Lata Mishra Bhabha Atomic Research Centre, INDIA · Regulatory Body Atomic Energy Regulatory Board (AERB) has been entrusted with the responsibility of laying down safety standards

Lata Mishra

Bhabha Atomic Research Centre, INDIA

Outline of presentation

Legal & Regulatory provisions / requirements

Safety criteria & Safety objectives

PIE’s

Safety & Seismic categorization

Safety provisions in various SSC’s

Conclusions

Legal provisions

In India activities concerning establishment and utilization of Nuclear Fuel Cycle Facilities (NFCF) and use of radioactive sources are carried out in accordance with the provisions of the Atomic Energy Act, 1962

Provisions of the Act

Power to the Government to provide for control over radioactive substances or radiation generating plant in order to

Prevent radiation hazards

Secure public safety and safety of persons handling the plant

Ensure safe disposal of radioactive wastes

Regulatory Body

Atomic Energy Regulatory Board (AERB) has been entrusted with the responsibility of laying down safety standards for such activities to ensure the safety of members of the public, occupational workers as well as protection of environment.

Compliance of Regulatory limits imposed by AERB ensure that air borne contamination and exposures to occupational workers and general public are maintained at levels that are “as low as reasonably achievable” (ALARA).’

Safety Codes & Guides

AERB has developed safety standards, codes of practice and related guides & manuals, covering all stages of a project

Codes set the minimum requirements that are to be fulfilled mandatorily by the facilities

Codes formulated on the basis of internationally accepted safety criteria

Guides contain detailed guidelines to implement specific parts of a safety code

Guide on consenting processes

AERB has issued a safety code on ‘Regulation of Nuclear & Radiation facilities’ &

Safety guide on ‘Consenting processes for NFCF’s

From site selection to decommissioning, a well laid out process for acquiring consent from regulators is in place

Following the procedure ensures that the system is reviewed for safety by the regulatory body and necessary submissions are made to the regulatory body by the agency seeking consent, at every stage.

Guide on consenting processes contd..

This guide is valid for Recycle plants comprising of spent fuel Reprocessing & Waste management plants

The consenting processes include review of safety aspects as presented in the Safety Analysis Report (SAR)

Typical format & contents of the SAR is a part of the guide

Experience

Good amount of experience has been gained in construction, commissioning, operation, decommissioning and decontamination of NRF’s

Importance to

Safety Safety

one step ahead

of functionality Functionality

Safety criteria for design

In line with this philosophy of according highest level of importance to safety

A document on Safety Criteria for Design of Nuclear Recycle Facilities has been made

It specifies the safety criteria to be followed for all systems at component level

OBJECTIVE

The document has been prepared essentially to

identify safety issues in the various systems and specify design provisions that should be followed

to prevent unsafe situations

BASIS

Safety criteria is based upon experience gained in the operating plants

&

AERB safety guidelines for design of Nuclear Recycle facilities

RELEVANCE

Will be relevant during

the various stages of the project

&

will be a reference for

Designers, Operating personnel

&

Regulators for ensuring the safety of the facility

Safety Related Systems addressed

Civil and structural safety

Safety & Seismic categorization of SSC’s

Process Systems including auxiliary systems

Ventilation System

Radiological and Criticality safety

Utility and services

Fire safety

Civil and structural safety

Possible design events under both normal & abnormal conditions are first postulated and structures designed to withstand or mitigate the consequences of these postulated conditions.

Postulated initiating events (PIE’s) that would result in an accident scenario are also identified and consequences of resulting accident analyzed to specify design inputs for the structure

Postulated Initiating Events (PIE’s) Anticipated normal events

Wind loading

Water Level (Flood) design

Seismic design &

Anticipated abnormal events

Red Oil formation

Criticality

Leakage from HLW tank

Beyond Design basis earthquake

Structural Design Structures designed for anticipated normal events

eg. Safe Grade Level , Seismic Design

Abnormal events avoided & safety ensured by :

Multiple physical barriers for radioactive source

Control of steam temp, organic in aqueous

Control of geometry, mass & conc. of fissile material

Selection of good material of construction

Safe Grade Level Final Grade Level is arrived at, considering :

a storm surge, calculated for the most severe storm in the vicinity of the site (probability of 1 in 100 years)

such a severe storm coincides with the highest high water level (joint probability of such an event will be still lower)

the most severe storm directly hits the site

The frequency of such an occurrence would be of the order of 1 in 1000 years or so

Safety & Seismic categorization Structures / Electrical systems / Process

equipment & piping / I&C systems of NRF’s are classified based on their safety functions

Purpose : to establish a gradation approach in the design, construction and maintenance of the SSC’s

Seismic categorization is based on the hazard potential of facility and its requirements of integrity & functionality during or after seismic event

Level of earthquake for design

During an earthquake the NRF’s do not have operability requirement like NPP’s, hence various systems and components are designed for a single level of earthquake load in line with international practices. All the static civil and mechanical structures are designed for structural integrity against the design basis earthquake loads

Design & Safety objective All systems are designed to achieve the functional

objectives of the plant while ensuring adequate safety

Fundamental safety objective is to protect

Occupational worker

Environment and

General public

from harmful effects of ionizing radiations.

