adiation Protec tion R ec om m endations f or Em ergenc y Work ers, Form 843, Inf orm al Assistanc e R equest NRR-2022-019, August 26, 2022, Agenc y w ide D oc um ents Ac c ess and M anagem ent Sy stem (ADAM S) Ac c ession N o. M L22259A017.
2. N uc lear Energy Institute, The Ec onom ic Benef its and C hallenges w ith U tilizing Inc reased Enric hm ent and Fuel Burnup f or Light-Water R eac tors, February 2019, M L21259A191.
3. NRC, Projec t Plan to Prepare the U.S. N uc lear R egulatory C om m ission f or Ef f ic ient Lic ensing of Ac c ident Tolerant Fuels, Version 1.2, Septem ber 2021, M L21243A298.
4. U.S. Code of Federal R egulations, C ritic ality ac c ident requirem ents, Sec tion 50.68, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc -

c ollec tions/c f r/part050/part050-0068.htm l )

5. NRC, R ulem ak ing Plan on U se of Inc reased Enric hm ent of C onv entional and Ac c ident Tolerant Fuel D esigns f or Light-Water R eac tors, SECY-21-0109, D ec em ber 20, 2021, M L21232A237.
6. NRC, Staf f R equirem ents SECY-21-0109R ulem ak ing Plan on U se of Inc reased Enric hm ent of C onv entional and Ac c ident Tolerant Fuel D esigns f or Light-Water R eac tors, SRM -SECY-21-0109, M arc h 16, 2022, M L22075A103.
7. U.S. C ode of Federal R egulations, Ac c ident sourc e ter m, Sec tion 50.67, C hapter I,

Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc -

c ollec tions/c f r/part050/part050-0067.htm l )

8. U.S. C ode of Federal R egulations, C ontrol room, G eneral D esign C riterion 19, G eneral D esign C riteria f or N uc lear Pow er Plants, Appendix A, Part 50, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc -

c ollec tions/c f r/part050/part050-appa.htm l#4_appa )

9. U.S. N uc lear R egulatory C om m ission, Be risk SM ART G uidanc e f or Integrating R isk Insights into N R C D ec isions, NUREG/KM -0016, M arc h 20 21, M L21071A238.
10. U.S. C ode of Federal R egulations, C ontents of applic ations; tec hnic al inf orm ation, Sec tion 50.34, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc-c ollec tions/c f r/part050/part050-0034.htm l )
11. U.S. C ode of Federal R egulations, C ontents of applic ations; tec hnic al inf orm ation, Sec tion 52.17, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc-c ollec tions/c f r/part052/part052-0017.htm l )
12. U.S. C ode of Federal R egulations, C ontents of applic ations; tec hnic al inf orm ation, Sec tion 5 2.47, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc-c ollec tions/c f r/part052/part052-0047.htm l )

19

13. U.S. C ode of Federal R egulations, C ontents of applic ations; tec hnic al inf orm ation, Sec tion 5 2.79, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc-c ollec tions/c f r/part052/part052-0079.htm l )
14. U.S. C ode of Federal R egulations, C ontents of applic ations; tec hnic al inf orm ation, Sec tion 5 2.137, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc-c ollec tions/c f r/part052/part052-0137.htm l )
15. U.S. C ode of Federal R egulations, C ontents of applic ations; tec hnic al inf orm ation in f inal saf ety analy sis report, Sec tion 5 2.157, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc -c ollec tions/c f r/part052/part052-0157.htm l )
16. U.S. C ode of Federal R egulations, D eterm ination of ex c lusion area, low population zone, and population c enter distanc e, Sec tion 100.11, C hapter I, Title 10, Energy.

(av ailable at https://w w w.nrc.gov /reading-rm /doc -c ollec tions/c f r/part100/part100-0011.htm l)

17. U.S. C ode of Federal R egulations, Planned spec ial ex posures, Sec tion 20.1206, O c c upational D ose Lim its, Subpart C, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc -c ollec tions/c f r/part020/part020-1206.htm l )
18. U.S. C ode of Federal R egulations, O c c upational dose lim its f or adults, Sec tion 20.1201, O c c upational D ose Lim its, Subpart C, C hapter I, Title 10, Energy.

