Characterization of Nuclear Waste from Decommissioning 

XiaolinHouTechnical University of Denmark

Center for Nuclear Technologies, Risø Campus, Roskilde, DenmarkE-mail: xiho@dtu.dk

Steps of decommissioning of nuclear facility• Preparation (investigating the background radioactivity around NPP)• Cleanout

– Removal of most radioactive component such as spend fuel elements, reactor internals, reactor vessel, etc. which is transferred for storage and disposal. (high level waste). (Evaluation of radioactivity before transferring)

• Decontamination– Removal of contamination from surfaces of facilities or equipment by

chemical or mechanical methods, which can reduce the waste volume and active level in the waste. (Measurement of radioactivity to evaluation the decontamination, and estimation of radioactivity in the waste)

• Dismantling– Equipments within the facility are dismantled and classified by

estimation of the radioactivity)• Demolition and site clearance

– Buildings demolished and radioactive wastes removed to storage or disposal facilities after estimation of the radioactivity in the waste.

• Release of the site to alternative use (measure the radioactivity level in the released area)

Production of main radionuclides in nuclear reactors

•Long-lived fission products137, 135Cs,106Ru, 90Sr, 99Tc, 129I, etc.

•Neutron activation products (long-lived)58,60Co, 133Ba, 134Cs, 152,154, 155 Eu, 3H, 14C, 36Cl, 41Ca, 63, 69Ni, 94Nb, 55,59Fe, 93Zr, 93Mo,54Mn, 110mAg, 238-241Pu, 241Am, 243,244Cm, 237Np, etc.

4 8 October 2013

• Gamma radionuclides60Co, 133Ba, 137Cs, 134Cs,

106Ru, 152,154, 155 Eu, 58Co, 54Mn,59Fe, 110mAg, 94Nb, etc.

No chemcial separation is normally needed.

5

Beta Emitter3H, 14C, 36Cl, 41Ca, 55Fe, 63, 59Ni, 90Sr, 99Tc, 129I,93Zr, 93Mo.

Difficult to measure, separation of individual radionuclide from matrix and all other radionuclides is needed before measurement.

3H 14C32P

Emax: 18, 156 and 1700 keV for H-3, C-14 and P-32 respectively

LSCGas flow multi-channel beta counter

6 8 October 2013

• -emitter (actinides)238-241Pu, 241Am, 243,244Cm, 237Np, etc.

High toxicity, difficult to measure, separation of individual radionuclide from matrix and all other radionuclides is needed.

238Pu

239+240Pu

242Pu

7 8 October 2013

• Graphite (reactor)– 3H, 14C, 55Fe, 63, 59Ni, 60Co, 152Eu

• Concrete (normal or heavy)– 3H, 14C, 41Ca, 60Co, 55Fe, 63, 59Ni, 133Ba, 152Eu

• Steel/stainless steel– 55Fe, 63, 59Ni, 36Cl, 93Zr, 93Mo, 94Nb, 60Co, 152Eu,

transuranics• Other metals (Aluminium, Lead)

– 60Co, 63Ni, 55Fe, 36Cl• Water

– 3H, 14C, 63Ni, 99Tc, 129I, 90Sr, 60Co, 137Cs, transuranics• Ion exchange resin

– 14C, 55Fe, 63,59Ni, 99Tc, 36Cl, 93Zr, 93Mo, 94Nb 90Sr, 129I, 137Cs,60Co, 135Cs, transuranics

Waste samples and the relevant critical radionuclides for decommissioning

Radiochemical Analysis of Radionuclides

Samples

Pre-concentration

- spectrometry measurement(137Cs, 134Cs, 60Co, 152Eu)

Radiochemcial separation of target radionuclides from matrix and interferring radionuclideds

- couting(3H, 14C, 55Fe, 63Ni, 90Sr, etc.)

