Decommissioning of MAX-lab Magnus Hrling 9 th International Workshop - - PowerPoint PPT Presentation

Decommissioning of MAX-lab

Magnus Hörling

9th International Workshop on Radiation Safety at Synchrotron Radiation Sources April 19-21, 2017 Taiwan Photon Source, Hsinchu, Taiwan

Outline

• Facility Description
• Objective & Conditions
• Regulations
• Approach
• Phase 1 - Radiological Characterization
• Phase 2 - Dismantling & Radiological

Clearance

• Outcome & Costs

Decommissioning of MAX-lab / Outline

Facility Description

Facility Description (1/4)

• Former Swedish national laboratory

for accelerator development, synchrotron light and nuclear physics research

• The history of MAX-lab dates back to

the early 80’s

• About 1000 users per year

Decommissioning of MAX-lab / Facility Description

Facility Description (2/4)

Injector

• Microtron

95 MeV 1984-2002

• Linac

200/400 MeV 2001-2015 MAX I

• Ø 32 m

200/550 MeV 1986-2015 MAX II

• Ø 90 m

1500 MeV 1996-2015 MAX III

• Ø 36 m

700 MeV 2007-2015 Nuclear physics

• Prolonged runs at 10 Hz using MAX I as a pulse-stretcher
• Significant losses in the injector and MAX I

Decommissioning of MAX-lab / Facility Description

Facility description (3/4)

Decommissioning of MAX-lab / Facility Description

MAX II MAX III MAX I Injector Nuclear physics

Facility Description (4/4)

Decommissioning of MAX-lab / Facility Description

Objective & Conditions

Objective & Conditions (1/2)

Objective:

• Building to be emptied and returned to

the landlord

• Building to be “cleared for free use” –

i.e. no longer subject to the terms and requirements of the Radiation Protection Act Physical conditions:

• Local decay storage not an option
• No dedicated or suited space for decay

storage on the MAX IV property

• Alternate solutions for decay storage

were briefly considered, but decided not to be an option

• → 3rd objective: Disposal of activated

material

Decommissioning of MAX-lab / Objective & Conditions

Objective & Conditions (2/2)

Time constraints:

• Facility to remain in operation until mid

December 2015

• Dismantling to start immediately after

shutdown

• Goal for (physical) completion set by

the management to the summer of 2016 Budget:

• Total budget: 1500 k€
• Estimated radiological cost: 650 k€

Decommissioning of MAX-lab / Objective & Conditions

Regulations

Regulations

The Swedish requirements for radiological clearance procedures are given by the regulatory code SSMFS 2011:2.

• Nuclide specific clearance levels (Bq/g
• r kBq/m2)
• Generally harmonized to levels in

related EC RP publications

• Before any clearance, a control

program has to be notified to the authority

• Decisions on the clearance of

buildings are taken by the authority

• n application by the licensee

Decommissioning of MAX-lab / Regulations

Approach

Approach

Given the time frame, personnel resources, legal requirements and lack of space the implementation of a comprehensive measuring and clearance program within the organization was not considered feasible. The decision was made to hire a contractor specialized in the field of radiological decommissioning and radioactive waste management. The radiological decommissioning was divided into two phases.

Decommissioning of MAX-lab / Approach

Phase 1 – Radiological Characterization

Phase 1 - Radiological Characterization (1/5)

The characterization - performed during the first half of 2015 - included:

• Summary of operating history
• Risk categorization of rooms and

material

• Inventory and marking, database –

~800 objects/sections/surfaces

• Pulse and dose rate measurements
• Sampling of concrete and metal
• Determination of nuclide vectors

Decommissioning of MAX-lab / Phase 1 – Radiological Characterization

Phase 1 - Radiological Characterization (2/5)

Risk categorization of rooms and material:

• Initially based on operating history

and facility knowledge

• Protected (and normal) areas deemed

Extremely Low Risk (~6700 m2)

• Conservative approach for controlled

areas (~1500 m2)

Decommissioning of MAX-lab / Phase 1 – Radiological Characterization

Phase 1 - Radiological Characterization (3/5)

Risk categorization of rooms and material:

