IRRADIATION OF VESSEL MATERIALS WITH USINGKORPUS FACILITY OF RBT-6 REACTOR

Golovanov V.N., Markina N.V., Raetsky V.M.,Seriodkin S.V. and Tsykanov V.A. (SSC RF RIAR)

Brodkin E.B., Egorov A.L. and

Zaritsky S.M. (RRC Kurchatov Institute)

Presented at the IAEA Specialists Meeting on Irradiation

Embrittiement and Mitigation

Espoo, FinlandOctober 22-30,1995

State Scientific Center of Russian Federation RESEARCHINSTITUTE Of ATOMIC REACTORS, 433510. Dimitrovgrad,

Ylyanovsk Region, Russia

Telephone: +84235/32021FAX: +84235/35648e-mail: fae (® omv.niiar. simbirsk. su

IRRADIATION OF VESSEL MATERIALS WITH USING KORPUSFACILITY OF RBT-6 REACTOR

GolovanovV.N., Markina N.V., Raetsky V.M.,Seriodkin S.V. and Tsykanov V.A. (SSC RF RIAR)

Brodkin E.B., Egorov A.L and

Zaritsky S.M. (RRC Kurchatov Institute)

ABSTRACT

The KORPUS facility for the RBT-6 reactor was designed and made for realization

of controllable irradiation with the possibility to simulate the working conditions of

WWER vessel materials. The KORPUS design and technical characteristics are

considered in this paper. Parameters of flux and neutron spectrum, irradiation

temperature of specimens are presented in this paper too.

Ernst B.Brodkin1, Alexander LEgorov1, Victor N.Golovanov2,Natalia V.Markina2, Vitaly M.Raetsky2, Sergei V.Seriodkin2,Vladimir ATsykanov2, Sergei M.Zaritsky1.

IRRADIATION OF VESSEL MATERIALS WITH USING KORPUSFACILITY OF RBT-6 REACTOR

REFERENCE: Brodkin E.B., Egorov A.L, Golovanov V.N., Markina N.V.,Raetsky V.M., Seriodkin S.V., Tsykanov V.A. and Zaritsky S.M. "Irradiation ofvessel materials with using KORPUS facility of RBT-6 reactor"

ABSTRACT: The KORPUS facility for the RBT-6 reactor was designed andmade for realization of controllable irradiation with the possibility to simulate the workingconditions of WWER vessel materials. The KORPUS design and technicalcharacteristics are considered in this paper. Parameters of flux and neutron spectrum,irradiation temperature of specimens are presented in this paper too.

KEY WORDS: vessel materials, specimen, irradiation embrittlement, neutronspectrum, flux, KORPUS facility

INTRODUCTIONThe results concerning the irradiation embrittlement of WWER vessel materials

prove the necessity of organizing experiments in controllable and adjustable conditionsensuring the unequivocal interpretation of the change of material properties underirradiation. The KORPUS facility for the RBT-6 reactor (RIAR 1) is designed and madefor the realization of conroilable irradiation with the possibility of a simulation of reactorVWVER vessel materials working conditions.

1. Senior scientist, senior scientist and head of departament respectively, RussianResearch Centre "Kurchatov Institute"

123182 Moscow, Russia.2. Head of department, head of laboratory, senior scientist, head of group, deputydirector, respectively, Research Institute of Atomic Reactors433510 Dimitrovgrad, Ulyanovsk region, Russia.

INTRODUCTION

The results concerning the irradiation embrittlement of WWER vssse! materialsprove the necessity of organizing experiments in controllable and adjustable conditionsensuring the unequivocal interpretation of the change of material properties underirradiation. The KORPUS facility for the RBT-6 reactor (RIAR 1) is designed and madefor the realization of controllable irradiation with the possibility of a simulation of reactorWWER vessel materials working conditions.

PURPOSE OF THE KORPUS FACILITY IN INVESTIGATION OF MATERIALEMBRITTLEMENT

- irradiation of large file of structural materials samplesin controllable and adjustable conditions ensuring unequal interpretation of materialproperty changes under radiation effects

- irradiation specimens in different regimes (irradiation- annealing-reirradiation)- creation of irradiation regimes was answered the purposes distribution neutron

spectrum, flux and temperature in the wall of the WWER-440 and WWER-1000 vessel.

