Fabrication of E110 Alloy Fuel Rod Claddings on Electrolytic ... - ASTM … · 2019. 6. 26. · The...

Fabrication of E110 Alloy Fuel Rod Claddings on Electrolytic Zirconium

Base with Removing Fluorine Impurity for Providing Resistance to

Breakaway Oxidation in High-Temperature Steam

V. Markelov1, A. Malgin1, N. Filatova1, V. Novikov1, A. Shevyakov1,

A. Gusev1, I. Shelepov1, A. Golovin1, A. Ugryumov2, A. Dolgov2, A. Ziganshin3,

V. Donnikov4, V. Latunin4

A.A. BOCHVAR HIGH-TECHNOLOGY RESEARCH INSTITUTE

OF INORGANIC MATERIALS (JSC «VNIINM»)

19TH INTERNATIONAL SYMPOSIUM ON ZIRCONIUM

IN THE NUCLEAR INDUSTRY

MAY 20-23, 2019, Manchester, UK

«ROSATOM» STATE ATOMIC ENERGY CORPORATION

1) 2)

3) 4)

Introduction. Problem essence.

2

The E110 alloy is used as the fuel rod claddings of VVER reactors. Electrolytic

zirconium powder with additives of iodide zirconium and remains of zirconium

production from these materials is used as a charge basis for the standard

version of alloy. The ingots are smelted by double vacuum arc melting (VAM).

Fuel rods with E110 alloy cladding satisfy the design parameters of operation.

At the same time the E110 alloy under certain high-temperature conditions of the

LOCA design basis accident is characterized by appearance of breakaway

oxidation.

In [9] on the basis of phenomenological ideas about the mechanism of influence

on oxidation of various impurities it was stated that the breakaway effect of E110

alloy was caused by the presence of residual fluorine (F) impurity, which

accompanied the fluoride technology for producing of electrolytic powder.

[9] Chung Hee M., «Fuel behavior under loss-coolant accident situations» // Nuclear Engineering and Technology, vol.37,

№4, August, 2005, p. 327-362.

19TH INTERNATIONAL SYMPOSIUM ON

ZIRCONIUM IN THE NUCLEAR INDUSTRY


3

Breakaway oxidation does not appear on the E110 alloy with a charge based on

sponge zirconium, in which F impurity is practically absent.

In [8] the negative effect of F was confirmed experimentally by comparative

studies of resistance to breakaway oxidation of fuel rod claddings made of ingots

from electrolytic zirconium based alloy after two, three and four melts.

It is shown that the key factor of a pronounced early breakaway effect of the

standard E110 alloy after 400-500 s of steam oxidation at 1000ºС is the residual

content of F in the amount of 4-5 ppm.

The content of F decreased to less than 1 ppm after four melts of the ingot and

breakaway effect at 1000°C does not appear at least during oxidation up to

5,000 s which corresponds to 20% ECRC-P.

Introduction. Ways to solve the problem.




[8] Markelov, V.A., Malgin, A.G., Novikov, V.V. “Providing durability in a LOCA design basis accident of fuel rod cladding made of

electrolytic zirconium E110 alloy”, Presented at the 2017 WRFPM, Jeju Island, Korea, September 10-14, 2017, Paper No F-162

Introduction. Aim and tasks of the work.

4

At the same time melts regimes were not specifically worked out but

corresponded to the current technological documentation for the melting of E110

alloy ingots.

The aim of this work was to develop a new technological process for

manufacturing of industrial ingots of the electrolytic zirconium based E110 alloy to

ensure a guaranteed and maximally uniform content of residual F impurity in the

ingot volume less than 1 ppm.

At the same time the tasks were to optimize the regimes and methods of melting

and to achieve the result using the least number of ingot melts.

Fuel rod claddings made of ingots manufactured by the new technology were

tested to breakaway oxidation resistance and as shown by the results satisfy

criterion of the material safety in conditions of LOCA design basis accident with

margin.




Scheme of standard manufacturing technology of E110 alloy

ingots and cladding tubes

5 19TH INTERNATIONAL SYMPOSIUM ON



Dynamics of reduction of F content in the manufacture of E110

alloy ingots based on electrolytic zirconium

6



Ion chromatography (Dionex ICS-2100 unit) was used to determine the F content quantitatively,

which has the detection limit of 0.5 ppm and the error of 15-44% in the range of F concentrations of

0.5-100.0 ppm (the smaller F content the higher error value).

Three samples per point were analyzed and the mean values were determined.

EBM – Electron Beam Melting

Using of EBM makes possible

to remove F more efficiently

compared to the VAM. This

feature of EBM is due to the

high vacuum in the chamber

of the electron-beam facility,

the fully open surface of the

melt in the ingot mold and the

possibility to widely vary the

power and rate of melting




New technology manufacturing of E110 ingots

7

𝐶0𝐶

= 𝑓(𝑃𝑠, 𝑉)

where: C0 – initial F concentration in the

consumable billet, mole/m3;

C – F concentration in the ingot after

EBM, mole/m3;

Ps – specific melting power of EBM, kW/cm2;

V – melting rate, kg/h.




F

F

Billet Vacuum System

Electron Beam

F

Ingot

Bath with

liquid metal Crystallizer

Drops

https://vti.ru/en/

Dependence of E110 alloy fluorine refinement coefficient

on EBM parameters

8

Optimized EBM parameters

compared to the fourfold

melting scheme (VAM-VAM-

EBM-VAM) in [8] were applied

to melt for the ingot in the new

technical process based on the

obtained dependence:

- specific melting power (Pspec)

is increased by ~ 20%;

- melting rate (V) is reduced

by ~ 80%.



