Ci a ion: Idoe a, R.; Pe isco-Fe e o,
S.; Rozas, S.; Olondo, C.; He anz, M.
P oposed De ec ion Limi s o
Radioac i i y Concen a ions in Wa e
in he Decommissioning and
Disman ling o Nuclea Facili ies.
En i onmen s 2024,11, 116. h ps://
doi.o g/10.3390/en i onmen s11060116
Academic Edi o : S e ano Falcinelli
Recei ed: 2 Ap il 2024
Re ised: 23 May 2024
Accep ed: 28 May 2024
Published: 1 June 2024
Copy igh : © 2024 by he au ho s.
Licensee MDPI, Basel, Swi ze land.
This a icle is an open access a icle
dis ibu ed unde he e ms and
condi ions o he C ea i e Commons
A ibu ion (CC BY) license (h ps://
c ea i ecommons.o g/licenses/by/
4.0/).
en i onmen s
A icle
P oposed De ec ion Limi s o Radioac i i y Concen a ions in
Wa e in he Decommissioning and Disman ling o
Nuclea Facili ies
Raquel Idoe a * , Susana Pe isco-Fe e o , Sa oa Rozas , Concepción Olondo and Ma ga i a He anz
Ene gy Enginee ing Depa men , Uni e si y o he Basque Coun y, UPV/EHU, Plaza To es Que edo, s/n,
48013 Bilbao, Spain
*Co espondence: [email p o ec ed]
Abs ac : The Disman ling and Decommissioning (D&D) o nuclea acili ies poses se e al challenges
o adioac i i y measu emen labo a o ies in ol ed in en i onmen al adia ion moni o ing plans.
One o hem is he de ini ion o he de ec ion limi s o be achie ed o he adionuclides analysis in
di e en samples. The de ec ion limi s should be se in such a way ha he ob ained concen a ion
alues o each adionuclide a e easily disc imina ed om ce ain maximum ac i i y concen a ion
le els. These maximum ac i i y concen a ion le els a e usually se in iew o he espec i e dose
con ibu ions om each adionuclide. The e a e some na ional legisla ions ha se le de ec ion limi s
o d inking wa e . Howe e , he e is no egula ion con aining de ec ion limi s o g oundwa e o
su ace wa e . In his way, di e en ins i u ions o companies equi e e y di e en de ec ion limi s o
adioac i i y concen a ion assessmen in hose ypes o wa e associa ed wi h D&D ac i i ies. In his
wo k, we ocus on he de ec ion limi s equi ed o he D&D ac i i ies in ainwa e , su ace wa e and
g oundwa e . We p opose de ec ion limi s ob ained by applying he WHO me hodology o maximum
ac i i y concen a ion le els and compa e wi h hose eques ed by adioac i e was e managemen
agencies and egula o y bodies. Some eal cases whe e ou p oposal allows iden i ica ion o e en s
a e analysed and conclusions a e ex ac ed.
Keywo ds: de ec ion limi s; Radiological En i onmen al Moni o ing; adionuclides in g oundwa e
1. In oduc ion
The p ocedu e o disman ling and decommissioning (D&D) a nuclea powe plan ,
and o a b oade ex en a nuclea acili y, is a complex and highly egula ed
ask [1–4]
ha
in ol es a ious s ages. Du ing all o hem, a p e iously de ined Radiological En i onmen-
al Moni o ing Plan (REMP) adap ed o he di e en phases o he D&D mus be ollowed.
A key aspec o his plan is he de ini ion o he adionuclides o be de e mined, a lis which
may e ol e du ing he di e en phases o he p ocess, as pa o he adap a ion o he plan
o he di e en phases o he D&D p ocess, bu which may also a ec he ypes o ma ices
o be adiologically cha ac e ised. The esul s o his cha ac e iza ion mus align wi h
egula o y equi emen s o ensu e he p o ec ion o he en i onmen and public heal h.
The basic aspec s o his adiological cha ac e isa ion a e he de ini ion o he de ec ion
limi s ha mus be achie ed o he adionuclides o be de e mined, he ma ixes o be
measu ed and he objec i es o he cha ac e isa ion.
In he con ex o D&D, he de ec ion limi s a e o majo impo ance wi hin he analysis
o he adionuclides, since hese e e o he lowes concen a ions o he adionuclides
ha can be eliably measu ed by a gi en labo a o y using i s analy ical me hods and
ins umen a ion. The consequences o es ablishing app op ia e de ec ion limi s canno
be unde es ima ed, as hey a e s aigh o wa d ega ding he accu acy and eliabili y
o he adiological cha ac e iza ion. The e o e, he de ec ion limi s o be eached a e a
undamen al inpu ha he labo a o ies in cha ge o hese de e mina ions mus know
En i onmen s 2024,11, 116. h ps://doi.o g/10.3390/en i onmen s11060116 h ps://www.mdpi.com/jou nal/en i onmen s
En i onmen s 2024,11, 116 2 o 11
since i allows hem o ou line hei measu emen s a egy (amoun o sample o be aken,
coun ing ime, e c.) including he mos app op ia e de e mina ion echnique.
