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Seminar on the Advanced Boiling Water Reactor (ABWR) by Hitachi [vendor of reactor]

Seminar on the Advanced Boiling Water Reactor (ABWR) by Hitachi [vendor of reactor]
University of Birmingham, 21st-22nd April 2015
Notes by William Gaskell MSc PTNR Birmingham

Introduction to ABWR

By Mr K. Moriya of Hitachi-GE
[Information in this seminar is based on the Japanese safety licence for ABWR which will vary from ABWR UK design after GDA process with ONR]
Hitachi aim to establish an ABWR chair in academia at undergraduate level. [–perhaps at Bangor University in Wales]
Interesting specifications of reactor:
·         Thermal power is 3975MW
·         Temperature of steam from core is 287˚C
·         10 pumps (RIPs) in the pressure vessel of reactor
→   Safety work using STAR-CD code to model pump trip in reactor so that we know how to control core in such situations
·         60 Hz 52” blade turbines used in ABWR to generate electricity from steam produced in core
·         Each emergency backup diesel generator has 4000kW capacity [I would think 50MW would be needed to keep reactor running normally as coolant pumps require large amount of energy to operate]
Inherently Safe:
·         Negative void feedback meaning no risk of Chernobyl style accident
·         Atmosphere Control (AC) system injects Nitrogen gas to prevent hydrogen gas burning (Fukushima-style)
·         Flammability Control System (FCS) recombines Hydrogen gas + Oxygen created by radiolysis (of water) in the reactor [radiation catalysing the disintegration of water at high temperature into oxygen and hydrogen gaseous molecules]
·         It would take at least 2 days to create explosive 5% concentration of Oxygen (+ Hydrogen)

Horizon Nuclear Power

Power company building and operating ABWR in UK at Wylfa in Anglesey, Wales  and Oldbury, in Gloucestershire in England
·         Next supply chain event in North Wales details are on Horizon’s website

Robot and Remote-Controlled Technology

Prof Hijime Asama, University of Tokyo

Fukushima 2011 Accident (Level 7 on International Nuclear Events Scale)

Situation:
·         There was explosion of Hydrogen in units 1, 3 & 4 and leakage of cooling water in all units 1-4.
·         Spent fuel pool was heating up and water evaporating.
Plan for recovery:
Phase 1: COMPLETED
Fuel removal from spent fuel ponds
Phase 2: Current phase
Removing fuel debris (to take 60 years)
Phase 3: Complete decommissioning of site

·         Need robots to achieve this!
·         ROBOTAD (Robotics Task Force for Anti-Disaster)
One of the problems faced by robots on site was stairs in Fukushima reactor being a different width in the reactor (70cm) to the specifications in the plans (90cm).
Robotics industry needs to set up long term
·         Projects
·         Facilities
·         Long-lived robots with A.I.
Lesson Learned from Fukushima:
Units 2 RCIC (emergency cooling system) managed to operate for 3 days after tsunami before melt-down – design expectancy was only 8 hours.

Construction of ABWR

ABWR reactor building dimensions: 60x60x60m – high power density!
Improving construction efficiency by visualising the final result

Control of ABWR

Mr Y. Koda, Hitachi-GE
Reactor is controlled using following techniques in order of preference:
1.       Using RIPs and controlling flow rate of coolant in core
2.       Control Rods – very fine reactivity control can be achieved with very small notches for each step of insertion [he seems to indicate on startup/low power regimes the other way around]
3.       Turbine control valve + dome pressure (has less effect in ABWR than in BWR)
Control systems:
1.       RFC (Recirculation Flow Control) + RC&IS (Rod Control and Insertion System)
→   Reactivity control (how much fission rate increases/decreases per generation of fissions – rate of propagation of chain reaction)
2.       EHC (Electric Hydraulic Control System)
→   Turbine speed
→   Pressure of coolant in core
3.       FDWC (Feedwater Control)
→   Core water level
Increasing the pump speed would increase the power of the reactor. Decreasing would reduce power as would inserting control rods.
No void positive reactivity coefficient (bubbles in coolant water in core causing the rate of fission to increase uncontrollably in core and create Chernobyl-style disaster) as Doppler effect of temperature on material coefficient lowers reactivity with increased temperature in fuel.
Shut down signal acronym SCRM
Suppression pool cools down steam when reactor depressurized in trip (accident like Fukushima Tsunami)
Next ABWR seminar at Imperial College, London, September 2015 location to be arranged.


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