DRAFT 1.0

2.1.1. Chernobyl accident

2.1.1.1. General informationOrigin of the accidentThe Chernobyl NPP consisted of four power blocks. Commissioning of the first power

unit of the Chernobyl NPP took place in 1977 and of the fourth one in March 1984. Units V and VI were under construction at the time of the accident. (See Figure 5.1 -Map of the industrial site)

Figure 5.1. Map of the industrial site

Anthropogenic accident occurred on 26 April 1986 in the night from Friday to Saturday at 1 hr 23 min 40 sec during a low-power engineering test of the Unit IV. Improper, unstable operation of the reactor, which had design flaws, allowed an uncontrollable power surge to occur, resulting in successive steam explosions, which severely damaged the reactor building and completely destroyed the reactor (Figure5.2- Destroyed Unit IV)

Figure 5.2. Destroyed Unit IV

SourceUncontrollable radioactive releaseThe accident released a mixture of radionuclides into the air over a period of about 10

daysThe following stages of release may be identified I – 26 April. Release due to explosions both as fine-dispersed fuel and violent

radionuclides released from fuel at Tfuel = 1600-1800 K II – 26 April - 2 May. Release due to graphite burning at Tfuel < 1600 K III – 2 -5 May. Release due to fuel overheating up to 2500-2800 K as a result of

radioactive decay IV – Later 5 May. Release reduction and sporadic volley emissions of

radioactivity Dynamics of radioactive release is shown in Figure 5.3

Figure 5.3. Dynamics of radioactive release

Spatial balance of nuclear fuelTotal spatial distribution of nuclear fuel was as follows: >96% - inside Unit IV, <0.3%, - industrial site<1.5% - 80-km zone (excluding industrial

site), < 1.5% - rest of the USSR, <0.1% - outside of the USSR Another words, spatial balance of released nuclear fuel was follows: 9% - NPP site, 44%

- 80-km zone, 44% - rest of the USSR, 3% - outside of the USSRTotal radioactive release was amounted more than 12,000 PBq, including 6,500 PBq – inert gases, 1,800 PBq – 131I, 85 PBq – 137Cs.

NPP site area (around 1 km2) mainly was contaminated by dispersed nuclear fuel following explosions on the night of accident. So contamination of industrial area occurred immediately following explosions on the night of accident. This is the first discrepancy compared Fukushima - 1. Just that area is very interesting from point of view on radiation protection of emergency workers.

General questions of emergency response What and how should be immediately done to take emergency process under

control? What and how should be done to mitigate consequences of the accident? What is crucial issues of radiological protection of emergency workers at the early

stages following an accident?

2.1.1.2. Emergency and preparedness regulation in the USSR to the Chernobyl accident

It was held 10 thousand days in September 11, 2013 from the day (more exactly, the night) of the Chernobyl accident. Past system of occupational radiological protection in the USSR should be considered and compared with the present system of EPR

Evolution of dose limitation for planned exposure situations before Chernobyl accident is given in Table 5.1

0

5

1015

20

25

30

35

40

45

50

1 2 3 4 5 6 7 8 9 10 11

Ряд1

Table 5.1. The USSR dose limits for occupational exposure

Year No Standard Annual dose limit, mSv Permissible daily dose, mSv

1948 Т- 1031 300 11950 2413 300 11953 129-53 150 0.51957 233-57 150 0.51960 333-60 50 -1969 BSS-69 50 -1976 BSS-76 50 -

This table demonstrates that for planned exposure situation (according to the current IAEA terminology) old-timer workers remembered their routine experience to operate in a heavy radiation conditions with annual and dose limitation. However, the main part of personnel had no such experience and proper trainning in time of the Chernobyl accident.

Basic regulation requirements of the USSR Radiation Safety Standards NRB-76 for emergency situation were as follows:

Emergency plan shall be prepared in any legal person All practicable measures shall be intended for minimize external exposure and

radionuclide intake for emergency workers (EWs) Overexposure of EWs above dose limits may be justified:- for the purpose of saving life, - averting a large-scale public overexposure, and - preventing the development of catastrophic conditions Elevated planned exposure (EPE) shall be below twice dose limit for single

undertaken action and five times over dose limit for all emergency period of time (i.e. 100 and 250 mSv)

Written permission of administration and personal consent of EW to EPE is required

Work Order shall include detailed list of actions, their time limitation and safety tips

EPE not be allowed if: - EPE+E(received before accident)>Dose Limit x T(radiation experience),- worker already received elevated exposure over 250 mSv,- worker is woman younger 40These national requirements were in accordance with IAEA documents, for instance, No