The KORPUS facility is placed in the RBT-6 pools near the core (Fig.1). There aretwo working spaces for irradiation:

1) near the reactor core restricted by a tube 700x350x480 mm in size;2) in the channel 1000 mm diameter connecting two pools of reactor.In this case the ampoules containing samples are located on mobile platform and

moved along the channel toward the core at the required distance. Ampoules movementagainst the core and within the tube is provided for.

Thus, the ampoules with samples can be precisely placed at the givendistance from the core. The neutron flux density /E>0.5 MeV/ fallen to the first layer ofsamples is changed from 3x109 to 1013 cm"V1 s.

The maximum number of ampoules that can be placed in the tube area - 24 (4rows, 6 ampoules in each), 10 ampoules are planned to be on the platform (2 rows, 5ampoules in each) and installation of structures imitating the reactor beyond-vesselspace is also possible. Several ampoule designs were developed for use in "KORPUS":ampoules for dosimetric measurements, ampoules for sample irradiation and ampoules-simulators.

Ampoules for samples irradiation differ structurally with the location in the facility.The 1-st type ampoules (Fig.2a) are used within the tube area, the 2-nd type ampoulesare placed on the mobile platform and have a bent cables outlet channel of measuringsensors. The 1-st type ampoules have 2 structural decisions. Ampoules placed near thecore have the temperature stabilizing device inside the ampoule called a "thermal tube".Ampoules placed far from the core including the 2-nd type ampoules are equipped withheaters (Fig.2b).

Samples in all types of ampoules are located on 6 levels and possess themaximum possible technically dense packing with the section 100x100 mm. Themaximum number of the SHARPY type samples in one ampoule is 600. Irradiation ofsamples with different type and configuration combinations is provided for (Fig.3a,b)samples eccentric tension, samples for 3-point bending test, for tensile test and samplesfor measuring the physical properties of materials. An additional requirement is careful

mechanical treatment of surface specimens for decreasing gaps between specimens incapsule no more than 20 mm.

If necessary, irradiation of samples can be performed in the air, in helium, nitrogenor water. Irradiation temperature of samples is 280-300°C and is maintained accurate to5°C. The irradiation temperature control is carried out by chromel-alumel typethermocouples placed along the height and section of ampoules. The number ofthermocouples in the ampoules is up to 16 depending on the ampoule types.

For timely recording of the thermal and fast neutron flux density there weredeveloped miniature fission chambers based on U-235 and Np. The size of chambervessels makes up: 5 mm diameter, 35 mm long, working part - 10 mm. Fissionchambers and direct charge detectors are placed in the central part of ampoules.

To determine the neutron flux spectrum and density along the ampoule height, andover the section - in the central part, standard sets of neutron monitors are located: Fe-58, CO-59, Au-192, Nb-93, Ta-181, Ti, Ni.

NEUTRON-PHYSICAL PARAMETERS OF IRRADIATION

Neutron-physical precalculation results were presented in paper IM.Further investigation was directed to accurate determination of irradiation condition

of specimens in KORPUS facility of preferable configuration (Fig.4).

MAIN RESULTS:-The core of the RBT-6 reactor was formed. The proportional distribution of

neutron flux along core was measured (Fig.5 a,b).

-Neutron flux was measured using dosimetry and simulated capsules (Fig.6,7).Changes of fast neutron flux are ±5% along the central part (200 mm) of capsules anddoes not change along the faces of two central capsules (OMi, <t>M2).The decrease ofneutron flux along the capsules thickness is 3 times.

-The stability of restorable neutron spectrum was investigated relatively of theselected aprior spectrum (spectrum WWER in aerial channel of diameter 100mm wasseparated from the water level of 2,5cm- library of spectrum RCF-89). The spectrumswere determined:the integral neutron flux with energy more than 3Mev=1. The neutronflux E>3Mev=5,5x1011cm"2.c"1 (Fig.8).

SPECIMENS TEMPERATURE IRRADIATION.

