The Preliminary Phase of a Hazard Analysis Process of a Nuclear Pressure Equipment for a French Experimental Device

The LORELEI experimental facility will be used in the JHR (Jules Horowitz Reactor, Cadarache, France) as a test device to examine the loss of coolant accident (LOCA). The device has a pressure vessel that contains a sample fuel rod, irradiated adjacent to the reactor core. Due to the potential pressure and radiological safety hazards (i.e., intended fuel burst), the design and manufacture of the device is subjected to French nuclear regulations and should be audited and approved by an Accepted Notified Body (ANB). The Hazard Analysis (HA) presented to the ANB comprises several stages, starting with the classification of the equipment, followed by the identification of the hazards and ends with the safety analysis. This article is limited to present the preliminary phase of the methodology, as a precursor of the detailed phase of performing the HA, upon ESPN requirements of the French regulatory body (ASN).
The performance of the HA should be processed in two stages: a) The preliminary phase and b) The detailed phase. During the preliminary phase, a recurrent interaction between the safety analyst and the designer, is highly recommended, to assure the implementation of the ESPN requirements into the design, from the early stages until the manufacturing drawings are completed.
The input data received from the LORELEI operator included: a) The description of all working/accidental situations in conformity with its specific SAR; b) The list of pressure loads anticipate for each situation; c) Data related to the radioactive compounds in the coolant; d) Requirements for: Highly Improbable Situations (HIS), in-service-inspections, etc...

The description of the equipment shall include: a) A functional division among parts (including spare parts) and joints, including temporary components (e.g., lifting eyes); b) Indication of the design assumptions, (e.g., the number of motions of moving parts); c) Indication of the joined equipment (e.g. lifting eyes, etc..); d) Information on accessibility conditions, to enable inspection under radiation protection measures; e) Information considering the environmental operating conditions as well as shipment conditions, and f) List of equipment limitations, such as physical boundaries in terms of peripheral support structures.

The categorization of the installation equipment is expected in a separate document, in which the safety analyst will identify and divide the installation into “parts” and “joints”, that should be analyzed and calculated separately. Moreover, “components” may be defined by several “parts” and “joints” upon their functional task.

Following the document of categorization, a functional analysis must be performed, for each “part” and “joint”. It is common practice to address two issues in the functional analysis of each element: a) the “Service” functions, by indicating the action or the activity, and b) the “Constrains” of operation. This information has to include mandatory design characteristics, such as: 1) dimensions, enable in-service inspectabilty; 2) limiting the maintenance due radiological protection requirements. Finally, the functional analysis has to include the classification of the NPE into four categories: Pressure Parts (PP), Oher Parts Contributing to Withstanding Pressure (OPCWP), Other Part Likely to Generate a Pressure Hazard in terms of Pressure strength (OPLGPHP) and Other Parts (OP). These four categories consider Pressure Hazards only, and for Radiation Protection Hazards the consideration is whether the Part is included in the radiation protection program or not.

Failure Modes Effect Analysis (FMEA) is one of accepted methods to meet the expectation of the ANB and perform the HA of LORELEI NPE. The analysis requires presenting a Table of the Identification, for each component of the installation. The Table should include the information mentioned previously along with the Causes of the Failure (COF), loss of service function and/or constraint. The FEMCA help to identify, for every possible FM, the applicable requirements applicable to equipment. The regulatory requirements that should consider are: 1) Essential Safety Requirements (ESR); 2) Radiation Protection Requirements (RPR), 3) Highly Improbable Situations (HIS), 4) Additional Requirements (AR). Technical measures and proof of implementation are complimentary for the specific cases where the requirements are not confirmed in the design.
The preliminary phase of the HA process for ESPN equipment, upon the requirements of an ANB on behalf of the French regulatory authorities, was explained in detail. It comprises of five major steps that enable the safety analyst to progress to the detailed phase of the process. The complete activity is underway in order to safe evaluate the LORELEI pressure equipment under international standards.