50-SG-D9, IAEA, Vienna, 1985Management system of EPR to 1986 at the Chernobyl NPP includes: Plan of emergency management at the Chernobyl NPP Plans of radiation protection of the NPP personnel and public Procedure of emergency notification Emergency system of the national operator “Souzatomenergy” Special medical provision General procedure for official inquiry and liquidation of major accidents in

industryFor clear understanding actual emergency response after the accident it is necessary to remind features of state power. The USSR was a totalitarian state. So existed national EPR system had a command-and-control management style:

Strict vertical of power Secrecy order in nuclear energy and atomic industry

As a consequence:

Guaranteed financial and resource provisions of any countermeasures Inability of serious decision making at a local level Restriction on exchange emergency experience between NPPs and informing of nuclear

workers

Special judgment No 1Formally, general approach to a problem of radiation protection regulation for rescuers and emergency workers by the time of the Chernobyl accident and currently not undergoes a change.From practical application point of view, existed national EPR system had a features agreeable to that command-and-control management style and national mentality

2.1.1.3. Categories of emergency workersAccording to the USSR, Belarus, Russia, Ukraine Laws specific cohort of emergency

workers and recovery workers are defined as participants of emergency response (so called “liquidators”):

“Citizens taken part in termination of the accident and in mitigation of its consequences on the affected areas in 1986-1990”

The total number of emergency and recovery operation workers (from 1986 to 1990) was 530,000 including 150,000 liquidators worked at the NPP site area

Within this period of time the duration of emergency exposure situation assumed to be 7 months (26 April - 30 November 1986 - completion of the SHELTER construction around Unit IV).

Attributes for categorization of emergency workers Management of emergency works, including radiation protection (national

governmental and functional EPR system) - Figure 5.4 Time after accident (first responders on scene, attracted units for urgent response,

emergency workers for restoration) - Table 5.2. Type of emergency work (saving life, preventing of catastrophic conditions,

source localization, evacuation, decontamination etc) Tables 5.3, 5.4.

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MINISTRY

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MINISTRYOF ATOMICINDUSTRY

MINISTRIESOTHER MINISTRY

OF DEFENCEMINISTRY OF

INTERNALAFFAIRS

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5

Figure 5.4. Governmental categories of liquidators

Table 5.2.Cohorts of liquidators (EWs) in 1986

No Cohort Number Dates1 Witnesses and first responders 1,000 April, 262 Urgent response teams 35,000 27.04 –20.052.1 Military 13,0002.2 Civil 22,0003 Emergency & Recovery workers 89,000 21.05 – 30.113.1 Military 49,0003.2 Civil 40,000Total 125,000 26.04 – 30.11

Table 5.3. Operating schedule in 1986

Category Type DurationChNPP personnel Shift work 15working days + 15days of

restEarly liquidators Single mission Till 15 daysAttached to ChNPP Shift work or single/repeated

missionsTill 30 days

US-605 personnel Single shift work 2 monthsMilitary liquidators Single frame

Single/repeated missionsShift work

3 min or E < 200mSvE < 250 mSv3/6 months

Attached into 30-km zone Shift work or single/repeated missions

3 months orE < 250 mSv

Table 5.4General activities

Measure Object DatesPreventing of release Ruined Unit IV 26.04 -10.05.1986Evacuation Pripyat town

Chernobyl town, rural settlements27.04.19863.05-7.05.1986

Decontamination Units I-III, industrial area, settlements, roads“Red” forest

1986-19901987

Construction “Shelter”Waste depositoryDampsFilter screen

21.05-30.11.19861986-198811.07-25.09.19861987

Building Shift industrial communitySlavutich town

15.05-31.10.198625.05.1986-1988

Guarding Scala-1M (10-km), 30-km zone PermanentlyRadiation monitoring Contaminated territories Permanently

Dose restrictions after the accident Evolution of occupational dose limitation was as follows:- 26 April 1986: without emergency dose constraints for personnel of the Chernobyl NPP;- 27 April: 20 May 1986 – 500 mSv for military liquidators and 250 mSv for civil

liquidators;- 21 May – 31 December 1986: 250 mSv for all categories of liquidators;- 1 January – 31 December 1987: 250 mSv the permission of the USSR Ministry of

Public Health for special works, 100 mSv – works at the Unit III and the NPP site, 50 mSv – everywhere except for the above-mentioned places.

