Radiological Work Management Aspects influencing Dose Reduction at the Ignalina NPP during Outages and coming Decommissioning Radiation Protection Centre Kalvariju 153, LT-08221 Vilnius Lithuania http://www.rsc.lt Gintautas KLEVINSKAS, MSc. Head of Subdivision of Supervision and Control 4th EC/IAEA/ISOE WORKSHOP on OCCUPATIONAL EXPOSURE MANAGEMENT AT NPPs Lyon, France, 24-26 March, 2004

Outline Introduction ALARA Programme at the Ignalina NPP – a Use of the Structured Approach Radiological Work Management Aspects Influencing Dose Reduction During Outages Challenges and Improvements in Radiation Protection in 2002-2003 during Outages Occupational Exposure Results Decommissioning of Ignalina NPP – Issues of Concern Application of ALARA Principle during the Decommissioning Conclusions

General Information – Ignalina NPP Two non-upgradeable nuclear reactors of RBMK-1500 (LWGR) series Located in north-eastern part of Lithuania, 160 km distance from Vilnius 2 Units Unit 1: 31 /12/ 1983 Unit 2: 15 /08/ 1987 Number of workers ~ 4500 Natural cooler - Lake Druksiai Designed thermal output -4200 MW Designed electrical output 1500 MW (actual - 700-1250 MW)

Fundamental Parameters of the RBMK – 1500 Reactor Coolant Water (Steam-Water Mixture) Heat Cycle Configuration Single Circuit Core Dimensions height 7 m diameter 11.8 m Number of Channels fuel 1661 control and shutdown system 235 reflector – cooling 156 Fuel Uranium Dioxide Initial Fuel Enrichment for 235U, % 2.0 (2.4, 2.6 with Erbium)

Ignalina NPP – Unique Features Identical to BWR Type, but: Each nuclear assembly bank located in a separately cooled fuel channel (pressure tube) Nuclear fuel assemblies are changed without shutting down the reactor For improvement of neutron characteristics, large amount of graphite is needed

Ignalina NPP – Unique Features Identical to BWR Type, however: Occupational exposure results are probably the highest if comparing with reactors of other types Main ,,contributors” to the annual collective dose are the annual outages of the units. Good and effective radiological work management programmes during the outages are needed (as a part of the radiation protection programme)

Sources of high dose rates at INPP Main sources of ionizing radiation at the INPP contributing to high dose rates during outages: Reactor Corrosion products in ,,blind” areas of the circuit Radioactive substances in steam and water

Requirements for Occupational Radiation Protection in Nuclear Facilities – Radiation Protection Programme The radiation protection programme addresses following issues: classification of working areas and access control; local rules, measures of supervision of safety at work and order of organization of work; procedures of monitoring of workplaces and individual monitoring of workers; individual protective equipment and procedures for their application; main premises, control systems for assurance of radiation protection; requiremenets for management of radioactive waste; radiation protection measures applied during the accident; application of optimization principle (ALARA) and measures on exposure reduction; health surveillance of workers; training of workers and their instructions.

Works mostly contributing to the annual collective dose Replacement of reactor fuel (technological) channels;   Maintenance of primary system pipes Du-300 (d=300 mm);   Maintenance of primary system pipes Du-800 (d=800 mm);   Control of metal;   Replacement of spherical valves used for measuring of outlet water flow (SHADR-32M) and replacement of removable parts of regulation valves;    Repair of pipes of the main circulation circuit, reactor emergency cooling system, blow-off and cooling system of the reactor;    Insulation works;

Use of a Structured Approach Recognition of Problem where Exposure Optimization is needed ALARA PROCEDURE Final Decision

ALARA Programme at the Ignalina NPP Work organization; Training of personnel; Improvement of working environment; Improvement of technological processes; Implementation of quality assurance programme; Improvement of safety culture; Evaluation of influence of ,,human factor” Implemented by ALARA Group

