Procedure for determining the specific activities of radionuclides in fish by gamma spectrometry

Transcription

1 Pocede fo detemining the specific activities of adionclides in fish by gamma spectomety G--SPEKT-FISCH-0 Athos: G. Kanisch U. Rieth A. Küge Fedeal coodinating office fo fish and fishey podcts, cstacean, shell fish and aqatic plants (Leitstelle fü Fisch nd Fischeeiezegnisse, Kstentiee, Schalentiee, Meeeswassepflanzen) ISSN Vesion Janay 06

2 Scope G--SPEKT-FISCH-0-0 Pocede fo detemining the specific activities of adionclides in fish by gamma spectomety The pocede descibed in the following is sitable fo gamma spectometical analysis of samples of fish that have to be monitoed accoding to the Geman Pecationay Radiation Potection Act (StVG) in the IMIS-otine pogamme and the Gideline fo the Monitoing of Emissions and Immissions of Nclea Installations ding Regla Opeation. The pocede is sitable fo low-level measing in the famewok of adio-ecological stdies de to its low limit of detemination afte dy-ashing of the sample. Sampling The sampling of fish especially maine fish ies to a wide extent on the coopeation of pofessionals in the espective indsties (pofessional fishemen) and the podct ange available at fish makets. It is in the esponsibility of the peson collecting the sample to ense that a sample taken can be taced back to the sampled wate body. The sampling position needs to be ecoded as exact as possible. The name of the samples fish species is also an essential pat of the sample label. In case of steams, the ive kilomete has to be additionally epoted, while fo saltwate fish the FAO fishing aeas o coodinates of the catch mst be epoted by the fishemen. Accoding to an EU eglation, maketed fish mst be labelled with its egisteed tade name and the fishing aea (). The eqied sample size depends on the type of stdy to be caied ot. Fo stdies accoding to the Pecationay Radiation Potection Act and the Gideline fo the Monitoing of Emissions and Immissions of Nclea Installations, at least,5 kg of fish flesh is eqied. This eqals a minimm of 3 kg non-filleted oiginal sample. If the samples ae to be sed fo additional analyses like stontim o isotopes of pltonim and ameicim, the sample size shold be enlaged to 5 kg of fish flesh. The fish flesh will sally be pefeed fo analysis, bt some species, e. g. spat, mst be examined as a whole fish becase of thei small size. The detemining facto fo sample pepaation is the typical consmption of this species. In case of individal fishes, the peson collecting the sample mst ense that only maketable fish is sampled. The feshly collected fish ae killed qickly at the point of sampling, soted by species, packed in plastic bags, and tanspoted to the laboatoy in ice-filled containes. The fish samples ae stoed deep-fozen at ca. -0 C ntil they can be pocessed fthe in the laboatoy. Vesion Janay 06

3 G--SPEKT-FISCH Analysis 3. Pinciple of the pocede The whole fish, o fish flesh obtained afte filleting, is died at 00 C to 0 C and then ashed at a maximm tempeate of 40 C. The specific activity of adionclides in the homogenised ash ae analysed sing a gemanim semicondcto detecto. The specific activities of iodine isotopes cannot be detemined qantitatively becase of the low boiling point of iodine (84 C). The qantitative detemination of iodine isotopes in fish eqies the se of the pocede G--SPEKT-FISCH Sample pepaation All items sed fo pepaation of the ashes, e. g. stainless steel bowls, ceamic bowls, measing beakes, etc. mst be cleaned sing cleaning soltion pio each se. Ding filleting of fesh o defosted fish, attention needs to be paid to deboning them as completely as possible. The obtained fish flesh is oghly chopped p. Chopped fish flesh o whole fish samples ae placed in sitably lage stainless steel o ceamic bowls that ae laid ot with ash-fee tanspaent pape. Fozen fillets ae defosted diectly in pepaed stainless steel bowls in ode to inclde tisse flids libeated ding the defosting pocess in the sbseqent dying and ashing steps. The total fesh mass sed is to be ecoded. Aftewads, fish samples ae died ntil constant mass is eached, i. e. abot one day o two days at a tempeate of abot 0 C. Theeafte, the dy mass (TM) is detemined. The atio between fesh mass and dy mass in fish meat is abot 5. The time to each the maximm ashing tempeate depends on the lipid content of the sample; fo nomal fish it takes 45 hos. If fish with high lipid content, e. g. eel, macke, heing o spat ae to be ashed, this time needs to be extended in ode to avoid the ignition of the sample. In ode to achieve a complete ashing of the sample, the maximm tempeate is held fo anothe 96 to 54 hos. The following tempeate pogam is commonly sed fo fish samples with aveage lipid content: Step : Step : Step 3: Linea incease of the tempeate to 30 C within 3 hos; Linea incease to the maximm tempeate 40 C within 4 hos; Hold the maximm tempeate fo at least 96 hos, optimal 54 hos. The final tempeate of 40 C is selected to avoid the volatilisation of caesim. Expeiments to this effect, sing the tempeate pogam listed above, evealed ashing-indced losses of abot %. Note The dange of ignition ding the ashing pocess ises, when the sample consists of mateial high in lipid content, e. g. cod live. Theefoe, the bowls mst contain only thin laye of these samples. The maximm tempeate mst be selected lowe than 380 C in these instances. Vesion Janay 06