- spectrometry(239,240Pu, 237Np, 226Ra)

AMS(129I, 36Cl, 59Ni,41Ca)

ICP-MS(239Pu, 240Pu, 237Np, 99Tc)

Other MS

LSC AMS ICP-MS

Radioanalytical Chemistry of important radionculides for decommissioning

9 8 October 2013

3Hand14C41Ca 36Cl 55Feand63Ni Automatedsystemforrapidanalysis

• Production of 3H in reactor• 2H (n, )3H• 6Li(n, )3H • 3He(n, p)3H

Determination of 3H and 14C in graphite, concrete, and other solid materials

• Production of 14C in reactor

– 13C(n, )14C– 14N(n, p)14C– 17O(n, )14C

Nuclides Half life Decay Emax, keV

3H 12.35 y 18.6

14C 5736 y 156

Rapid separation of 3H and 14C waste samples by combustion using Packard Oxidizer

...h7\Q010601N.001 11

...h7\Q010601N.001 12

...h7\Q010601N.001 21

...h7\Q010601N.001 22

Sample Spectrum

1,0009008007006005004003002001000

550

500

450

400

350

300

250

200

150

100

50

0

...C0\Q014001N.001 11

...C0\Q014001N.001 12

Sample Spectrum

1,0009008007006005004003002001000

500

450

400

350

300

250

200

150

100

50

0

14C

3H

3H and 14C in concrete and graphite

Nootherimpuritynuclideswere seenintheH‐3andC‐14spectrum 0

1

10

100

1000

100 150 200 250 300

conc

entr

atio

n of

3H

, B

q/g

Distance to the core, cm

Core-A

Core-B

Average SD % Average SD % Average SD %C-14 TK5.5 Yi 2,12E+02 4,50 2,08E+02 5,2 2,17E+02 3,8C-14 TK7.5 Yi 2,67E+04 2,19 2,54E+04 2,93 2,64E+04 4,27H-3 TK5.5 Yi 4,70E+03 17,33 4,72E+03 3,74 4,66E+03 4,12H-3 TK7.5 Yi 1,11E+06 3,39 1,05E+06 5,79 1,05E+06 4,8

Nuclide code

15-01-2003 Room temperature 110 °C (first measurement) 4 months for 5 days

3Hand14Cingraphiteandtheirstability

0

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100

100 150 200 250 300

conc

entra

tion

of 1

4 C, B

q/g

Distance to the core, cm

Core-A

Core-B

14C in concrete

EC (421.4 keV, 100%)

41Ca (21.03x105y)

41K (stable)

Nuclide Target isotope Aboundance %

Reaction Cross section, bar

Half life Decay

41Ca 96.94 40Ca(n, )41Ca 0.41 1.03105 y EC45Ca 2.086 44Ca(n, )45Ca 0.84 162.7 d -47Ca 0.004 46Ca(n, )47Ca 0.7 4.54 d , 49Ca 0.187 48Ca(n, )49Ca 1.0 8.72 min. ,

41Ca in concreteActivation products of calcium isotopes

Energy of X-rays and Auger electrons : 0.3-3.6 keVDetermination: X-ray spectrometry (<0.08%)

LSC (10-20%)

Determination 41Ca in concrete

• Separationfromatrix

– Decompositionofheavyconcretebyalkalifussion

– LeachingCabyacids

• Separationfromactivemetalssuchas60Co,152Eu,55Fe,63Ni,65Zn,54Mn,51Cr,etc.

– PrecipitationwithFe(OH)3 byhydroxidesatpH9

• Separationfromotheralkalinemetals,suchas133Ba,226Raand90Sr.