Evaluation and Feedback The ALARA Procedure Analysis and Evaluation of the Exposure Results from Previous Years Establishment of List of Works during which the Exposure Reduction is needed Evaluation and Feedback Evaluation and Discussion on Optimization Measures for Specific Tasks Selection and Analysis of Options with Respect to Dose Reduction Factors Approval of Measures, Allocation of Necessary Resources Implementation of Measures, Cost-Benefit Analysis 26493

Dose Planning (dose distribution maps, annual ,,dose budget”) Radiological Work Management Approaches for Exposure Reduction during Outages Work Planning and Organization Description of Works Dose Planning (dose distribution maps, annual ,,dose budget”) Description of specific operations 26493

EXAMPLE OF DOSE MAPS USED FOR DOSE PLANNING AT IGNALINA NPP (DOSE MAP OF LEFT LOOP OF PRIMARY CIRCUIT) Box 506/1 Between the DS: 1-4.5 mSv/h Downcomers, horizontal parts: 1.2-2 mSv/h Downcomers about plugs: 0.8-1 mSv/h Drum Separator Connection (500 cor.): 1.5 Sv/h Main Circulation Pumps Box 409/1 mark 10.0 Pressure pipes: 0.3-0.5 mSv/h Box 208/1 mark 6.0 ECCS T-joints: 0.7-5 mSv/h Welded joints to GDH: 2.2-3.6 mSv/h Box 117/1-7 Service foot-plates: 0.15-0.31 mSv/h Nearby valves Du800: 0.08-0.13 mSv/h Drainages of Du800: 0.02-0.14 Sv/h Pipes PH-GDH: 0.5-1 mSv/h Box 409/1 Connections PH-SH: 0.01-0.05 Sv/h Downcomer: 0.3-0.85 mSv/h

Work Permits Preliminary measurements of: Dose rates Radiological Work Management Approaches for Exposure Reduction during Outages Work Permits Preliminary measurements of: Dose rates Surface contamination levels Air contamination levels   Preparation of workplaces by operational workers;   Estimation and appointment of individual protective equipment;  Instructions to team workers before the beginning of works;   Issuance and approval of work permits by the Shift Head of WS Department. 26493

EXAMPLE OF CONTENTS OF THE WORK PERMIT USED AT IGNALINA NPP (PART: RADIATION PROTECTION MEASURES)

Decontamination of Systems Radiological Work Management Approaches for Exposure Reduction during Outages Decontamination of Systems Gives very positive results in exposure reduction (main forced circulation circuit, outage of Unit 2 in 2003)   Room No. Gamma dose rate, mSv/h Deconta- mination factor Before decontamination After decontamination 117/1-7 1-400 0.6-1.2 1.7-330 409/2 50-400 2-2.3 25-170 213; 214/1,2; 215 1.5-100 0.2-1.1 75-90

Without radiation shielding With radiation shielding Radiological Work Management Approaches for Exposure Reduction during Outages Installation of Temporary Radiation Shielding Led blankets used Approach: averted dose should be higher than received during installation Room No. Gamma dose rate, mSv/h Without radiation shielding With radiation shielding Room 506/2, near the blind pipes 5.0-2000 5.0-45 Room 208/1, near the the joints 6,8 of headers of the emergency cooling system 8.0-400 8.0-70

Radiological Work Management Approaches for Exposure Reduction during Outages Training of Personnel ALARA questions are included in personnel training programmes Educational book on radiation protection is introduced since 2002 (Russian translation), since 2004 (Lithuanian translation) Self - assessment procedures Regular training and instructions, advanced training is performed Training on mock-ups before the beginning of jobs Positive experience and involvement of individual awareness

