GE-Hitache ESBWR technology and safety design parametres

GE-Hitachi ESBWR  technology and safety design parameters

GE-Hitachi nuclear energy

Based    in Wilmington N.C. GE -Hitachi nuclear energy (GEH) is world leading provider of advanced  reactors alliance created by GE and Hitachi to serve the global nuclear industries . The nuclear alliance executes a single, strategic vision to create a broader port folio of solutions expanding its capabilities for new reactor and serve opportunities. The alliance offers customers around world the technologies , leadership required to effectively enhance reactor performance power out put and safety.

GE -Hitachi nuclear energy announced recently its next generation reactor model, the economic simplified boiling water reactor (ESBWR) has  passed a crucial safety review performed by advising committee for  U.S. nuclear regulatory commission (NRC). Completion of this view clear a key hurdle in the company’s bid for design certification of ESBWR , which now begins the federal rule making process. This sets the stage for final NRC certification by 2011.

In October 2010 letter to public, the NRC ’s independent advisory committee on reactor safeguards (ACRS) issued its safety recommendation for ESBWR design which is required before a new reactor technology can achieve  final certification. From this point the process takes approximately one calendar year to complete, this keeping to NRC schedule. As  a result GEH technology is on target to become a certified “Generation 111+ “ reactor model. GE submitted the ESBWR to NRC in 2005.

‘The ( ESBWR) design is robust and there is reasonable assurance that it can be built and operated  without undue risk to health risk to the health and safety of public “ ACRS chairman written in the agency’s  safety recommendation .

The 1520-megawatt (MW) ESBWR offers what GE believe is the world most advanced passive safety features, simplified construction and operation and lowest core damage frequency on the market today. In addition the ESBWR ’s innovative digital instrumentation and control design and development process are rigorously complaint to nuclear regulation and globally recognized standards.

“ Our team has been successful in keeping the ESBWR on track to become the first reactor with the extent of passive safety features and reliance on natural circulation cooling yet to be certified “ said  Caroline Roda, president of CEO of GEH. “ The team  has done a great job demonstrating that this technology is safe and reliable. This independent recommendation from ACRS, along with expanding GEHs’ global supply chain and nuclear foot print  shown the commitment of GEH to long -term nuclear projects”.


GEH and Michigan utility DTE energy are collaborating on a potential ESBWR project adjacent to its Fermi . 2 nuclear plant, 35 miles south of Detroit . NRC is currently reviewing the utility license application for the proposed  “ Fermi unit 3 “ DTE energy ,which operates Detroit Edition, Michigan’s largest electric utility, has not yet made a decision to proceed with construction of the new reactor. GEH offers utility customers what it believes is most complete portfolio of NRC-Certified reactor models. The ESBWR is an evolutionary based on GEH s 1350-Mwe advanced boiling water reactor (ABWR ) the first and only generation 111+ reactor to be fully certified by NRC (in 1997). GEH intends to renew its ABWR certification for an additional 15 years beyond 2012.

Safety enhancement features in ESBWR

The ESBWR is direct cycle, natural circulation BWR and has passive safety features to cope up with range of design basis accidents (DBAs). Within the containment structure are the isolation condensers (IC) to be elevated gravity driven cooling systems (GDCS) water pools, a passive containment cooling system (PCCS) and an elevated suppression pool. These systems can remove decay heat under all conditions. The ESBWR standard design includes a reactor building that surrounds the containment, as well as building dedicated exclusively or primary to housing related systems and equipment.

The limiting ESBWR DBA is an  main steam line break (MSLB). In this DBA water and steam are initially discharged from break into dry well. As the dry well pressure increases the horizontal vents between dry well and wet well clear. Subsequently , a steam water mixture from break flows through the vents into wet  well  suppression pool, where steam is condensed and water is cooled to the pool temperature. As primary system pressure fall to the dry well pressure, water makes up  to the reactor vessel is provided by actuation of GDCS I.e.GDCS squib valves open and water flows by gravity head into the vessel from GDCS pools. This occurs ten minutes after the initiation of accidents. The reactor core is never uncovered during the limiting of DBA . The steam condensation in the suppression pool and pressure equilibrium between dry well and wet well through the vacuum breakers reduce the dry well pressure causing the horizontal vents to close. The remaining non-condensable gases and steam in dry well then follow up through the POCS heat exchanger. The steam is condensed as it passes thorough the PCCS tubes. Water condensate is collected and return to GDCS pools and the non condesable  gases flow into  the wet well gas space .This establishes a passive long term recirculation cooling mode for over 72 hours-non safety related recalculating fans are credited after 72 hours and result in further reduction in containment pressure. However calculations show that even in purely passive mode the containment pressure remains below design pressure for over 30 days.

Probabilistic risk assessment

The ESBWR design certificate included a PRA ( probabilistic risk assessment) in according with regulatory requirements. The ESBWR PRA is level 3 PRA covers full power operation and shut down conditions. The scope of initiating  events include internal events and assessment of internal plant fires and floods. The only quantified external events are high winds and tornadoes. A seismic margin analysis was performed, but risk from seismic events and other possible external events was not quantified. Although many of the analysis elements are consistent with AS ME-RA-Sb-2005 capability  2 standard, those attributes were not consistently achieved at this stage of the PRA development. For example some aspects of human performance, models for equipment lasting and maintenance and details of fire and flood damage cannot be anal sized in the absence of physical plant, procedures and operating staff.

In these cases surrogate analysis were performed and assumptions were  applied to encompass potential plant configuration, operations and maintenance program mes and organization . In addition any analysis requiring site specific characteristics were  treated in a generic manner.

Over view found that this PRA was acceptable for design certification purposes. The estimated frequencies of core damage and large releases provide confidence that ESBWR design achieves NRC staff expectations for advanced plants. The PRA was an integral part of the ESBWR design process, and risk unsightly influenced a number of design changes though the review. The integrated risk perfectibility was an important contribution to achieving the estimated low -risk.

The ESBWR design is robust and there is reasonable assurance that it can be built and operated without undue risk to the health and safety of the public