Operating experience from the BN600 sodium fast reactor (O.A. Potapov)

Operating experience from the BN600 sodium fast reactor

Beloyarsk NPP: BN600 power unit

Power unit No. 3 with BN600 fast neutron reactor of 600 MW power has been commissioned in April 1980 and is under routine operation now.

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BN600 power unit: performance indicators Measurement units

2012

Since the beginning of operation

The best value

MW

610

600

625*

Running hours

hours

7376

233631

7449

Number of the unplanned shutdowns (scrams)

pieces

-

23

0

million kW-hr

4256.93

124988,07

4401.96

%

80.77

74.4

83.52

man*Sv

0.42

20.86

0.08

Ci/year

103.2

40581

60

%

42.60

Indicators Electrical power

Electrical generation Availability factor Annual collective exposure dose Atmospheric discharge Efficiency

* maximum achieved value

40.8 (design value) 3

BN600 power unit: availability factor Maximum value: 83.5

Average value: 74.4

4

BN600 power unit: availability factor Planned inspections and refuelings

Equipment failures and personnel errors

Other causes (district heating, load dispatcher’s restrictions) Commissioning of the unit

Electrical generation

5

2011

2010

2009

2 008

2007

2006

2004 2 005

2003

2002

2 001

2000

1999

1997 1 998

1996

1995

1993 1 994

1992

1 991

1990

1989

1988

1986 1 987

1985

1 984

1983

1982

1981

1 980

Number of scrams

7

Theзначение average value: 0.72 scrams/year. Среднее - 0,72 срабатывания/год

6

5

4

3

2

1

0

6

Number of the deviations with power reduction 18 17 16

The average value: 3.65 events/year. Среднее значение - 3,65 событий/год

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 2011

2010

20 09

2008

2007

2006

2005

2004

2003

2002

2001

2000

1999

1998

1997

1996

1995

1994

1993

1992

1991

1990

1 989

1988

1987

1986

1985

1984

1983

1982

1981

1980

0

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Discharges of BN600 inert radioactive gases, Ci/day 30 25

Ки/сут Ci/day

The average value (the median): 0.85 Ci/day. Среднее значение (медиана) - 0,85 Ки/сут The total discharge for the whole period of Суммарно завесь период эксплуатации – 40581 Ки operation: 40581 Ci.

20 15

Release of inert radioactive Выход gases ИРГ

10 5 0 8081828384858687888990919293949596979899 0 1 2 3 4 5 6 7 8 9 1011 8

Personnel exposure

Year 2010 – installation of the “K-17u” flasks into the casks at the 1st phase

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Solid and liquid radioactive waste

Solid radioactive waste Annual limit of the solid radwaste arrival at the Beloyarsk NPP: 55 m3 (VVER: 250 m3, RBMK: 400 m3) Liquid radioactive waste Annual limit of the liquid radwaste arrival at the Beloyasrsk NPP: 110 m3 (VVER: 140 m3, RBMK: 300 m3)

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BN600 power unit: operation problems • sodium leaks on primary and secondary circuit equipment: the problem is practically solved, no leaks since 1993.

• sodium-water reactions in the steam generators: these have not occurred since 1991.

• trips of the primary and secondary sodium pumps due to damages to brush gears of motors and increased vibration: the problem was solved in the 80-s.

• fuel cladding failures: the shutdowns due to the loss of integrity of standard fuel have not occurred since 1999.

• trips of the generators due to ingress of hydrogen into the distillate circuit: the problem was practically solved in the 90-s.

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Operating experience from the sodium circuits

Detection means: detection by the closing of the helixes of the heat zones of the trace heating system, fire annunciators in premises, system of radiation and temperature monitoring in premises.

Causes of the leaks: parent metal flaws, welded joint flaws.

Causes of the sodium leaks on the secondary circuit valves: poor procedure of the repair and inspection of the welded joint of the cover with the body.

Measures: the repair and inspection procedure was updated, the additional sodium leak detectors were installed.

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Operating experience from the steam generators

Steam generators stage failures with water-sodium reactions (water-to-secondary-sodium leaks and sodium-to-watersteam-pipeline leaks).

Over the entire period of the BN600 steam generator operating period 12 water-sodium reactions occurred and nearly half of these occurred in the first year of operation.

Failure causes: hidden flaws (weld joint flaws) of which detection is difficult during manufacture.

Causes of experience.

the

consequences:

insufficient

personnel

Measures: the welding procedure was changed and the metal inspection was strengthened.

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Operating experience from the primary (PSP) and secondary (SSP) sodium pumps

Increased vibration, cracking of the shafts, damage to the clutches engaging the pump shaft with the motor rotor.

Causes: the resonance caused by the coincidence of the pulses of the output power of the electric drive with the natural frequency of the torsional oscillations of the shafts and half-clutches.

Measures: design improvement of the shafts and halfclutches; the operation practice was changed, i.e. the uncontrolled mode of operation at the rated power level was introduced.

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Repairs of the central rotating column Since the 1995 autumn outage the moment of the resistance to the rotation of the central rotating column has been observed to grow.

Cause: distortion of the shell due to the graphite swelling during the ingress of the sodium vapours into the column as a result of its loss of integrity.

Measures: the repair was carried out, the counterpressure system was introduced to avoid the possibilty of the ingress of sodium vapours into the central rotaing column.

Installation of the central rotating column during construction-andassembling operations prior to the commissioning of the unit

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Irradiation of the materials and structures material testing fuel sub-assemblies designed for the achievement of the ultimate damage doses at the maximum dose rate,

material testing sub-assemblies for the irradiation of the specimens of the structural materials at the reactor periphery at the minimum damage dose rate. two structural units for production of 小芯-60 isotope: - upgraded shim rod, - upgraded radial blanket fuel sub-assembly.