De ec ion limi s depend on he ype o sample o analyze [
5
]. In his amewo k,
he p esen pape aims o be a con ibu ion o he discussion ega ding wa e and he
adionuclides ha a e likely o appea in i du ing he di e en phases o he D&D p ocesses.
We ha e decided o s a by choosing wa e as i is a ma ix ha is highly egula ed [
6
–
13
]
and can ha e a s ong impac on he adiological p o ec ion o he popula ion because i
can end up being inges ed.
F om a adiological p o ec ion pe spec i e and applying he ALARA adia ion p o-
ec ion philosophy (doses as low as easonably achie able), i is c ucial ha he doses o
he popula ion s ay well below maximum allowable alues. This equi es ha he ac i i y
concen a ions o adionuclides in en i onmen al samples, as one o he con ibu o s o ha
dose, a e kep as low as easonably achie able. In his ega d, egula o y au ho i ies o en
se maximum allowable le els o adionuclide concen a ions in di e en en i onmen al
sec o s o p o ec public heal h and he en i onmen .
Fu he mo e, hese maximum le els should be signi ican ly highe han he co e-
sponding de ec ion limi s [
14
]. This would ensu e ha he concen a ions measu ed a e
easily dis inguishable om he de ec ion limi s, allowing o p ecise and eliable assess-
men s o he adiological impac [15,16].
In he con ex o D&D, ce ain en i onmen al compa men s s udied in he a o emen-
ioned REMP a e o pa icula conce n due o hei po en ial impac on public heal h and
he en i onmen . Wa e is o g ea impo ance due o i s g ea capaci y o ans e sub-
s ances con ained in i o o he en i onmen al compa men s and anspo hem o e long
dis ances. In addi ion, a signi ican pa o ainwa e , su ace, and g oundwa e may end up
being exploi ed o domes ic use o i iga ion and hence, human consump ion [
6
,
7
,
17
–
20
].
Acco dingly, he men ioned ypes o wa e may ul ima ely be used o domes ic pu poses,
including human consump ion, which calls o ho ough adiological moni o ing.
As he de ec ion limi is de ined as he smalles ue alue o he measu and ha
ensu es a speci ied p obabili y o being de ec able by he measu emen p ocedu e, hey
depend on many ac o s [
21
]. These ac o s a e he backg ound ound in he measu emen ,
he coun ing ime, he olume o he sample being ea ed, and he whole pe o mance
o he adionuclide analysis [
22
]; in ol ing ha hey a e in insically a iable o each
ype o de e mina ion; he e o e, o any measu emen esul o be meaning ul, bo h he
unce ain y and he de ec ion limi mus be s a ed.
The discussion abo e b ings he issue o es ablishing he maximum de ec ion limi e-
qui ed o each speci ic adionuclide de e mina ion. In he case o d inking wa e , guidance
le els and de ec ion limi s ha e ound a s aigh o wa d solu ion: o e e y adionuclide
ele an o he pa icula si ua ion o acili y, he de e mined de ec ion limi should be se
signi ican ly below ce ain guidance le els. Co esponding guidance le els can be ound in
di e en s anda ds and legisla ion [
8
,
9
]. Howe e , he ma e is mo e in ica e in he sce-
na io we a e add essing. Speci ically, in he analysis o ainwa e , su ace, and g oundwa e
wi hin he icini y o he nuclea acili y, guidance le els o hei co esponding de ec ion
limi s a e no con ained in any s anda d o egula ion.
In summa y, while some na ional and in e na ional o ganiza ions ha e es ablished
de ec ion limi s o speci ic adionuclides in d inking wa e , he e is a no able absence o
egula ion con aining de ec ion limi s equi ed o all adionuclides in D&D analysis and
o o he ypes o wa e . This gap unde sco es he need o a uni ied app oach o se ing
de ec ion limi s ha ensu es consis ency and accu acy in adiological cha ac e iza ion.
In his con ex , he bodies in cha ge o he D&D p ocess a nuclea acili ies do no ha e
a egula o y amewo k o de ine he de ec ion limi s o be achie ed by he labo a o ies in
he de e mina ion o adionuclides wi hin he plan.