– Ca(OH)2 precipitationinNaOHsolution

Element Recovery,

%

redionuclide Decontamination

factor

Ca 97.73.9 137Cs (4.50.3)105

85Sr 97.92.1 60Co (1.20.4)105

133Ba 97.32.8 152Eu (8.50.5)105

59Fe (2.50.1)105

63Ni (2.50.2)105

• Separation of Sr from Ca by Ca(OH)2 precipitation• Ca(OH)2: insoluble, Ksp = 5.2 10-6

• Sr(OH)2 and Ba(OH)2: Soluble in alkine solution

Separation of Ca from Sr and Ba using hydroxide precipitation

Precipitate Ca as Ca(OH)2 at 0.5 –0.8 mol/l NaOH, repeat 3 times, 85% Ca can be recovered, and the decontamination factor for Sr and Ba are higer than 5x104

41Ca in heavy concrete from DR-2

...A6\Q024201N.002 12

...A6\Q044401N.002 12

...A6\Q054501N.001 12

Sample Spectrum

1,000800600400200

0.2870.2660.2460.2250.2050.1840.1640.1430.1230.1020.0820.0610.0410.02

0

Spectrum of 41Ca in concrete

Features of Method for 41Ca

• Aseparationof41Cafromconcrete iseasy tooperate

• Gooddecontaminationfrominterferringradionuclides (>104)

• Thechemicalyieldsoftheseparationproceduresfor41Cais80‐90%.

• Thedetectionlimitsfor41Ca is0.020Bq.

Hou X.L., Radiochim Acta, 2005

36Cl is long-lived radionuclides (3x105 yrs) 36Cl decays mainly by pure beta emission of

Emax=708.6 keV. 36Cl measurement is normally carried out by LSC

and AMS

Determination of 36Cl

Determination of 36Cl in graphite--- Sample decomposition

• Ashingat900˚C:‐‐‐iodineandpartofClarelost.

• Decompositionat900˚CwithO2 andtrappingiodineinNaOHsolution:‐‐‐notgoodforchlorine

• Leachingwithacid(HNO3)atheating:‐‐‐ notcompleteremoveiodineandClfromgraphite,andlossoftheleachediodine.

• DigestionwithHNO3 andtrappingiodineandchlorinewithNaOH:‐‐‐‐ Notcompleteremovalofiodineandchlorine

• How to Do?

• Aciddigestion(graphite,steel,Al,Pb,) Graphite(H2SO4:HNO3:HClO4=15:4:1) Steel,aluminum(8mol/lH2SO4) Lead(8mol/lHNO3)

Decomposition of sample to release chlorine and iodine

Flask9:3H,129I,99Tc,36ClFlask10,11:14C,129I,Sampleflask:non‐voltile elements,Ca,Ni,Fe,Cs,Co,Ba,tritium,Cl,Tc,transuranics,etc.

Determination of 36Cl in concrete--- Sample decomposition

Digestion with HNO3 and trapping iodine and chlorine with NaOH: ---- Not complete removal of iodine and chlorine

Alklinal fussion using NaOH and Na2CO3, dissolution of fused cake in water, the supernatant is used for 129I and 36Cl: ---- sample is completely decomposed and iodine and Cl are released. Iodine and Cl are not lost in alkaline medium.

Determination of 36Cl in stainless steel--- Sample decomposition

Stainless steel is normally dissolved with HCl or HCl+HNO3: --- could not be used for 36Cl because of too much Cl in HCl is introduced.

Single acid, HNO3, could not dissolve stainless steel.

10M H2SO4 with H3PO4 is sucessfully used for dissolve stainless steel 36Cl: ---- sample is completely decomposed and iodine and Cl are released.

Separation of Chlorine and iodine from

matrices and other radionuclides

Specific precipitation of Cl- with Ag+ (AgCl) can be used to selectively separation of Cl from matrix and other radionuclides (except iodine and bromine).

The separated AgCl can be dissolved in NH4OH and mixed with scintillation cocktail for LSC: But less AgCl can be used and high quench effect. How to improve?