Unit 2: 05/04/01-01/06/03 (unplanned 01-06/11/03) Planned doses: Occupational Exposure Results during the Outages at Ignalina NPP in 2003 Outages: Unit 1: 12/07/03-21/10/03 Unit 2: 05/04/01-01/06/03 (unplanned 01-06/11/03) Planned doses: 7.59 manSv (plant personnel) 2.57 manSv (contractors) Actual doses: 6.66 manSv (plant personnel) 1.88 manSv (contractors)

Main Exposure Optimization Measures implemented During Outages in 2002-2003 Replacement of fuel (technological) channels Installation and training on mock-up Purchase of equipment and putting into operation of non cable connection Installation of equipment for removal of filing Preparation and implementation of additional equipment for replacement of fuel channels Maintenance of pipes Du-300, Du-800 Training of personnel on replacement of welded seams on the mock-up Purchase of equipment and training of welders on welding of pipes with equipment VAS 120 Purchase of equipment for cutting and replacement of parts of pipes Du-800 Training of personnel on repairement technology of pipes Du-300 on the mock-up Application of automatic welding for pipes Du-300 Replacement of spherical valves used for measuring of outlet water flow (SHADR-32M) and replacement of removable parts of regulation valves Training of personnel on repair technology on the mock-up

Achievements in Radiation Protection in 2002-2003 new whole body counter "ACCUSCAN 2260-G2KG " was putted into operation (in 2003 – 2659 of personnel was monitored) ; new system for training of personnel in the field of radiation protection has been introduced: educational book ,,Radiation Protection” is issued. New programmes for training and checking of knowledges of personnel have been applied replacement of equipment for measurement of radioactive contamination at the exits from controlled area (RZB-04 have been replaced to RTM-860, PPM-1, PMW-3e) set of dosimetric equipment is renewed (50 items of RAD-62-, 4 items of TELETECTOR, 2 items of FH40 G with detector FHT 752).

Evolution of Occupational Exposure at INPP, man mSv/Unit, 1984-2003

Planned Decommissioning Activities and ALARA Approach Nuclear Safety Agreement in 1994 - Closure of the Ignalina NPP at the time of so-called ,,gap closure” Closure of Unit 1 in 2005, Unit 2 – probably in 2009 Nov. 2002 – Immediate Dismantling Strategy for Unit 1 Dismantling will continue at least 30 years Can be treated as extended outage Predicted total collective dose : ~ 35 manSv Need for advance preparation, which is already started The draft of the Final Decommissioning Plan is prepared (appr. 500 pages) Radiation Protection Programme is included

Interfaces with ALARA Commitment during Decommissioning The compliance with the ALARA policy objectives for the plant personnel basically relies on 2 key issues: on careful engineering, technical, administrative preparations of the activities to be carried out on monitoring of their implementation in the controlled area and implementation of corrective actions in case of individual and collective dose exceed the ALARA objectives

Interfaces with ALARA Commitment during Decommissioning PREPARATORY ACTIVITIES Keeping the personnel exposure in accordance with ALARA principle during decommissioning will require: Authorization of works in the controlled area by work permits; Establishing the dose maps in the to be accessed areas; Carrying out computer simulations of the activities to be performed in the controlled area.; Implementation of countermeasures to reduce the background: decontamination, installation of temporary shielding, use of remotely operated equipment, additional ventilation capacities, additional confinement zones, etc.; Careful review of the lessons to be learned from previous similar activities already carried out either at INPP or at other NPPs and, when relevant, adaptation or optimization of the operation procedures; Checklists of the equipment to be consigned (isolated). ...............

Conclusions A set of procedures, forming of the radiation protection program, was created and is effectively implemented at INPP. Good radiological work management procedures applied during the outages give successful results in reduction of occupational exposure. Keeping the personnel exposure in accordance with ALARA principle during the decommissioning of Ignalina NPP will require careful engineering, technical, administrative preparations of the activities to be carried out. Positive experience gained in optimization of protection during the normal operation of the Ignalina NPP will be taken into account.

Acknowledgement I would like to thank the IAEA for the financial support provided for participation in this Workshop