• Pulse rate measurements used

primarily to confirm initial categorization

• Results allowed for modifications of

the categorization (less conservative) – mainly exclusion of stands in MAX II and MAX III and recategorization of less critical room surfaces

Decommissioning of MAX-lab / Phase 1 – Radiological Characterization

Phase 1 - Radiological Characterization (4/5)

General categorization of controlled areas and material inside. Injector, MAX I and Nuclear Physics BL:

• Vacuum system, magnets etc
• Other equipment, incl. stands
• Room surfaces

MAX II and MAX III:

• Vacuum system
• Magnets, incl. IDs etc
• Stands and peripheral equipment
• Room surfaces

Decommissioning of MAX-lab / Phase 1 – Radiological Characterization

Above Clearance Level Risk Low Risk Extremely Low Risk

Phase 1 - Radiological Characterization (5/5)

Determination of nuclide vectors

• Sampling of concrete, wall filling

material and activated metal

• Large uncertainties
• Concrete samples showed induced

activity, but only up to ~ 60% of the clearance level

• For all concrete samples, the naturally
• ccurring radionuclides (mainly 40K

and 232Th) still dominated the activity content

Decommissioning of MAX-lab / Phase 1 – Radiological Characterization

Steel Co-60 1,0E+00 Sc-46 1,6E-01 Cr-51 1,6E+01 Mn-54 3,4E+01 Co-56 2,4E+00 Co-57 4,8E+01 Co-58 2,2E+00 Fe-59 1,8E-02 Y-88 5,0E-02 Zn-65 2,1E-02 Nb-95 2,6E-01 Concrete Co-60 1,0E+00 Na-22 1,1E+00 Sc-46 1,9E-01 Mn-54 4,0E-01 Co-58 1,0E+00 Cs-134 3,8E-01 Cs-137 2,9E-01 Eu-152 2,1E+00 Eu-154 5,2E-01 Eu-155 6,8E-01 Wall Filling Material Co-60 1,0E+00 Mn-54 1,9E+00 Zn-65 8,2E-01 Cs-134 3,7E-01 Eu-152 1,6E+00

Radionuclides measured in samples and average ratios to 60Co

Phase 2 – Dismantling & Radiological Clearance

Phase 2 – Dismantling & Radiological Clearance

(1/7)

Dismantling began with categorized material in controlled areas in January 2016.

• Dismantling
• Separation & Sorting
• Packaging
• Registration (contractor’s data base)
• Shipping to contractor’s site

A separate contractor, hired for general dismantling and demolition of (the rest

• f) the facility started work two months

later.

Decommissioning of MAX-lab / Phase 2 – Dismantling & Radiological Clearance

Bulk shielding of the injector, nuclear physics and parts of MAX I:

• Walls of 2-3 m thickness
• Made out of gravel including stones of

varying sizes, supported by corrugated metal and beams

• ~800 m3 of concrete like mass
• Probably a great idea back in the day…
• Turned out to be very challenging (and

costly) to remove

Decommissioning of MAX-lab / Phase 2 – Dismantling & Radiological Clearance

Phase 2 – Dismantling & Radiological Clearance

(2/7)

Bulk shielding of the injector, nuclear physics and parts of MAX I:

• Innermost 40 cm of the wall filling

material were separated for clearance measurments

• Filled into big-bags and measured
• When the innermost parts had been

separated and removed, the remaining masses could be dealt with in a less delicate way

Decommissioning of MAX-lab / Phase 2 – Dismantling & Radiological Clearance

Phase 2 – Dismantling & Radiological Clearance

(3/7)

Local clearance of material:

• Concrete blocks and wall filling

material was not shipped to the contractor – measured for clearance at MAX-lab

• Dedicated measuring station set up by

the contractor (NaI probes)

• 60Co content quantified and nuclide

vector applied

• < 1000 kg material per measurement
• Formally cleared by MAX-lab (control

program notified to authority)

Decommissioning of MAX-lab / Phase 2 – Dismantling & Radiological Clearance

Phase 2 – Dismantling & Radiological Clearance

(4/7)

Clearance measurements of concrete bulk shielding and room surfaces:

• Rooms completely emptied
• HPGe equipment, collimated
• Low Risk – one measurement per

surface, critically chosen area

• Risk – measurements in a 1 x 1 m2 grid
• 5 m2 measured at once when practical

(tm increased accordingly)