4 G--SPEKT-FISCH-0-03 Once ashing has been completed and the sample has cooled down, the mass of the ash is ecoded. Fo fish meat, a atio of fesh mass to ash mass of abot 80 (ange 65 to 95) has sally to be expected; in whole fish, it may be lowe by a facto of. Cabon esides still contained in the ash will not affect the eslts of the gamma spectometic analysis. The ash is homogenised sing a mota, filled into a sitably lage measing beake, and then caeflly manally compessed with a stamp. The obtained filling height is ecoded. The measement geomety is calclated fom the mass and filling height of the sample and the diamete of the measing beake. The compessed density is commonly aond 0,5 g cm Radiochemical sepaation No adiochemical sepaation is eqied. 4 Measing the activity 4. Geneal The basics of gamma spectomety ae discssed in the basic chapte -SPEKT/GRUNDL of this pocedes manal and in the liteate (, 3, 4). 4. Calibation 4.. Detemination of the detection efficiency Fo detemining the enegy-dependency of the detection efficiency, efeence is made to the basic chapte -SPEKT/GRUNDL of this pocedes manal. A calibation sing a calibation soce is descibed hee. A sitable calibation soce is e. g. an aqeos soltion of a taceable standad o a esin containing taceable amonts of adioactive componds. Mathematical calibation of the detection efficiency may also be sed if the eqied pemises ae flfilled. The ative standad ncetainties of the activities sed shold be less than %. The ative standad ncetainty of Pb-0 may be lage de to conditions of manfacting. The measement dation of the calibation has to be selected to ense standad ncetainties of the net cont ates to be below %. An example of a calibation sing an aqeos soltion with a density of,03 g cm -3 (hydochloic acid, mol l - ) is descibed in the following. Two altenatives ae available which diffe in the selection of adionclides and depend on the consideation of coincidence smmation. Vesion Janay 06

5 4... Calibation sing single-line adionclides G--SPEKT-FISCH-0-04 A calibation soltion containing sfficient activity of a gamma emitting adionclide with only one emission line in the enegy ange between 00 kev and 00 kev, e. g. S-85, Cs-37, Mn-54 o Zn-65, espectively, is sed. To extend this calibation cve to enegies smalle than 00 kev, a second soltion containing e. g. Pb-0, Am-4, Cd-09 nd Co-57 is eqied. A cve is fitted to the vales obtained by eqation (): R n,, i W E, i f E, i f4, () A p E, i The symbols in eqation () mean: A E,i activity of the adionclide sed fo the calibation at the efeence date in ; enegy of the gamma line i of adionclide in kev; W(E,i) detection efficiency fo wate, depending on enegy and fill level in - s - ; R n,,i net cont ate of line i of adionclide in s - ; f (E,i) self-absoption coection facto in wate ative to hydochloic acid ( mol l - ): H O f ( E, i ) MC ; MC HCl MC detection efficiency, calclated by Monte Calo (MC)-simlation in - s - ; f 4, t A the decay coection facto of adionclide f4, tm e tm e t A ; time peiod between commencement of measing and efeence date of the standad in s; t m dation of measement in s; p (E,i) pobability of gamma emission of line i fom adionclide. K-40 is the only available single-line emitting adionclide in the enegy ange geate than 00 kev, bt it eqies lage peiods of measement. Theefoe, the mlti-line gamma emitting nclide Y-88 is sed instead, bt aftewads a coection fo coincidence smming effects is needed to avoid a bias in the calibation cve (see section 4...). Vesion Janay 06