Special judgment No 2

Liquidators were not homogeneous cohorts of professional rescuers and nuclear workers

Cohort of liquidators were composed of independent groups met certain tasks within own management and dose control

Activities of liquidators took place in emergency exposure situation, existing exposure situation and planned exposure situation

Air Air kermakerma rate, rate, mGy/ hmGy/ h. 26 April 1986. 26 April 1986

100

10

1

10001000

Pripyattown

Cooling pond3000

Chernobyl NPP area

Pripyatriver

Figure 5.6A. Air kerma rate, mGy/h. 26 April 1986One can see that levels of exposure rates (or air kerma rates) were very high in the NPP

site Gy –tens Gy/h, i.e. typical levels of exposure rate exceeded the natural background in 106 - 108 times (Fig. 5.6A). Unfortunately this fact timely has not been confirmed by measurements. Dangerous situation was outside NPP. Dose of 1 Gy which corresponded to threshold of deterministic effects was formed in the 4-km locality during 2 days (Fig. 5.6B). Annual doses of 100 and 30 mSv which required intervention for public were predicted for settlements in the 30 km territory and far from here (Fig 5.6C). Refractory radionuclides gave the big contribution to total activity in the first year after the accident (Fig 5.6D). This is the second discrepancy compared Fukushima-1.

Special judgment No 3Unfortunately emergency dose monitoring was absent during

reflex phase: The first radiation data were reported after 1 -3.5 hours later explosion Individual dose monitoring has not been carried out on April, 26. Only film

badges (the upper level of registration of 20 mGy) were present. Routine individual dose monitoring has been carried out for 4,750 ChNPP workers and attracted personnel before the accident (data on 1 January 1986)

Actual doses for witnesses were in the range of 40- 15,000 mGy Dose of 40 mGy was received only during one trip from Pripyat town to the NPP

Number of emergency workers and witnesses is given in Table 5.7 and urgent actions - in Table 5.8.

As a result of a heavy radiation conditions, lack of occupational exposure monitoring from one hand, and professional courage of workers and firemen, from other hand, overexposures were occurred (Table 5.9)Table 5.7.First responders & witnesses of accident

Contingent Number of witnessesAt the accident moment 8 hours later

Personnel of Units I-IV 176 374Builders of Units V, VI 268 -Firemen 24 69Guards 23 113Medical staff - 10Subtotal 491 566

Table 5.8.Actions of the first respondersNo Action1 Fire control2 Saving life3 Cut-off ventilation/ electricity, switching of cooling system , lube swap4 Examination of equipment5 Radiation reconnaissance#6 Water supply

# Radiation data were reported after 1 -3.5 – 8.5 -17.5 hours later explosion

Table 5.9Individual and collective doses of the first responders

Category Number Dose, mGy Collective dose, person GyMean Median

Witnesses 1,057 550 450 581Clinics patients 134 3400 2400 455

Internal exposures took a lower values compared with external doses .Average committed equivalent dose (lung) for alive 125 witnesses of accident, treated in clinics was about 400 mSv. Distribution of thyroid doses is shown in Figure 5.7

Internal thyroid doses: first respondersInternal thyroid doses: first responders

1

10

100

1000

75%

25%

min

max

Industrial area Inside Unit IV Inside Unit IVfew hrs later

Outside industrial area

HT mSv

Group of Chernobyl workers, 26 April 1986

A B C D

Figure 5.7. Internal thyroid doses: first responders

Management at the reflex phaseIn general, chaos and uncertainty are essential feature a of major nuclear accident which

characterized the following attributes:- prevalence chance over the order; - violation of information channels;- total uncertainty concerning radiation situation, exact personnel location and severity of

technology violations.These uncertainties create risks of decision making1. Decision maker under a great stress2. The more uncertainty the greater risk of decision 3. Range of alternative decision options: to do any available actions or to do nothing

excepting actions directed on reducing uncertainties 4. Breach of management hierarchy: informal leaders with a great professional

experience come to the first plan5. Simple and robust decisions are optimal in a case of great total uncertainty Management structure at the Chernobyl NPP is demonstrates in the table 5.10.

Table 5.10. Management during the first 18 hours

No Manager Arrival Operator guide1 Director NPP +45 min Emergency headquarters actions2 Main engineer NPP +3 hr Water supply, s/m measurements3 Shift man NPP: Formal

head of reflex response0 Collect witnesses, notification. Actually

transmit his duty to No 4, 74 Deputy Main engineer on

operation Unit III+Unit IV0 Actual head: call the fire, switch on

diesel generator, ventilation, switch off power supply cables, saving life, stop Unit III

5 Shift man Unit III 0 Complete and strict compliance with emergency plan & instructions

6 Shift man Unit IV 0 Translation of No 4 guides7 Deputy head of safety

department+1 hr Radiation monitoring, zoning 30

mGy/h#, switch off ventilation# Radiation zoning has not be applied on April, 26There are two alternative retrospective estimates of reflex management View I– Decision making was chain of mistakes orView II – Decision making would have been logical timely resolute actions (water supply, preventing panics, challenging data of radiation reconnaissance, switch off long-distance telephony etc) if reactor of Unit IV had not been destroyed.

