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Safe storage of radioactive waste

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IAEA

Contents

• Good practice for storage

• Types of storage package

• Centralised storage facilities

• Centralised storage facilities (continued)

• Siting, shielding, handling, monitoring etc

• Commissioning and operation

• Security and access control

• Decommissioning

• Long-term storage

• Storage examples from various countries

• Summary

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Key references

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2006 2009 2006

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A missing step..

In the absence of known disposal option

• Conflicting processing requirements – safety vs. flexibility

• Storage may be have to be extended in time

• Risk of additional processing and higher cost

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Storage of RW - Definition

Holding of radioactive

waste in a facility –

containment;

For retrieval;

An interim measure.

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Waste Storage

Characterization

• Activity, other necessary characteristics

• Should be done as early as possible

Transport

Storage

• May take place between and within basic waste management steps

• May be extended in time

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Requirement 11: Storage of radioactive

waste

Waste shall be stored in such a

manner that it can be inspected,

monitored, retrieved and preserved

in a condition suitable for its

subsequent management. Due

account shall be taken of the

expected period of storage, and, to

the extent possible, passive safety

features shall be applied. For long

term storage in particular,

measures shall be taken to prevent

degradation of the waste

containment. 7

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Requirement 11: Storage of radioactive

waste (cont)

• Waste shall be stored such manner that it can be inspected, monitored, retrieved

and preserved in a condition suitable for

subsequent management;

• Due account shall be taken of the expected period of storage, and, to the

extent possible, passive safety features

shall be applied;

• For long term storage in particular, measures shall be taken to prevent

degradation of the waste containment.

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Requirement 11: Storage of radioactive

waste (cont)

• Design depends on the type of RW, its characteristics and associated hazards,

radioactive inventory, and anticipated

period of storage;

• Regular monitoring, inspection and maintenance of the waste and of the

storage facility is required to ensure their

continued integrity;

• Adequacy of the storage capacity has to be periodically reviewed (prediction in waste

arising, availability of disposal options). 9

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Storage of RW - Objectives

To allow for the decay before

discharge, exclusion, clearance,

re-use or recycling;

To collect and accumulate

sufficient conditioned waste prior

to disposal;

To allow for a reduction in the heat

generating capacity of HLRW;

For long term storage when there

is no a suitable disposal facility.

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Storage of RW - Peculiarities

May occur several times during the waste’s lifecycle;

At different locations or facilities;

Periods - from days to years;

Facilities - from a small compartment to a large building.

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Storage of RW - Planning

Duration of

storage period;

Forecasts on

quantities and

types of RW.

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Storage of RW – Good Practices (I)

Segregation at origin;

Radioactive - separated from non-radioactive;

Centralized storage = economy + security;

According to physical, chemical & pathogenic characteristics;

According to expected duration;

Personal and area monitoring;

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Storage of RW – Good Practices (II)

Waste packaging tracking system:

To provide

• identification of waste packages,

• recording of location of packages,

• inventory of stored waste,

Sophistication according to

• the quantity of packages to be stored,

• the duration of storage,

• the level of associated hazard;

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Storage of RW – Good Practices (III)

Sound engineering and

operational practices and

administrative controls:

pre-work assessments & training

mock-ups,

remote handling technologies,

contamination controls,

planning and careful conduct of

activities,

safety envelope.

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Actions before storage

Pre-treatment;

Treatment;

Conditioning –

Immobilization &

Packaging.

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Actions during storage

Waste receipt;

Storage;

Retrieval;

Monitoring;

Inspection of packages and facility;

Maintenance of both the wastes and the facility.

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Actions after storage

Transfer to another facilty;

Clearance;

Re-use or recycling;

Disposal.

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Roles and responsibilities.

Roles of centralised RAW store

May receive a wide variety of waste types from different sources

Design and operation of the facility according with the associated potential hazards (waste type, inventory, non-radiological hazards)

All duties and responsibilities should be well established and documented

An adequate waste packaging track system should be implemented

Safety culture and improvements initiative

COVRA centralised RAW storage facility

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Roles and responsibilities.

