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									   Úrad jadrového dozoru SR

Power uprate and I&C

                              Benčat M., Bobály P.
  IAEA meeting, Slovenia, 14 – 18.4.2008, Portoroz

             Reasons for power uprate
             NPP EBO, EMO actual information
             PU acceptance
             Technical conditions for PU
             PU type & technical solution
             PU & I&C requirements
             I&C in EMO,EBO NPP
             Persisting problems
             Some data before and after PU
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    Urad jadroveho dozoru                                              www.ujd.gov.sk


      Eight WWER-440 units in Slovakia
          Bohunice (units 1-2, type V230, 1978/1980, 1st unit was shut down in
           2006 and 2nd will be shu tdown in 2008), operation with profiled fuel
          Bohunice (units 3-4, type V213, 1984/1985), operation with profiled and
           Gd-2 fuel
          Mochovce (units 1-2, modernized type V213, 1998/2000), operation with
           profiled and Gd-2 fuel
          Mochovce (units 3-4, modernized type V213, start-up in?)

      Utility projects on power uprates - different stages of preparation
       and implementation for different NPPs in Slovakia

      UJD duties
         Issue of legislative documents (regulations, guidelines)
         Performance of state supervision of nuclear safety

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                        Reasons for power uprate

             Lack of electricity due to:
                 Closing of both V1 units, loss of 800MW
                 Mochovce 3rd and 4th unit delayed construction
                 Dynamic industry development and high gross product
             Plans for future
                 Immediate power uprate of all existing units
                 Completion of two units at Mochovce site up to 2011
                 Built a new nuclear sources after 2010

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    Urad jadroveho dozoru                                                    www.ujd.gov.sk

                 Bohunice NPP (units 3-4) actual information

               Safety upgrading and power increasing in process of preparation
               Reactor thermal power 107 ± 2% Nnom (1471 MW) is planed for next
                outage in2008
               Increasing of temperature difference over the reactor core, no change of
                coolant flow through the reactor, no significant change of secondary SG
               Increasing of steam flow to TG but without increasing TG efficiency
               Use of new fuel, Gd-2 (U235 enrichment - 4,4%), now is in process of
                licensing for 107 ± 2% Nnom
               Scorpio monitoring system is in the operation
               I&C TELEPERM system, sensors and all measurement chains for safety
                systems were changed with increased accuracy
               Operational measurements remains on the same level and they are not
                very accurate
               Planning upgrading of operational measurements- at the next outage

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    Urad jadroveho dozoru                                                    www.ujd.gov.sk

                 Mochovce NPP (units 1-2) actual information

               Safety upgrading in 1998, 1999, 87 measures implemented and power
                uprate is in the process of implementation
               First unit is shut down for refuelling from 1st of April 2008
               Loading prepared for reactor power 107 ± 2% Nnom (1471 MW)
               The second unit will go to outage in summer
               Increasing of temperature difference over the reactor core, no change of
                coolant flow through the reactor, no significant change of secondary SG
               Increasing of steam flow to TG at existing TG efficiency
               Use of Gd-2 fuel (U235 enrichment - 4,4%), now licensed for 107 ± 2%
               I&C classical Siemens system, not digital

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                   Power uprate acceptance

             Government supports nuclear energy
             Slovak public generally accepts nuclear power
              uprates and nuclear program
             Some environmental groups are again the power
              uprate and also again completion of 3rd a 4th units
             EU formal consent
             Negotiation with representatives of neighboring
              countries was finished, only Austria require more
              information and the negotiation are still in process.

