POLICY ON RADIOACTIVE MATERIALS

Transcription

1 POLICY ON RADIOACTIVE MATERIALS HEALTH & SAFETY UNIT SUMMER TERM 2010

2 CONTENTS 1 AIM OF THE POLICY INTRODUCTION MANAGEMENT ORGANISATIONAL STRUCTURE FOR RADIATION PROTECTION Radiation Protection Adviser (RPA) Radiation Protection Officer (RPO) Radiation Protection Supervisor (RPS) Radiological Protection Sub-Committee WORK PRACTICES AND JUSTIFICATION RESOURCES QUALIFIED AND EXPERIENCED STAFF... 6 a) Staff Training... 6 b) Training Records USE AND STORAGE OF UNSEALED RADIOACTIVE MATERIAL... 7 a) Practices... 7 b) Appropriate Method... 7 c) Ordering and Storage of Radioactive Material GENERATION AND DISPOSAL OF RADIOACTIVE WASTE... 7 a) Segregation of Waste... 7 b) Estimation of liquid/solid waste ACCUMULATION OF RADIOACTIVE WASTE DISPOSAL OF RADIOACTIVE WASTE... 8 a) Liquid Waste... 8

3 b) Solid Waste COMPLIANCE WITH THE RADIOACTIVE SUBSTANCES ACT... 9 a) Open Source Registration... 9 b) Waste Disposal Authorisation... 9 c) Audit... 9 d) Documents GENERAL... 9 a) Radiological Protection Sub-Committee... 9 b) Reports APPENDIX I RSA3 ASSESSMENT SUMMARY

4 1 AIM OF THE POLICY To demonstrate the employment of Best Practicable Means (BPM) for the usage of radioactive materials and disposal of radioactive waste in accordance with the provisions of the Ionising Radiations Regulations 1999 (IRR1999), The Environmental Permitting (England and Wales) Regulations 2010 and associated guidance. 2 INTRODUCTION This document sets out to demonstrate that Manchester Metropolitan University is committed to complying with the standard conditions issued with its authorisation to accumulate and dispose of radioactive waste, and in particular applying best practicable means for the work that is carried out at the University. To this end, the document refers to: An assessment of the radiological impact on members of the public and the environment of the release of radioactive waste in liquid form. Whilst details of that assessment is contained in Appendix I, it is noted that the total committed effective dose to a member of the public or sewage worker under the worst possible scenario is unlikely to be greater that 3 microsieverts. Interim guidance from the Environment Agency states that the Agency expects the amount of work undertaken to demonstrate that BPM is applied to be proportionate to the assessed environment risk. In addition, the amount of time, money and trouble expending BPM measures should also be proportionate to the environment risk being mitigated. This statement, together with the assessment of total committed effective dose, has been taken into account for the work undertaken. The role of management and the procedures employed to adopt the delegation of responsibility and organisation of formal meetings etc. The work practices on site, the resources allocated for them and their justification. The role of staff, the use of radioactive material and the procedure of waste disposal. Since the assessment assumes that the waste disposed of is the maximum limit set in the authorisation, any changes in the authorisation will necessitate a review of the assessment. 3

5 3 MANAGEMENT The University Health and Safety Policy identifies the senior individuals who are responsible for delivering the policy commitments. Details of their duties and responsibilities are set out in the University s Health and Safety Policy Manual. 4 ORGANISATIONAL STRUCTURE FOR RADIATION PROTECTION ORGANISATIONAL CHART FOR RADIATION PROTECTION Vice Chancellor Deputy Vice Chancellor Deans/Pro Vice Chancellors University Secretary Human Resources Director (Appointed Safety Director) Financial Director Heads of School/ Departments University Health & Safety Adviser Departmental Radiation Protection Supervisor University Radiation Protection Officer Radiation Protection Adviser (External Appointment) For the purpose of Radiation Protection, the University will appoint the following to ensure compliance with all relevant legislation in order to protect the health and safety of its students, staff and visitors. 4