Special judgment No 4Along with positive action and results, delay of reflex administrative response concerning occupational radiation protection is obvious:

“Dose Order form” did not apply during the first day for organization of any work

Forbidden and restricted working radiation zones have not be applied

Procedure of “Elevated Planned Dose Permission” did not apply during the first day

Ignoring danger of overexposure by administration and personnel excepting dosimetrists and the turbine shop workers

Urgent evacuation of unnecessary personnel

Lessons learnt from the reflex response are as follows: Transition from routine planned exposure situation to emergency

management is a crucial point of reflex response Urgent actions of the first responders corresponded with

emergency situation, purposes, plan and instructions However delay of adequate decisions was 11 -15 hours due to

great uncertainties Absence of appropriate radiometric and dose monitoring led to

serious radiological consequences among emergency workers and witnesses

Under a great stress dominant behaviour of nuclear workers to carry out their duties prevailed over personal safety, including radiation safety

2.1.1.4. Reflex Phase – 26 April 1986 Key issues in reflex phase were as follows:(1) To clarify situation and arising threats → Collection and comprehensive analysis of

witness evidence (2) To introduce emergency plan into action → Emergency management and urgent

actions directed on maintenance of the viability of the object (3) To limit the number of involved EWs → Evacuation of unnecessary witnesses,

functionality of security check-points(4) To measure exposure rate and surface radioactivity contamination → Emergency

zoning(5) To prevent radionuclide carrying over → Functionality of sanitary check-points

All of above-mentioned actions carried out in extremely heavy radiation conditions (figures 5.5, 5.6, 5.6A and table 5.5). It is nesessary to note that mostly retrospective estimation of radiological situation are presented below.

48A

83A

93A

21A2A

57A30A

7A 7A

6A 5A

7 7

6 517

1634

23A 9A

15A

42A

4 82

89A

50

42A24A

83

87

80 85

42A

27A

28A

24

19

91 3835

40

12

1315

56

10

95

2389

42 30

Coordinates in meters

Spatial distribution of exposure rate, Spatial distribution of exposure rate, mGymGy/ hr/ hr

1000

1000

300

20003000

3000

300100

30 10

1000

4000

Figure 5.5. Spatial distribution of exposure rate, mGy/hr at the NPP site

Table 5.5. Total beta-activity. 26 April 1986Sample Place of sampling Concentration, Bq m-3

Air Premises of Unit III 109 – 10 10

Pumped water# Flooded basement Up to 10 13

# 57, 700 m3 of water was pumped out of the basement to cooling pond

30 mGy

100mGy

A C

B D

1Gy

A - Kerma rate, mGy/h on April, 26 – 4 km zone C – Annual kerma – 30 km zone

B – Kerma within first 2 days – 4 km zone D – Fuel radionuclide composition with time

Relative content,%R

1000

100

10

1 1mGy/h

Fig 5.6. Gamma radiation near the Chernobyl NPP and radionuclide composition of fuel and fallout

2.1.1.5 Early Phase: 27 April -20 May 1986

Harmful working conditions at the early phase included chemical, physical, radiological and psychological factors.

Table 5.11.Chemical factor at working places

Origin Initial materials PollutantsFire at the Unit IV Graphite, building & organic

containing materials, bitumenCO, NO2, hydrocianide, phosgene, smoke, superfine aerosols

Sublimation of materials dumped on the reactor

Sand, clay, lead, dolomite, boron compounds

Depositions of lead

Dust catching for building, roof, industrial site and roads of 30-km zone

Sulphite-alcohol barda, oxalic & hydrochloric acids, formalin; resinas, oil-slime

Superfine acid aerosols, sulfer/organic–containing vapour

Physical factor was ionizing of air. Ionization levels exceeded permissible level many times (103- 105 greater near Unit IV). This factor led to oropharyngeal syndrome estimated to be 58% among liquidators in 1986 (3000 questionnaires)

Structure of radiological factor is shown in Figure 5.8.

Total exposure

External photons

External neutrons

Externalbeta-particles

-

Internal Alpha-

beta-rays

Directed to“forward-back”,

Isotropic,Rotary

Directed to“forward-back” Distant &

contactInhalated

radionuclides

Radiological factorRadiological factor

Figure 5.8. Structure of radiological factor

Neutron exposure The first wrong measurements of neutron flux were evidence of nuclear chain

reaction. This suggestion became start point in the set of early countermeasures directed to nuclear safety

Neutron exposure gave minor impact to the total dose (up to 1-2% of gamma exposure nearby Unit IV, June-July 1986)

Distant beta exposure Ratio of beta to gamma-exposure for different types of work is given in the Figure 5.8.