Decommissioning of MAX-lab / Phase 2 – Dismantling & Radiological Clearance

Phase 2 – Dismantling & Radiological Clearance

(5/7)

Demolition of bulk shielding:

• Could start when the data from the

clearance measurements had been analyzed

• Cast concrete was segmented by

circular cutting and wire sawing

• None of the bulk shielding concrete

could leave MAX-lab until the decision by the authority on the clearance of the building was received

Decommissioning of MAX-lab / Phase 2 – Dismantling & Radiological Clearance

Phase 2 – Dismantling & Radiological Clearance

(6/7)

Clearance measurements and waste treatment of material shipped to contractor:

• Nuclide specific measurements (HPGe)
• f Low Risk and Risk material
• Material categorized as Above Clearance

Limit is treated as Low Level Waste (LLW) – i.e. melted

• Low Risk and Risk material found not to

be subject to clearance is also treated as LLW

• Ingots from melting are measured and

either

– Subject to clearance – Stored for decay, or – Shipped to the national Final Repository (SFR)

Decommissioning of MAX-lab / Phase 2 – Dismantling & Radiological Clearance

Phase 2 – Dismantling & Radiological Clearance

(7/7)

Outcome & Costs

Outcome & Costs (1/8)

Local clearance of material:

• Concrete blocks

230 t

• Wall filling material

190 t

• 60Co detected in 22 out of ~500

packages

• Induced activity content was below

the clearance level for all packages

Decommissioning of MAX-lab / Outcome & Costs

Outcome & Costs (2/8)

Clearance measurements of concrete bulk shielding and room surfaces:

• ~400 m2 measured (75% of which in

the injector and MAX I areas)

• An area constituting the floor of the

injection/extraction straight in MAX I and roof in the injector was found to have induced activity content well above the clearance level (up to x 8)

• Concrete sampling during the

characterization phase included this area of MAX I – however, the clearance measurements revealed sharp gradients

Decommissioning of MAX-lab / Outcome & Costs

Outcome & Costs (3/8)

Removal of room surfaces above the clearance level:

• ~40 m2 of floor (including margin) and

supporting concrete beams had to be removed and reconstructed

Decommissioning of MAX-lab / Outcome & Costs

Outcome & Costs (4/8)

Clearance of the building:

• The application for clearance of the

building, along with the project reports, was submitted to the authority in October 2016

• The decision (positive) was received in

mid December 2016 – one year to the day after shutdown of the facility

• Removal of the stored concrete could

begin (~1700 t)

Decommissioning of MAX-lab / Outcome & Costs

Outcome & Costs (5/8)

Decommissioning of MAX-lab / Outcome & Costs

Outcome & Costs (6/8)

Decommissioning of MAX-lab / Outcome & Costs

Outcome & Costs (7/8)

Outcome of material shipped to contractor:

(preliminary figures)

• Low Risk

108 t

• Risk

45 t

• Low Level Waste

47 t

• In total ~70 t to be melted
• A few of the ingots from the melting will

have to be stored for decay, ≤ 2 years

• Yet a few will have to be sent to final

repository

Decommissioning of MAX-lab / Outcome & Costs

Measured activity in ~ 50 t , of which 23 t were above the clearance level.

Outcome & Costs (8/8)

Radiological costs:

(preliminary figures)

• Total cost Phase 1:

~110 k€ ~650 h

• Total cost Phase 2:

~1130 k€ ~6600 h

– Dismantling & measurements ~250 k€ ~3600 h – Management & administration ~400 k€ ~3000 h – Measurements (at contractor) ~170 k€ – Material management/treatment ~270 k€ – Other costs (e.g. shipping) ~40 k€

Prices per kg for material shipped to contractor (based on contract):

• Clearance measurements

– Low Risk 0.40 €/kg, minimum 190 €/package – Risk 1.90 €/kg, minimum 930 €/package

• Waste treatment

– Melting 3.80 €/kg

Decommissioning of MAX-lab / Outcome & Costs

Decommissioning of MAX-lab

Decommissioning of MAX-lab / The End

Thank you for your attention!