4.0 Summary of Major DCISC Review Topics, 17th Annual Report - July 1, 2006 thru June 30, 2007
4.10 Radiation Protection
4.10.1 Overview and Previous Activities
DCPP Technical Specifications contain requirements on radiation protection, and DCPP has corresponding programs, and procedures to specify the details of their radiation protection programs. Although numerical limits are specified, plant operators are also required to use the philosophy of As Low As Reasonably Achievable (ALARA) to minimize excess radiation exposures and releases. DCPP has a formal ALARA program; the program applies to personnel exposure in the plant as well as normal releases to the environment. PG&E files reports semi-annually regarding personnel exposures, releases outside DCPP and regular soil, vegetation, water and air samples taken around the plant.
The DCISC regularly monitors DCPP personnel exposure. Collective radiation exposure is one of DCPP’s and INPO’s performance indicators. DCPP also reviews any radiation protection events or incidents in the industry that are reported in LERs or NRC violations. DCPP performance in radiation protection has been satisfactory; however, PG&E collective doses have not been in the lowest quartile of the industry.
The majority of personnel exposure occurs during refueling outages when most of the work in the Radiation Control Area (RCA) is performed. DCPP sets outage and annual goals for exposure, and reports these at each DCISC public meeting. DCPP also submits a semi-annual report to NRC on any planned, normal radioactive releases from the plant; DCISC reviews this report. Any abnormal releases are reported in special reports, typically LERs, although there have been none since the DCISC began in 1990.
The DCISC reviewed the following specific RP items during the previous reporting period:
- Outage 1R13 Radiation Protection Goals and Performance
- Refueling Outage 1R13 ALARA Results and Plans for 2R13
- Refueling Outage 2R13 ALARA Program and Results
- DCPP Tritium Levels and Radioactive Effluents Compared to Industry
The DCISC concluded in the previous period that DCPP appears to be controlling plant radiation releases well in maintaining releases to small fractions of Technical Specification limits. It has lowered its collective plant personnel radiation doses by aggressively pursuing radiation source term reductions and improved work practices without reductions in outage work scope.
4.10.2 Current Period Activities
The DCISC reviewed the following DCPP radiation protection items at its Fact-finding and public meetings:
- ALARA Overview
- Outage 1R14 ALARA Plans
- 2006 Annual Radioactive Effluent Release Report
- 2006 Annual Radiological Environmental Operating Report
The five-year DCPP personnel collective radiation dose results through June 2007 are as follows:
DCPP Collective Radiation Doses (person-Rem)
| Year | Unit 1 Outage | Unit 2 Outage | Other | Total | 3-Year per Unit Annual Dose |
|---|---|---|---|---|---|
| 2003 | - | 125 | 10 | 135 | 66 |
| 2004* | 149 | 98 | 10 | 257 | 90 |
| 2005 | 117 | - | 7 | 124 | 86 |
| 2006 | - | 74 | 9 | 83 | 77 |
| 2007** | 103 | - | 5 | 108 | 53** |
- - No outage
- * Two-outage year
- ** Through June
Through 2006, the nuclear plants reporting lowest collective radiation dose levels in the U.S. had doses at about 60 person-Rem average per reactor per year for a rolling three-year average. The DCPP end-of-year 2004, 2005 and 2006 comparables were 90, 86 and 77 person-Rem per unit, respectively. Substantial dose reduction will be required to reach lowest quartile performance, especially with 2004 being a two-outage year; however, they are showing substantial progress toward industry best.
ALARA Overview
The DCISC Fact-finding Team met with Bob Hite, RP Director; Jeff Harker ALARA Manager; Dr. Linda Sewell, Dosimetry Supervisor; and Curtis Hanson, ALARA Supervisor of the Radiation Protection Group at the August 2-3, 2006 (Volume II, Exhibit D.1, Section 3.3) to discuss DCPP ALARA (As Low As Reasonable Achievable).
The concept of ALARA is a commitment to reduce unnecessary radiation exposures and reducing exposures when procedures or technology can be applied to reduce exposures and still complete reactor work and improvements that are important to safety, reliability and performance. A good ALARA program calls for planning, innovation and attention to training and detail. ALARA encourages good management.