6 4... Calibation sing mlti-line adionclides G--SPEKT-FISCH-0-05 The expeimental effot may be edced when coections fo coincidence smmation can consideed aleady ding calibation, becase then the enegy ange between 47 kev and 836 kev may be coveed by a single soltion containing a mixte of adionclides. This mixte consists of the adionclides fo the lowe enegy ange mentioned in section 4... and additional mlti-line adionclides like Te-3m, C-5, Sn-3, Cs-34, Co-60 and Y-88. A calibation cve is fitted to vales calclated by eqation (): R n,, i W E, i f E, i f E, i f4, () A p E, i The additional symbol in eqation () means: f (E,i) coection facto fo coincidence smmation of line i emitted by the adionclide Filling height dependent calibation cves The calibation mst be caied ot fo diffeent filling heights. The filling heights of the measing pepaations ae selected accoding to the ange of filling heights expected in samples. Fo enegy-dependent calibation cves fo diffeent filling heights ae shown in Fige. Fig. : Detemined detection efficiency in % and fitted calibation cves fo diffeent filling heights between mm and 56 mm, odeed fom top to bottom; the calibation was caied ot on an n-type detecto with alminm endcap. Vesion Janay 06

7 4.. Coection fo self-attenation G--SPEKT-FISCH-0-06 The self-attenation of a sample depends on its density, its elemental composition and the enegy-dependent mass attenation coefficients of the single elements. A self-attenation coection facto f 5(E) is sed to coect the detection efficiency fo wate as obtained in section 4.. to those of fish-ash. This coection facto depends on the gamma-ay enegy, the density of the pepaation, the elemental composition of the ash and the beake and finally the filling height, espectively. Softwae-tools ae essential fo its calclation. Theein, an appoximate knowledge of the detecto s geometic dimensions is sfficient. The elemental composition listed in Table may be sed to calclate the selfattenation coection facto of ash fom fish flesh as weighted mean of the massattenation facto fom single elements (5, 0). Tab. : Typical composition of ash fom fish flesh Element esp. compond ative mass faction K 0,45 PO4 0,460 Cl 0,09 Na 0,067 ZnO 0,0576 CaO 0,0308 MgO 0,0305 The following eqation is sed to calclate the enegy depending self-attenation facto f 5(E) in the enegy ange lage than 45 kev: with: f 5(E) E a H O a 4 MC f 5 E a E a3 E (3) Ash MC self-attenation coection facto fo ash ative to wate; gamma-ay enegy in kev; a k paamete obtained thogh cve fitting (k =,,4). Fige shows fo cves fitted to calclated vales of the enegy dependent selfattenation facto obtained fo ash fom fish flesh and hydochloic acid ( mol l - ). It is obvios that f 5(E) stongly inceases in the enegy ange below 45 kev. Fo enegies significantly below 40 kev it might be necessay to inclde a thid powe fnction tem in eqation (3). Vesion Janay 06

8 G--SPEKT-FISCH-0-07 Fig. : Calclated self-attenation coection factos as fnction of the gammaay enegy afte calibation sing hydochloic acid ( mol l - ) and in ash fom fish flesh; the filling-height ae 40 mm, the density of the ash is 0,47 g cm -3 and that of hydochloic acid,03 g cm -3. Vales of the ative standad ncetainty of f 5(E) fo photon enegies above 00 kev have been detemined to be aond,5 %; the inflence of measement geomety and elemental composition of the ash inceases fo lowe photon enegies, which leads to a stong incease in ative standad ncetainty Detection efficiency in ash The analysis fo specific activities of gamma-ay emitting adionclides in the sample eqies to detemine the detection efficiency in fish ash A(E). It is calclated as the qotient of the detection efficiency in wate W(E) and the self-attenation coection facto f 5(E). W E A E (4) f E 5 In case that the standad ncetainty of the activities sed fo calibation is less than %, vales of the ative combined standad ncetainty of the detection efficiency in ash A(E) in the ange of % to 4 % fo photon enegies lage than 00 kev ae achievable; they may be mch lage fo photon enegies below 00 kev. Vesion Janay 06

9 G--SPEKT-FISCH Backgond Backgond specta need to be ecoded at egla intevals to check the gamma spectomete fo contaminations. Measing peiods fo this ppose shold be at least,5 days to 3 days. It is ecommended to obtain a mean vale and standad deviation of the net cont ate of each individal backgond gamma-ay enegy fom two o thee backgond specta. This will typically encompass lines ating to Ra-6 decay podcts which may exhibit some cont ate flctation depending on the ventilation of the oom. They may be edced by e. g. the spply of gaseos nitogen escaping fom the dewa sed fo cooling of the detecto to the measement chambe. Fo samples of fish, iably detemining the K-40 backgond cont ate of the backgond effect is impotant in ode to be able to se the K-40 activity detemined in fish fo veifying the coectness of the sbseqent sample spectm analysis. 4.4 Gamma spectometical measement The detemination of the specific activity of gamma emitting adionclides in fish ash does not necessaily eqie a low-level gamma spectomete, becase a significant inpt to the plse height spectm oiginates fom the Compton spectm of K-40. This inpt may incease the backgond of the sample compaed to the backgond checks by a facto of thee. Geneally, the specific activity concentation of K-40 in fish flesh is aond 0 kg - FM and in whole fish aond 80 kg - FM. Cylindical polyvinylchloide (PVC) beakes with plane bottom ae sed fo the analysis. Note Compaed to othe plastic mateials, PVC has got the advantage that the detection efficiency fo X-ay enegies is edced de to the highe absoption of smalle enegies. This may inflence the smming of coincidences (see section 4... and basic chapte -SPEKT/GRUNDL of this pocedes manal). The measement is nomally caied ot ove night. The measing peiod may be enlaged, depending on the scope of the analysis o the eqied detection limit (see section 5.). A coection of coincidence smming effects accoding to section 4... in -SPEKT/GRUNDL has to be applied, if nclides with the emission of mltiple gamma-ay enegies ae to be detemined; see also (6, 7, 8). Vesion Janay 06