The e o e, hese a e de ined on a case-by-case basis. See, o example, he case o
he adiological cha ac e iza ion o he en i onmen a di e en nuclea acili ies in he
p ocess o D&D in Spain. Di e en de ec ion limi s o he cha ac e iza ion o g oundwa e ,
En i onmen s 2024,11, 116 3 o 11
ainwa e , su ace wa e , and d inking wa e in di e en adiological moni o ing plans
se led wi hin he scope o hose D&D ac i i ies we e asked o . Speci ically, as examples,
o H-3, S -90, and Cs-137 he manda o y de ec ion limi s we e always he same, i.e., 6,
0.025, and 0.2 Bq/L, espec i ely, bu o C-14 i anged be ween 1.8 and 6 Bq/L, o Fe-55
be ween 0.05 and 0.5 Bq/L, and o Ni-63 be ween 0.018 and 0.1 Bq/L.
An examina ion o he de ec ion limi s e eals signi ican di e ences, pa icula ly
o Fe-55 and Ni-63, ac oss di e en moni o ing plans. This a iabili y sugges s a lack
o ha moniza ion in he es ablishmen o de ec ion limi s o adionuclide analysis in
D&D. Such inconsis encies can lead o unce ain y in he adiological cha ac e iza ion
p ocess, making i di icul o d aw clea conclusions abou he adiological impac o a
decommissioned nuclea powe plan .
This example highligh s he need o y o ha monize hese de ec ion limi s, and o
con ibu e o his discussion is he objec i e o his pape , conside ing ha he ollowing
key elemen s a e essen ial o achie ing consis ency and eliabili y in se ing any de ec ion
limi s in any adia ion p o ec ion amewo k:
1.
Clea and Comp ehensi e Regula ions: Regula o y au ho i ies should de elop clea
and comp ehensi e egula ions ha speci y de ec ion limi s o a wide ange o
adionuclides. These limi s should conside he po en ial pa hways o exposu e, such
as inges ion, inhala ion, and ex e nal exposu e, o ensu e a comp ehensi e adiological
assessmen .
2.
Scien i ic Consensus: Es ablishing de ec ion limi s should in ol e scien i ic consen-
sus. This p ocess should conside he speci ic cha ac e is ics o each adionuclide,
including i s hal -li e, decay scheme, and adiological impac . Addi ionally, i should
accoun o di e en en i onmen al ma ices, such as soil, wa e , and ai .
3.
Risk Assessmen : De ec ion limi s should be se wi h he aim o minimizing isks o
he en i onmen and public heal h. The limi s should be based on he p inciple o
ALARA (As Low As Reasonably Achie able) o ensu e ha he adiological impac is
kep well below accep able le els.
4.
Me hod Valida ion: Labo a o ies should alida e hei analy ical me hods o ensu e
ha he es ablished de ec ion limi s can be eliably achie ed. This in ol es igo -
ous es ing and quali y con ol p ocedu es o e i y he accu acy and p ecision o
measu emen s.
To add ess he challenges ela ed o he es ablishmen o de ec ion limi s o adionu-
clide analysis, in labo a o ies in cha ge o he adiological de e mina ions, in he adio-
logical cha ac e iza ion o D&D ac i i ies, we p opose a s anda dized app oach wi hin
he scope o his pape . This app oach aims o p o ide clea guidance o labo a o ies
esponsible o adiological de e mina ions o ainwa e , su ace, and g oundwa e in he
D&D adiological amewo k.
Fo ha aim, we s a om he assump ion ha all ypes o wa e may e en ually
be used o public consump ion; he e o e, he annual e ec i e dose limi s o d inking
wa e will apply in his case. Then, we apply he me hodology desc ibed in he Guidelines
o d inking-wa e quali y o he Wo ld Heal h O ganiza ion (WHO) [
8
] o se maximum
ac i i y concen a ion le els o adionuclides and make a p oposal o se ing hei co e-
sponding de ec ion limi s as 1% o hose maximum ac i i y concen a ion le els.
2. Me hods
In he con ex o adia ion p o ec ion, ou app oach is based on wo cen al assump-
ions as ollows.
Fi s , o main ain a conse a i e s andpoin conce ning adiological sa e y in e ms o
adiological p o ec ion. This in ol es adop ing p o ec i e measu es and s anda ds ha , in
he e en o ins abili y o unexpec ed si ua ions, a e mo e han adequa e o mi iga e any
po en ial isks.