Distant beta exposureDistant beta exposure

Ratio

of b

eta-

to g

amm

a-ex

posu

re ra

te

Types of work

Gamma exposure, mGy

Figure 5.8. Ratio of beta to gamma-exposure

Gamma exposureEnergy dependence of different dosimeters was in a range of 0.8 – 1.7 compared with the

known good device. This uncertainty should be taken into account when analyzing dosimetric data (Table 5.12)

Table 5.12.Sources and average energy of photons at the typical working places

Eγ, MeV Source distribution/working place

~ 0.5 Local sources, surface contamination/Roof, contaminated premises

~ 0.2 Volumetric distribution activity in soil/Contaminated territory

~ 0.1 Behind light shield materials (concrete, crushed stone)

Comparison of measured external and internal exposures show that external exposure was dominant component of total dose (Figure 5.9)

Comparison of measured Comparison of measured external and internal exposuresexternal and internal exposures

External dose/ Dose limit

Inte

rnal

dose

/ALI 111

1 1000.01

1

0.01

0.0001

0.0001

1

1

Figure 5.9. Ratios of measured external and internal exposures for early liquidators

Key issues in early phase 1. To identify list of urgent actions, available means and man power according to

radiation situation and predictable threats2. To use graded approach for operational planning 3. To estimate resources for urgent measures4. To apply system of emergency management in proper manner

Management system change at that time. Governmental Commission began to manage emergency response instead of internal facility administration. Probably, excessive activity of governmental body is inevitable attribute of early response on a major accident. Twenty five years later similar process of excessive management activity was repeated in Fukushima-1

Actions of early liquidators are presented in the Table 5.13.Table 5.13Actions of early civil and military liquidators

Industrial site 4-km zone 30-km, 70-km zonesCivil liquidatorsDecontamination Construction “wall in ground” Public evacuationDrilling of wells Works in river port “Pripyat

town”Evacuation of cattle

Digging of foundation pit near Unit III

Dyking of riverside Sanitary measures

Building of tunnel under Units III, IV

Evacuation of equipment from “Jupiter” factory

Art concert activity

Freezing of soil under Unit IV

Loading sand and lead to helicopters

Domestic service

Transportation Transportation TransportationMilitary liquidatorsFire control near reactor coolant pump on 23 May

Decontamination of vehicles Public evacuation

Laying in reactor with the help of helicopters

Decontamination of Pripyat town

Evacuation of cattle

Air reconnaissance Transport examination Radiological surveyDecontamination of site, machinery hall, roof

Fire control around Pripyat town

Fire control

Building of concrete wall between Unit IV and depository of SNF

Guarding of Pripyat town, 10-km, 30-km zones

Decontamination shower facilities

Transportation Adjustment of road traffic Decontamination of settlements

Reasonability of complete urgent actions Useful actions

Maintenance of operated ChNPP technologies Evacuation of public Water pumping out bubbler-basin Removal of valuable imported equipment from the building base Investigation of the accident reasons Fire control on May, 23

Useless actions Covering the reactor with materials by helicopters Dust catching and decontamination on the industrial area and settlements Building of concrete slab (30mx30mx2.5m) with cooling system under reactor Liquid nitrogen supply into under-reactor premises

Reasonability of incomplete urgent actions Useful actions

Nuclear fuel diagnostics of under-reactor premises Radiation, fire, thermal reconnaissance Personal dose monitoring Optimized emergency management Sanitary and hygienic measures

Useless actions Construction of horizontal holes for soil freezing under reactor IV Building of underground wall around NPP

Doses and dose distribution for early civil liquidators are presented in Table 5.14..

Table 5.14. Individual and collective doses

Individual dose distribution for early civil liquidators Dose range, mSv <10 10-30 30-100 100-300 300-1000 >1000Percent 21.5 13.2 27.7 30.8 6.2 0.6

It is important to estimate part of collective dose related to useful actions. Figure 5.10 demonstrates distributions of man-power and collective dose among general actions had been carried out within first days following the accident.

Fig.5.10. Distributions of man-hours and collective doses during first 5 days after vthe accident

One can see that movement and loss of time account for ¾ of total collective dose.

Category Number Dose, mGy Collective dose, person GyMean Median

Civil liquidators 21,600 115 56 2,487

Special judgment No 4Optimization of traffic on contaminated area is important issue from occupational radiological protection point of view.

Evolution of dose monitoringDose monitoring of Chernobyl NPP workers 27 April - Regional Civil Defense unit handed condenser dosimeters DKP-50 to

the ChNPP safety engineering department 28April – Two TLD devices were deployed at the dosimeter point of industrial

camp “Skazochniy” 28April – WBC was deployed at the dosimetry point. Then WBCs were placed in

the after-work sanatorium Occupational dose monitoring of the Chernobyl personnel was satisfactory

established by 10 May 1986 Results of dose monitoring were daily reported to Governmental commission in

May-June 1986Dose monitoring of military liquidators Both instrumental and calculated techniques Application of different types of dosimeters Fabricated dose records Value of elevated planned exposure was considered 500 mSv till 20 May

Negative lessons: early phase1. Absence of adequate personal dose monitoring means and dosimeters for measurements

of high levels of air kerma rate2. Working assumption that reactor was not destroyed for water supply operation3. Working assumption that active core was placed inside reactor4. Political decision on Unit III restoration without economic justification

Link between gaps or wrong assumptions or unfounded decisions and non-justified exposure is given in Figure 5.11.

