An Ergonomic Assessment of Workers at Nuclear Power Plant (NPCIL)

 

Amol B. Hadke¹, Dr. M. M. Gupta²

¹Student M. Tech, Industrial Engineering, S.R.C.O.E.M., Nagpur India

²Head of the Department, Dept. of Mechanical Engineering, S.R.C.O.E.M., Nagpur India

 

ABSTRACT:

Every Human operator plays a vital role in the safe and efficient operation of nuclear facilities. Human actions (or inactions) that fail to achieve what should be done in a given situation can be important contributors to facility risk. Operators contribute to a plant’s defense-in-depth hierarchy in a number of ways and nuclear safety cases may make human-based safety claims in respect of reliable interventions for monitoring and control of both normal and abnormal conditions. 

 

It has been observed that there, is vast scope for the improvement of work place environment and working conditions of the workers working at Nuclear power Plant in India. The purpose of this Project is to examine the work place, work environment and evaluate the work performance at normal and abnormal condition at Nuclear power plant. Evaluation of the key factors in the employee’s workplace environment that impact greatly on their level of work performance. Also to assess the effect of employees’ health on their work performance. And to give the necessary suggestion to optimize the situations in terms of work place design and optimizing the work environmental parameters.

 

 

 

INTRODUCTION:

Work place and the work environment in which human-based safety actions are conducted are potentially significant human performance influencing factors. A workers’ sactual or proposed workplaces/spaces are compatible with the types of task to be conducted and human characteristics, in order that risks to the health and safety of workers and the potential for human error is reduced as low as is reasonably practicable .

 

It is therefore follows that relevant good practice in ergonomics should be included and evident in the design and modification of all workplaces/spaces. Application of human factors good practice can also have a positive effect in promoting efficiency and productivity in the workplace. Many organizations still do not give much importance to workplace design.

 

As Mostly employees, believe that the organization want to keep their costs low that is why their workplaces have bad designs; and people think that the priority list of their company does not have workplace design on top.

 

THE OBJECTIVES OF THE PAPER:

To assess the effect auditory environment and Radiation on employees’ health and their work performance, while working near Nuclear Reactor.

 

Every Human play a vital role in the safe and efficient operation of nuclear facilities. Human actions (or inactions) that fail to achieve what should be done in a given situation can be important contributors to facility risk. Operators contribute to a plant’s defense-in-depth hierarchy in a number of ways and nuclear safety cases may make human-based safety claims in respect of reliable interventions for monitoring and control of both normal and abnormal conditions. 

 

SIGNIFICANCE OF THE PAPER:

Innovation is the major driving force in organizations today. With the rise of truly global markets and the intensifying competition for customers, employees and other critical resources, the ability to continuously develop successful innovative products, services, processes and strategies is essential.

 

While creativity is the starting point for any kind of innovation, ergonomic design is the process through which a creative idea or concept is translated into reality.

 

Many organizations still do not give much importance to workplace design. As Mostly employees, believe that the organization want to keep their costs low that is why their workplaces have bad designs; and people think that the priority list of their company does not have workplace design on top.

 

Methodology for Assessment of Ergonomic requirement of work place and work Environment - Auditory Environment (Noise) and Radiation, I am going to follow following methodology.

·        Research Design,

·        Study Population, and

·        Data Collection

 

Environmental Factors:

Environmental factors can increase both physical and mental stress, resulting in distortion or filtering of important sensory information and increased human error potential and/or direct health and safety risks.

 

To Asses the Auditory Environment at Nuclear Power plant site:

Noise in the workplace can be a source of distraction, discomfort and can lead to decrements in human performance and ineffective communication. Exposure to high and/or prolonged levels of noise can also lead to hearing damage. Workplace noise can also have a strategic effect on human performance causing an individual to modify their style of task performance which can lead to increased human error potential.

 

 

Study of Work Environment at Nuclear Power Plant

Data Collection – Noise

 

 

RESULTS AND CONCLUSION:

•        The overall noise of Pressurized water reactor, Steam generator operating room with log average 87.20.

•        Though it is below the  prescribed standard but this  level may be sufficient exposure to create a chronic health hazard problem after long exposure, since the subject  exposed  to high noise level may come out from the noise source after his duty hours but  the  physiological  change  and  psychological  stress occurred in his system. 

•        For the operator who is looking after Turbine floor there is a fare chance of exposure  to >90  dB(A) noise.  So the operator is under risk zone.

•        However, there is no unsteady / impulse  noise in the Nuclear power plant which affect more adversely  than steady  noise.

 

RECOMMENDATIONS:

Green belt design (GBD):

A wide green belt of thick vegetation can be produced around the plant premises. This will absorb to a large extent and dissipate sound energy and thus act as buffer zone. A tree belt 50 m wide and of different height can reduce the noise level up to 20-30 dB(A).[22] GBD will reduce  the noise intensity  by creating  obstruction in its transmission path. In addition it can decrease substantial amount of the air pollution load.

