ML20197J452
| ML20197J452 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 04/11/1985 |
| From: | Muller D Office of Nuclear Reactor Regulation |
| To: | Jordan E, Scarano R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V), NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| References | |
| CON-WNP-0796, CON-WNP-796 TAC-55288, NUDOCS 8504220324 | |
| Download: ML20197J452 (22) | |
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DISTRIBUTION:
M ppg 7 y 1933 RAB READING FILE AD:RP FILE MEMORANDUM FOR: Ross A. Scarano, Director Division of Radiological Safety and Safeguards Programs, Region V Edward L. Jordan, Director Division of Emergency Preparedness and Engineering Response, I&E FROM: Daniel R. Muller, Assistant Director for Radiation Protection, DSI
SUBJECT:
EMERGENCY RESPONSE FACILITIES APPRAISAL AT WASHINGTON NUCLEAR POWER, UNIT 2 (TAC N0. 55288)
During the week of 25 March 1985 a dose assessment team provided by the Division of W tems Integration appraised the Emergency Response Facilities (ERF) at Washington Nuclear Power, Unit 2 (WNP-2). This memorandum summaries their findings during the appraisal.
In reviewing the dose assessment capabilities at WNP-2, the staff used the guidance contained in Draft I&E Inspection Procedure 82212, " Emergency Response Facilities, Revision 5." The staff found that the dose assessment capability at the ERF at WNP-2 is generally adequate. No deficiencies or open items were noted. However, several items of improvement were identified by the staff.
Among these items are better source term determination, comprehensive documentacion of the validatio~n and verification of the computer models used, and modification to the atmospheric dispersion projection capabilities. These and other items of improvement are detailed in Enclosures 1 to this memorandum.
In addition, Enclosure 2 summarizes our observations and findings regarding the dose assessment capabilities at the Technical Support Center and Emergency Operations Facility for use in the ERF appraisal report.
This review was performed by E. Markee, METB, M. Wangler, RAB, and n. Wohl, AEB.
Origirmi signed by 1
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^WDaniel R. Muller, Assistant Director for Radiation Protection k0324850411 DOCK 0500039 Division of Systems Integration VDiL y V '
Enclosures:
As stated
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F. Congel W. Gammill L. Hulman E. Branagan L. Soffer I. Spickler E. Markee M. Wangler M. Wohl R. Fish, Region V G. Temple, Region V E. Williams .
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ENCLOSURE 1 Items for Improvement The following findings summarize desirable improvements in the dose assessment capability at the WNP-2 Emergency Response Facilities (ERF).
Source Term
- 1. Establishment of methods for defining plausible unmonitored release pathway source terms including possible means of estimating isotopic distribution and flow rate to the environment, along with recommendations for assuming ground level, elevated, or mixed-mode releases for these pathways. .
- 2. Correction of the error in the F-factor curve for I-131 decay in Nuclear Performance Evaluation Procedure 9.3.22 (Figure D-1).
- 3. Establishment of a severe accident source term / dose assessment implementation capability.
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l Meteorology
- 4. Reorientation of the temperature aspirator shield openings on the meteorological tower to point north instead of west.
- 5. Improvement of the annual joint data recovery of wind direction, wind speed, and vertical temperature difference on the primary tower to exceed 90%.
- 6. Improvement of the primary and backup EDPS models by including the effect of building wake mixing, by deleting the mixed mode effective plume height formulation and by including atmospheric dispersion rates based on experimental data form the Hanford Reservation.
- 7. Inclusion in EPIP 13.8.2, Manual Offsite Dose Calculations, a methodology for reading average (e.g. 15 minute) conditions from the strip charts indicating meteorological parameters.
- 8. Installation in the control room of strip chart recorders for meteorological parameters from the backup tower.
- 9. Improvement of the primary EDPS dispersion model to include calcul.ation of variable trajectories in time and space, to make
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diffusion estimates during calm wind conditions, to limit plume travel during a given time interval, and to accumulate doses.
Dose Assessment
- 10. Modification of the GDS to include, in addition to the classi-fication indicator, a display of doses continuously calculated at the EAB or some other explicit indicator of the basis, and additionally, provision for overriding the classification if other plant conditions do not indicate a more serious classification.
- 11. Modification of the main EDPS programs to prevent abnormal .
termination of execution when incompatible data are used.
- 12. Further training for TSC personnel in the use of the main EDPS program.
- 13. Review and modification of MES01/GASPAR to incorporate decay and depletion of radionuclide in transport from the release point
- to the receptor location.