Second, assessmen o po en ial impac s o su ace and g oundwa e con amina ion
mus add ess all he associa ed ecep o s o hose ypes o wa e (d inking wa e sou ces,
En i onmen s 2024,11, 116 4 o 11
we lands, s o age, geo he mal uses, e c.). We make he assump ion ha su ace and
g oundwa e could be di ec ly consumed o d inking needs. We place ou sel es in a mo e
p o ec i e and conse a i e posi ion in isk assessmen , due o he po en ial se e i y o he
consequences o d inking wa e supplies con amina ion.
The e o e, ou adiological p o ec ion amewo k akes in o accoun he possibili y o
adionuclide con amina ion in such wa e sou ces and endea ou s o se app op ia e limi s
o ensu e ha he po en ial adiological isks a e wi hin accep able le els.
Wi h hese assump ions in mind, we p opose he es ablishmen o de ec ion limi s
ha a e se a a le el co esponding o one pe cen o he de i ed maximum ac i i y
concen a ion le els.
These maximum ac i i y concen a ion le els a e de e mined using he me hodology
ollowed by he WHO o de ining he guidance le els in d inking wa e (Wo ld Heal h
O ganiza ion [
8
]. The WHO p o ides a sys ema ic app oach o de e mining he adionu-
clide ac i i y concen a ion le els ha would be sa e o consump ion. These le els a e
calcula ed conside ing ac o s such as he in ake a e (2 L pe day o one yea o adul s)
and “indi idual dose c i e ion” in e ms o an annual e ec i e dose se led by he WHO as
0.1 mS /yea .
Essen ially, he maximum ac i i y concen a ion le els o each speci ic adionuclide
a e de ined as he concen a ion a which said adionuclide, when consumed a a a e o
2 L each day o one yea by an adul , esul s in he 0.1 mS e ec i e dose pe yea . The
WHO [
8
] conside ed ha he e is no su icien e idence o in oduce sepa a e le els o
di e en age g oups, as al hough in an s and child en consume lowe olumes o d inking
wa e , he age-dependen dose coe icien s o child en a e highe han hose o adul s,
accoun ing o highe up ake o me abolic a es, balancing he esul .
Each ac i i y concen a ion le el, ACLj o adionuclide j is ob ained by using he
exp ession o Equa ion (1)
ACLj=0.1 mS /yea
ej(50)·Cj,(1)
whe e,
ej(50)
is he e ec i e dose coe icien o inges ion o adionuclide j o he membe s
o he public (mS /Bq). These coe icien s a e p o ided by he In e na ional Commission
on Radiological P o ec ion (ICRP) [23].
Cjli es
yea
is he consump ion a e o d inking wa e o adul s; assumed o be 2 L/day
o adul s [8].
Fo he sake o conse a i eness in e ms o adia ion p o ec ion, when we look a
he annual e ec i e dose limi s se by a ious o ganiza ions o adionuclides in d inking
wa e , we obse e a spec um o alues (Table 1).
Table 1. Annual e ec i e dose limi s se up by di e en na ional and in e na ional o ganiza ions.
O ganiza ion
Scena io
Annual E ec i e Dose Limi
Re e ence
mS
WHO D inking wa e 0.1
(Wo ld Heal h O ganiza ion (WHO), [
8
]
Eu opean
Commission D inking wa e 0.1 (Council o he Eu opean Union, [9])
IAEA D inking wa e 1 (In e na ional A omic Ene gy
Agency—IAEA, [10])
USA EPA
D inking wa e , no including na u ally
occu ing adia ion sou ces 0.04 (Uni ed S a es En i onmen al
P o ec ion Agency, [11])
US NRC
C i e ion o license e mina ion o
nuclea acili ies wi h
un es ic ed elease, including he
esidual adioac i i y om
g oundwa e sou ces o d inking wa e
0.25 (Uni ed S a es Nuclea Regula o y
Commission, [6,7])
Canada D inking wa e 0.1 (Heal h Canada, [12])
En i onmen s 2024,11, 116 5 o 11
As can be seen in Table 1, hese alues a y om he smalles limi o 0.04 millisie e s
(mS ) es ablished by he U.S. En i onmen al P o ec ion Agency (EPA) o a limi o 1 mS
de ined by he In e na ional A omic Ene gy Agency (IAEA). The WHO, Canada, and he
Eu opean Commission ad oca e o a limi o 0.1 mS .
In ou commi men o main aining a conse a i e s ance in adiological p o ec ion, we
ha e chosen o align wi h he WHO and he Eu opean Commission by adop ing he 0.1 mS
limi as ou e e ence, which is he mos es ic i e e ec i e dose, in e na ionally accep ed
i he DOE limi a ion o 0.04 mS , which excludes na u ally occu ing adionuclides, is
no conside ed.