Responsibilities of the regulator

Regulator should:

provide guidance to operators on requirements relating to the storage of RAW and the clearance of material

adopt a graded regulatory approach which commensurate with the level of hazard

confirm that the operator is providing the necessary human, technical and financial resources for the lifetime of the storage facility

periodically verify the acceptability of key aspects of the storage operation

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Roles and responsibilities.

Responsibilities of the operator

The responsibilities usually include:

making an application to the regulatory body to site,

construct, operate, modify or decommission a

facility

conducting appropriate EIA and safety assessments

to support the application for a licence

operating the facility in accordance with the licence

conditions and the applicable regulations

developing and applying acceptance criteria for the

RAW storage

providing periodic reports to the regulatory body in

relation to the safety of the facility

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operations, including limits and conditions;

commissioning;

quality management system;

maintenance, inspection, and testing;

training;

modifications in design, construction, commissioning and operation;

Procedures

recording, reporting and investigating of events;

radiation protection and safety performance;

contingency and emergency arrangements;

safeguards, if applicable;

security measures;

control of radioactive discharges;

decommissioning. 22

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Emergency preparedness

Assessment of the potential radiological impacts of incidents and accidents;

Provision to ensure that there is an effective capability for reaction to incidents and accidents: identification of scenarios, establishment of response procedures;

Emergency response procedures should be documented;

Organization of training exercises, if needed.

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Safety documentation – Contents (I)

expected volume and characteristics of the waste and the acceptance criteria;

description of handling and storage activities;

description of the facility and its components, equipment and systems;

site characterization;

the organizational control of the operations;

procedures and operational manuals for activities with significant safety implications;

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Safety documentation – Contents (II)

safety assessment;

monitoring programmes;

the training programme for staff;

the safeguards aspects, where applicable;

the physical protection arrangements;

the emergency preparedness and response plan;

the quality management system;

decommissioning. 25

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Waste characterization

The waste should be characterized and the results documented at appropriate stages of processing and storage;

It is necessary to characterize wastes that are not characterized or are partially characterized;

If it is not possible to characterize some waste exhaustively, precautions should be considered for handling;

Waste characterization, process control, and process monitoring should be applied within a formal management system framework.

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Waste Acceptance Criteria (I)

Waste acceptance criteria should take into account all relevant operational limits and future disposal requirements, if available;

Waste packages arriving at a storage facility should be of acceptable quality;

Sampling or checking of packages – based upon a cost benefit analysis.

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physical, chemical, radiological and biological

characteristics of existing wastes and of those

foreseen to be managed in the facility

types of containers that are planned to be used in the

facility

principles and methods used to identify radioactive

waste or sources which have not been or will not be

possible to characterize

a description of the acceptance criteria for waste

which will be managed in the storage facility

Waste characterization

and acceptance criteria - II.

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WAC should take into account all relevant operational limits and future disposal requirements, if available

Waste packages arriving at a storage facility should be of acceptable quality

Sampling or checking of packages – based upon a cost benefit analysis

Waste characterization

and acceptance criteria - III.

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Waste form and waste package (I)

Untreated waste and

intermediate products should

be stored according to their

characteristics;

Waste form must guarantee

retrievability;

Reduction, as far as

reasonably achievable, of the

hazard potential of waste for

each stage in the storage

process. 30

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Waste form and waste package (II)

corrosion resulting from interactions waste - container,

metals with pyrophoric behaviour or ability of producing chemical reactions,

porosity of inorganic, non-metallic waste,

alkalinity of the pore water in concrete,

combustibility of organic waste,

dispersibility of powders and ashes,

sedimentation of solids suspended in liquid wastes,

possible expansion of compacted waste,

reaction of different wastes compacted in the same container,

possible generation of gases,

gaseous wastes,

generation of corrosive substances due to radiolysis.

Properties of radioactive waste to be taken into account

in the design of containers and/or storage facilities:

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Waste form and waste package (III)

Containers should ensure waste containment under all conditions of operation for their lifetime;

Containers performance should ensure the protection of workers and the public in the event of incidents and accidents;

Design of storage containers should take into account the storage environment;

Certain types of waste (corrosive, liquids) may require a secondary containment/barrier and accesibility for periodic monitoring;

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Waste form and waste package (IV)

Consideration of the dynamic and static loads resulting from handling and stacking of the containers;

Venting of storage containers should be considered in the safety assessment;

The design should facilitate monitoring for the early detection of any failure of the containment;

For liquid waste with suspended solids able to settle or precipitate on the bottom of the container a mixing device should be provided.

