CATALYTIC EFFECTS OF Tс IONS ON THE Np-HYDRAZINIUM - NITRIC ACID SYSTEM

 Daria Nikolaevna Tumanova1 , Konstantin Eduardovich German1, Philippe Moisy2

Michael Lecomte2 and Vladimir Fedorovich Peretrukhin1

1- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry of RAS,

Leninsky pr. 31/4, Moscow, Russia; e-mail : german@ipc.rssi.ru

2- DEN, CEA Marcoule, BP 17171 - 30207 BAGNOLS sur CEZE Cedex France

AIMS

Two main PUREX Products: Pu & U

Supplement possible products Np, Tc, Pd, MA..

Interest in Np-237 – Source for Pu-238 (cosmic conquests, heart electric source… )

Np(V) – much more stable compared to all An

in Russian reprocessing is redistributed in two streams

Tc (FP) accumulation with increase of burn-up Technetium causes problems:Variable Tc species in PUREX solutions : various complexes

of Tc(VII) and variable oxidation states Tc(VI,V, IV) Redistribution in different both product and waste streams Already known : catalytic Tc effects on U, Pu and hydrazine

redox reactions Limited data for Np-Tc interaction

KNOWN: In absence of Tc the reaction of Np(V) with hydrazine is very slow

Investigation of Np(V) chemical behavior in presence of Tc(VII) and Tc(V) in hydrazine – HNO3 system Determination of the reaction orders in Np, Tc, N2H5

+, H+

400 500 600 700 800 900 1000 11000,00

0,04

0,08

0,12

0,16

0,20

0,24

0,28

0,32

0,36

0,40

0,44

D

wavelength,nm 400 500 600 700 800 900 1000 11000,00

0,04

0,08

0,12

0,16

0,20

0,24

0,28

0,32

0,36

0,40

0,44

D

wavelength,nm

400 500 600 700 800 900 1000 11000,00

0,04

0,08

0,12

0,16

0,20

0,24

0,28

0,32

0,36

0,40

0,44

D

wavelength,nm

400 500 600 700 800 900 1000 11000,00

0,04

0,08

0,12

0,16

0,20

0,24

0,28

0,32

0,36

0,40

0,44

D

wavelength,nm

N2H5+

+Tc(VII)Np (V)

Tc(IV)- Tc(V)Tc(IV)Np(V)Tc(V) Np(IV)

0 20 40 60 800,0

0,1

0,2

0,3

0,4

D

time,min

200 4000,00

0,15

0,30

D

time,min

Np(V) reduction to Np(IV) catalized by Tc in variable Tc concentration (1-st order in Tc)

y = 1,0589x + 0,2618

R2 = 0,9952

0

0,2

0,4

0,6

0,8

1

1,2

1,4

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

Lg(C(Tc))

Lg(K

0)

0

0,2

0,4

0,6

0,8

1

1,2

1,4

0 0,2 0,4 0,6 0,8

Lg(CHNO3)

Lg(K

0)

Np(V) reduction to Np(IV) catalized by Tc in variable [HNO3] ) (3.7-th order in CHNO3 till 3.5 M)

Chemical mechanism changed

y = 3,68x - 0,99R2 = 0,988

Np(V) reduction to Np(IV) catalized by Tc in ( [HNO3] + [NaNO3] = 5 M ) (1-st order in aH+)

y = 1,0099x + 0,7416

R2 = 0,9966

1

1,05

1,1

1,15

1,2

1,25

1,3

1,35

0,2 0,3 0,4 0,5 0,6

lg(aH+)

LgK

o

• Np(V) reduction with N2H5+

catalyzed by Tc(V) follows : zero order in Np(V) 1-st order in Tc, 1-st order in H+ at constant ionic forth(HNO3 + NaNO3 = 5M)

The Use of previously prepared Tc(V) as a catalist in Np(V) reduction with N2H5

+ provide the immediate start-up of the reaction with no induction period

Determination of the dependence of Np(V) reduction with N 2H5+ catalyzed by Tc(V) over Tc, H+ , ( HNO3 and NaNO3 ) concentrations (temp = 36oC)

Determination of the dependence of Np(V) reduction with N2H5+ catalyzed by Tc(VII) over Tc, H+ , ( HNO3 and NaNO3 ) concentrations (temp = 45oC)

4323524 NHHNNTcHNOHNTcO IVVVI

Np(V)Tc(IV)- Tc(V)

• Absorption at 980 nm is completely due to Np(V) (checked also by the peak at 1095 nm) in some complex with the reduced Tc

• Convolution of the absorption at 970 nm is less than calculated from Np(V) reduction = Np(IV) is probably bounded

(10exp-5)Tc-Np-N2H5NO3-1.6HNO3

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0,4

950 1000 1050 1100

Wavelength, nm

D

23456789

1011

0 2 4 6 8

Time, min

[Np(

V)],

mM

/l

10,0 mM Tc

15,3 mM Tc20,1 mM Tc

31,1 mM Tc8,02 mM Tc

12,5 mM Tc

Np(V) reduction by hydrazine catalyzed by previously prepared Tc(V)

[Tc], mM K0, *104 mol/l*min

8.02 1.0

10.0 1.3

12.5 1.8

15.3 2.3

20.1 3.0

31.1 4.7

C(Np)=1,6*10-3 M/l,С(Tc)=1,15*10-3 M/l, C(HNO3)=1,67 M/l,C0(N2H5NO3)=0,3 M/l, t=450C,l=1 cm

– d[NpV]/dτ = d[NpIV(total)]/dτ = k3·[NpV] = k3·([ NpIV]∞ – [ NpIV])

0 10 20 30-3,8

-3,6

-3,4

-3,2

-3,0

lg(C

)

time,min

k3=2*10-2 min-1

1-st order in the consumed Np(V)

0 10 20 30

-4,5

-4,2

-3,9

B Data2B Polynomial Fit of Data2_Blg

(C)

time,min

Not evident for the appearing Np(IV)

Np(IV) forms probably A complex with Tc (V)

3][ OTcNpTcNp VIVIVV

Tc(IV) and Tc(V) form a catalytic cyclewith stationary concentration of the latter in the process of Np(V) reduction with N2H5

+