Ha ing es ablished he 0.1 mS limi as ou e e ence, he nex s ep in ol es calcula ing
he co esponding ac i i y concen a ion le els o each adionuclide. The esul s ob ained
wi h his app oach a e shown in Table 2 o some adionuclides.
Table 2. De ec ion limi s p oposed calcula ed o some adionuclides.
Radionuclide ej(50) ACLj De ec ion Limi
S /Bq Bq/L Bq/L
H-3 1.80 ×10−11 7610 76.1
C-14 5.8 ×10−10 236 2.36
Fe-55 3.30 ×10−10 415 4.15
Co-60 3.40 ×10−940 0.40
Ni-63 1.50 ×10−10 913 9.13
S -90 2.8 ×10−84.90 0.05
Cs-137 1.3 ×10−810.5 0.11
Fo ins ance, one can conside he speci ic alues o i ium, Fe-55, and Ni-63 (see
Table 2). The calcula ed ac i i y concen a ion le els o i ium amoun o 7610 Bq/L,
o Fe-55 hey a e 415 Bq/L, and o Ni-63 hey s and a 913 Bq/L. These alues indica e
he concen a ion o each adionuclide in d inking wa e ha would esul in an annual
e ec i e dose o 0.1 mS , aking in o accoun an in ake o 2 L pe day o one yea by
an adul .
This calcula ion could be pe o med o any a i icial adionuclide ha could be inally
ound in ainwa e , su ace wa e , and g oundwa e a ound any NPP in a si ua ion o D&D.
Re e ence [
24
] p oposes a lis o such a i icial adionuclides in he amewo k o speci ic
NPP adiological moni o ing plans.
As es ablished be o e, ou adiological p o ec ion p oposal akes his a s ep u he
by aiming o es ablish de ec ion limi s ha a e su icien ly s ingen . IAEA [
25
,
26
] also
judges he se lemen o good de ec ion limi s as a challenge and conside s ha moni o ing
echniques o e i y exemp ion o p ac ices o sou ces o o ou ine eleases should ha e a
de ec ion limi well below he co esponding exemp ion le els o discha ge limi s, espec-
i ely. As an example, bu in ano he ield, IAEA [
26
] p oposes ha he lowe de ec ion
limi s o on-line sou ce moni o ing p og ams could be less han 1% o discha ge limi s, in
o de o adequa ely co e he eleases o each adionuclide g oup and o sa ely demons a e
compliance wi h he au ho ized limi s.
We p opose de ec ion limi s ha a e se a 1% o he co esponding ac i i y concen-
a ion le els. Some o hese de ec ion limi s appea in he las column o Table 2. By
se ing de ec ion limi s a his le el, we ensu e ha any ace p esence o hese adionu-
clides in d inking wa e can be iden i ied and managed swi ly, well be o e hey each
concen a ions ha could pose a isk o public heal h. Fu he mo e, he Wo ld Heal h O ga-
niza ion (WHO) [
8
] also se s he de ec ion limi s o chemicals unde he 1/100 h o he
guideline alue.
F om a quali a i e a he han quan i a i e poin o iew, i mus be conside ed ha
i should be possible o accu a ely assess he p esence o an indi idual adionuclide wi h
de ec ion limi s much lowe han i s maximum ac i i y concen a ion le el since wa e may
con ain mo e han one adiological con aminan . Such is he case o con amina ion due o a
En i onmen s 2024,11, 116 6 o 11
D&D p ocess, whe e he doses due o he di e en adionuclides should be summed up
and he esul will always be less han he dose limi s.
Acco dingly, he de ec ion limi s o he di e en adionuclides es ablished in his
way should be i o pu pose, as hei achie emen would assu e ha he objec i e o he
Radiological En i onmen al Moni o ing Plan is me . The e o e, any concen a ion alue
measu ed would be clea ly dis inguished om each adionuclide ac i i y concen a ion
le el, aking in o accoun he unce ain ies associa ed wi h he measu emen p ocess. This
way, any labo a o y unde ou ine ope a ing condi ions would achie e de ec ion limi s ha
would be a below he ac i i y concen a ion le els.
Thus, he co esponding de ec ion limi s o he adionuclides s udied as examples
would be 0.05 Bq/L o S -90, 0.11 Bq/L o Cs-137, 76 Bq/L o i ium, 2.36 Bq/L o
ca bon-14, 4.15 Bq/L o Fe-55, and 9.13 Bq/L o Ni-63. These de ec ion limi s ep esen
a igilan and p ecau iona y app oach o adiological p o ec ion, enabling he imely
iden i ica ion and mi iga ion o po en ial isks, assuming ha all hese wa e s could end up
as public d inking wa e s.