 

Sound absorbing material:

Noise pollution should not be neglected since performance in the plant depends on the individual health of the employees. Outer surfaces of control room should be covered with sound absorbent material e.g., glass wool covered with perforated aluminum Sheet. Glass wool is of different types and has different density.  Higher the density more is the absorbing capacity.

 

To assess the Radiation Environment at Nuclear Power Plant.

Radiation Sources at Nuclear Plant –

·        Nuclear fuel decay

·        Fission process

·        Fission product decay

·        Activation products

·        Calibration sour

 

 

Radiation dose limits:

For workers and operators, occupational exposure to radiation should not be higher than  50 mSv in any one year, and the annual average dose over five years must not exceed 20 mSv.

 

The dose limits chosen mean that the occupational risk to radiation workers is no greater than the occupational risk in other industries generally considered safe.

 

Dose Meter

 

Dosimeters measure doses:

The dose is measured with a dosimeter and the dose rate with a dose rate meter.

 

At nuclear power stations, worker are required to wear dosimeters like a badge. Some types,worn during the performance of a short task, can be read on demand. Others, used routinely, need to be placed in a dosimeter reader for

evaluation, typically every one to three months. The traditional dosimeter is based on photographic fi lm in a light-proof casing. Radiation passes through the fi lm and exposes it. By developing the fi lm and measuring the degree of darkness, say every month, the radiation dose received by the wearer can be estimated.Each time the fi lm ischecked, it is replaced with a new fi lm. Another newer type of dosimeter is The TLD or Thermal Luminescence Dosimeter, which is more sensitive than a fi lm dosimeter and immediately reusable after reading. At nuclear power stations, electronic real-time dosimeters are carried and can be checked at any time.

 

The dose rate - The dose rate tells the dose received in a unit of time,

1 hour. - dose of 0.5 mSv is received in an hour, the dose rate is 0.5 mSv/h.

2 hours - dose received is 1 mSv

6 hours - 3 mSv.

If the dose rate in a room where a person works  is 0.1 mSv/h and the dose limit for that person is 20 mSv, then the work must be completed in  200 hours.

Dose limits for occupational workers at NPCIL:

Exposures to ionizing radiations for occupational workers:

Effective dose (whole body)

1.1 Twenty Milli- Sievert (mSv)/year averaged over five consecutive years,  calculated on a sliding scale of 5 years. (The cumulative effective dose in the same 5-year period shall not exceed 100 mSv.)

1.2 A maximum of 30 mSv in any year.

Equivalent dose (individual organs)

2.1 Eye lens 150 mSv/year.

2.2 Skin 500 mSv/year.

2.3 Extremities 500 mSv/year (hands and feet).

The occupational exposures of any worker shall be so controlled that the following limits are not exceeded:

•        an effective dose of 20 mSv/yr averaged over five consecutive years (calculated on a sliding scale of five years);

•        an effective dose of 30 mSv in any year;

•        an equivalent dose to the lens of the eye of 150 mSv in a year;

•        an equivalent dose to the extremities (hands and feet) of 500 mSv in a year and

•        an equivalent dose to the skin of 500 mSv in a year;

•        limits given above apply to female workers also. However, once pregnancy is declared the equivalent dose limit to embryo/fetus shall be 1 mSv for the remainder of the pregnancy.

 

Radiation Doses Received by Workers in Nuclear Power Plant (NPCIL):

 

 

Radiation Doses Received by Workers in Front End Fuel Cycle Facilities at NPP

 

RESULT:

The information on number of workers in NPPs who received dose between 20 to 30 mSv and above 30 mSv during the year is given in Tables.  There are four cases of exposure above 20 mSv during the year at KAPS – 1 & 2.

 

DISCUSSION:

Reducing radiation dose is accomplished by thorough and effective planning and scheduling, using proven and innovative engineering techniques, performing engineering reviews of design changes and establishing and achieving challenging radiation dose goals.

 

Planning and scheduling identifies those jobs that should be reviewed for radiation dose reduction and allows time to develop methods, write procedures, evaluate design, and train personnel. Personnel familiar with dose reduction techniques should be involved in the long-term planning of work to be conducted in radiological work areas. Radiological engineering in cooperation with work and outage management personnel provide methods to reduce dose rates or the time spent in radiation areas.

 

Radiation dose goals are used as a management tool for involving all station groups in actively reducing radiation dose and provide a means of assessing the effectiveness of radiation dose reduction actions.

 

Radiological protection of workers:

Radiological protection of the workers is ensured by the design considerations that have a bearing on radiation protection. Proper design, plant layout and adequate shielding -  Design values are prescribed for the  radiation level at a specified distance from the equipment/ components as well as for the general radiation fields in different areas of the plant. The plant layout is such that the areas are segregated according to their radiation levels and contamination potential. The  design, layout of areas and  equipment, maintenance approach and  shielding, etc. are made such that the  collective dose to the station personnel would be “as low as reasonably achievable” (ALARA) and meet the  specified regulation on collective dose. Limits of air contamination levels in different zones of the plant - Provision of ventilation is made such that in  full-time occupancy areas of the plant, the airborne contamination are maintained below 1/10 Derived Air  Concentration. Source control by proper selection of materials/components - Materials used in plant systems are selected in such a way that the activation products arising from the base material or the impurity content do not significantly Contribute to radiation exposures. Design limit for collective dose - A limit on the collective dose is specified at the design stage of each NPP so that adequate provisions for radiation protection are made in the design of the plant to keep radiation levels in different  areas below design levels.

