ML23027A059

Control Room Design Criteria and Radiological Health Effects, Iar NRR-2022-019 Report

ML23027A059
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Issue date:	06/30/2023
From:	Terry Brock, John Tomon NRC/RES/DSA
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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.

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