3. Resul s and Discussion
In o de o plan and conduc moni o ing o compliance wi h le els o exemp ion
and clea ance in D&D, he co esponding o ganiza ion needs o es ablish a planned moni-
o ing plan in a esponsible and e ec i e manne . Among he managemen issues, da a
quali y objec i es o he moni o ing p og am a e o be conside ed, including, o cou se, he
speci ica ion o de ec ion limi s o all measu emen echniques and adionuclides. This is
he case o moni o ing o ins alla ions in he D&D s age.
The ocus is now on he deba e as o wha he de ec ion limi s should be, since hey
do no depend on he labo a o y i sel , bu on he body esponsible o he p ocess and,
ul ima ely, on he egula o y au ho i ies.
Much e o has been expended in ecen yea s in ha monizing de ec ion limi s wi h
espec o concep s wi h he ISO s anda d ea ing decision and de ec ion limi s [
21
]. How-
e e , no hing is es ablished abou he alues hey mus ob ain in di e en en i onmen al
adia ion moni o ing plans. I is s ill an open ques ion o egula o y bodies, go e nmen s
o o he ele an au ho i ies ha inally p i a e o public en i ies in cha ge o ca ying ou
he adia ion moni o ing plans mus cope wi h. In his si ua ion, he e is a clea lack o
ha monisa ion in he es ablishmen o he de ec ion limi s o be eached o he di e en
ma ices o be analysed.
This wo k makes a echnical p oposal o he adiological analysis o wa e based
on ensu ing an adequa e le el o adiological p o ec ion. Ha ing es ablished he me hod-
ology o es ablishing de ec ion limi s o he cha ac e iza ion o adionuclides in wa e
in D&D scena ios, i becomes easible o compa e hese de ec ion limi s wi h he cu en
adop ed alues.
As an illus a i e example, we can compa e he esul s o S -90, Cs-137, i ium,
C-14, Fe-55, and Ni-63 om Table 2wi h he de ec ion limi s equi ed by some REMPs o
di e en ins alla ions in he D&D s age in Spain shown on he in oduc ion sec ion. Fo
S -90 he equi ed de ec ion limi is 0.025 Bq/L, o Cs-137 i is 0.2 Bq/L, o i ium (H-3) i
is always 6 Bq/L, o ca bon-14 (C-14) i is be ween 1.8 and 6 Bq/L, o i on-55 (Fe-55) i is
be ween 0.05 and 0.5 Bq/L, and o nickel-63 (Ni-63) i is be ween 0.018 and 0.1 Bq/L.
No ably, he p oposed de ec ion limi s in Table 2a e ound o be a leas an o de o
magni ude g ea e han hose p esen ly in use, excep o S -90, Cs-137, and C-14, which
a e o simila magni ude.
On he one hand, he a ainmen o he p oposed de ec ion limi s in his s udy would
enable he unequi ocal iden i ica ion o any ac i i y concen a ion in wa e capable o
esul ing in an annual e ec i e dose h ough inges ion o 0.1 mS , which s ands as he mos
s ingen in e na ionally accep ed e ec i e dose c i e ion.
On he o he hand, achie ing e en lowe de ec ion limi s would acili a e a mo e com-
p ehensi e adiological cha ac e iza ion, he eby enabling he iden i ica ion o exceedingly
En i onmen s 2024,11, 116 7 o 11
small adionuclide ac i i y concen a ions in wa e . This heigh ened sensi i i y would
se e as a aluable ool o diagnosing aul s wi hin he nuclea powe acili y and also o
check he quali y and de elopmen o some s eps o he D&D p ocess. Fo ins ance, in he
e en o a mino wa e leakage, ea ly de ec ion and esponse could be ini ia ed.
In summa y, he es ablishmen o lowe de ec ion limi s would yield a mo e exhaus i e
and s ingen quali y con ol amewo k o D&D asks, ul ima ely enhancing he sa e y
and e iciency o nuclea acili y decommissioning p ocedu es.
Clea examples o his conclusion a e wo di e en si ua ions de ec ed by ou labo a-
o y a ound a acili y in decommissioning. Sampling o g oundwa e was made a di e en
poin s a ound he acili y o e se e al yea s. All samples we e analysed looking o di -
e en adionuclides. Ni-63 and H-3 we e analysed using liquid scin illa ion spec ome y
echniques. A ull explana ion o he esul s and moni o ing p og am can be ound in [
27
].
In he i s case, he ac i i y le els o Ni-63 de ec ed, in Bq/li e, can be seen in Figu e 1.
En i onmen s 2024, 11, x FOR PEER REVIEW 8 o 11
Figu e 1. E olu ion o Ni-63 ac i i y concen a ion, in Bq/L, o e 10 yea s in a poin a ound a nuclea
acili y in decommissioning. P oposed de ec ion limi in g een.