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- 14. Improvement of documentation for the verification of the main EDPS programs.
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- 15. Systematic verification and documentation for the backup micro-computer program.
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ENCLOSURE 2 1.2.4.2 Dose Assessment at the Technical Support Center Dose assessment capabilities in the Technical Support Center (TSC) and Control Room (CR) are provided through the Emergency Dose Projection System (EDPS).
The EDPS is a set of computerized models that may be used to calculate radiation doses from radioactive materials released in gaseous effluents during an accident. Doses to the whole body from plume exposure, to the thyroid from inhalation of radioiodines, and to internal organs from ingestion of contaminated food are available. In the TSC 2 of the computerized models are available, a main computer system that calculates whole body and thyroid doses, and a backup battery-powered microcomputer system (Radio Shack TRS-80) that performs calculations similar to the main system. Calculations of the whole body and the thyroid doses at the Exclusion Area Boundary (EAB) are continuously made by the main EDPS without intervention and are displayed on the GDS system as an indicator that classifies an emergency.
l The following meteorological data are directly available to the EDPS from the primary tower: wind direction, wind speed and sigma theta at the 10 and 75 m levels, vertical temperature difference between the 10 and 75 m levels, dry l bulb temperature and dew point temperature at the 10 m level, and precipitation l
, near ground level. Also, data for wind direction, wind speed and sigma theta l
l at.the 23 m level and dry bulb temperature and dew point temperature at the 10 i
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m level are directly available to the EDPS from the backup tower. Redundant and/or backup power is available to both towers. All of the onsite meteorological data are available from the GDS. In the event that site meteorological data are not available, EPIP 13.8.2, Manual Offsite Dose Calculations instructs that weather information can be obtained from the PNL Weather Forecaster at the Hanford Reservation and from the National Weather Service Forecaster at Portland, Oregon. Based on meteorological data presented at the appraisal for the calendar year 1984, during which the joint data recovery of wind direction, wind speed, and vertical temperature difference from the primary tower was 88%, it is indicated that the historically reliable indication of meteorological variables may be marginal. However, due to the fact that the licensee has an acceptable instrument surveillance and calibration program and the capability to utilize an equally reliable backup measurements systems, the reliability of obtaining onsite meteorological data is acceptable. An inspection of the meteorological tower during the appraisal revealed that the temperature aspirator shield openings are pointed toward the west. According to ANSI /ANS 2.5-1984, the openings should be point toward the north to minimize the chance of reflected sunlight influence on the temperature sensors.
During an emergency the EDPS is used by TSC and CR personnel only for a short period of time. The EOF is staffed during an emergency at about the same time as the TSC and has the primary responsibility for assessing doses and recommending protective actions during an emergency. Thus the dose assessment functions will quickly transfer to personnel in the E0F. For this reason l
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specific EDPS capabilities are described in Section 3.2.4.2, Dose Assessment at the E0F.
Although the use of the EDPS in the TSC and the CR is limited, the NRC staff did find that the dose assessment capability at the TSC and CR is generally adequate to respond to accident. The NRC staff noted 2 areas for improvement.
In the first area CR and TSC personnel did not seem to be cognizant of the continuous dose assessment at the EAB. It is therefore recommended that a readout of the whole body and thyroid doses or some other more explicit indicator be displayed in the GDS system in addition to the classification indicator.
The second area for improvement involves the main computer system. In several instances abnormal termination of program execution was observed. This condition was apparently caused in part by the use of incompatible input data, e.g. use of predictive effluent data and actual meteorological data. The abnormal termination necessitated the assistance of a second party to reset the system. This necessity may seriously affect TSC and/or CR response during an emergency when the EDPS may be used. We understand that the problem has been identified and is being corrected. It is recommended that high priority be given to the problem and corrected as quickly as possible.
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1.2.7 On-shift Dose Assessment During the appraisal personnel in the CR and the TSC were observed in their use of the EDPS. CR personnel used the backup, battery-powered microcomputer as described in EPIP 13.8.2, Manual Offsite Dose Calculations; personnel in the TSC used the main EDPS computer program as described in EPIP 13.8.1, Offsite Dose Calculations. Each individual was presented with a problem and was as.ked to make a whole body and thyroid dose calculation at the EAB.