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Storage of RW - design

To guarantee:

•Containment;

• Isolation;

•Retrieval.

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The design should ensure that all the activities could be carried out without undue occupational and public radiation exposure or environmental impact;

Specific waste acceptance criteria for each facility in accordance with its design;

A defence in depth approach should be adopted, as appropriate for the given situation;

Consideration of industrial (non radiological) hazards.

Design of facilities - general

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Design (normal operations) should provide for:

containment of the stored

materials;

prevention of criticality

(when storing fissile

materials);

radiation protection

(shielding and

contamination control);

the removal of heat (if

applicable);

ventilation, as necessary;

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inspection and/or

monitoring of the waste

packages, as necessary;

retrieval of the waste,

whether for processing,

repackaging or disposal;

inspection of waste

packages and facility if

there is uncertainty

about their condition;

decommissioning.

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Design reserve storage capacity

There should be reserve storage capacity available to

accommodate various situations. Such situations

may include abnormal conditions (e.g, the need to

empty a leaking tank) or periods when modifications

or refurbishments are being undertaken

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Factors to be taking into account in the design:

chemical stability against corrosion;

protection against radiation and/or thermal

damage;

resistance to any kinds of impacts.

Interactions between facility systems and

waste

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Siting

Two cases:

The storage facility is associated with

another nuclear installation;

The waste storage facility is built

separately from other licensed nuclear

installations.

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Shielding

It should be provided adequate shielding for

workers and the public;

Prevention of radiation streaming through

penetrations of shielding barriers;

Considering the necessity of neutron

shielding.

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Containment

using materials that can be easily monitored and decontaminated;

access and internal movement control;

adequate pressure balance between rooms;

provision of filters in the exhaust ventilation;

removing gaseous radionuclides if needed;

provision of sumps or catchment areas, measures for leak detection.

Features to be incorporated:

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Waste handling - Equipment

To provide for:

safe operation;

to avoid damage to the packages;

safe handling of defective or damaged packages;

minimise the contamination to the equipment;

avoid spreading of contamination.

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Waste handling

The handling system design should be part of the overall facility safety assessment;

Equipment should have suitable interlocks or physical limitations to prevent dangerous or incompatible operations;

Consideration of remote handling in cases of high radiation dose rates, release of radioactive aerosols or gases and existence of non-radiological hazards;

Remote handling devices should be designed for providing means for safe maintenance and repair, as well as for recovering in case of anomalies.

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Waste retrievability

Retrieval of the waste following storage must be possible and the associated operations should be as straightforward as possible;

Design of tanks for the storage of liquid waste should guarantee the maximal retrievability, using additional devices (mixers, pumps, etc.) if needed.

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Ventilation (I)

The need for a ventilation system should be assessed on a case by case basis;

Area zoning for ventilation within the facility should be considered;

Ventilation systems can also be designed to control the accumulation of hazardous substances and their design should be compatible with explosion safety and fire protection measures;

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Ventilation (II)

Design of ventilation

systems should consider

the potential for drawing in

hazardous gases, airborne

radionuclides or humid air

from external sources;

Consideration in the design

of possible impact of

facility releases in both

normal operation and

accidental situations. 46

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Temperature control

Heat removal systems capable of providing cooling of the waste may be necessary, especially for high level waste;

Heat removal should ensure not to exceed the maximum design temperature;

A reliable heat removal system should be utilized;

Heating may be required in order to prevent freezing and/or precipitation of substances in cold climates.

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It should be ensured that the waste will be kept at a concentration, in a configuration and in conditions that would prevent criticality during waste emplacement, storage and retrieval;

Consideration should be given to the consequences resulting from a change in the configuration of the waste as a consequence of an internal or external event.