In he second scena io, he ac i i y concen a ion o i ium, measu ed in Bq/L, a
h ee dis inc sampling loca ions o e he cou se o ou yea s is depic ed in Figu e 2. I is
e iden ha he concen a ion o i ium exhibi ed empo al a ia ions, a imes display-
ing p onounced luc ua ions. Wi h he adop ion o he p oposed de ec ion limi , a signi i-
can po ion o i ium leakages du ing his pe iod would ha e been eadily iden i ied.
Howe e , i is no ewo hy ha e en a he highes obse ed ac i i y concen a ion le el,
he esul ing annual effec i e dose o he public, assuming yea - ound consump ion o
his wa e , would amoun o a me e 13 µS , a negligible le el o exposu e.
0
5
10
15
20
25
0 700 1400 2100 2800
Ac i i y concen a ion, Bq/l
Days om s a
Figu e 1. E olu ion o Ni-63 ac i i y concen a ion, in Bq/L, o e 10 yea s in a poin a ound a nuclea
acili y in decommissioning. P oposed de ec ion limi in g een.
The ac i i y concen a ion o Ni-63 exhibi ed empo al a iabili y, cha ac e ized by
wo dis inc sha p inc eases since he onse o he disman ling p ocess. Upon applying
he p oposed de ec ion limi , only he la e su ge in ac i i y would ha e been disce nible.
Ne e heless, i is c ucial o bea in mind ha , e en a he highes eco ded ac i i y con-
En i onmen s 2024,11, 116 8 o 11
cen a ion le el, he p ojec ed annual adia ion dose o he public, assuming yea - ound
consump ion o his wa e , would amoun o a negligible 2.2 µS .
Howe e , ha ing wo ked wi h much lowe de ec ion limi s han hose now p oposed,
i was possible o analyse he causes o his sligh inc ease in he wa e and o ake, i
needed, co ec i e measu es.
In he second scena io, he ac i i y concen a ion o i ium, measu ed in Bq/L, a
h ee dis inc sampling loca ions o e he cou se o ou yea s is depic ed in Figu e 2. I is
e iden ha he concen a ion o i ium exhibi ed empo al a ia ions, a imes displaying
p onounced luc ua ions. Wi h he adop ion o he p oposed de ec ion limi , a signi ican
po ion o i ium leakages du ing his pe iod would ha e been eadily iden i ied. Howe e ,
i is no ewo hy ha e en a he highes obse ed ac i i y concen a ion le el, he esul ing
annual e ec i e dose o he public, assuming yea - ound consump ion o his wa e , would
amoun o a me e 13 µS , a negligible le el o exposu e.
En i onmen s 2024, 11, x FOR PEER REVIEW 9 o 11
Figu e 2. E olu ion o H-3 ac i i y concen a ion, in Bq/L, o e 4 yea s in 3 diffe en poin s (o ange,
blue and g ey colo ed lines) a ound a nuclea acili y in decommissioning. P oposed de ec ion limi
in g een.
Se ing a uni e sal de ec ion limi o each adionuclide a 1% o he le el o he max-
imum pe missible ac i i y concen a ion in wa e is eliable in e ms o adia ion p o ec-
ion, o p ac ical in e es o he labo a o ies in ol ed in adionuclide analysis, and o
maximum in e es o egula o y au ho i ies as hey could compa e esul s om hose
analyses independen ly om he moni o ing plan hey come om. Mo eo e , since i is
accep ed p ac ice o de i e ac i i ies om a ac ion o he de ec ion limi in cases whe e
ac i i ies a e below hose limi s, i would make mo e sense o de i e he esul knowing
ha hose limi s a e 1% o he maximum allowable ac i i y concen a ion.
4. Conclusions
The adiological cha ac e iza ion o a eas su ounding decommissioned nuclea a-
cili ies is a c i ical s ep in he D&D p ocess. To gua an ee he accu acy and eliabili y o
his cha ac e iza ion, i is essen ial o es ablish app op ia e de ec ion limi s o adionu-
clide analysis. De ec ion limi s should be ha monized, well-de ined, and in acco dance
wi h egula o y equi emen s o ensu e ha he adiological impac emains wi hin sa e
limi s.
To add ess he challenges and o p o ide clea guidance in labo a o ies in cha ge o
he adiological de e mina ions in ela ion o he de ec ion limi s o adionuclide analysis
0
200
400
600
800
1000
1200
0 200 400 600 800 1000 1200
Ac i i y concen a ion, Bq/l
Days om s a
Figu e 2. E olu ion o H-3 ac i i y concen a ion, in Bq/L, o e 4 yea s in 3 di e en poin s (o ange,
blue and g ey colo ed lines) a ound a nuclea acili y in decommissioning. P oposed de ec ion limi
in g een.