 

Protection of plant personnel during operational states:

The design of plant layout should take into consideration personnel access required for operation, calibration, inspection, and maintenance including replacement of equipment in radioactive areas of the plant.

 

The layout should facilitate these tasks besides limiting the exposure of plant personnel and spread of contamination. For this the following need to be provided:

·        Shielding,

·        Area segregation and zoning system,

·        Change room facilities,

·        Access control,

·        Appropriate ventilation arrangements,

·        Equipment handling facilities,

·        Remote handling facilities, and

·        Decontamination facilities.

 

Protection of Plant personnel under accidental conditions:

·        Minimization of individual exposure and collective dose shall be ensured by: Reduction of dose rate in working areas by:  source reduction, adequate shielding, remote handling techniques including robotics, and periodic decontamination of active systems.

·        Minimization of occupancy in radiation areas by: conducting time and motion study for different operations, use of equipment with low failure rates, ensuring ease of maintenance or removal/replacement of equipment, use of CCTV to minimize personnel entries, provision of stand-by equipment, separation/segregation of radioactive/non-radioactive , equipment and  ensuring ease of access and good lighting.

·        There should be provision for remote collection, transfer and analysis of gaseous and liquid samples from the containment during accident conditions without incurring excessive individual exposures.

·        There should be provisions for alerting and assembling all site personnel including those not involved in accident control or fire fighting.

·        Communications are required between the main control room, supplementary control room and emergency assembly areas and emergency control centre.

·        The assembly areas should be chosen such that the radiation background is expected to be low.

·        Provisions should be made for easy identification of rooms with clearly marked signs and free passageways to enable quick movement of site personnel.

·        All other facilities required as per the On-site Emergency Plan for the plant should be provided.

 

Monitoring for Radiation Protection:

For demonstrating compliance with prescribed limits and for providing information on changes in radiation levels, installed radiation monitoring systems should be provided in the design. Provisions should be made for workplace and environmental monitoring. Facilities should be provided for individual external and internal monitoring of the occupational workers.

 

Workplace monitoring should include monitoring for external radiation, airborne contamination and surface contamination. Monitoring for protection of public should include monitoring of effluents from the plant as well as the environmental monitoring during normal operations well as during accident conditions.

 

CONCLUSION:

The goal of minimizing radiation dose is based on the assumption that even small doses could involve some risk of cancer. At Nuclear power plant a Radiological Safety Circle concept should be implemented to control the radiation Protection programme. The RSC would carry the responsibility for providing radiological surveillance and safety support functions. These include radiological monitoring of workplace, plant systems, personnel, and effluents, carrying out exposure control (Regulatory limit 30 mSv), exposure investigations and analysis and trending of radioactivity in plant systems.

 

Nuclear Power plant should have radiation safety programme and work procedures intended to control the occupational exposures. As per AERB guidelines, for an occupational worker annual dose limit is 30-mSv, with the condition that it should not exceed 100 mSv in a span of 5 years. For better exposure control, the individual cases should be investigated periodically and controlled at an early stage so as to avoid reaching the AERB specified dose limits.

 

REFERENCES:

1)       Safety Assessment Principles for Nuclear Facilities. 2006 Edition, Revision 1. Health and Safety Executive. www.hse.gov.uk/nuclear/saps/saps2006.pdf

2)       Set up workstation to ergonomic, Occupational health and safety (OHS) law

3)       Safety in nuclear power plants in India Indian J Occup Environ Med. 2008 December; 12(3): 122–127. doi: 10.4103/0019-5278.44693 PMCID: PMC2796747 R. Deolalikar

4)       Atomic Radiation Protection Aspects In Design For Pressurized Heavy Water Reactor Based Nuclear Power Plants  AERB Safety Guide , Government of India , Atomic Energy Regulatory Board Mumbai-400 094 India

5)       Radiation, Health and Society Courtesy: Radiation, Health and Society by Dr. Bjorn Wahlstrom, IAEA(97-05055IAEA/ PI/A56E) (November1997)

6)       Nuclear Installations Inspectorate (2010) T/AST/058 - Human Factors Integration.

7)       International Atomic Energy Agency, Safety of Nuclear Power Plants: Design Safety Requirements, NS-R-1, IAEA, Vienna (2000).

8)       Literature on International Atomic Energy Agency, Instrumentation and Control Systems Important to Safety in Nuclear Power Plants, NS-G-1.3, IAEA, Vienna (2002).

 

 

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