ML20198D037
| ML20198D037 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 05/15/1986 |
| From: | Fiedler P GENERAL PUBLIC UTILITIES CORP. |
| To: | Martin T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737 NUDOCS 8605230109 | |
| Download: ML20198D037 (10) | |
Text
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GPU Nuclear Corporation Nuclear
- = = : 8: 388 Forked River, New Jersey 08731-0388 609 971-4000 Writer's Direct Dial Number:
Thomas T. Martin, Director Division of Radiation Safety and Safeguards Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406
Dear Mr. Martin:
Subject:
Oyster Creek Nuclear Generating Station Docket No. 50-219 Response to Unresolved Items, Inspection 86-01 The purpose of this correspondence is to respond to the unresolved items contained in the subject inspection report dated February 18, 1986.
Attachment I contains those items found to be deficient and our responses to those findings. Also included is our estimated time schedule for completing these items.
Should you require any further information, please contact Brenda Hohman, Oyster Creek Licensing Engineer at (609)971-4642.
Very truly yours, T.
ter M edler Vice President and Director Oyster Creek PBF/BH/ dam (0178A)
Attachment cc: Dr. Thomas E. Murley, Administrator Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406 Mr. Jack N. Donohew, Jr.
U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue, Phillips Bldg.
Bethesda, MD 20014 Mail Stop No. 314 g52ggggggg, O
PDR NRC Resident Inspector Oyster Creek Nuclear Generating Station GPU Nuclear Corporation is a subsidiary of the General Public Utilities Corporation I
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- L 1
ATTACHMENT I I'
Responses to Unresolved Item 86-01-03 i
Finding:
A..
The' licensee should demonstrate that the current upper range capability of the installed gas monitors would not be exceeded in a worst case accident.
Response
t A.
The current upper range capacity of the installed high-range gas monitor will be calculated to be sufficient to monitor a worst case design basis accident. The design basis accident releases 100 percent of the noble gases and 25 percent of the halogens in the reactor fuel to the drywell. These species then leak into the secondary containment at a rate of 1 percent per day. The worse case accident occurs when the loss of off-site power reduces the flow of air used to dilute the standby gas treatment system's discharge.
i Air dilution for the Standby Gas Treatment System (SGTS) discharge is provided by the Turbine Building Ventilation System (TBVS). The TBVS is powered by a bus which may be loaded onto the diesel manually by the operator following a loss of offsite-power. The availability of TBVS air is assured during an event that produces a high concentration of radioactive gas in the plant vent effluent because operators will be procedurally required to verify TBVS operation or to place it in operation whenever the RAGEMS low range gas monitor produces an upscale alarm. The only case in which the TBVS dilution is not available is if there has been a single failure, such as the e
failure of one of the two emergency diesel generators. This approach is consistent with the design philosophy embraced by NUREG 0737.which l
requires the post accident radiation monitoring system to be highly reliable but does not require it to be redundant.
The air dilution provided in the plant stack is enough to prevent the concentration of radioactive gases from exceeding the upper range limit of the RAGEMS high range gas monitor. The discharge of the i
SGTS is 2600 cfm and it is diluted by the TBVS which has a flow rate of 69000 cfm. This gives a dilution ratio of 26.5:1. A calculation of the concentration of radioactive gases expected to be in the plant vent discharge following a design basis accident has been made. From the results of this calculation and the available dilution factor for l
the SGTS discharge it can be calculated that the maximum concentration of radioact; ve gas that may be present in the plant stack effluent is 3.3x10-uci/cc. Furthermore, in the extremely l
improbable case in which all air dilution is lost the concentration 1
in the stack effluent is approximately 9 uci/cc. This concentration is well below 1x103 uct/cc, which is the upper range limit of the currently installed RAGEMS high range gas monitor.
i
. ~. -
Finding:
B.
Calibration over multiple decades using transfer sources of varying energy should be performed. The results should be incorporated into the dose assessment function.
Response
B.
The high range gas monitor is to be calibrated using a combination of calculation and measured response to radioactive gas.