10 G--SPEKT-FISCH Calclation of the eslts 5. Eqations When detemining specific activities of adionclides in ash fom fish flesh, intefeences de to gamma lines of diffeent adionclides ae scacely occing. Theefoe, specific activities of adionclides may be calclated eithe fom a single gamma line o, in the case of mltiple-line adionclides, by sing a weighted mean. If intefeences occ, efeence is made to the basic chapte -SPEKT/INTERF of this pocedes manal. 5.. Eqations fo calclating the specific activity fom a single gamma line If a net cont ate R n, at the gamma-ay enegy of the adionclide has been detected, the eslting specific activity a, ative to fesh mass (FM) and the date and time of sampling, is calclated accoding to eqation (5): a t A f f3 e Rn, Rn, (5) A p m A qf with: f3 Heein ae: tm e tm R n, net cont ate of the line of the adionclide in s - ; pocedal calibation facto in s kg - ; f f 3 coection facto fo coincidence smming; coection facto fo the decay of the activity of the adionclide ding the measement; A detection efficiency in ash in - s - (see section 4..3); p emission pobability of the gamma line of the adionclide ; m A q F mass of the ash sed fo the measement in kg; atio of fesh mass to ash mass; t A time peiod between sampling and beginning of the measement in s; t m dation of measement in s; decay constant of the adionclide in s -. The net cont ate of the gamma line of the adionclide is calclated accoding to eqation (6): R n, R b, R T, R 0, Heein ae: (6) R b, goss cont ate of the line of the adionclide in s - ; R T, backgond cont ate ndeneath the line of the adionclide, e. g. as cont ate of a tapezoidal backgond, in s - ; R 0, net cont ate at the line of the adionclide in a backgond spectm in s -. Vesion Janay 06

11 G--SPEKT-FISCH-0-0 The genealized expession to calclate the ncetainty of the net cont ate is given in eqation (7), with the coefficients µ k ae to be detemined accoding to eqation (8): Rn, 0 Rn, Rn, (7) with coefficients: 0 0 ; tm R R T, R0, tm T, 0, ; R (8) Using the tapezoidal method (assming a linea backgond continm) the coefficient µ is given by eqation (9): R T, b R T,0, b0 R 0, (9) t m L tm t 0 t 0 L0 Heein ae: t 0 dation of the backgond measement in s; b, b 0 line widths of sample and backgond specta at the espective peak baselines in channels; L, L 0 nmbes of channels fo the sample and fo the backgond spectm, espectively, ove which the backgond continm to the left and to the ight of the peaks ae estimated; R T,0, backgond continm cont ate at the line of the adionclide within the backgond spectm, e. g. as a tapezoidal backgond cont ate in s -. Eqation (9) is also a sfficient appoximation fo a backgond estimated by an empiical backgond step fnction. The standad ncetainty of the net cont ate (R n,) calclated by eqations (7) to (9) is given by: R R R T, b R T,0, b0 R µ R0, (0) tm tm tm L tm t0 t0 L 0 When no cont ate occs at coesponding gamma-ay enegy of backgond spectm eqation (0) is edced by the last two tems. The ative standad ncetainty of the pocedal calibation facto is detemined accoding to eqation (), whee the ncetainty of the decay coection may be neglected: f f p m q () 3 A A F The combined standad ncetainty of the specific activity a sing eqation (5) is calclated as: a R R () Vesion Janay 06