For manual offsite dose calculations, EPIP 13.8.2 provides procedures for obtaining meteorological data for insertion into the backup EDPS computer program on the TRS-80 microcomputer. The procedures states that data can be obtained from the GDS, or by telephone from the PNL Weather Forecaster or the National Weather Service Forecaster in Portland. The use of strip charts indicating meteorological parameters measured at the primary tower in the control room is not addressed in the procedure. Since it is likely that information from the strip charts will be used for manual calculations, the procedure could be improved by including a methodology for reading average (e.g., 15 minute) conditions from these charts, the units of measurements, and any conversion factors. Also, consideration should be given to installation of strip chart recording of meteorological parameters from the backup tower.
For the observation in the CR then no GDS displays were allowed to be used. It was observed that CR personnel retrieved the appropriate information from other control room indicators for source term and meteorological data for input into
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I the backup computer program and performed the necessary calculation with little trouble. For the observation in the TSC the main EDPS program with effluent (nonitor input was exercised. Here personnel had some difficulty interpreting the map in 1 square mile grids for the EAB doses. Some further training is i recommended.
The NRC staff observed that in general the licensee has the capability for providing rapid dose calculations with minimal interference in the. response to an accident, and that this capability is adequate to scope the magnitude of the potential impacts. Although the procedures provides for inherent classification of an accident based on the calculation, as indicated in Section 1.2.4.2 an improvement should be made in the GDS to faci?' tate interpretation of the classification indicator.
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3.2.4.2 Dose Assessment in the E0F For the E0F dose assessment procedures are described in EPIP 13.11.14, Meteorology and Unified Dose Assessment Center (MUDAC) Operations. This center is used by the Supply System and offsite authorities to coordinate field team operations, project doses rates, and determine protective actions. As with the TSC the EOF uses the EDPS for dose assessment during an emergency as described in EPIP 13.8.1 and EPIP 13.8.2.
The EDPS is a system of computer programs, effluent monitors, and meteorological instrumentation used to determine radiation exposure from gaseous effluents during an emergency. For the purposes of this section only the dose assessment capabilities as embodied in the computer programs of the system were examined. The system interfaces between hardware, such as radiation monitors, and software, such as a computer program, have been appraised elsewhere.
The EDPS has 3 computer codes available. The first main computer program is used to calculate external whcle body dose and thyroid inhalation doses. This program may use either real time data from effluent and meteorological monitors in the automatic / manual mode or projected data in the predictive mode. The second main computer program is a code consisting of 2 combined computer codes, MES0I, a variable trajectory dispersion model and GASPAR, a dose calculation program using meteorology input from MES0I and manually input source terms.
ThisMES01/GkSPARprogramcalculatesdosesfromingestionofcontaminatedfood.
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L The third program is the backup, battery-powered microcomputer (Radio Shack TRS-80) used in the event that the main computer programs are unavailable.
Like the first main computer program the backup program calculates external
- whole body and thyroid inhalation dosas. The following paragraphs summarize '
some of the features of these programs and staff comments in the 3 major technical areas. '
Source Terms .
Leakage of radionuclides to the environment can take place mainly from the
- Reactor Building, the Turbine Building, and the Radweste Building. The Reactor Building has high, intermediate and low range gas monitors, and normal and high l activity particulate and iodine samplers. The building ventilation flew rates ,
are 97,000 CFM for normal operations for the Reactor Building (4,000 CFM when '
the SGTS is in use), 260,000 CFM for the Turbine Building, and 84,000 CFM for the radwaste building. The source terms (Ci/sec) are computed by coupling the apprcpriate instrument readings (R/hr) to the instrument response factor (Ci/n per R/hr) and the flow rate to the environment (CFM) with filtration factors where appropriate. ,
Source terms may also be determined, in the event of failure of building effluent monitors, from grab semples of the gaseous effluent streams.
Constituent radionuclide determinations of these samples may be perf rmed either in-plant or at the EOF, using an Intrinsic Germanium Detector and an ND 66 computer terminal coupled to an ND 6580 mainframe computer. This system
- d i I identifies gamma peaks in the 70 Kev to 2 Mev energy range with high resolution. Re:ults of the laboratory analyses are stated as individual isotopic concentrations or as I-131 and Xe-133-equivalent concentrations.
Coupling these radionuclide concentrations with the building ventilation flow r6tes, the scurce term release rates are computed.
Additionally, dose calculations may be inade based on samples taken by Licensee and DOE monitoring teams in the field, which can be quickly dispatched. For purposes of data reduction for monitoring team data, a mobile van equipped with a Davidson 1024 tialtichannel Analyzer with Nal detectors is available.