The collective dose for Outage 2R13was a record low for a DCPP outage, and the Radiation Protection Group has been given credit for its performance; however, DCPP has appropriately given much of the credit to its line organizations for their efforts in taking ownership of ALARA. The collective dose for 2R13 shows a significant drop in exposure from the previous outages (74 vs 130 person-Rem typical). RP notes that collective doses were reduced by using fewer man-hours in containment and reducing the number of reactor containment area entries. RP is continuing to review the initiatives they used to see which were most effective and where training will result in repeated performance.
In the 2R13 Quality Performance Assessment Report (QPAR) section on Radiation Protection Performance/ALARA, RP reported six areas in which significant dose reductions were achieved. One is "Change in Work Scope." DCPP stated that this did not represent side-tracking any essential or safety-related work. Although most of the DCPP published information on 2R13 highlights the reduction in dose, Leadership continues to remind all that safety has the highest priority, and that work that has been scheduled after careful review of priorities will not be deferred to avoid radiation exposures, and certainly not in order to improve a performance indicator.
Regarding efforts to raise awareness and to motivate employees to suggest ideas, Radiation Protection believes that the “idea contest” and use of posters and TV reminders were valuable tools. Incentive awards and a “Daily Dose report” have been well-received by the plant. Some of the new ideas came from benchmarking visits by members of the Radiation Protection group. Benchmarking visits were made to Seabrook and TMI. These plants are rated as “top performers” in Radiation Protection by INPO.
The DCPP Radiation Protection Group is performing its work well, and applying its experience and initiatives to provide quality service to DCPP. This has resulted in improved line ownership of ALARA and a record low collective radiation dose in Outage 2R13.
Outage 1R14 ALARA Plans.
Mr. Knisley, Outage Manager, presented DCPP ALARA plans for Outage 1R14 at the DCISC January 31 – February 1, 2007 Public Meeting (Volume II, Exhibit B.6).
Outage 1R14 is scheduled to commence on April 30, 2007. The goals established for 1R14 include an outage dose of less than or equal to 84 person-Rem which was based on the work to be performed during 1R14 and on the results, work and estimates from 2R13, which had an outage does goal of less than or equal to 100 Rem and actual performance during 2R13 of 84 Rem. DCPP does not consider 84 Rem to be a ‘stretch goal,’ and confirmed that none of the goals were so categorized.
The major scope items to be addressed during 1R14 include the following. The items marked with an asterisk (*) are considered to be relatively high radiation dose jobs.
- Containment Sump Modification*
- 4kV Vital Bus “F” Hinge Wire & Cable Replacement
- Reactor Coolant System (RCS) Batch Make-Up Integrator Replacement
- Centrifugal Charging Pump Installation
- Auxiliary Saltwater (ASW) 1-2 Pump, Motor & Concrete Work
- Main Feedwater Flow Accelerated Corrosion/Piping Replacement
- Main Bank Transformer (Cooler Replacement)
- Auxiliary 1-1 Transformer Bushings
- Service Cooling Water (SCW) Chemical Cleaning
- Reactor Coolant Pump (RCP) 1-1 10-year Inspection*
- RCP 1-1 and 1-3 Seal Replacement*
- Steam Generator (U-1) Replacement Activities*
2006 Radiological Release Report to NRC
DCPP submitted the 2006 Annual Radioactive Effluent Release Report to the NRC on April 27, 2007. The report describes the quantities of radioactive gaseous and liquid effluents released from the plant during the period of January 1 through December 31, 2006. The report also includes the dose due to release of radioactive liquid and gaseous effluents.
The charts showed liquid mixed isotopes discharged in calendar years 1998 to 2006 and airborne gases from 1995 to 2006. There were no unusual or unexpected discharges during the year 2006. In all cases, the plant effluent releases were well below Technical Specifications limits for the year.
Based on radioactive releases, the following radiation whole body doses to a theoretical “maximum exposed individual” for the year 2006 were as follows:
| Effluent Type | Calculated Radiation Dose | Percent of Tech. Spec. Limit |
|---|---|---|
| Liquid | 0.0096 milliRem | 0.32% |
| Gaseous | 0.0002 millirad | 0.04% |
| Direct | 0.0031 milliRem | 0.001% |
2006 Radiological Environmental Operating Report
DCPP submitted its 2006 Radiological Environmental Operating Report to NRC on April 27, 2007. This report contained results from the Radiological Environmental Monitoring Program (REMP). PG&E reported no unusual findings from plant operations. The ambient radiation levels in the DCPP environs did not change and were within the pre-operational range. No plant-related radionuclides were detected in surface water samples. Food crops and milk sampled showed only naturally-occurring radioactivity.