0 .0

1 .0

2 .0

3 .0

4 .0

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0

v o lu m e , m l

Cl-3

6, B

q or

Ag,

x10

0 m

g

100m g C l, 0 .2 M N H 4N O 3-0 .6 M N H 4O H e lu t ing200m g C l 0 .2 M N H 4N O 3-0 .6 M N H 4O H e lu t ing50 m g C l, 0 .1 M N H 4N O 3-0 .6 M N H 4O H e lu t ing100 m g C l, 0 .1 M N H 4N O 3-0 .6 M N H 4O H e lu t ing

b )

c )

d )

a)

A g +

C l-

Separation of Ag+ and Cl– in anion exchange chromatography

Performance of the chemical separation procedure

Element AgClprecip.

Anion exch.

Whole proced.

Cl (recovery, %)

96.5 98.3 94.73.2

I (125I) 1.4 103 1.4 103 8.9 105

S 1.5 103 5.6 105

tritium 2.1 103 4.8 106

14C (CO32-) 1.5 103 2.8 106

Co (60Co) 1.9 103 2.5 103 1.5 106

Eu (152Eu) 4.7 103 6.5 103 8.9 106

Cs (137Cs) 3.8 103 5.1 103 7.9 106

Ba (133Ba) 6.7 103 4.9 103 5.6 106

Sr (85Sr) 4.7 103 3.3 103 6.7 106

Ni (63Ni) 5.9 103 3.8 103 4.8 106

Fe (55Fe) 1.9 103 2.8 103 2.1 106

Before separation

After separation

LSC measurement of 36Cl in waste samples

...L1\Q015101N.001 11

...18\Q010101N.001 11

...18\Q020201N.002 11

...19\Q010101N.001 11

...19\Q020201N.001 11

...19\Q030301N.001 11

Sample Spectrum

1,0009008007006005004003002001000

0.737

0.655

0.573

0.492

0.41

0.328

0.246

0.164

0.082

0

36Cl in Steel and graphite from DR-2

40

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0 100 200 300 400Cou

ntin

g ef

ficie

ncy,

%

Cl concentration, mg/ml

NaCl

NH4Cl

80

85

90

95

100

500 600 700 800

Effic

ienc

y, %

SQP(E)

100 mg Cl (NaCl)200 mg Cl (NaCl)

Recovery of Cl: >70%

Detection limit using LSC : 14 mBq

Hou et al., Anal. Chem., 2007

63Ni and 55Fe

Fe-55 decays by electron capture emitting X-rays, conversion electrons and Auger electrons (5 - 6 keV)

X ray (5.89 keV, 25.4%)

55Fe (2.73 y)

55Mn (stable)

EC (232 keV, 100%)

No gamma ray

(66.95 keV, 100%)

No gamma ray

63Ni (100.1y)

63Cu (stable)

• 63Ni: – 62Ni(n, Ni =14.5 b; Ni=3.63%)– 63Cu(n, p)63Ni, ( Cu=69.17%)

• 55Fe:– 54Fe(n, Fe =2.3 b; Fe=5.85%)– 56Fe(n, 2n)55Fe, (Fe=91.75%)

Atomic ratio: 59Ni/63Ni=6.5:1

Activity ratio: 59Ni/63Ni=1:133

Separation of Ni and Fe by anion exchange chromatography

• Ni can be completely separated from Fe, Co, Cu, Zn, U, Pu, etc.

• Fe can be separated from Ni, Cr, Mn, Th, etc.

• Ni cannot be efficiently separated from Cr, Eu, Sm, Mn, V, Sc, Ti, Zr, Ba, Th, Am.

Element

Content, %

Ni fraction Fe fractionFe3+ <0.001 >98.5Ni2+ >99.5 <0.001Co2+ <0.01 <0.001Ba2+ <7.5 <0.001Eu3+ >99.8 <0.001Cs+ >99.5 <0.001Sr2+ >99.5 <0.001

Element Recovery or decontamination factor

Ni2+ > 98.5%

Fe3+ 104

Co2+ 103

Ba2+ 104

Eu3+ 104

Cs+ 104

Sr2+ 104

Purification of Ni by specific Ni-extraction chromatography

Ni specific extraction chromatography has a higher decontamination to most of elements, such as Fe, Co, Cu, Cr. Mn, Ba, Eu, transuranics, etc.