Alternatively, samples may be analyzed in the E0F discussed above. Also available in the field are 12 permanent airborne particulate and iodine environmental monitors, 56 TLD's and 3 PIC's, also to measure environmental radiation.
A method of estimating fission product release fractions from core damage evaluation estimates is embodied in the Plant Procedures Manual, Section 9.3.22, entitled " Core Damage Evaluation". Core damage evaluation by these procedures depends on several plant parameters, including reactor water level, containment atmosphere radiction levels, containment hydrogen concentrations, and fission product radionuclide concentrations in the reactor coolant and containment atmosphere.
In this procedure core water level history is first noted. If the core has been uncovered, fuel or fuel cladding damage may exist. Containment atmosphere
radiation ' levels are the quickest sources of data to estimate core damage in the event of a LOCA. Containment atmosphere hydrogen concentration is an indicator of the extent of clad damage from the amount of Zircaloy-water reaction, producing hydrogen, that has occurred. Water and gas samples of the reactor coolant and/or the containment atmosphere are analyzed for fission product and hydrogen concentration. The presence of radiciodines and cesiums in the coolant and for noble gases in the containment atmosphere is indicative of core damage. The presence of less volatile fission products such as barium, lanthanum, or stror. tium, indicates fuel melting. Additionally, the ratio of concentrations of short-lived noble gas isotopes to Xe-133 and iodine isotopes to I-131 helps in distinguishing between fuel assembly gap and plenum releases dua to clad failure and releases from the core by fuel melt / degradation. The ,
Pcst-Accident Sampling System (PASS) is used to obtain the aforementioned reactor coolant and/or containment atmosphere samples. The staff found and incorrect slope for the I-131 F-factor curve (Figure D-1) of procedures 9.3.22, and recommends that this be corrected.
Although the Reactor Building, Turbine Building, and Radwaste Building leakage ,
pathways are very important, and may cover the majority of pathways from design basis accidents, there are other release pathways that could be postulated in both design basis and beyond-design-basis accidents. An example would be post-LOCA leakage thrcugh a partially failed-open main steam isolation valve. ;
Other unexpected unmonitored release pathways may become manifest during the course of other accidents, such as primary and secondary containment .
penetration seal / integrity breach pathways. Methods for defining a number of
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representative plausible unmonitored release pathway source terms should be established, includino possible means of estimating isotopic distribution and flow rate to the environment, along with recommendations for assuming ground level, elevated, or mixed-mode release. An additional recommendation is that a severe accident source term / dose assessment implementation capability be ,
established. This capability should include assessment capabilities for the
{ generation of offsite radiological consequence estimates for immersion, inhalation, ingestion, skyshine, and groundshine sources for BWR severe accident sequences. These types of analyses are important in generating real-time emergency response actions as described in NUREG-0396 (see, for l example,FigureI-11)andinNUREG-0654.
i Finally, the control room Steam Jet Air Ejector Condenser Outlet Radiation
! Monitor visual display has no physical units designated on it, so that the reading would be useless in the event of a leak in the area.
Meteorology l
Three atmospheric transport and diffusion models are used in the EDPS. On the i backup EDPS a straightline Gaussian diffusion model for a ground level release is used. On the primary EDPS a straightline Gaussion diffusion model with provisions to consider elevated and mixed mode releases, and wet and dry deposition is available. Both of these mo'dels can be considered as Class A models, using the definition of models in Appendix 2 of NUREG-0654. These l models are acceptable for use in the TSC, since only initial assessments 1
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primarily at the site boundary (1.2 miles) will be made from this location, before the enhanced assessment capability is being activated at the EOF.
However, both of these models could be improved substantially. Building wake mixing factors should be included. The errors associated with the mixed mode effective plume height formulation for use during accidents can lead to large underestimates of doses and therefore should be deleted from the model.
Atmospheric dispersion rates based on the experimental data from the Hanford Reservation (i.e. " desert sigmas") should be included in the model.
Capability exists to run a third atmospheric transport and diffusion model called MES01, a variable trajectory Gaussian puff dispersion model, to estimate doses primarily through the ingestion pathway over longer time frames and larger distances than the straightline trajectory models. Currently, the licensee is evaluating whether the MESOI model is an adequate and cost effective approach to satisfying dispersion evaluation requirements.