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                 Technical conditions for PU

              The Russian nuclear reactors 213 were designed with
              conservatism resulting in a large safety margins.
              We have implemented broad aging program on all components
              Existing I&C with a small modifications allow the power uprate
              The all reactors operate with Gd_2 or profiled fuel which has
              reserves on rod power.
              The overflow for all reactors are between 41000- 43300m3, no
              need for adjustment of MCP impellers
              Turbines and generator are able operate without any
              modernization at 235MW (72 hours overloading tests last year)

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               PU type & technical solution

             The NPP’s apply the stretch power uprate combined with
             measurement uncertainty recapture
               All units are now operating at 1375MW with ± 4% uncertainty (2% for
                determination of power and 2% for power maintain) for 2σ
               New thermal power level will be 1471MW with ± 2% uncertainty (1%
                for determination of power and 1% for power maintain) for 2σ
               Safety analyze report chapter 15 was work out for 109% (1499MW)
               All units must be flexible and work at primary, secondary and tertial
               The power uprate is reached by smoothing and flatting of power
                distribution curve. The average rod power was increased, but the
                maximum rod operational power remain the same due to decreasing of
                rod peaking factor.
               The enthalpy rise in hot channel remain the same as before power
               The power jumps stay inside limit curve.

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                           PU & I&C requirements

               The power uprate to 7% ± 2% does not require the large
                instrumentation and control systems upgrading.
               The I&C for our 213 reactors fulfill next expectations
                   All devices have sufficient ranges, reliability and accuracy
                   Sensors for temperature and pressure measurement have required
                   The calibration ensure that the all sensors and devices will be enough
                   Core monitoring system is capable to monitor all fuel safety parameters
                    (peaking factors, DNBR, reserve to saturation), input output temperature
                    of reactor loops and assemblies.
                   Possibility to define the new limits for DNBR and reserve to saturation
                    for hot channel
                   New set points will be defined for actuation of safety systems

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                                      I&C in EMO NPP
               Nuclear power plant at Mohovce is 10 years in operation. Both units
                were constructed with upgraded safety level and I&C.
                   RPS, RLS (ROM), MRC (ARM) analog original Russian design
                   Primary circuit pressure is maintained 12.26 MPa ± 200KPa. When we
                   contemplate uniform distribution than the 200kPa represents 3σ.
                   Core monitoring (Russian) system was systematically upgraded with the
                   new fuel, but without possibility to monitor DNBR and reserve to
                   saturation in hot channel.
                   By adding the new module to the monitoring system it will be able to
                   fulfill all functions.

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                               I&C in EBO NPP

               Bohunice units are more than 20 years in operation. Both
                units had undergo the large I&C modernization during last
                several years.
                   Installed new TELRPERM system
                   Sensors and measurement chains were modernized only for
                   safety systems
                   Sensors accuracy for normal operation doesn’t reach required
                   Pressure measurement, uncertainty reach ±200KPa for 3σ
                   Core monitoring system Scorpio was systematically upgraded
                   with new fuel, allows monitoring DNBR and reserve to
                   saturation in the hot channel.
                   In this year outage the sensors for operational measurements
                   will be changed
                   Installation of new calibration module….no more information
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                            Persisting Problems

               Justification of ± 2% uncertainty for 2σ
                   The report was not accepted by regulatory body
                   The temperature measurement on loops have to be
                   Our assessment tends to 3% with existing temperature
                    measurement uncertainty.
               Russian again change the Gd-2 fuel rod diameter from 9.07
                to 9.1 mm and the core is combine not only with profiled and
                Gd-2 fuel, but also with assemblies with various rod
               Different values of input water temperature in different

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              RB requires new report for ± 2% uncertainly
              Require the new calculation for hot channel with
               defined input water temperature.
              Answer about 300 questions related to power
              Upgrade of existing operational measurements.
              Possible license issue not for full power, depend on
               uncertainty e.g. 106% ± 3% ???

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              Some data before and after power uprate
              Thermal power           1375MW      1471MW
              Uncertainty             4% (2σ)     2% (2σ)
              Fuel type               Gd-2        Gd-2
              Rod power limit         56.6kW      56.6kW
              Average rod power       31.6kW      33.45kW
              Kr rod peaking factor   1.66        1.546
              Rod max. oper. power    52.46kW     51.7kW

              Average assembly power 3.9MW        4.2MW
              Reactor overflow        42300m3/h   42300m3/h
              Hot channel output      321°C       321°C
              Assemblies output       312°C       314°C
              ΔT on reactor           28.9°C      30.8°C

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                 Thank you
              for your attention

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