6 4.1 Radiation Protection Adviser (RPA) The University has appointed Peak RPA as it s Radiation Protection Adviser, as outlined in Schedule 5 of IRR99 and the Approved Code of Practice. Advice from the RPA will be sought as necessary for implementation of IRR99 and RAS Radiation Protection Officer (RPO) The University has appointed a Radiation Protection Officer to provide guidance and support to ensure that the requirements of the Ionising Radiation Regulations and The Radioactive Substances Act are met. The RPO will provide support and co-ordinate on ionising radiation issues with both the RPA and the RPS s. 4.3 Radiation Protection Supervisor (RPS) The University will appoint Radiation Protection Supervisors from all Departments that use ionising radiation to provide an adequate level of dayto-day supervision of each Department s work with radiation, as required by the IRR99. Where the work with ionising radiation is such that RPSs are not required (for example where there are no Controlled Areas), appropriate staff will be delegated duties to oversee compliance with RSA93 and any other relevant legislation. 4.4 Radiological Protection Sub-Committee The University s Health and Safety Committee will appoint a Chairperson to lead the Radiological Protection Sub-Committee. The Radiological Sub- Committee will report to, and will be responsible for advising, the University s Health and Safety Committee on measures to permit the legal and safe use of sources of radiation, and the protection of persons liable to be exposed to radiation hazards. The Sub-Committee will provide advice to the University on the state of compliance with the Regulations, and will identify specific problems relevant to the use of ionising radiations and other issues relating to the radiological safety of the University s activities. The RPA will be a member of the Sub-Committee. 5 WORK PRACTICES AND JUSTIFICATION Unsealed radionuclides are used to label proteins, RNA and DNA to develop assays to increase the sensitivity of detection of the above. Radioactive sources are in liquid form and uptake in the probe for protein, RNA and DNA is normally very little of the original activity. The unattached activity is treated as aqueous waste. 5

7 This is vital work that uses established techniques in the field. Many Universities and research facilities employ these methods. In these techniques enough radioactivity has to be incorporated in the probe to be able to get statistically viable results. The least amount of radioactivity that will yield meaningful results is normally employed. It is normal policy at the University to ask researchers to consider nonradioisotopic methods when carrying out a prior risk assessment before starting any new work. The use of radioactivity has diminished quite significantly when compared to its use a few years ago, as new nonradioisotopic techniques are employed. 6 RESOURCES At present all of the usage of unsealed radioactive sources is carried out in the John Dalton Building. Handling of unsealed radioactive sources is carried out in the Radiation Laboratory in the John Dalton Tower. There are adequate storage facilities, and non-porous bench surfaces which are easy to clean. The floor covering is hard wearing lino, which is coved up the wall surface. The laboratory has a designated sink for disposal of liquid waste. The sink is labelled appropriately and monitored as part of the routine monitoring. Any leakage from the sink is reported immediately to the Property Management Performance Team (PROMPT). Any work to be carried out by PROMPT is done after a risk assessment has been carried out, taking into consideration the amount of waste disposed of, the half life and the energy of emission of the radionuclides concerned. The laboratory has a suitable contamination monitor and dose monitors are available from the Health and Safety Unit if required. Work with P-32 is carried out in a work station behind a Perspex barrier of adequate thickness. A Radiation Waste Store is provided for accumulation of radioactive waste. Funding is allocated and routes identified for the collection and disposal of radioactive waste. 7 QUALIFIED AND EXPERIENCED STAFF a) Staff Training All users of radioactive sources must have received training or have previous experience that is adequate and sufficient for the work to be carried out. All Radiation Protection Supervisors receive training on an appropriate Radiation Protection Supervisors course. All users of radioactive sources must read and co-operate with all instructions set out in the local rules. 6