During the course of an accident, the Meteorology and Unified Dose Assessment Center (MllDAC) will be staffed with a corporate meteorologist and will use the primary EDPS, a straightline model (primary EDPS) and the subjective climatological and terrain input of the corporate meteorologist. To satisfy the requirements to represent conditions up to 10 miles from the plant site, the primary EDPS atmospheric dispersion model should include the capability to calculate. variable trajectories in time and space, to make diffusion estimates during calm wind conditions, to limit plume travel distance during given time intervals, and to accumulate doses. While it is recognized that the corporate
meteorologist will subjectively accommodate this lack of computational capability on the computer, these capabilities should be implemented on the computer since the meteorologist may not be available at the time of an accident.
Dose Assessment As previously indicated the EDPS incorporates 3 dose assessment programs for use during an emergency. The main EDPS and backup EDPS programs calculate external whole body dose and thyroid inhalation doses from subnersion in a radioactive gas cloud. A third program identified as MES01/GASPAR calculates organ dose for 4 age groups from ingestion of contaminated foodstuffs within 50 miles of the plant.
The main EDPS program is used to project doses within 10 miles of the plant.
This program accommodates 13 noble gases and 5 radiciodines. Scurce terms are provided by effluent monitors. Mateorology data is also provided by monitors.
Doses and dose rates to the whole body are calculated using submersion dose factors from Table B-1 of Regulatory Guide 1.109. Thyroid innalation doses assume the child to be the critical receptor. Inhalation dose factors from Table E-9 of R.G. 1.109 and the breathing rate form ICRP Publication 23, Reference Man, for the child are incorporated into the program. The results of '
this EDPS program calculations are presented on a computerized map of the area around WNP-2. This map is divided into a series of 1 mile square grids. These grids are colored according the radiation levels that are calculated at the
t center of each grid. In addition, barely readable values for the actual calculations are presented within each grid. Because of the grid system only individuals experienced in using this program can extract doses at specific distances.
The backup computer programs calculates doses in a manner similar to the main EDPS program. Like the more complex program the backup program will accommodate 15 noble gases and 5 radioiodines. Source terms and meteorology data are entered manually. Unlike the main program this program will calculated doses at a user-specified distance. Thus users should have little difficulty in using the information obtained from this program.
MES01/GASPAR is used to calculate' doses from food ingestion at specified locations in the environment. This program accommodates approximately 35 radionuclides including noble gases, radiciodines, particulates, tritium, and C-14. As with the other EDPS programs, MES01/GASPAR calculates external who.le body doses from noble gases and organ inhalation doses from submersion in a radioactive cloud. In addition, MESOI/GASPAR deposits radioactive materials to calculate external whole body dose from a contaminated ground plar.e and to calculate organ doses from various ingestion pathways, including cow-milk, goat-milk, beef, and vegetation consumption. Eight organs are incorporated into the code. This program as implemented at WNP-2 can be used to direct environmental teams to areas of substantial contamination. However, the use of this program to calculate doses is limited since no consideration of sucn factors as radionuclide decay and depletion of pcrticulates in transport has
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been accomodated. For these reasons the actual environmental measurements more accurately assess the potential impacts of the radioactive plume. Thus it is recommended that MES01/GASPAR be reviewed and modified as appropriate to Supply System needs.
Although the problems identified above may have a potential impact on protective action decision making, MUDAC personnel include a Health Physicist whose knowledge and experience will be used to review calculations prior'to recommendations for protective actions. Additionally, these calculations will be reviewed with offsite authorities also stationed in the EOF prior to issuance of a protective action recommendation. Consequently, the dose assessment methods are generally adequate to meet the needs of the center.
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1 3.3.2.3 Implementation of Mitigating Actions Mitigating or protective .:ction recommendations generally are the responsibility of the E0F rather than the TSC. The Supply System Decision Center in the E0F has the responsibility for implementing mitigative actions I
and coordinating environmental assessments and is supported by MUDAC in this area. Coordination with offsite authorities occurs in the decision center.
The E0F activity in this area is acceptable.
3.3.3.2 Dose Assessment .
The EDPS programs were reviewed in accordance with I&E Inspection Procedure 82207, Dose Calculation and Assessment. Sample calculations were made by WNP-2 personnel and have been checked by NRC staff. Although the check was complicated by the lack of intermediate calculations of radionuclide concentrations, the results indicate reasonable agreement between the models and NRC staff calculations. As mentioned previously, all calculations will be reviewed by trained personnel prior to a protective action recommendation.
In reviewing the models it was noted that the verification of the programs was not well documented. Additionally, the backup EDPS program had not been subject to the same verification program as the main EDPS programs. As a result during the appraisal a flaw in the determination of the atmospheric b
stability in the backup system was identified. It is therefore reconrnended that the model in the backup program be verified and documented.
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