Subcriticality

For the storage of waste containing fissile material:

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Monitoring (I)

Monitoring of the radiological conditions in the waste storage facility should be provided;

Portable or mobile dose rate meters should be provided for monitoring individual locations in any contamination controlled areas;

Fixed or portable instruments to detect external contamination on workers should be provided at exits from any controlled areas or when moving from a higher contamination zone to a lower zone;

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Monitoring (II)

Monitoring of chemical conditions and non-radiological parameters should also be included where warranted;

Monitoring instruments with measurement ranges adequate to cover the expected range of observations, periodically tested and calibrated;

Monitoring equipment for detection of leaks should be provided. 50

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Control and Instrumentation

Whenever practicable, process system controls should be independent from protection systems;

Alarms and indications to the operator should be clear and should not cause confusion;

Non readily accessible information on the status of systems important to safety should be made available to the operator by appropriate means.

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Inspection of facility and stored waste

The storage facility should be designed to facilitate inspection of the structures, systems and components of the facility and of the waste and waste packages stored in the facility;

Consideration may be given to including inactive packages or corrosion coupons to monitor conditions and performance.

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Utilities and auxiliary systems

Definition of necessary systems on a case by case basis;

Illumination for normal operation and in case of emergencies;

Appropriate fire protection system;

Adequate internal and external communications for normal operation and in case of emergencies.

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Commissioning

Usually is carried out in several

stages: construction completion and

inspection; equipment testing;

performance demonstration; non-

active commissioning and active

commissioning;

A final commissioning report, which

provide assurance to the operator

and/or the regulatory body that all the

conditions of authorization have been

satisfied should be produced.

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Operation (I)

Supporting activities:

radiation protection;

monitoring and surveillance;

testing,

examination of waste packages, inspection of the components of the facility;

maintenance and repair;

waste package labelling and record keeping.

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Operational activities:

waste receipt,

processing,

emplacement,

storage and retrieval of waste packages;

preparation for disposal.

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Operation (II)

According with written procedures;

Modification of the storage

conditions: planning and/or

procedures, authorizations;

Sound operational procedures: pre-

work assessments and training,

remote handling technologies,

contamination controls, optimization

of occupational exposures.

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Operational limits and conditions (I)

Developed by the operator and subject to approval by the regulatory body;

Facility-specific;

Administrative margins below specified limits as an operational target to help avoid any breach of the operational limits and conditions.

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maximum levels of surface contamination of containers;

requirements for training and qualification and minimum staffing;

cumulative inventory characteristics.

Operational limits and conditions (II)

waste package specification;

requirements for safety systems;

periodic testing of equipment;

maximum radiation dose rates;

Operational limits and conditions should

include:

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Operational procedures

Procedures for management and

operation under normal conditions,

during incidents and under postulated

accident conditions;

Responsibilities should be clearly

defined;

Deviation from operational procedures

should be justified and its safety

implication determined;

Periodic reviews should be

undertaken to take account of

operational experience.

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Radiation protection

Program to ensure that radiation doses to workers and members of the public are below regulatory limits and are kept ALARA under all predictable circumstances;

Additional procedures may be needed for application to non-routine activities;

Radiation dose rate limits should be specified and radiation levels should be adequately monitored.

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Maintenance, testing and inspection (I)

Program for maintenance, testing and inspection of:

waste containment systems;

waste handling systems;

heating/cooling systems;

radiation monitoring systems;

instrument calibration;

ventilation systems;

normal and standby electrical power supply systems;

utilities and auxiliary systems;

the physical protection system;

building structures and radiation shielding.

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Maintenance, Testing and Inspection (II)

Appropriated frequencies;

Not under nor over testing;

Approved and performed by

qualified, trained and

experienced personnel;

Keeping (and periodic

review) of records

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Security and access control

Sufficient to deter or restrict

intrusion into the facility;

Account of safeguards, where

required;

Zoned approach;

Provisions to detect

unauthorized intrusions and

react correspondingly.

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Decommissioning

A decommissioning plan should be prepared prior to decommissioning;

For independent facilities, a specific decommissioning plan should be prepared;

Where the storage is part of a larger nuclear facility, the decommissioning plan can be a part of that for the larger facility.

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Long-term storage (I)

Storage for longer than

several decades;

Based on a

governmental waste

policy or an

unanticipated need;

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Long-term Storage (II)

If the design life of the facility

may be exceeded, the waste

storage strategy should be

re-evaluated;

For storage beyond the

original storage duration,

testing, examination, or

evaluation may be needed to

assess waste package

integrity;

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Long-term Storage (III)

Consideration of changes in the stored waste:

generation of hazardous gases and the build up of overpressure;

generation of combustible or corrosive substances;

acceleration of corrosion of metals;

degradation of the waste form.