8 b) Training Records Training records for courses organised by the Health & Safety Unit will be kept by the Health and Safety Unit. Other training records will be kept by the Department concerned. 8 USE AND STORAGE OF UNSEALED RADIOACTIVE MATERIAL a) Practices At present, work with radioactive materials is carried out in the Radiation Laboratory in the main John Dalton Tower where sources of fairly low activity may be handled. All new work is only undertaken after a prior Risk Assessment has been completed. At present most of the work is confined to P-32, S-35, C-14 and I-125. b) Appropriate Method The prior Risk Assessment asks the researcher if non-radioactive methods have been considered and a reassurance that the quantity of radioactive material in use is as low as possible and compatible with obtaining good quality results. The cost of disposal of solid waste is also evaluated, and this in itself focuses the attention of future users. c) Ordering and Storage of Radioactive Material All ordering of radioactive sources is via a central system, where it is possible to spot an unusually large order or an order for a radionuclide not in normal use. All laboratories which use radioactive sources have a lockable refrigerator or a suitable safe. The entrance to most laboratories is via a key coded door. 9 GENERATION AND DISPOSAL OF RADIOACTIVE WASTE a) Segregation of Waste The nature of the work allows segregation of radioactive waste at source. This also ensures that the volume of solid waste is kept to a minimum most of which is in the form of counting vials, contaminated tissues and gloves. Liquid waste is disposed of via the designated sink. Aqueous waste is disposed of as soon as possible. Organic liquid waste and solid waste is stored in appropriate containers which are then transferred to the Radiation Waste Store. 7

9 b) Estimation of liquid/solid waste In most of the laboratory techniques currently employed, it has been established that the vast majority (greater than 95%) of the waste is liquid and only a small fraction will bind to the protein RNA or DNA. For new techniques, researchers are asked to carry out preliminary work (e.g. measuring aliquots) in order to establish the ratio between liquid and solid waste. The results of this are then used for continued work. It is usually expected that the radioactivity of the solid waste will be overestimated, however, when disposing of the waste it is additionally checked using appropriate monitors as a precaution against underestimation of the radioactivity. 10 ACCUMULATION OF RADIOACTIVE WASTE All solid radioactive waste is stored in the Radioactive Waste Store. The security of the contents of the store and its adequacy for space is continually under review. Waste can be allowed to accumulate up to 6 months or two years depending on the half life of the radionuclide. This allows disposal of the two most commonly used radionuclides, namely S-35 and P-32 to such levels that they may be disposed of as either non-radioactive waste or very low level radioactive waste. Records are kept of all the waste taken to the Store. At the end of each month current waste is recorded to ensure that the limits set in the authorisation are not exceeded. When considered necessary, external monitoring of the store is carried out using dose monitors or environmental film badges. If any leaks are suspected additional monitoring can be carried out using either contamination monitors or swabs in a liquid scintillation counter. 11 DISPOSAL OF RADIOACTIVE WASTE a) Liquid Waste Liquid waste is disposed of via the designated sink in the Radiation Laboratory. Small amounts of organic liquid waste are disposed of via a contractor. b) Solid Waste Solid waste may be transferred to one of three contractors but is usually allowed to decay before disposal as very low level radioactive waste. 8

10 12 COMPLIANCE WITH THE RADIOACTIVE SUBSTANCES ACT a) Open Source Registration A review is undertaken periodically of the maximum holding levels of various radionuclides required in each Department and from the Registration each Department is given a radionuclide allocation limit. This ensures that the overall registration limits are not exceeded and that the Department has a sufficient limit for work to be carried out. It is the responsibility of each Department to make certain that their limits are not exceeded. Ordering of radioactive sources is via one member of staff who has sufficient experience to note any unusual radionuclide or quantity of radioactive material being ordered. He/She has the authority to refuse to sign any order which breach the registration limits. b) Waste Disposal Authorisation Each Department is given an allocation of radioactive material which may be disposed of each month via each authorised route. The disposal limits are set out in Receipt, Keeping and Disposal of Radioactive Sources which is issued to any Department wishing to use unsealed radioactive material. It is the responsibility of each Department to make certain that their limits are not exceeded. c) Audit Annually the RPA carries out an audit of radiation protection issues in the Departments. All Departments using radioactivity are visited and compliance with the Radioactive Substances Act and other legislation is checked. d) Documents The system of accumulation, record keeping and disposal of radioactive waste is detailed in Receipt, Keeping and Disposal of Radioactive Sources which is issued to any Department wishing to use unsealed radioactive material. 13 GENERAL a) Radiological Protection Sub-Committee The Radiological Protection Sub-Committee which includes the RPA, RPO and RPS s will meet at least twice per academic year in order to examine and update on current radiation issues within the University. 9

