CDRL Company Dose Restriction Level Simon Morris HSED Radiation Protection Adviser British Energy Generation

BEG Annual Collective Dose Man mSv

CDRL Influences Predecessor devised a 15 mSv CDRL Previous achievements / future expectations Source related dose constraints (BEG sites only) Revised dose limits for year 2000 onwards Tolerability of an exposure or risk acceptable, tolerable & unacceptable Trivial < 3 uSv/h Acceptable to 10 mSv Tolerable mSv Unacceptable >20 mSv RISK

BEG CDRL Policy Maximum dose that can be planned for a person whilst working on a BEG site in advance of work. HSED Director authority to > CDRL. CategoryRestriction Level Employees and Contractors aged 18 years or over (not being a trainee or other person). 10 mSv effective dose per calendar year. Any female employee who has informed her employer that she is pregnant. 1 mSv equivalent dose to the surface of the abdomen for the remainder of the pregnancy.

Pre-Work ALARP Assessments Report Dose constraints applied to planned tasks Expressed as individual or collective dose Work planning if > 0.5 mSv/month RPS > 3 mSv or 10 man mSv ALARP report prepared by HP > 6 mSv or 100 man mSv ALARP report issued by SHP and sent to HSED Director > 10 mSv exceptional case requiring sanction from HSED Director

1mSv/h

0.6mSv/h 0.2mSv/h 1.0mSv/h

Practice Hunterston B & Hinkley Point B in-vessel outage strategy with single contractor 1999 BEG did not plan for emergent work 1999 Collective dose 880 man mSv and 18 exceeded target dose of 10 mSv 2000 changed to include emergent work In-vessel team size is capability limited CDRL compliance considered difficult

2000 Team Prediction Document 1053 man mSv Large No > CDRL Hunterston B impact on Hinkley Point B Continued employment for 2000 HSED forecast of 2.9 man Sv for 2000 compared with target of 3 man Sv

BEG Health Physics Involvement HSED considered predictions pessimistic Suggested 650 man mSv for 2000 No need to > CDRL HSED perform outage self regulation review Pre-work ALARP assessments provided by both sites and reviewed by HSED Both sites produced post outage reviews Hinkley confirmed no request to > CDRL

2000 Outage Dose Comparison Station Planned Collective Dose man-mSv Actual Collective Dose man-mSv Individual target Dose mSv Max individual Dose mSv Hunterston B Hinkley Point B Sizewell B

Plant Failure May 2000 a Hunterston reactor suffered a boiler tube failure, output reduced BEG assured regulator to inspect and repair After statutory outage completion, reactor shutdown with dose prediction < CDRL BUT inspections revealed that extensive repairs were required (across 2000 – 2001)

Circulator entry point Swagepiece repairs 0.3mSv/h 0.5mSv/h Bifurcation repair area.

CDRL Implications of Work Estimate of additional 2500 man mSv Finite specialist manpower Relevant experienced manpower required Manpower already close to CDRL Pre-Work ALARP assessments provided and reviewed by HSED HSED Director authorised doses > CDRL & specific conditions (CRPA consultation) CEO, Regulator, Contractor, Trade Union and Safety Representatives all involved

Applied Measures Proven dose reduction good practices Alternative bottom vessel entry requiring removal of gas circulator Benefits of improved safety and psychological well being Improved manpower flexibility, productivity and dose sharing Contractor adopted alternative work management methodologies Decision made to perform immediate inspections at Hinkley Point B

Dose Performance#1 BEG Dose performance by year 1999 Man mSv 2000 Man mSv 2001 Man mSv Hunterston B Hinkley B Sizewell B Company

Dose Performance#2 39 of 130 contractors who undertook vessel entry > CDRL in at Hunterston B & 6 at Hinkley B 2000 highest = mSv Hunterston B 2000 highest = 13.8 mSv Hinkley B ALARP Investigation reports completed Hunterston B repair 2000/1 was 1307 Man mSv (cf. 2500) 2001 highest = 8.6 mSv Hunterston B & nil > CDRL

Lessons CDRL a motivator that resulted in reduced individual and collective dose Post ALARP reviews invaluable for dose management & reduction improvement Independent self-regulated function influential Burden to monitor BEG CDRL performance, consolidation of ADS & EPD for improvement ALARP considerations integrated into project plans for management decision Review strategy for reactor in-vessel work, with some remote inspection

CDRL Company Dose Restriction Level Simon Morris HSED Radiation Protection Adviser British Energy Generation