12 5.. Eqations fo calclating the specific activity fom mltiple gamma lines G--SPEKT-FISCH-0- The specific activity a ative to fesh mass (FM) and the time of sampling of a nmbe of intensities ( geate than ) at gamma-ay enegies of adionclide sfficiently detected ae calclated accoding to eqation (3): a t A e f3 M A A (3) m A q F Heein, A epesents the activity () at the time of measement, which is calclated as a weighted mean fom the intensity of a nmbe of single gamma-ay enegies of nclides, A A A (4) A wheein the standad ncetainty (A ) is given by eqation (5): A A (5) The index in these eqations identifies single gamma-ay enegies. The activities A of the individal gamma-ay enegies ae calclated accoding to eqation (5): A R n, f, R n, A, p, (6) Heein ae: M pocedal calibation facto in kg - ; pocedal calibation factos in s; R n, net cont ate of the gamma-ay enegy in s - ; A, detection efficiency of the gamma-ay enegy in ash in - s - (see section 4..3); p, emission pobability of the gamma-ay enegy ; f, coincidence smming coection facto fo the gamma-ay enegy ; f, self-attenation coection facto of the gamma-ay enegy, fo ash ative to wate soltion: H O MC f ; MC Asche The vaiances of A ae calclated accoding to the following eqation: A R R (7) n, n, Vesion Janay 06

13 G--SPEKT-FISCH-0- When the net cont ates ae calclated sing the tapezoidal backgond pocede, thei standad ncetainties ae calclated accoding to eqation (0). If peak fitting is sed instead, that facto (+b/(l)), epesenting the tapezoidal backgond pocede, changes into a facto f B, which depends on the method sed fo peak fitting: R, n, R n, (8) tm R T, R T,0, b0 µ, fb R0, (9) tm tm t0 t0 L0 The facto f B geneally depends on the aveaged backgond continm pe channel ndeneath the gamma-ay enegy and on the atio R n, tm R T, tm Fo net cont ates close to the detection limit o the decision theshold, f B may be appoximated by a fixed vale; see the calclation example in section 5... Finally, the standad ncetainty of the specific activity is calclated as follows: with a A A (0) M M m q () M A F Note The calclations pesented in this section ae laboios if caied ot manally; theefoe, the softwae UncetRadio has been sed to calclate the paametes of the example (see section 5..). Sch softwae is eqied fo the calclation of the decision theshold and the detection limit by linea nfolding, which ses iteation, and theewith diffes fom the example shown in section 6.. Vesion Janay 06

14 5. Woked examples 5.. Detemining the specific Cs-37 activity G--SPEKT-FISCH-0-3 The following vales ae sed fo calclating the specific Cs-37 activity in, kg fish flesh (FM): m A = 0,037 kg; q F = 83,54; R n,cs-37 = 0,0063 s - ; = 0, s - ; R T,Cs-37 = 0,007 s - ; b/(l) = 0,53; p = 0,8499; f =,000; f 5 = 0,976; (m A) = 0,004; (q F) = 0,0 ; (R n,cs-37)= 0,00038 s - ; (ε) = 0,09; (p ) = 0,0035; (f ) = 0; (f 5) = 0,008. The standad ncetainties of the following inpt qantities ae negligible: t A =, s; t Cs-37 = 9, s; t m = 7000 s. This leads to the coection facto f 3 fo the decay ding the measement dation: f 3 0 7, , e,00003 The detection efficiency in ash A is calclated accoding to eqation (4): A 0,03056 s 0,033 s 0,976 The pocedal calibation facto accoding to eqation (4) is obtained fom:,0, , , e - s kg 0,033 0,8499 0,037 83,54 34,655 - s kg The specific activity in the fish flesh ative to the fesh mass (FM) eslts fom eqation (5): a Cs ,655 0,0063 kg 0,9 kg - The ative standad ncetainty of the pocedal calibation facto is calclated by eqation (): 0,008 0,09 0,0035 0,004 0,0 0, 0364 Vesion Janay 06

15 G--SPEKT-FISCH-0-4 The standad ncetainty of the net cont ate is obtained by eqation (0) with neglecting the last two tems: 0,0063 0,007-4 s 3,809 0 s R 0,53 Cs The ative standad ncetainty of the specific activity is calclated accoding to eqation (): 0, ,0063 a 0,0364 0, 0704 Cs -37 Finally, the specific Cs-37 activity is obtained as: a Cs-37 = (0,9 ± 0,05) kg - (FM) 5.. Detemining the specific Cs-34 activity Fo calclating the specific Cs-34 activity, the two main gamma enegies at 604,7 kev and 795,9 kev wee evalated in a sample 3,7 kg (FM) of flesh fom Noth Atlantic cod off Geenland, whose ash was meased ove a peiod of abot 5 days on a Gemanim detecto with ative efficiency of 35 %. The nmeical vales sed fo the calclations ae the following: m A = 0,05 kg; q F = 7,4; (m A) = 0,004; (q F) = 0,0. The vales fo calclating the activities of the two Cs-34 gamma lines ae: Gamma line at 604,7 kev: R n, = 4, s - ; = 0,007 - s - ; R T, = 4, s - ; p, = 0,9763; f, =,33; f 5, = 0,943; ( ) = 0,0950; (p,) = 0,0008; (f,) = 0,009; (f 5,) = 0,0. Gamma line at 795,9 kev: R n, = 3, s - ; = 0, s - ; R T, = 4, s - ; p, = 0,854; f, =,368; f 5, = 0,93; ( ) = 0,063; (p,) = 0,0005; (f,) = 0,045; (f 5,) = 0,0. Vesion Janay 06