•A higher recovery of Ni can be obtained in the procedure.

• Yellow colour Fe3+ is a very effective quenching agent

• Reduction of Fe3+ to Fe2+ using suitable reductant, such as ascorbic acid can reduce the quench, but Fe2+ is not stable and can be oxidize to Fe3+ again, and Fe2+ also has some colour quench.

• Solvent extraction of Fe3+ using some organic compounds such as di-2-ethylhexyl phosporic acid can reduce the Fe3+ colour quench, but not effective for large Fe content sample.

• In H3PO3 solution, a stable and colourless Fe-H3PO3 complex can be formed, therefore can significantly reduce the Fe3+ colour quench.

• As high as 40% counting efficiency of 63Ni in 1.5 ml of 2 mol/l H3PO3 solution.

Preparation of separated 55Fe for LSC

0

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Effic

ienc

y, %

Content of Fe (mg)

FeCl3 solutionFe3+ +H3PO3(2M)

Combined analytical procedure for 36Cl, 129I, 41Ca, 63Ni, and 55Fe

29 8 October 2013

1.0E-03

1.0E-02

1.0E-01

1.0E+00

1.0E+01

100 150 200 250 300

Distance to core, cm

Activ

ity c

once

ntra

tion,

Bq/

g

55Fe63Ni36Cl

Sample 36Cl measured, Bq

Value Uncertainty

SWIPE-111-2 2.14 0.18

SWIPE-111-1 2.04 0.19

36Clin2swipsamplesfromIgnalinaNPP

0

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Activ

ity o

f 41Ca

, Bq/

g

Distance to core, cm

Core A

Core B

41Ca in concrete core

Sample Code 36Cl, Bq/g

meanSD

63Ni,

Bq/g

36Cl/63Ni

Activity ratioGraphite 5.5 Yi 0.180.03 5.76 0.030Graphite 5.5 Yy 3.580.13 102 0.035Graphite 5.5 Ii 22.61.5 499 0.045Graphite 5.5 Iy 6.610.52 74.9 0.088Graphite 7.5 Yi 6.370.48 134 0.048Graphite 7.5 Yy 5.570.54 88.3 0.063Graphite 7.5 Ii 39.93.4 758 0.053Graphite G 3.330.28 61.2 0.054

Aluminum B1 0.0270.003 15.6 0.0017Aluminum B2 0.0230.03 15.5 0.0015

lead B4 0.00320.0012 2.58 0.0012

36Cland63Niingraphite,AluminumandleadfromDR2

Automatation of of radioanalysis

ICP-MS/ AMS

HC

SV

SP

Carrier

S WE

R2R1

Flow/Sequential injection

30

Eluates

Extraction or anion exchange chromatography

Sample solution, with Pu (IV) and Np(IV) in 8M HNO3 medium

Sequence 2: Wash with 100mL of 9M HCl, 1.2mL/min

Matrix (Ca, Mg, Fe, Pb…) Am, U

Sequence 3: Elute with 40mL of 0.5M HCl, 1.2 mL/min

Th

ICP-MS

Sequence 1: Wash with 100 mLof 8M HNO3, 1.2 mL/min

2 mL AGMP-1M

Pu and Np

Sequence 1 Sequence 2 Sequence 3

Load, 1.2 mL/min

31

An automated method for determination of 99Tc, Pu and Np

ICP-MS for 99Tc

Shi, Hou et al. Anal. Chem. 2012

One column is not enough

Two TEVA columns

1) High chemical yield of Tc

2) Sufficient removal of Mo and Ru

Separation of 99Tc from Mo and Ru

Developed methods Reported methods

Decontamination factor for Mo 4×104 ~ 1×106 < 5×103

Decontamination factor for Ru 1×105 ~ 7×106 < 1×104

Analytical time (h) < 24 > 30

Recovery (%) 60-95 60-90