Figure 5.11. Negative lessons 1 - 4: Logical chain

Positive lessons: early phase1. Reliable system of security check-points and sanitary check points2. The ranking of the harmful factors: external gamma → external beta→ internal

exposure3. Development of retrospective dosimetry techniques4. Timely triage of victims and system of three-stage medical treatment5. Stable iodine prophylaxis

Special judgment No 5Involvement a great number of people in emergency response and

recovery operations without proper selection and training is professional and social phenomenon of the Chernobyl event

2.1.1.6. Intermediate phase: 21 May – 30 November

Strategy of emergency and recovery works has been elaborated on May 1986, less than one month after the accident. This strategy was adopted on the highest state level by Decree of Central Committee of CPSU and the USSR Council of Ministers (29 May 1986, No 634-188). Planned vs actual dates and results of works is shown in Table 5.12 Table 5.12 Strategy of works: goals and schedule Work Completion date

Planned Actual Public returning into 30-km zone

Sept -Dec 1986 Not reevaluated

Construction of the Shelter September 1986 November 1986Decontamination on-site NPP September 1986 December 1987Unit I startup July 1986 October 1986Unit II startup July 1986 October 1986Unit III startup August 1986 December 1986Recovery of Units V and VI projects

October 1986 Never

Involvement of large number of common people was needed to fulfill this strategy. Above-mentioned Decree resolved:

“To accelerate decontamination operations in the Chernobyl NPP zone, which operations are of social and political importance and the first priority

to call up reservists for 6 month-term above limits provided to Ministry of Defense by the USSR Council Ministers of 20 August 1985”.

However, targets has have been achieved with delay or other results have not been achieved at all.

Special sanitary regulation Special sanitary regulation covered all objects and aspects of emergency works. Firstly, radiation zones has been established as follows;Zone I – (so called, zone of strict control) – area between isolines 3.0 -5.0 mR/hr (30-50

µGy/h) decay-corrected on May, 10. Projected annual external dose below 50 mSv;Zone II – (including 30-km zone and excluding or prohibited 10-km zone) - area

between isolines 5.0 -20 mR/hr (50-200 µGy/h) decay-corrected on May, 10Zone III – area of prohibited 10-km zone above isoline 20 mR/hr (>200µGy/h), excluding

industrial site of NPP, Pripyat town Zone IIIA – industrial site of NPP, Pripyat town

Secondly, different regulatory and administrative documents were adopted, applied and renewed. Types of adopted documents in May and June 1986 are given in Tables 5.13, 5.14Temporal permissible levels for surfaces were used at the sanitary check-points and applied as criteria of decontamination. Primarily, values of flux density of beta-particles were identified. However gamma-exposure rate was more convenient value for large scale radiometric examination of surface contamination: 10,000 β/(cm2 min) →1 mR/hr or 1,000 β/(cm2 min) → 1 µGy/h (Table 5.15) . Change of temporal permissible levels is illustrated in Table 5.16.

Table 5.13 Sanitary regulation: May 1986

Document type Brief title Approved by IssuedTemporary permissible levels

Surface radioactive contamination

Regulatory body 7 May

Interim methodic recommendation

Management of occupational protection

Regulatory & Government bodies

27 May

Recommendation Using of cleaning agent “Z” for skin decontamination

Regulatory body 29 May

Recommendation Using of pharmaceutics for nuclides washout

Regulatory body 29 May

Statement Monitoring and records of individual doses in 30-km zone

Chair of Governmental Commission

30 May

Interim guidance Sanitary supervision of dose monitoring

Regulatory body 31 May

Table 5.14 Sanitary regulation: June 1986

Document type Brief title Approved by IssuedInstruction Decontamination of

protective clothes etc in laundries of other NPPs

Regulatory body 11 June

Temporary permissible levels

Contamination of skin, linen, clothes, protective means, vehicles

Regulatory body 12 June

Temporary Residual exposure Regulatory body 12 June

permissible levels rates after decontamination

General requirements Recommendation

Interaction between the USSR State Sanitary Inspectors and radiation safety services: dose monitoring

Regulatory & Government bodies

22 June

Table 5.15Temporary permissible levels (TPLs) of surface radioactive contamination. Adopted on May, 7, 1986

Surface Flux density, β/(cm2 min) Exposure rate, µGy/hSkin, underwear, towel, bed linen, footwear, protective device & clothes