Thermal-physical calculation and measuring were perfomed for maximumhomogeneous temperature guarantee in volume capsules of several types ofconstructions most of all usage (Fig.2 ).

For the capsule with thermal tube the calculation and experiments wereconducted without the lead screen in KORPUS facility (Fig.2a).

The distribution of temperature in capsules of first and second rows(Fig.9a,b) show the strong influence on gamma heating temperature of specimens incapsules of first row.

For the capsules with side heaters, calculations and experiments wereperformed with the lead screen in KORPUS facility. Decreasing of gamma heatingguarantee the possibility of operation temperature regime in volume of capsule (Fig. 10).

The difference of the temperature in volume of the capsule does not exceed15°C. It is allow turning capsule in facility. Optimum quantity of specimens may tochoose with the same neutron fluence, when the temperature doesn't differ more then 3-

MAIN DIRECTIONS OF KORPUS FACILITY USAGE

Design of experimental working capsules continues for development ofdifferent tasks of materials irradiation by problems irradiation embrittlement.

Dosimetry measures of flux and neutron spectrum prolongate in the volumeKORPUS facility.

Research programs of irradiation perform for different orders.

Main experiments in KORPUS.

N

1.

2.

3.

4.

5.

6.

NAME

Methodicalexperiment in-boiling capsule-capsule forreirradiation

Irradiation steels ofvessels WWER-440,NP-500

Irradiation steels ofvessel WWER-1000

Irradiationmaterials ofwelding vesselWWER-440

Irradiationmodelingalloys and steel

Dosimetryexperiment

Beginning

1995

1996

1995

1995

1995

1996

1995

Finish

1996

1997

1996

1997

1997

1997

1996

CONCLUSION

The "KORPUS" facility was worked out, produced, mounted and prepared for useat RBT-5. The following items can be irradiated in "KORPUS".

-samples for various types of investigations (up to 2000)-metal samples of large-sized vessels;-fragments of irradiated reactor vessels.Replacement and re-irradiation of samples are possible at the facility.

Modeling of irradiation conditions can be performed for-WER-440 and WER-1000 reactor vessel materials;- surveillance samples irradiated in NPP reactors.Modeling of real change of neutron-physical characteristics for metal

thickness is possible on vessel fragments. The design of neutron fluence can beachieved for 0.5-5 years.

Investigations of samples irradiated in the "KORPUS" facility allow:-juxtaposition of the results obtained previously and at present at the

research and NPP reactors;-revealing the most significant effect factors in the problem of vessel radiation

embrittlement;-studding the effect of alloying elements, heat treatment methods, impurities

concentration, temperature, neutron flux intensity, etc. on the vessel materialsproperties:;

-certification experiments of vessel materials;-comparison of radiation resistance of different materials under simultaneous

irradiation in identical conditions;-testing the calculation programs of neutron and gamma-fields;-collation of methods and means for determining irradiation conditions within

a wide range of their change.

REFERENCE:

1 Brodkin E.B., Egorov A.L, Golovanov V.N.,Markina N.V., Raetsky V.M., Sulaberidze V.S.,Tsykanov V.A., Zaritsky S.M., 'THE IRRADIATION FACILITY KORPUS FORIRRADIATION OF THE REACTOR STRUCTURE MATERIALS", Reactor Dosimetry,ASTM STP 1228, Harry Farrar IV, E.Parvin Lippincott, John G. Williams, and David W.Vehar, Eds., American Society for Testing and Materials, Philadelphia, 1994.

Fig.l. KORPUS facility 1 - reactor pond; 2 - platform; 3, 6 - capsules;4 - samples; 5 ,7- vertical tube

l"ig.2a Capsule with thermal tube1- specimens; 2- Al-blockj3-thermal tube; 4-wrapper;5- thermocouples; 7-heater

Fig .2b Capsule with side electric heater

1 - imitator 2 - specimens: 7> - tubefor neutron monitoring; 4 - wrapper;5 - JhcrtnocnulLs: 6 - electric heater

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Fig.4.Configuration of KORPUS facility

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a - electric current in heater 0-3,5 A;b - electric current in heater-0,48 A