The energy response of the monitor is to be determined in a two-step process. The first step involves calculating the response of the monitor, taking into account geometric factors, the effect of shielding by monitor components, and the energy dependence of the ion chamber (detector) as described by its manufacturer. The second step is the measurement of the monitor's response to various concentrations of Xe-133. This directly establishes a Xe-133 calibration for the monitor.
In addition, the response of the monitor can be used to establish the relationship between a radioactive gas and the calculated energy dependent monitor response discussed above. This will produce a scale which converts the calculated relative monitor response into a calibration curve for the range of energies originally considered.
The radioactive gas measurement can also be used to establish the background current of the ion chamber.
Another important parameter to determine is the response of the high range gas monitor to l
radiation incident to the outside of its shielding. This is best calculated because very large dose rates will be necessary to make direct measurements.
The energy dependent calibration curve can be used to determine the
[
response of the high range gas monitor to any radioactive gas.
Since the response of the high range monitor to any radioactive gas can be found, it is possible to correct the monitor's measurement to Xe-133 equivalency at any time after an accident. This can be done because the relative proportion of various radioactive gases is fixed at the time of reactor shutdown and given the composition of the gas it is possible to calculate the monitor's response.
If core equilibrium is assumed for a starting gas composition, then a curve of Xe-133 equivalency can be prepared as a function of time. The result of this calculation will be used with the gas composition to provide a dose assessment function.
This is scheduled for completion prior to restart from 11R outage.
Finding:
C.
A low range monitoring capability should be installed on the turbine building monitor or it should be demonstrated that it is not required.
I
Response
C.
A low range radioa:tive gas monitor will be provided for the turbine building RAGEMS.
This is scheduled to be completed during Cycle 11 operation.
Finding:
D.
The overlap of the high and low range monitors should be demonstrated.
Response
D.
The overlap of the ranges of the high range gas monitor and the low range gas monitor will be demonstrated by the calibration of these monitors. The lower range limit of the high range monitor will be found by calibration. The upper range limit of the low range monitor will be extended into the non-linear region until a one-decade overlap is achieved.
This is scheduled for completion during Cycle 11 operation.
Finding:
E.
A method to deactivate the low range monitor near the upper bound of its dynamic range and to reactivate it when the high range monitor returns to the low end of its range should be devised.
Response
E.
The low range gas monitor will be automatically deactivated if radioactivity beyond its upper limit is detected. A ratemeter will be provided to measure the output of the low range gas monitor. A setpoint will be placed at a level above the upper level of the overlap of the low and high range gas monitors.
If thi; setpoint is exceeded, the high voltage to the low range gas monitor detectors will be automatically turned off.
The high voltage to the low range monitor detectors will be manually restored upon reduction of the high radiation condition.
This is scheduled to be completed during Cycle 11 operation.
Finding:
F.
A study on the effects of other nearby radiation sources on the response of the low range monitor should be made.
1
Response
F.
A study is being made of the effects of various radiation sources on the performance of the RAGEMS low range gas monitors to determine the extent to which shielding is required to protect the performance of these monitors under post accident conditions. The lower the background contribution to the countrate, the better; however, a practical balance between shielding and background countrate must be found.
The significant sources of post accident radiation are being identified and their radiation dose contributions estimated.
Calculations have been made estimating the radiation doses to the RAGEMS buildings from other buildings, the plant stack, and from sources within the RAGEMS buildings. These estimates of the number of curies collected by the sample filters are used with tables of the dose rate per curie of each isotope, as a function of distance, to make estimates of the does rate in the vicinity of the low range gas monitor. Consideration of various filter handling scenarios, i.e.,
short collection period, storage of used filters in the RAGEMS building, or stuck filter will be made. Since the dose rates are based on the spectrum of gamma rays produced by each isotope, the gamma ray spectrum for each isotope is available for possible shielding calculations. The dose rates from all sources, buf1 dings, equipment, and filters can be added to produce the total dose rate at the low range gas monitor or at any other point in the RAGEMS building.