1000 1

Dwelling, internal surface of transport facility

2000 2

External surface of transport facility

3000 3

Table 5.16Temporary permissible levels (TPLs) for surface contamination (mR/hr) Adopted on 02.06.1986 /on 14.10.1986

Contaminated objectZone I II III III-A Outside

Skin, underwear 5/ 3 10/ 7 20/ 15 20/ 15 0,1/-Bed linen, outerwear 5/ 3 10/ 7 - - 0,1/-Personal footwear 10/ 7 - - - 0,1/-Protective device & working clothes -/ 10 30/ 20 50/ 40 100/ 70 -Internal face of transport facility 10/ 10 30/ 30 50/ 50 100/

1000,2/-

External face of transport facility 15/ 10 50/ 40 200/ 150 400/ 300

0,3/-

Individual dose monitoringFormally, Chernobyl NPP administration had to provide appropriate dose monitoring of

attached liquidators both civil staff and military reservists. However it was not able because of lack of resources, equipment and operators. Management of dose monitoring of civil and military staff was carried out independently.

Quality of dose monitoring during the first year after the accident is estimated in Table 5.17.Table 5.17Quality levels of dose monitoring during the first year after the accident

Level Description Percent StaffHigh Only instrumental data.

Less than 10% of gaps and mistaken records

13 ChNPPUS-605

Satisfied Mixture of high and low quality levels

4 Attached to NPP

Low Both instrumental and calculated techniques. Incomplete or/and doubtful records

58 Attached to 30-km zone,Military men

Zero Absence of personal dose monitoring procedure and data

25 Victims &WitnessesEarly liquidators &Belarus liquidators

Positive experience of dose monitoring management connected with construction of

“Shelter” around Unit 4 from June to November 1986 (special enterprises of US-605). Heavy radiation conditions at working places were existed in that time (maximum values

are given in Table 5.18).Table 5.18.Source parameters during construction of “Shelter” around Unit IVInfluencing factors Maximum levelsGamma-radiation of fuel fragments, surfaces, soil

100Gy/h – reactor4 Gy/h –working places

Alpha-, beta-aerosols 300 permissible concentration – dusty workAlpha-, beta-contamination of surfaces 102-105 α/(cm2 min)

104-108 β/(cm2 min)Neutron radiation 4-400 µSv/h – machinery hall

Total number of involved workers was 21,500. Maximal shift of workers was 11,000, including 6,000 of military staff and 5,000 of civil workers. Monitoring procedure was the same both civil and military staff. Numerical structure of dose monitoring department was 150 - 270. System of dose monitoring management included radiation technical survey, dose monitoring, radiation protection and research function. It was delineated 12 working zones of industrial area during the US-605 activity according to radiation situation and operation technologies. Administrative daily dose of 10 mSv was established for permanent control of received dose. Also set temporary permissible levels of surface radioactive contamination were adopted and timely revised by both regulatory body and emergency operator. A noticeable dose decreasing gave using separate shuttle mobile means in different zone.

Figure 5.12. Dose distributions for civil and military liquidators of US-605 enterprises

Special study shown influence of behavior factor (both professional and psychological origins) on individual dose value. Dose distribution for group of liquidators carried out a certain operation at the same working place may be approximated by lognormal dependence with GSD = 1.75±0.20 (see Figure 5.13)

Figure 5.13. Individual doses for the same working places

In general, results of individual dose monitoring are presented in Table 5.19

Table 5.19. \Individual and collective doses: 26 April – 31 December 1986): official data

Category Number Dose, mGy Collective dose, person GyMean Median

Clinics patients 134 3400 2400 455Witnesses 1,057 550 450 581Early civil liquidators 21,600 115 56 2,484ChNPP personnel 2,358 87 48 205US-605 personnel 21,500 82 50 1,763Military liquidators 61,762 204 220 12,600Attached into 30-km zone 31,021 20 6.3 620Total 139,432 134 18,708

Efficiency of protective equipment, radiation protected mechanisms and managing

Large scale application of protective means is one of important lesson of Chernobyl, Briefly,results of this experience in heavy radiation conditions are illustrated in Tables 5.20-5.22

Table 5.20 Personal protective equipment PPE Organ /tissue Reduction factorFilter mask & respirator Lung 40 – 200 (without violation of

obturation)Lead screen 3mm Red bone marrow 1.9Lead band 3mm Gonads 1.83 ± 0.15Dust proof spectacles 2mm Eyes 36 - 200Plexiglass helmet visor 2-5mm Skin, lens of the eyeLead inner soles 1.5mm Feet 1.4Lead rubber apron Body 1.6Lead rubber gloves Hands 1.4

