1. E.I.M. Meijne NRG Radiation & Environment The Netherlands
Operational aspects of decommissioning installations containing mineral wool
E.I.M. Meijne
NRG Radiation & Environment
The Netherlands

2. Contents Dutch legislation with respect to mineral wool
What is mineral wool?
Dutch legislation with respect to mineral wool
Decommissioning of a fossil fuelled power plant
operational aspects
estimated doses
waste handling
Conclusions

3. What is mineral wool? Insulation material produced from slag
Slag wool is produced from tin slag and contains enhanced concentration NORM
Produced in The Netherlands from
Typical brown colour, tight glass-like matrix
[Th-232sec] = 11.2 and [U-238sec] = 4.0
Has been used as insulation materials in a number of different types installations: in ovens, doors, steam generators, boilers e.a.

4. Dutch legislation relevant to slag wool
Nuclide specific exemption/clearance levels
Exemption level = clearance level
Sum rule applies
Weighted sum:
> 1 and < reporting requirements (not yet published)
> authorisation required
Disposal options waste
sum > COVRA
sum > 1 and < dedicated landfill or incinerator
sum < no restriction from a radiological/legal point of view

5. Application of exemption levels to slag wool
Nuclide
Measured
concentration
(Bq/g)
Exemption
value (Bq/g)
Contribution to
weighted sum
U-238sec
Th-232sec
Total
4.0
11.2 1
4.0
11.2
15.2
Possessing, handling and disposal of slag wool requires authorisation
Dismantling requires radiation protection measures
Waste considered as radioactive waste

6. Decommissioning of a fossil-fuelled power plant
Started in 1998
presence of radioactive material unknown
In 1999 dismantling of boiler I and II started
Scrap with adherent slag wool triggered a portal monitor at a scrap yard
Inspectorate was notified
Dismantling stopped immediately
Investigation was carried out

7. Building was already partly demolished

8. Covering of boilers was partly removed exposing the slag wool

9. Slag wool was spread over the entire plant

10. Actions taken
Work plan prepared describing the activities and radiation protection measures to be taken
Authorisation obtained for remediation and further decommissioning - activities were carried out under the permit of NRG
Survey was made of the entire plant to identify slag wool containing parts of the installation (Microcont H-13420, Xenon filled)
Measures were were taken to prevent further spreading of the slag wool

11. Slag wool insulated demi-water tanks
Measured dose rates
On surface tank: 970 nSv/hr
At 1 m: nSv/hr

12. Slag wool insulated coal feed bunkers
Measured dose rates
On surface bunker: 1000 nSv/hr
At 1 m: nSv/hr

13. Measures taken to prevent spreading of slag wool to the environment

14. Measures taken to prevent spreading of slag wool to the environment

15. PPE used: RPE: full-face mask (power assisted) Disposable coveralls
Gloves
Safety boots

16. Measures taken to prevent spreading of slag wool in the building

17. Measures taken to prevent further spreading of slag wool in the building

18. Collection of slag wool

20. Dose coefficients for inhalation of nuclides from slag wool and those listed in BSS
Lung
class DC
Sv/Bq
BSS
lung class DC
Sv/Bq
Ratio DC
slag wool / BSS
U-238++
Ra-226+
Pb-210+
Po-210
Th-232
Ra-228+
Th-228+ S
2.6 E-5
4.0 E-5*
4.9 E-6
3.2 E-6
1.2 E-5
1.3 E-5
3.5 E-5 M F
2.2 E-6
1.2 E-6
1.8 E-6
18.0
4.1
1.5
7.2
U = U-238, Th-234, Pa-234m, U-234, Th-230 and U-235 (4.5%)
* = (no radon emanation)

21. Dose coefficients for inhalation of slag wool based on 5 µm AMAD and type Slow
Nuclide
DC in
Sv/Bq
Average conc.
in slag wool (Bq/g)
DC in
Sv/g
U Ra-226
Pb Po-210
Th Po-212
6.6 E-5
8.1 E-6
6.0 E-5 4 3 11
2.6 E-4
2.4 E-5
6.6 E-4
Total dose
9.5 E-4

22. Estimated exposure during decommissioning of the power plant under various conditions
Respiratory
Protective
Equipment (RPE)
Protection
factor
Internal
exposure
mSv
External
exposure
mSv
Total
exposure
mSv no
2.27
0.30
2.58
Full-face masks*
2000 (NPF)
40 (APF)
0.001
0.057
0.30
0.30
0.36
Exposure time: 1000 hours, dust concentration: 2 mg/m3

23. Slag wool remaining after decommissioning

24. Slag wool remaining after decommissioning

25. Compression of the slag wool

26. Containers containing compressed slag wool
Measured dose rates
On surface containers: µSv/hr
At 1 m: µSv/hr

27. Temporary storage of slag wool
Dose rate at fence : 150 nSv/hr

28. Appearance of slag wool after compression

29. Conclusions
Slag wool containing installations require an authorisation
DCs for radionuclides from slag wool are higher than those listed in the BSS
Proper radiological protection measures avoid potentially significant exposure during dismantling
Main problems are the unawareness at the start of the decommissioning and disposal of the slag wool
Volume reduction by compression results in pulverisation of the wool and is thus not preferable if reuse options are possible
The negative public opinion regarding radioactive material complicates the development of reuse options even if the resulting doses are negligible.