No plant-related radionuclides were detected in surface water samples except that Nickel-63 was detected on one water sample collected at Diablo Cove and Iron-55 was detected in one water sample at the plant outfall. All other surface water samples contained only naturally-occurring radionuclides. Groundwater samples showed concentrations of Tritium beneath the DCPP power block. These concentrations were well below the EPA drinking water standard of 20,000 pico-Curies per liter.
DCPP did not have any unusual or unexpected discharges in 2006, and the plant effluent releases were well below Technical Specification limits. The plant environmental sampling program showed no unusual concentrations of plant-related nuclides.
Three-year weighted industry waterborne mixed release data appears as follows:
This puts DCPP just into the fourth quartile, although the numbers are all small, and no water discharges from DCPP go to domestic water supplies. Compared to NRC 10CFR50 Appendix I which permits 5 milliRem (mRem) per year dose to the most-exposed member of the public, DCPP’s releases are calculated to generate 0.02 mRem. DCPP’s water mixed-activity releases have steadily decreased since 1997, although not as fast as the industry. Many other nuclear plants have installed advanced filtration to lower water mixed-activity releases, primarily Antimony, and to a lesser degree, Cesium, in colloidal form. DCPP plans to add connections to its water processing systems for mobile advanced filtration in 2008.
Tritium levels surrounding DCPP do not appear to be a concern. Low levels of Tritium have been detected in a building foundation sump but not in any of 36 surrounding environmental sampling locations. Notwithstanding this, all surface and ground water on the site leads to the Pacific Ocean and not to any domestic water supplies. DCPP radioactive liquid releases are in the industry fourth quartile; however, they are small fractions of regulatory limits and PG&E plans to add additional processing to further reduce discharges. Environmental sampling has shown no unexpected levels.
2005 Radiological Release Report to NRC
DCPP reported the 2005 Annual Radioactive Effluent Release Report to the NRC on April 24, 2006. The report describes the quantities of radioactive gaseous and liquid effluents released from the plant during the period of January 1 through December 31, 2005. The report also includes the dose due to release of radioactive liquid and gaseous effluents.
The charts showed liquid mixed isotopes discharged in calendar years 1998 to 2003 and airborne gases from 1995 to 2003. There were no unusual or unexpected discharges during the year 2003. In all cases, the plant effluent releases were well below Technical Specifications limits for the year 2003.
Based on radioactive releases, the following radiation whole body doses to a theoretical "maximum exposed individual" for the year 2005 were as follows:
| Effluent Type | Calculated Radiation Dose | Percent of Tech. Spec. Limit |
|---|---|---|
| Liquid | 0.0017 milliRem | 0.057% |
| Gaseous | 0.0002 millirad | 0.018% |
| Direct | 0.0046 milliRem | 0.0009% |
DCPP submitted its 2005 Radiological Environmental Operating Report to NRC on April 28, 2006. This report contained results from the Radiological Environmental Monitoring Program (REMP). PG&E reported no unusual findings from plant operations. The ambient radiation levels in the DCPP environs did not change and were within the pre-operational range. No plant-related radionuclides were detected in surface water samples. Food crops and milk sampled showed only naturally-occurring radioactivity. Several samples of algae from Diablo Cove showed various levels of plant-related nuclides at or near the minimum level of detectability in a random fashion. One mussel sample and one kelp sample from Diablo Cove contained small levels of Zinc-65; however, this was expected. Two fish samples contained small concentrations of Cesium-137, considered not unusual because of the routine nature of fish world-wide to accumulate this isotope from past nuclear weapons tests. There were no increasing trends of plant-related nuclides.
DCPP did not have any unusual or unexpected discharges in 2005, and the plant effluent releases were well below Technical Specification limits. The plant environmental sampling program showed no unusual concentrations of plant-related nuclides.
4.10.3 Conclusions and Recommendations
- Conclusions:
- DCPP appears to be controlling plant radiation releases well in maintaining them within small fractions of Technical Specification limits. It has lowered its collective plant personnel radiation doses by aggressively pursuing radiation source term reductions and improved work practices without evident reductions in outage work scope.
- Recommendations: None