(av ailable at https://w w w.nrc.gov /reading-rm /doc -c ollec tions/c f r/part020/part020-1201.htm l)

19. U.S. N ational Bureau of S tandar ds, Maximum Permi ssible Body Burdens and M ax im um Perm issible C onc entrations of R adionuc lides in Air and in Water f or O c c upational Ex posure, H andbook 69, J une 5, 1959 (av ailable at https://nv lpubs.nist.gov /nistpubs/Legac y /hb/nbshandbo ok 69.pdf).
20. U.S. C ode of Federal R egulations, Standards f or Protec tion Against R adiation, Part 20, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc -

c ollec tions/c f r/part020/index.htm l)

21. International C om m ission on R adiologic al Protec tion (ICRP), Re c om m endations of the ICRP, Annals of the ICRP 1(3), ICRP Public ation 26, 1977 (av ailable at https://w w w.ic rp.org/public ation.asp?id= IC R P%20Public ation%2026).
22. N R C, Standards f or Protec tion against R adiation, Federal R egis ter, Vol. 56, N o. 98, pp. 23360- 23401, M ay 21, 1991. (av ailable at https://arc hiv es.f ederalregister.gov /issue_slic e/1991/5/21/23349-2 3474.pdf #page= 12 )
23. U.S. Env ironm ental Protec tion Agenc y, PAG M anual: Protec tiv e Ac tion G uides and Planning G uidanc e f or R adiologic al Inc idents, EPA-400/R -17/001, J anuary 2017 (av ailable at https://w w w.epa.gov /radiation/protec tiv e-ac tion-guides -pags#pagm anual).
24. ICRP, 1990 R ec om m endations of the International C om m ission on R adiologic al Protec tion, Annals of the ICRP 21(1-3), ICRP Public ation 60 (U sers Edition), 1991

20 (av ailable at https://w w w.ic rp.org/public ation.asp?id= IC R P%20Public ation%2060%20(U sers%20Editi on)).

25. ICRP, The 2007 R ec om m endations of the International C om m ission on R adiologic al Protec tion, Annals of the ICRP 37(2-4), ICRP Public ation 103, 2007 (av ailable at https://www.ic rp.org/public ation.asp?id= IC R P%20Public ation%20103).
26. NRC, Em ergenc y R esponse Planning and Preparedness f or N uc lear Pow er R eac tors,

R egulatory G uide 1.101, R ev ision 6, J une 2021, M L21111A090.

27. NRC and Federal Em ergenc y M anagem ent Agenc y, C riteria f or Preparation and Ev aluation of R adiologic al Em ergenc y R esponse Plans and Preparednessin Support of N uc lear Pow er Plants: Final R eport, NUREG -0654/ FEM A-REP-1, R ev. 2, D ec em ber 2019, M L19347D 139.
28. U.S. C ode of Federal R egulations, U se of proc ess or other engineering c ontrols, Sec tion 20.1701, R espiratory Protec tion and C ontrols to R estric t Internal Ex posure in R estric ted Areas, Subpart H, C hapter I, Title 10, Energy. (av ailable at https://w w w.nrc.gov /reading-rm /doc -c ollec tions/c f r/part020/part020-1701.htm l )
29. H ealth Phy sic s Soc iety, Position Statem ent of the H ealth Phy sic s Soc iety PS010-4:

R adiation R isk in Perspec tiv e, H ealth Phy s ic s 118(1), pp. 79-80, J anuary 2020.

(av ailable at https://journals.lw w.c om /health-phy sic s/f ulltex t/2020/01000/position_statem ent_of _the_health_phy sic s_soc iety.8.aspx)

30. ICRP, Applic ation of the C om m ission s R ec om m endations f or the Protec tion of People in Em ergenc y Ex posure Situations, Annals of the ICRP 39(1), ICRP Public ation 109, 2009 (av ailable at https://w w w.ic rp.org/public ation.asp?id= ic rp%20public ation%20109).
31. International Atom ic Energy Agenc y, Portable D igital Assistant f or First R esponders to a R adiologic al Em ergenc y: Em ergenc y w ork er turn-bac k dose guidanc e, n.d. (av ailable at https://www-pub.iaea.org/m tc d/public ations/pdf /epr-f irst_res -pda/htm l/ti2-turn-bac k -

dose.htm #f tn.10).

32. N ational C ounc il on R adiation Protec tion and M easurem ents (NCRP), M anagem ent of Ex posure to Ionizing R adiation: R adiation Protec tion G uidanc e f or the U nited States, NCRP R eport N o. 180, 2018 (av ailable at https://nc rponline.org/shop/reports/report-no-180-m anagem ent -of -ex posure-to -ionizing-radiation-radiation-protec tion-guidanc e-f or -

the-united-states -2018-2018/ ).

33. NRC, I nstruc tion Conc erning Risk s f r om O c c upational Radiation Ex posure, R egulatory G uide 8. 29, R ev. 1, February 1996, ML003739438.

21

Retrieved from "https://kanterella.com/w/index.php?title=ML23027A059&oldid=3714053"