9 ingots




9

Sampling scheme of fluorine content

distribution analysis in longitudinal

(c) and in radial (d) directions in

ingot

Ingot appearance after first

EBM melting (a) and after

second EBM-VAM melting (b)

Ingots and sampling scheme of fluorine analysis

(c) (d)




Fluorine content distribution in the ingot after each

melting




EBM-VAM

EBM-VAM-VAM EBM-VAM-VAM-VAM

EBM 2.7

2.3

Average fluorine content in semi-finished products

and cladding tubes

11

The total of 465 samples taken from ingots melted three and four times semi-finished

and finished tubes were analyzed for F content.

All data showed that the concentration of F in the metal is below 1 ppm.

This result indicates that the new technology of melting the electrolytic zirconium based

E110 alloy ensures sufficiently uniform distribution of F throughout the ingot and the

required quantity.

Melting scheme

Average fluorine content, ppm

Billet

(2 pc.)

Billet after

mechanical

treatment

(18 pc.)

Hot

extrusion

sleeve

(18 pc.)

Tube after

1-st

pillgering

(10 pc.)

Tube after

2-nd

pillgering

(10 pc.)

Cladding

tube

(10 pc.)

EBM-VAM-VAM 0,75±0,05 0,70±0,05 0,79±0,06 0,83±0,06 0,86±0,06 0,89±0,06

EBM-VAM-VAM-VAM 0,72±0,05 0,65±0,05 0,62±0,05 0,72±0,05 0,77±0,06 0,85±0,06




Impurity elements content in ingots of investigated materials

12

Melting

scheme Alloy marking

Impurity element, ppm

Fe O Ni N С Si Al Cr F

EBM-VAM-VAM E110-3m 100 400 20 30 65 30 20 15 0.8

EBM-VAM-VAM-VAM E110-4m 100 390 20 30 70 30 20 15 0.7

VAM-VAM E110-2m (lot1) 100 600 30 25 100 25 20 20 4-5

VAM-VAM E110-2m (lot2) 160 520 40 20 55 30 20 30 2-3

VAM-VAM-VAM E110opt

Sponge based 510 820 30 30 60 30 25 40 <1.0

The most pronounced breakaway effect at high temperature steam oxidation for fuel

claddings made from the E110 alloy appears at the temperature of 1000 ºС.

Therefore, the oxidation tests for evaluating E110 alloy breakaway resistance were

conducted at that temperature.

Resistance to breakaway oxidation in

high-temperature steam




Reference material

Oxidation procedure and examination of tube samples

13

VTI experimental setup

Oxidation Kinetics Appearance analysis

RCT at 135°C

Microstructure analysis

Hydrogen measurements

Full length cladding tube / sampling scheme (E110-2m/lot2; E110-3m; E110-4m)

High-temperature

oxidation scheme

Max oxidation time for E110-2m - 4000 s

for E110-3m, E110-4m, E110opt – 10,000 s




Results of steam oxidation tests at 1000°C




↑ therm

ocouple

spot

#1

600s

E110-2m(lot1)

4,000s 700s 4,000s 5,000s 10,000s 5,000s 10,000s 10,000s 5,000s 10,000s 10,000s

E110-2m(lot2) E110opt (Sponge based) E110-3m E110-4m

nodule nodule nodules oxide spallation

Ap

pe

ara

nce

https://vti.ru/en/

Ring compression tests results at 135°C

15

The lowest degree of residual ductility at 135ºC is observed in E110-2m samples made of

ingot with two melting.

The residual ductility degree of oxidized samples from E110-3m and E110-4m alloys was the

same and comparable with the residual ductility of E110opt alloy on sponge base.




https://vti.ru/en/

Conclusions

16

■ Removal of F impurity to the level below 1 ppm by means of the

new technology for manufacturing of E110 alloy ingots on electrolytic

zirconium based using optimized electron beam melting as the first

melt and then at least two optimized vacuum arc melting provides

fuel claddings resistance to breakaway oxidation in high-

temperature steam.

■ The breakaway effect in water steam at 1000°C for 5,000 s up to

oxidation state 20% ECRC-P is not observed on the fuel rod

claddings from the electrolytic zirconium based E110 alloy ingots

with the F content less than 1 ppm. This is similar to the behavior of

the fuel rod claddings from E110 alloy based on zirconium sponge

and meets the relevant safety criterion in the conditions of LOCA

design basis accident.




Thank you for attention!




Hydrogen content in oxidized tube samples

18

Alloy Oxidation Time, s Hydrogen Content, ppm

E110-2m 700 10-15

4000 650-810

E110-3m 5000 10-20

10000 (10-20) / 150*

E110-4m 5000 10-20

10000 (10-20) / 250*

E110opt 5000 10-20

10000 20

* - the hydrogen level in nodules area on some samples




nodule area

(a)

(b)

https://vti.ru/en/

Microstructure analysis

19

E110-2m

E110opt

E110-3m

E110-4m

τ = 4,000 s

τ = 10,000 s

τ = 10,000 s

τ = 10,000 s




https://vti.ru/en/

Fabrication of E110 Alloy Fuel Rod Claddings on Electrolytic ... - ASTM … · 2019. 6. 26. · The...

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