11 b) Reports The RPA and RPO shall submit annual reports to the University Health & Safety Committee. 10

12 14 APPENDIX I RSA3 Assessment Manchester Metropolitan University Assessment of Radiological Impact Due to Disposal of Radioactive Waste Values of Parameters for calculating Committed Effective Dose for inhalation and ingestion and skin dose Radionuclide Ingestion: Committed effective dose per unit intake ced Sv Bq -1 Inhalation: Committed effective dose per unit intake ced Sv Bq P 2.4 x x Contamination: Skin dose msv h -1 per 1kBq cm I 1.5 x x H 4.2 x x Section A The following critical groups and scenarios are considered. Critical Group Scenario Sewage worker at the MMU site i. Inadvertently ingests 2 litres of sewage at the institute ii. Spills 10mls of sewage on his hands Member of public Obtains annual drinking supply after sewage treatment Methodology It is assumed that the maximum monthly limit of aqueous disposal of radioactive waste is uniformity disposed of per 20 days per month. The concentration of the radioactivity is uniformly distributed through the site s aqueous waste system (relevant to the point of disposal) and a sewage worker inadvertently ingests 2 litres of this waste. The waste eventually flows into the sewage treatment works, where further dilution is taken into consideration.. Calculations The site is authorised to dispose of the following per calendar month 32 P 0.5 GBq 125 I 0.1 GBq 3 H 15 GBq If it is assumed that the discharges are uniform throughout the month (20 days/month), then Daily disposals 32 P 25 MBq 125 I 5 MBq 3 H 750 MBq The main out flow points where radioactivity is used if from the John Dalton Campus, where on average, 3550m3 of water is disposed of per month. 11

13 Therefore the daily concentration in the waste from the Institute per m 3 would be 32 P 212 kbq 125 I 42 kbq 3 H 6356 kbq A person inadvertently drinking 2 litres from this discharge would consume 32 P 424 Bq 125 I 85 Bq 3 H Bq and his committed effective dose is calculated by multiplying the above numbers with the ced per unit intake. This works out to 32 P (2.4 x 10-9 x 10 6 ) x 424 µsv 125 I (1.5 x 10-8 x 10 6 ) x 85 µsv 3 H (4.2 x x 10 6 ) x µsv This equals 2.82 µsv The waste eventually flows into the Davyhulme Sewage Works. The daily average flow of waste through the sewage works is about m 3. The concentration of radioactivity per m 3 at the sewage works is:: 32 P 139 Bq 125 I 28 Bq 3 H 4167 Bq A person obtaining his/her annual drinking supply from this source would consume 0.6m 3 annually and his committed effective dose would be, calculating as above: This equals 0.56 µsv The sewage at the Davyhulme Waste Water Treatment Works is treated by conventional activated sludge followed by ammonia removal in a BAFF plant. Sludge is typically 6% of dry solids, which is transferred by pipeline to Shell Green facility where it is pressed into cake prior to incineration. Grit is taken to landfill. Treated water follows into the Manchester Ship Canal The concentration of radioactivity prior to treatment plant is Bq/gm. It is highly unlikely that the concentration in the sludge or grit would be greater than 0.4Bq/gm 12