16 G--SPEKT-FISCH-0-5 The standad ncetainties of the following inpt qantities ae negligible: t A =, s; t Cs-34 = 6, s; t m =, s. In this example, a vale of,08 is attibted to the facto f B. Fo the facto M fom eqation (3) a vale M = 0,3406 kg - A is obtained with e f3 =,644; its ative standad ncetainty accoding to eqation () is obtained as 0,00396 kg -. Vales = 5,7973 s (604,7 kev) and = 75,6845 s (795,9 kev) ae obtained fo the in eqation (6). By mltiplying vales of R n,i and the activities associated with the two lines ae calclated as A = 0,0484 and A = 0,0903. The ncetainties of the two net cont ates calclated by eqations (8, 9) ae (R n,) = 6, s - and (R n,) = 6, s -, espectively. The sqaed ative ncetainties of the vales become: 0,009 0,0 0,0950 0,0008 s t 6, s 0,045 0,0 0,063 0,0005 s 5, s The vaiances of the activity vales of the two lines ae calclated accoding to eqation (6): 4-4 A 6,67 5,7873 4, , ,7873, A 6, ,6845 3, , ,6845, Fist, the vaiance of the Cs-34 activity is calclated accoding to eqation (4): A Cs -34,36 5 0, ,7 3933,7 8, A,88 0 Cs -34 Vesion Janay 06

17 Aftewads, the activity of Cs-34 is obtained sing eqation (3): G--SPEKT-FISCH-0-6 A Cs -34 ACs -34 A A A Cs -34 8, ,0484 5,36 0 0,0903 5, , ,808 38,95 0,06 Finally, the vale and the associated standad ncetainty of the specific Cs-34 activity ae detemined accoding to eqations (, 0): a Cs ,3404 0,06 kg 8,78 0 kg acs -34 8, , ,88 0 0,06 - kg 9, kg 5.3 Consideation of ncetainties The combined standad ncetainty of the specific activity of Cs-37 amonts to be less than 0 % in the IMIS otine measement pogam, whee the lagest contibtion oiginates fom the net cont ate. If the self-attenation coection fo ash fom fish flesh is neglected, anothe systematic eo of p to 5 % will be the eslt. Fo mlti-line adionclides sch as Cs-34, the ncetainty contibtion of the coincidence smming coection facto (see basic chaptes SPEKT/GRUNDL and -SPEKT/SUMESC of this pocedes manal) has to be taken into accont, which may lead to additional few pe cents in case of significant coections. Vesion Janay 06

18 G--SPEKT-FISCH-0-7 Vesion Janay 06 6 Chaacteistic limits of the pocede The calclations of decision theshold and detection limit follow the standad ISO 99 (9). Fo single-line emittes (see section 5..) explicit eqations fo calclating decision theshold and detection limit can be applied. Fo this ppose an Excel file (see section 7.3.) as well as a poect file fo the pogam UncetRadio (see section 7.3.) ae available on the website of this pocedes manal. Fo mlti-line emittes (see section 5..) these eqations can only be calclated with softwae sppot. At pesent, a coesponding poect file fo the pogam UncetRadio (see section 7.3.) is available on the website of this pocedes manal. 6. Eqations 6.. Eqations fo calclatation of the detection limit of the specific Cs-37 activity Befoe calclating the detection limit a # the decision theshold of the adionclide s specific activity a * is detemined sing eqation (): 0, T, 0, T, m * R R R R t k k a () This allows the detection limit a # to be calclated by eqation (3): * # k k a a (3) with axiliay qantities: m * t a k k Heein ae: k - qantile of the nomal distibtion associated with the eo of fist kind; k - qantile of the nomal distibtion associated with the eo of second kind.