Se ing a uni e sal de ec ion limi o each adionuclide a 1% o he le el o he
maximum pe missible ac i i y concen a ion in wa e is eliable in e ms o adia ion
p o ec ion, o p ac ical in e es o he labo a o ies in ol ed in adionuclide analysis, and
o maximum in e es o egula o y au ho i ies as hey could compa e esul s om hose
analyses independen ly om he moni o ing plan hey come om. Mo eo e , since i is
En i onmen s 2024,11, 116 9 o 11
accep ed p ac ice o de i e ac i i ies om a ac ion o he de ec ion limi in cases whe e
ac i i ies a e below hose limi s, i would make mo e sense o de i e he esul knowing
ha hose limi s a e 1% o he maximum allowable ac i i y concen a ion.
4. Conclusions
The adiological cha ac e iza ion o a eas su ounding decommissioned nuclea acili-
ies is a c i ical s ep in he D&D p ocess. To gua an ee he accu acy and eliabili y o his
cha ac e iza ion, i is essen ial o es ablish app op ia e de ec ion limi s o adionuclide
analysis. De ec ion limi s should be ha monized, well-de ined, and in acco dance wi h
egula o y equi emen s o ensu e ha he adiological impac emains wi hin sa e limi s.
To add ess he challenges and o p o ide clea guidance in labo a o ies in cha ge o
he adiological de e mina ions in ela ion o he de ec ion limi s o adionuclide analysis
in he adiological cha ac e iza ion amewo k o D&D ac i i ies, we ha e p oposed a
s anda dized app oach.
We assume adia ion p o ec ion as he main pu pose o sample analysis and adio-
logical cha ac e iza ion and moni o ing. The adiological p o ec ion amewo k assumed
is i mly based in he p inciple o conse a ism, assuming he WHO me hodology o
guidance le els in d inking wa e o es ablish ac i i y concen a ion le els and he mos
es ic i e in e na ionally accep ed annual e ec i e dose limi o 0.1 mS . Fu he mo e,
we p opose de ec ion limi s se a 1% o hese ac i i y concen a ion le els o ensu e ea ly
iden i ica ion and managemen o po en ial adiological isks. This app oach embodies a
commi men o obus adiological p o ec ion and he well-being o indi iduals who ely
on su ace and g oundwa e o hei d inking wa e needs.
The p oposed s anda dized app oach p o ides a amewo k o labo a o ies o se and
achie e hese limi s, ul ima ely con ibu ing o he sa e and e ec i e decommissioning o
nuclea acili ies and he p o ec ion o he en i onmen and he public heal h. The de ec ion
limi s p oposed he e ill he gap in e ms o ha moniza ion in adiological cha ac e iza ion.
Mo eo e , he de ec ion limi s p oposed he e a e easily achie ed in adiological labo-
a o ies equipped wi h s anda d adiome ic equipmen using con en ional me hods, wi h
a e age sample olumes and low coun ing imes.
In any case, i lowe de ec ion limi s would be equi ed by egula o y au ho i ies, a
mo e comple e adiological cha ac e iza ion could be achie ed so ha , al hough negligible
om he adia ion p o ec ion poin o iew, i would be possible o disco e some echnical
p oblems in D&D. I is jus a ques ion o cos –bene i analysis: lowe de ec ion limi s
suppose highe cos s in e ms o adionuclide analysis, bu a he same ime, i can educe
echnical cos s i he isks o any possible echnical p oblems we e assessed be o ehand.
Au ho Con ibu ions: Concep ualiza ion, M.H.; me hodology, M.H., R.I., S.R., C.O.; so wa e, S.P.-F.;
alida ion, R.I.; in es iga ion, all au ho s.; w i ing—o iginal d a p epa a ion, R.I.; w i ing— e iew
and edi ing, M.H. and R.I.; unding acquisi ion, M.H. All au ho s ha e ead and ag eed o he
published e sion o he manusc ip .
Funding: The au ho s acknowledge unding om SENyRAD (IT1694-22), a esea ch g oup a he
Basque Uni e si y Sys em o he Basque Go e nmen (Spain). Open Access unding is pa ially
p o ided by he Uni e si y o Basque Coun y.
Da a A ailabili y S a emen : The o iginal con ibu ions p esen ed in he s udy a e included in he
a icle, u he inqui ies can be di ec ed o he co esponding au ho .
Con lic s o In e es : The au ho s decla e no con lic s o in e es .