Table 5.21. Radiation protected mechanisms

Class Reducing factor Exposurerate, mGy/h

Mechanisms

I >1000 >1000 Bathyscaphe, heavy craneII 100-200 n 100 Heavy bulldozer, obstacle clearing

engineering machineIII 3-20 <100 Excavator, ditcher, concrete pump, motor

transport

Table 5.22. Decontamination planning and carrying outPrinciple ProcedureChoice of main source 1. To estimate exposure rate and collective dose due to

local areas2. To select area raised maximal dose on other areas

Step-by step recapture of territory 1. To start from the most contaminated part removing

sources from a back space2. To use local shield against radiation from front space

Application of unmanned techniques 1. To use building technology, robots, remote control guidance2. To equip point of control with monitors and speakerphone

The reduction of operational duration 2. To work out operations in normal radiation condition2.To analyze detailed operational time study

Positive lessons Dose management on the base of Dose Order Form Change of routine managers to the emergency managers in the field of radiation

protection Dual personal dose monitoring of external exposure: daily and cumulative Application of “Choice of main source”, “Step-by step recapture of territory” approaches,

“Optimal impact on radiation situation” concept Application of unmanned techniques the reduction of operational duration Dose distribution analysis in ALARA procedure Lead protective equipment was not optimum in the limited time conditions for intensive

manual operations Suitable and adequate personal protective equipment (including protective clothing,

respiratory equipment, protective aprons and gloves) is required from radiation protection of EWs

Specific judgment No 6 Involvement a great number of people in emergency response and recovery operations

without proper selection and training is professional and social phenomenon of Chernobyl event

Large-scaled application of Elevated Planned Exposure in excess of 50 mSv conflicts with IBSS-2011 (4.15). However justification of such decision was outside of the SRP

Conclusions to 2.1.11. Both positive and negative lessons of the Chernobyl accident

concerning radiation protection of emergency workers are still valid for international community.

2. Two issues are considered extremely important, i.e. (1) management and dose control for the first responders and (2) involvement of a great number of common people to recovery operation.

3. Chernobyl experience has demonstrated change of priorities and key issues in different phases of mitigation consequences:

Reflex phase:- To clarify situation and arising threats by forces of collection and

comprehensive analysis of witness evidence; - To introduce emergency plan into action. Emergency management and

urgent actions should be directed on maintenance of the viability of the object; - To limit the number of involved emergency workers by means of

evacuation of unnecessary witnesses, functionality of security check-points;- To measure exposure rate and surface radioactivity contamination for

delineation of emergency zones;

- To prevent radionuclide carrying over by managing and functionality of sanitary check-points.

Early phase: - To identify list of urgent actions, available means and man power

according to radiation situation and predictable threats;- To use graded approach for operational planning; - estimate resources for urgent measures;- To apply system of emergency management in proper manner.Recovery phase:- Strategy planning based on holistic approach;- Stakeholder involvement; - Transition from emergency management to management for existing

exposure situation;- Implementation of analytic ALARA procedure;- Design and application of optimized technologies and protective means4. Brief list of negative lessons are as follows: (1) Absence of adequate personal dose monitoring means and dosimeters for

measurements of high levels of air kerma rate;(2) Working assumption that reactor was not destroyed for water supply

operation;(3) Working assumption that active core was placed inside reactor;(4) Political decision on Unit III restoration without economic justification5. Positive lessons are as follows: (1) Reliable system of security check-points and sanitary check points;(2) The ranking of the harmful factors: external gamma → external beta→

internal exposure;(3) Development of retrospective dosimetry techniques;(4) Timely triage of victims and system of three-stage medical treatment;(5) Managing stable iodine prophylaxis;(6) Dose management on the base of Dose Order Form;(7) Change of routine managers to the emergency managers in the field of

radiation protection;(8) Dual personal dose monitoring of external exposure: daily and

cumulative;(9) Application of “Choice of main source”, “Step-by step recapture of

territory” approaches, “Optimal impact on radiation situation” concept;(10) Application of unmanned techniques the reduction of operational

duration;(11) Dose distribution analysis in ALARA procedure;(12) Application of suitable and adequate personal protective equipment

(including protective clothing, respiratory equipment, protective aprons and gloves). It was proved that lead protective equipment was not optimum in the limited time conditions for intensive manual operations

References1 Chernobyl’ 88. Proceedings of the Union scientific-technical Conference. Ten volumes. Edited by Ye. I. Ignatenko. Ministry of Atomic Energy. Chernobyl, 19892. R.M. Alexakhin et al. Large Radiation Accidents: Consequences and Protective Countermeasures. Edited by L.A. Ilyin, V.A. Gubanov. Moscow, IzdAT, 2004. Book was printed in Russian - 2001, in English - 2004 and in Japanese3. V.P. Kruchkov et.al. Mitigation of accident consequences at Chernobyl NPP: Radiation and dosimetry issues. Edited by V.G. Asmolov, O.A. Kochetkov. Moscow, IzdAT, 2013 Book was printed in Russian - 2011, in English - 2013