14 External Doses As 32 P comprises of the majority of the waste and it is a beta emitter, and only 100MBq of 125 I are disposed of per month, external doses are not considered. However, a sewage worker working outside MMU might inadvertently spill sewage on his hands. Therefore dose to the skin is considered. Note that skin dose due to 3 H is 0 Concentration of activity at sewage leaving MMU is 32 P 212 Bq l I 42.4 Bq l -1 and if it is assumed that 10mls of this sewage is spilled on a hand of area 100cm 2, then it can be shown that the skin contamination would be 32 P 2.12 x 10-5 kbq/cm I 4.24 x 10-6 kbq/cm 2 and the total skin dose works out to be just over 0.04µSv/hr 13

15 Section B The following critical groups and scenarios are considered. Critical Group Sewage worker at the sewage treatment works Scenario i. Inadvertently ingests radioactivity from the sewage ii. Inadvertently inhales radioactivity from the sewage Methodology As detailed in reference 2 Calculations Ingestion H ing = C unf m D ing O where H ing is the ced for ingestion of radionuclides (Sv y -1 ) C unf is the conc. of a radionuclide in a untreated sewage (Bq kg -1 or Bq l -1, assuming a density of 1 tonne m -3 ) m is the intake rate for inadvertent ingestion of sewage (kg h -1 ) (5 x 10-5 ) D ing is the cede per unit intake by ingestion (Sv Bq -1 ) O is the occupancy ( 2000 hours) C unf : At the sewage plant, 180,000 m 3 per sewage flows per day. This is equivalent to 1.8 x 10 8 litres per day. C unf, and the ced is then 32 P Bq l -1 leading to a ced of 3.33 x Sv y I Bq l -1 leading to a ced of 4.17 x Sv y -1 3 H Bq l -1 leading to a ced of 5.00 x Sv y -1 This sums to a total of 9.25 x Sv y -1 ie 9.25 x 10-5 µsv y -1 Inhalation H inh = C unf s r V D inh O where H inh is the cede for ingestion of radionuclides (Sv y -1 ) C unf is the conc. Of a radionuclide in a untreated sewage (Bq kg -1 or Bq l -1, assuming a density of 1 tonne m -3 ) s r is the re-suspended sewage load (0.1 mg m -3 ) D inh is the cede per unit intake by inhalation (Sv Bq -1 ) O is the occupancy (2000 hours) Using C unf from above (ingestion scenario) and ced per unit intake of inhaled activity, the ced due to inhalation is: This sums to a total of 1.96 x Sv y -1 ie 1.96 x 10-7 µsv y -1 14

16 Summary 1. It has been shown that a sewage worker inadvertently consuming 2 litres of waste from the MMU site would receive a committed effective dose of 2.82 microsieverts. 2. If he were to spill 10mlson his hands, he would receive a skin dose of 0.04 microsieverts for the first hour, when it is assumed that he would wash his hands. 3. A person obtaining his annual supply of drinking water from the Manchester Ship Canal, where the waste from MMU goes to, would receive a committed effective dose of 0.56 microsieverts. 4. A sewage worker at Davyhulme Sewage Treatment Works would receive a annual committed effective dose of 9.25 x 10-5 microsieverts due to inadvertent ingestion and 1.96 x 10-7 microsieverts. due to inadvertent inhalation due to the spray. 5. As the vast majority of radionuclides do not emit gamma radiation, his external dose is not considered. 6. The concentration of the affluent would be approximately Bq/g. 7. It is pointed out that the treated water from the Davyhulme Treatment Works does not constitute a potable supply, and therefore some of the assessments are very pessimistic. 8. Because the concentration of radioactivity in the affluent is so low and all the doses above so small, no consideration has been given to marine life or the uptake of the radioactivity by plant life if some part of the sludge is used for the purpose of manure. References 1. NRPB-R162: Doses from Intakes of Radionuclides by Adults and Young People. 2. NRPB-M744: Assessment of the Radiological Consequences of Accumulation and Disposal of Radioactive Waste by Small Users of Radioactive Materials 3. Radiation Protection Dosimetry 15