Process Systems : General

High standards of MOC, fabrication

Remote operations for handling high active equipment

Adequate shielding wherever necessary to prevent exposure of working personnel

SS lining in areas for easy decontamination

Provision of redundancy w.r.t critical equipment used for containing radioactivity

Process systems Negative pressure in equipment always better than

the specified value with requisite interlocks & cut offs

Suitable provisions for detection, collection & disposal of spills/ leakages from in-cell equipment

Provisions to prevent unintended & Inadvertent transfers & minimize entrainment of active liquids

Hold ups in pipelines minimized

Provisions to avoid blow back of active fluids into inactive areas

Avoiding Blowback

Process systems

Cooling provisions for vessels handling high active liquids, including emergency cooling

Provisions to prevent entry of organic into evaporators

Provision for accurate accounting of SNM

Sampling provisions

Suitable enclosures with mechanized handling for powder processing equipment

Shielded cubicles planned in inactive areas (as in pumps) to facilitate maintenance

Shielded Cubicles

Niches

Process & Waste Management

HLLW storage tanks provided with two sets of cooling coils for removal of the decay heat

Cooling & off gas system availability enhanced with dedicated Class III DG sets for vessels handling high active liquids

Storm water system to be totally isolated from PAD system

All kinds of wastes discharged from the plants to meet stipulated guidelines of regulatory bodies

Lines laid underground to have secondary containment with provisions for inspection

Instrumentation

Monitoring of plant parameters & radiation status under normal & anticipated operational occurrences

Seismically qualified UPS & dedicated air reservoir with sufficient back up for monitoring critical plant parameters for safe shut down of plant

Instrumentation

Control systems & Interlocks designed to maintain important process variables

Hardwired backup for important safety alarms & trips

Auto restart of devices on electrical power resumption prevented

Utility & Services

Class III power supply for critical systems

Elaborate off gas cleanup system with adequate capacity & static pressure & redundancy

Remote operation & auto changeover during failure of blowers

Steam temperature to be limited to set value

Communication system, emergency alarm & response system – first priority selection

Ventilation system Operation capability during normal power outage

to confine contaminants

Fire resistant system

Designed to support radiological zoning

Graded flow from less potential area for contamination to higher potential area

Once through ventilation in areas with potential for contamination

Redundancy of equipment with auto changeover

Class III supply to exhaust fans, with auto changeover on Class IV failure

Ventilation pattern

Radiological & Criticality safety

Adequate shielding for radioactive sources

Segregation of active & inactive areas with radiation zoning for contamination control

Emergency exit doors at suitable points

Radiation monitoring & survey equipment

Adequate breathing air stations

Safety interlocks for preventing mal operations

Geometry, mass & concentration control

Exposure limits Safety provisions in design shall ensure that under

Design Basis Accident conditions, accident analysis should demonstrate that the exposure to a member of the public at the site boundary does not exceed

30 mSv per year & 100 mSv in a 5 year block for occupational workers and

1 mSv/year for members of public

All radiation sources provided with adequate shielding so that the field on contact outside the shielding is less than 1 μSv/h (as per AERB guidelines) where full occupancy is envisaged

Criticality safety

Criticality safety is achieved by keeping one or more of the following parameters of the system within sub critical limits in normal operations, for anticipated occurrences and for design basis accident conditions

Mass of fissile material present in process

Geometry of processing equipment

Concentration of fissile material in solutions

The safety of the design for the facility is demonstrated by means of a specific criticality analysis wherein the K-eff of individual tank / equipment and as a layout does not exceed 0.9 under all circumstances.

Fire safety Principle of defence-in-depth adopted in design of

fire protection systems

System shall consist of fire prevention, detection and suppression systems & shall be achieved through

Structural safety –

Detailed fire hazard analysis in initial design

Appropriate fire detection & annunciation systems -

Fire & Smoke detection & alarm system

Adequate fire fighting systems

Conclusion

The document identifies various safety issues related to Nuclear Recycle Facilities in India

The provisions specified in the document are as per International practices

Design ensures safety even during anticipated abnormal events

Thank You