19 6.. Eqations of calclation of the detection limit of the specific Cs-34 activity G--SPEKT-FISCH-0-8 While the decision theshold fo mlti-line emittes may be calclated diectly, the sbseqent deivation of the detection limit eqies iteation. Details ae given in the basic chapte EKG/NWG-ISO-0 of this pocedes manal. The decision theshold of the specific Cs-34 activity is obtained by eqation (4): * a k M A 0 k M R T, tm f B (4) The detection limit of the specific Cs-34 activity is estimated accoding to eqation (5). # a * a k # a ' (5) with an iteated standad deviation (a # ): * # a ' a a k- * # a a ' k - a 6. Woked examples 6.. Decision theshold and detection limit of the specific Cs-37 activity Using the vales of the inpt qantities fom section 5.. the coefficient µ is deived accoding to eqation (9): 0,007 0,53 s 5, s 7000 * Using this vale, the decision theshold of the specific activity a Cs -37 is obtained fom the pocedal calibation facto and the nomal distibtion qantile k - = 3: * a Cs ,65 3,0 5, kg 0,049 kg Vesion Janay 06

20 G--SPEKT-FISCH-0-9 Accoding to eqation (4) the detection limit of the specific activity # a Cs -37 is: # a Cs -37 0,049,06 0,996 0,996,06,645 3,0 kg 0,0565 0,9460 0,30067 kg 0,0406 kg with vales of the axiliay qantities,645 0,0374 0, 996,645 0,049 34, , Decision theshold and detection limit of the specific Cs-34 activity Fist, the following axiliay qantity fom eqation (4) is calclated sing the vales of qantities fom section 5.. and the nomal distibtion qantile, k - = 3: 5,340 0 R T, f B tm Theewith, the decision theshold of the specific Cs-34 activity amonts to: * a Cs -34 3,0 0,3404, kg, kg This decision theshold vale agees qite well with that vale obtained fom sing UncetRadio (see section 7.3.). It is smalle compaed to the two single-line decision theshold vales, which ae 3, m kg - and 4,55 m kg -, espectively. The detection limit of the specific Cs-34 activity is estimated with a fist step of iteation accoding to eqation (5) as follows: 3 #, a ' 9, 0 3,0 3,645 3, , ,0 8, kg 4-8,888 0 kg # a Cs ,5736 0,645 8,888 0 kg 4,036 0 kg This iteatively estimated detection limit is in good ageement with the eslt fom UncetRadio, 4, kg - (see section 7.3..). Vesion Janay 06

21 7 Cataloge of chemicals and eqipment 7. Chemicals Cleaning agent: e. g. RBS-50-Spe-Flüssigkonzentat %. 7. Eqipment Odinay eqipment of a adiochemical laboatoy. 7.. Sampling ice containe / cooling boxes; plastic bags; deep feeze (ca. -8 C), if the samples have to be stoed. 7.. Sample pepaation filleting boad made of plastic; shapened filleting knifes; ct-esistant gloves Dying/ashing G--SPEKT-FISCH-0-0 incineation ovens with catalytical teatment of exhast gases; oganic exhast gases shall lagely be bned to CO nd H O; stainless steel bowls (V4A) o ceamic bowls adapted in size to the intenal volme of the oven, tanspaent pape with an aeal density of abot 90 g m - as backing mateial fo the stainless steel containes; 7..4 Calibation and measment gamma mitting adionclides, pefeably single-line emittes; if applicable, within a single soltion coveing the whole enegy ange to be calibated; cylindical plastic containes, e. g. made fom PVC, with an inne diamete of abot 7 cm and a capacity of ca. 0 ml, pefeably with plane bottom; High-pity Gemanim-semicondcto detecto with a ative efficiency pefeably between 0 % and 60 % ative to a 3 x 3 NaI(Tl)-cystal and a fllwidth-at-half-maximm less than,0 kev fo the,33 MeV gamma-line of Co-60; measing electonics; lead shielding with ca. 0 cm wall thickness Evalation softwae fo accmlating and evalating gamma-ay specta; softwae tools fo calclating the peak and total efficiencies and coection factos fo coincidence smming and self-attenation. Vesion Janay 06