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Technical elements for Long -Term storage

More robust, or more actively maintained systems, facilities and controls;

Information should be retained in a readable, understandable and reliable form to future generations;

Special attention to inadvertent or deliberate intrusion into waste storage facilities in the safety assessment.

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Summary (I)

Large Storage Facilities:

• Procedures;

• Emergency Preparedness;

• Safety Documentation;

• Waste Characterization and Acceptance Criteria;

• Waste Form and Waste Package;

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Summary (II)

Design of Facilities:

• Interaction Facility’s Systems – Waste,

• Sitting,

• Shielding,

• Containment,

• Waste Handling,

• Waste Retrievability,

• Ventilation,

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Summary (III)

Design… (cont.)

• Temperature Control,

• Subcriticality,

• Monitoring,

• Control and Instrumentation,

• Inspection of facility and stored waste,

• Reserve Storage Capacity,

• Utilities and Auxiliary Systems;

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Summary (IV)

• Commissioning;

• Operation: Operational Limits and Conditions,

Development of Operational Procedures,

Radiation Protection,

Maintenance, Testing and Inspection,

Security and Access Control;

• Decommissioning;

• Long-term Storage.

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Example of storage facility - Austria

Location: Seibersdorf

Type of storage: Engineered - Warehouse

Category of waste: Cemented LILW

Type of package: 200 L drums

Capacity: 3000 m3

Design life: < 20 years

Operating since: 1982

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Example of storage facility - Belgium

Location: Mol

Type of storage: Engineered – Shelf pilling

Category of waste: LILW, liquid NIW

Type of package: 30 L PE bottles

Capacity: 120 m3

Design life:

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Example of storage facility - Egypt

Location: Inshas

Type of storage: Engineered – Modules

Category of waste: LILW cemented

Type of package: Concrete canisters

Capacity: Variable

Design life: > 30 years

Operating since: 1997

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Example of storage facility - France

Location: La Hague (R7)

Type of storage: Engineered – Heavily shielded concrete vaults

Category of waste: HLW glass

Type of package: 150 L SS canisters

Capacity: 4500 canisters

Design life: < 50 years

Operating since: 1989

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Example of storage facility - Germany

Location: Ahaus

Type of storage: Engineered – Warehouse

Category of waste: Spent fuel

Type of package: CASTOR casks

Capacity: 420 casks

Design life: 50 years

Operating since: 1983

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Covra, Netherlands

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Covra, Netherlands

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Covra, Netherlands

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Brinje, Slovenia

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Chisinau, Moldova

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Types of packages (LILW)

200 L drums

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Types of packages (LILW)*

Type Country Dimensions

(mm)

Volume

(L) Material

Maximal

weight

(kg)

Waste

form

NIROND

53 bottle Belgium Ø310×600 30 PE 50 Liquid

COGEMA

220 drum France Ø583.5×883 190 SS 300 Bitumen

VBA

container Germany Ø1060×1500 1300 Concrete - Solid

BNFL

box UK

1850×1850× 1370

3000 MS,

concrete

lined 10000

Individual

items

*Some examples, taken from IAEA’s TRS 390

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Types of packages (HLW)

CASTOR cask

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Types of packages (HLW)*

Type Country Dimensions

(mm)

Volume

(L) Material

Max.

initial

activity

(GBq)

Max.

initial

dose rate

(Sv/h)

Heat

produc-

tion (W)

Waste

form

Pamela

60

canister

Belgium Ø298.5×1200 60 SS 5.6E5

(β) 140 70 Glass

COGEM

A 1425

drum

France Ø1130×1707 1300 SS 6.3E4

(137Cs) - 115

Cemented

cladding

hulls

BNFL

canister UK Ø420×1300 150 SS 4.5E7 4500 2500 Glass

CASTOR

V/19 Germany Ø2440×5680 7150 DCI 5.3E8

1.3E-3

(γ+n) 39000

LWR

spent

fuel

*Some examples, taken from IAEA’s TRS 390

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