Safety system settings

Forming the safety leadership team (SLT) and arranging an external safety and health audit are already steps toward structuring a safety system. Setting up the system also calls for the constitution and establishment of different-tiered safety committees. It also establishes a safety culture baseline based on the audit findings. The big question now is What is the next step in the implementation of a safety system, and how is it done The short reply is that it s like eating an elephant—one bite at a time. Bite one is getting the workplace in order. 

Safety is a line responsibility that is shared by the operators, facility supervisor, facility manager. Director, and Vice President. The staff is procedurally trained to understand and obey the Technical Safety Requirements (TSRs) of the facility. If plant conditions change such that TSRs are threatened by operations, experiments, equipment failures or external forces, then operations are immediately terminated to minimize the possibilify of a TSR violation and a potential unanalyzed or unsafe condition. The Hot Cell Facility Periodic Maintenance/ Surveillance Operating Procedure (SNL 1997c) requires periodic inspection and checkout of important safety equipment and safety system settings to minimize the chance of "undetected" degradation of safety equipment that could lead to a safety function failure. 

Established safety system settings shotrld ensirre automatic actuation of safety systems within parameter values assirmed in the safety analysis report, despite the... 

The following are typical parameters, operational occurrences and protective system devices for which safety system settings are necessary. Note that the settings may be dififerent in different plant states. For example, at a low operating temperature, the reUef system for the reactor pressure vessel may necessitate lower pressure settings. 

The actions to be initiated as described in para. 5.1 for the items listed here may vary according to reactor type and design, or some of the settings may not be applicable. For particular reactor types, additional parameters may be described in the safety analysis report, for which safety system settings should be specified. 

Limits and conditions for normal operation are intended to ensure safe operation that is, to ensure that the assumptions of the safety analysis report are valid and that established safety limits are not exceeded in the operation of the plant. In addition, acceptable margins should be ensured between the normal operating values and the established safety system settings to avoid undesirably frequent actuation of safety systems. Figme A-1 in the Annex demonstrates a correlation between safety limits, safety system settings and limits for normal operatioa... 

In order to ensitre that safety system settings and limits and conditions for normal operation are met at all times, the relevant systems and components should be monitored, inspected, checked, calibrated and tested in accordance with an approved smveillance programme. 

A-I. Figure A-I explains and illustrates the interrelationship between a safety limit, a safety system setting and an operational limit. 

A-3. It is assumed for the purposes of Fig. A-1 that a correlation has been established in the safety analysis report between a monitored parameter (in this case, coolant temperatnre) and the maximiun fuel cladding temperature, for which a safety limit has been estabhshed. The safety analysis would show that actuation of the safety system by the monitored coolant temperature at the safety system setting should prevent the fuel claddiug temperature from reaching the set safety limit beyond which releases of significant amounts of radioactive material from the fuel might occur. 

A-7. In the event of malfunction of the control system or operator error or for other reasons, the monitored parameter might reach the safety system setting at point A with the consequence that the safety system is actuated. This corrective action only becomes effective at point B owing to inherent delays in the instrumentation and equipment of the safety system. The response should be sufficient to prevent the safety limit being reached, although local fuel damage carmot be excluded. 

The Limiting Safety System Setting for fuel temperature is ... 

Identify each of the following as either a Safety Limit (SL), Limiting Safety System Setting (LSSS), or a Limiting Condition for Operation (LCO). 

A set of OLCs important to reactor safety, including safety limits, safety system settings, limiting conditions for safe operation, requirements for inspection, periodic testing and maintenance and administrative requirements, shall be established and submitted to the regulatory body for review and assessment. 

Requirements shall be established for the frequency and scope of inspection, periodic testing and maintenance, operability checks and calibrations of all items important to safety to ensure compliance with safety system settings and limiting conditions for safe operation. 

Design requirements to ensure that safety system settings are not adversely affected and... 

A. 1701. This chapter of the SAR shall contain the operational limits and conditions (OLCs) important to safe reactor operation which have been derived from the safety analysis. The OLCs represent an envelope of parameters, developed by the operating organization, which will protect the reactor, the staff, the general public and the environment from undue exposure if they are not exceeded. Therefore, it is essential that the OLCs are understood by the responsible operating personnel. The OLCs include safety limits, safety system settings, limiting conditions for safe operation, and surveillance and administrative requirements. Additional information is contained in paras 601-608 of Safety Series No. 35-S2. 

The nominal safety system settings for each variable or combination of variables. 

Where required, the bases for Limiting Safety System Settings will be included in a setpoint document (ROMP Item IM-74). DOE approval of this document is required prior to the approval of the final Technical Specifications revision prior to restart. 

Limiting safety system settings shall be specified for automatic protective devices for those variables having significant safety functions. Where a limiting safety system setting is specified for a variable on which a safety limit has been placed, the setting shall be so chosen that automatic protective action will correct the abnormal situation before a safety limit is exceeded. 

To achieve these functions, appropriate Safety System Settings (SSS) shall be defined to limit safety variables. Typical safety variables are shown in Table II. Safety variables, which are monitored by the reactor protection system, are typically grouped in different types of channels as shovra below. 

This module monitors analog conditioned safety signals for their rationality, validity, and conformity to defined operational ranges and upon comparing with safety system settings provides binary outputs. 

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