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Measures taken to improve the BN600 reactor design parameters During operation of the BN600 power unit the lifetime of the following main components was extended: • the core components: 1.5 times, • the steam generator evaporator stage: 2.5 times (from 50 thou. hours to 125 thou. hours), • the primary sodium pump: 2.9 times (from 20 thou. hours to 57 thou. hours), • the secondary sodium pump: 2.5 times (from 50 thou. hours to 125 thou. hours), • the intermediate heat exchanger: 2.25 times (from 20 to 45 years).

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Measures taken to improve the core operational reliability

As a result of the core modification among other matters to prevent fuel failures the following took place: - the peak linear rating was reduced from 540 down to 480 W/cm at the expense of the increase in core height from 750 to 1000 mm, - the new structural materials for the fuel subassembly wrapper (ferritic-martensitic steell EP450 c.w.) and ChS-68 c.w. for the fuel cladding were applied.

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Lifetime extension Safety provision and improvement make a foreground task.

Fields of work on lifetime extension

Safety improvement

Equipment replacement

Examination and lifetime extension of the components not planned to be replaced

Licensing

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Lifetime extension Main results of the lifetime extension On April 7, 2010, Rostekhnadzor issued license No. GN-03-1012342 for operation of Beloyarsk NPP power unit No. 3 at reactor power up to the authorized rated one valid until March 31, 2020.

The integrated material, methodological and theoretical studies were performed to justify the serviceability of the irreplaceable components of the BN600 reactor for 45 years of operation.

Because the new specified lifetime until 2025 has been validated for the power unit components there is a possibility of the subsequent prolongation of the license by 5 years more.

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Lifetime extension: emergency shutdown cooling system based on sodium-to-air heat exchanger

SSP Expansion tank

BASIC DIAGRAM OF THE EMERGENCY SHUTDOWN COOLING SYSTEM CONNECTION

5IHX-Đ?

SG module AHX EMP

Sodium-to-air heat exchanger (AHX)

Fans 21

Lifetime extension: emergency shutdown cooling system based on sodium-to-air heat exchanger

Emergency shutdown cooling system fan with air ducts in the central hall

Stand-alone diesels for power supply to the emergency shutdown cooling system based on the sodium-to-air heat exchanger

Outlet branch of the air duct of the emergency shutdown cooling system based on the sodium22 to-air heat exchanger

Lifetime extension: multicyclone Air duct of ventilation system 3PS-A,B

Purified air outlet to the filters of ventilation system 3PS-A,B

The multicyclone is designed to trap the air-borne aerosol sodium combustion products formed during Beloyarsk NPP BN600 reactor primary coolant leaks.

It is used as a preliminary purification stage in emergency fire ventilation system 3PS-A,B for reducing the amount of the aerosols arriving at the subsequent purification stage.

Upper header

Individual cyclone

Upper header

Header Maximum solution level

Minimum solution level Bin

Cooler

Air duct of ventilation system 3PS-A,B

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Lifetime extension: multicyclone

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Measures taken after the accident at the Japanese Fukushima NPP

Considering the measures taken at the power unit its resistance to the external impacts typical for the site was confirmed.

It is unnecessary to extend the designer’s list of the beyondthe-design-basis accidents.

At the same time to improve the power unit safety in case of the extreme external impacts the following were done: 1. The main components ensuring the possibility of the reactor heat removal, i. e. main building, reactor, primary and secondary circuit equipment of the reactor installation including pipelines and steam generators and a complex of the reactor refueling mechanisms, were studied and confirmed to be stable and maintain the safety functions during an earthquake of 7 point magnitude (i. e. 1 point higher than the safe shutdown earthquake).

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Measures taken after the accident at the Japanese Fukushima NPP

2. The power unit was additionally outfitted with the following: 0.4/6 kV, 2.0 MW mobile diesel set for power supply of the most critical mechanisms, 0.4 kV, 0.2 MW mobile diesel set for the recharging of the storage batteries and power supply of the instrument panels and standby control desk, the mobile pumping unit 250/150 designed to make up the water storage of the water-steam circuit, the mobile pumping units 150/120 and 500/50 designed to be used in the additional system of the water level maintaining in the spent fuel cooling pond.

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BN600 power unit: Conclusions • For 32 years of operation the main task, i. e. the mastering of the operation both of the powerful plant with the sodiumcooled fast reactor and sodium steam generators, has been fulfilled. • About 500 experimental fuel sub-assemblies have been tested in the BN600 reactor to research into the cladding materials and different design types. Among other things this has allowed the fuel burnup to be increased from 7 % to 11.4 % of h. a. • The technologies of maintenance and replacement of the large-size reactor and steam generator components (72 steam generator stages, 3 low pressure cylinders, 6 feedwater pumps, 1 emergency feedwater pump) have been mastered.

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BN600 power unit: Conclusions

• The experience from the production of the isotopes of high concentrations has been gained.

• The license for operation until 2020 has been obtained.

• Long run life tests of large-size equipment operating in sodium have been conducted.

• The conditions of the strength are observed for all the reactor critical components for 45 years of operation.

• The important output of the operation is a justification of the construction of the new fast reactor power units (BN800, BN1200).

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CONCLUSION The operating experience from the BN600 reactor power unit for more than 32 years is positive in terms of the demonstration of the feasibility of the utilization of a sodium-cooled fast reactor for commercial electric generation.

The BN600 reactor is an important key link ensuring the continuity and succession of the development of the fast reactors in Russia of which the reliable and steady operation confirms good prospects of this line of the nuclear power industry.

In the course of the BN600 power unit operation the valuable operating experience from the individual systems and components which should be preserved and utilized when developing the advanced designs of the sodium-cooled fast reactors was accumulated.

Thank you for your attention!

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