An additional step in this study is to experimentally evaluate the effectiveness of the low range gas monitor's shielding. These tests will be made using small solid radioactive sources to expose the monitor to several different dose rates from several different directions with recording of the resultant monitor count rates. From this experiemental data, the effectiveness of the monitor's shielding can be found. Since the energy of the incider.t radiction is known, an estimate of the effectiveness of the monitor's rnielding over a range of energies can be made.
The final step in this study is to use the estimated dose rates or gamma ray fluxes and the shielding efficiency to estimate the low range gas monitor's count rate.
If the count rates from some of the dose rate cases reach significant levels, then shielding or an operational change will be considered to eliminate the condition.
This is scheduled for completion during Cycle 11 operation.
Finding:
G.
Additional personnel should be trained so as to provide "round-the-clock" readout of the effluent monitors or a simple readout should be provided to the control room operator.t
Response
G.
Additional personnel will be trained to provide around the clock fon chamber readout capability prior to startup from the 11R outage.
Finding:
H.
Routine calibration and maintenance procedures should be provided and training to the operational personnel be accomplished, such that normal surveillance of the RAGEMS will be performed.
Response
H.
Appropriate procedures will be in place upon startup from the llR
- outage, i
Responses to Unresolved Item 86-01-04 Finding:
A..
An appropriate site specific source term for release of radiofodines should be documented.
Response
A.
Site specific source term for the release of radiofodines is being calculated based on a design basis accident.
In this model 100 percent of the noble gases and 25 percent of the halogens are released into the drywell atmosphere and subsequently leak into the secondary containment at a rate of 1 percent per day. Air leaving the secondary containment is passed through the standby gas treatment system, which has a greater than 90 percent collection efficiency for iodine, before release to the environment.
This is scheduled for completion prior to restart from the 11R outage.
Finding:
B.
The sampling method should be redesigned to increase the sample time to provide a representative sample.
Response
B.
The site specific radiotodine source term is significantly smaller than the generic maximum source terms presented in NUREG 0737. Using these source tems it is possible to calculate the accumulation of radiofodines on the sample filters and to estimate the' radiation dose to personnel handling the filters and the ability of on-site equipment to analyze their content. From these data a minimum time and/or flow throughout will be detemined that will provide a representative sample.
This is. scheduled for completion during Cycle 11 operation.
Finding:
C.
A procedure to apply appropriate correction factors during non-isokinetic conditions should be provided.
Response
C.
Procedures to apply appropriate corrective factors for non-isokinetic sampling are unnecessary for the RAGEMS. The'RAGEMS unit associated with the plant stack will be able to maintain automatic isokinetic sampling control over the entire range of stack flow. The minimum stack flow is supplied by air exhausted from the turbine building.
This same air is used as the minimum dilution factor in calculations of airborn radionuclide concentrations.
The fans supplying this flow -
can be supplied by the emergency diesels.
2 The RAGEMS associated with the turbine building vents takes air samples from two ducts which will have an operating flow span that will be enveloped by the span of the RAGEMS automatic isokinetic flow control.
Finding:
D.
Heat tracing of the sample lines on vital power should be extended to the sample flow paths within the sampling shacks.
Response
I D.
Heat tracing will be extended to the sampic flow paths within the sampling buildings, up to the halogen sample filter. The power for this heat tracing will be backed up by the emergency diesels.
This is scheduled for completion during Cycle 11 operation.
i Finding:
E.
A comprehensive time / motion and exposure study to insure the GDC-19 criteria can be met for the retrieval and analysis of filters.
r
Response
E.
A time / motion and exposure study will be performed prior to startup from the 11R outage.
Finding:
F.
Appropriate procedures should be provided and the needed training of personnel conducted.
Response
F.
Procedures are presently in place and personnel have been trained in the retrieval and analysis of RAGEMS iodine and particulate filters.
t
Finding:
~G.
Routine maintenance and calibration of the particulate and gaseous radiofodine sampling system should be implemented.
Response
G.
Appropriate calibration procedures will be in place upon startup from the llR outage.