22 G--SPEKT-FISCH Pogam sppoted evalation 7.3. View of the Excel sheet Calclating the specific Cs-37 activity Pocede fo the gamma spectometic detemination of the specific activities of adionclides in fish G--SPEKT-FISCH-0 Vesion Janay 06 (ISSN ) Sample identification: Vaiant : single-line adionclide Cs-37 #Nmbe of paametes p: 3 Colos: vales fom Vbasic k_alpha: qantile fo (-) 3 Excel fomlae (se) k_beta: qantile fo (-),645 Manal inpt of vales gamma: pobability fo conf.limits 0,05 Def. Excel-Vaiable (se) #Keywods Data inpt: vaiable names: Uncetainty bdget: #Vales of paametes p: Unit: Inpt vales patial ncetainty bdget StdDev: deivatives bdget: in % p #Nmbe of goss conts Ng: Ng 650,6 5, , , ,34 p tapezoidal BG cont ate /s RT,7000E-03 0, , , ,938 p3 b/l bl 5,3000E-0 0,00000E ,000 p4 detection efficiency eps 3,05600E-0 8,8640E-04-7, , ,958 p5 emission pobability, 66,7 kev p_gamm 8,49900E-0,99700E-03-0, , , p6 ash mass kg ma 0, ,6800E-05-6, , ,33 p7 atio fesh mass / ash mass qf 83, ,67080E+00-0, , ,066 p8 Time elapsed Sampling-->StatMeasm s ta,97880e+07,6008e-0 0 0,000 p9 half-live of Cs-37 s tcs37 9,48300E+08-3,3466E- 0 0,000 p0 self-attenation coection facto _f 0, ,80800E-03 0, , ,9 p conting dation s tm 7000,00 0,00000E+00-4,346E ,000 p net cont ate of the BG peak /s RnNE 0,000E+00 0,00000E+00-34, ,000 p3 conting dation of the BG spectms tne 7000,00 0,00000E ,000 (the list may be contined hee) Model section c = Facto * Rn axiliay eqations: (fomlae) #Goss conting ate Rg: /s Rg 9,03000E-03 h decay coection measing peiod _f3 9,99974E-0 h decay coection Sampling-->StatMes _f4,0457e+00 (the list may be contined hee) (fomlae) #Net conting ate Rn: /s Rn 6,3000E-03 #Calibation facto, poc.dep.: *s/kg Facto 34, #Vale otpt qantity: /kg Reslt,9007E-0 0, <-- otpt vale modifiable by VBA #Combined standad ncetainty: /kg Reslt,5430E-0 #Decision theshold: /kg 0, #Detection limit: /kg 0, fthe deived qantities (ISO 99): axiliay qantity omega Omega, Best estimate /kg BestWet,9007E-0 Uncetainty of best estimate /kg,5430e-0 lowe confidence limit /kg,88779e-0 ppe confidence limit /kg,4936e-0 Calclate! The Excel file can be fond on the website of this pocedes manal Calclating the specific Cs-34 activity Becase of the complexity of the calclations an Excel file is not available. Vesion Janay 06

23 G--SPEKT-FISCH View of the eslt page of UncetRadio Calclating the specific Cs-37 activity The UncetRadio poect file can be fond on the website of this pocedes manal Calclating the specific Cs-34 activity The UncetRadio poect file can be fond on the website of this pocedes manal. Vesion Janay 06

24 G--SPEKT-FISCH-0-3 Liteate () Veodnng (EG) N. 065/00 de Kommission vom. Oktobe 00 mit Dchfühngsbestimmngen z Veodnng (EG) N. 04/000 des Rates hinsichtlich de Vebacheinfomation bei Ezegnissen de Fischeei nd de Aqaklt. Amtsblatt de Eopäischen Gemeinschaften , L 78/6 () Gilmoe, G.: Pactical Gamma-Ray Spectomety. nd Edition. Chicheste: John Wiley & Sons Ltd., 008. ISBN (3) Knoll, G. F.: Radiation detection and measement. 4th Edition. New Yok: John Wiley & Sons Inc., 00. ISBN (4) Debetin, K., Helme, R. G.: Gamma- and X-Ray Spectomety with Semicondcto Detectos. Amstedam: Noth Holland, 988. ISBN (5) Bege, M. J., et al.: XCOM: Photon Coss Sections Database. NIST Standad Refeence Database 8 (XGAM) [Online-Datenbank]. Letztes Update: Novembe 00 [Zgiff am: ]. Vefügba nte: (6) Debetin, K., Schötzig, U.: Bedetng von Smmationskoektionen bei de Gammastahlen-Spektometie mit Gemanimdektoen. PTB-Ra-4. Banschweig: Physikalisch-Technische Bndesanstalt, 990. ISBN (7) Kanisch, G., Vidma, T., Sima, O.: Testing the eqivalence of seveal algoithms fo calclation of coincidence smming coections. Appl. Radiat. Isot., 009, Vol. 67, S (8) Vidma, T., Kanisch, G.: Intinsic eo of the point-soce and the LS-cve appoximations in teatment of te coincidence smming. Appl. Radiat. Isot., 00, Vol. 68, S (9) ISO 99:00, Detemination of the chaacteistic limits (decision theshold, detection limit and limits of the confidence inteval) fo measements of ionizing adiation Fndamentals and application. (0) Soci, S. W., Fachmann, W., Kat, H.: Lebensmitteltabelle fü die Paxis. 5. Aflage. Stttgat: WVG, 0. ISBN Vesion Janay 06