ML20126C102
| ML20126C102 | |
| Person / Time | |
|---|---|
| Site: | Reed College |
| Issue date: | 06/18/1990 |
| From: | Joseph E Pollock REED COLLEGE, PORTLAND, OR |
| To: | Michaels T Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20126B910 | List: |
| References | |
| FOIA-92-35 NUDOCS 9212220360 | |
| Download: ML20126C102 (14) | |
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June 18,1990 Ted Michaels Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555
Dear Mr. Michaels:
Accompanying this letter are two items which we discussed on the phone the other e"" ' * "
day related to 41Ar releases from the Reed Reactor Facility. First is an evaluation of the gaseous releases from the Facility based on a review of some of the chart recorder records from the Gaseous Stack Monitor; second is a revision of the Standard Operating Procedure for the calibration of this monitor. I am simultaneously providing the same information to Bob Carpenter, EG&G Idaho, and to Region V.
The evaluation shows that, if all of the detected activity were from 41Ar, we would be close to the 10CFR20 release limits at the point of release,10, within the stack itself.
However, I believe that much of this activity is 16N based on the rate at which a pseudo equilibrium is reached in the stack air, the rate at which the activity drops after a short reactor operation, and undocumented gamma spectra taken in the reactor bay.
Unfortunately, it is not easy to quantify. Never the less, even if the activity eventually proves to be primarily 41Ar, I believe that wo are still within 10CFR20 limits at the point of release because of the conservative assumptions used.
The Standard Operating Procedure version enclosed has now been approved by both of our oversight committees. The version you received from our previous Director dated 4/90 and reviewed was never approved or implemented. I apologize for the handwritten amendments on this version; these changes were requested by the Reactor Operation Committee as part of their approval. I had hoped to have them incorporated before I sent them; I decided to send it in this form rather than delay any longer..
As you will note in these documents, the selection of alarm set points is no longer directly tied to 10CFR20 release limits. The reasons for this are discussed above and in the evaluation. We are committed to working this summer to evaluate the contribution of 16N to the readings on this monitor. We are not requesting that we be f
allowed to consider dispersion or decay in demonstrating compliance with 10CFR20
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Tod Michaels-Jurle 18,1990 Page 2 -
because we believe we are in full compliance at the point of release without these, and we do not believe that any restrict ons on reactor operation are warranted.
If you have any questions concerning this matter please contact me at (503)777-7222.
Sincerely, o,3,u 6W 'l4
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i J. Michael Pollock Acting Director
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B. Carpenter, EG&G Idaho D. Bennett, Provost gScarano, Region V y, Mog,m,ey,,ODOE
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REACTOR Calibration of the FACILITY Gaseous Stack Monitor h319NMGA[9eppn :!?.
Standard Operating Procedure g,, $ ;., (
.%h 31.1 Scope:
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This procedure describes the actions to be taken for calibrating the gaseous stack monitor (GSM), which directly measures the concentration of radioactive gases released to the environment through the air ventilation system.
al.2 Schedule:
The GSM shall be calibrated once every sh months and at intervals not to exceed seven and a half months. The establishment of isokinetic stack sampling contained in this SOP shall be completed within one month prior to completion of the calibration.
31.3 Personnel Requirements:
Any individual designated by the Reactor Supenisor or the Director may calibrate the * '"""
GSM. A licensed operator is required for the irradiation of the gold and argon samples. An individual trained in the use of the gamma spectrometer will be needed to measure the activity of the gold foil.
31.4 Prerequisites:
31.4.1 The following equipment should be availabic; hokmetic Sampling airflow transfer standard transfer standard calibration curve in Stack Log duct tape ladder for access to side of stack.
scale (centimeter) masking tape weau GSM Calibration digital thermometer small portable source such as a beta check source argon gas gold foil or wire two 24 ram polyvials 2 hypodermic syringes 2 rubber stoppers, one with a hole containing a rubber septum a water bath a complete and signed irradiation request form for irradiating argon and gold insulated screwdnver suitable for adjusting the liv 31.4.2 A startup shall be completed.
SOP 31: Calibration of the Oaseous Stack Monitor, Page 1
4$
in 0.5 cfm increments to 8.5 cfm (or maximum attainable flow), then begin l
I lowering the Dow in 0.5 cfm increments back to 4.5 cf m. After each change, be sure that the new Dow reading is stabillud. Tum off the pump and remove the i
l transfer standard from the stack monitor now circuit. Leave the pump off.
31.7.0.8 Insen the transfer standard into the system at the inlet from the stack.
Again, make sure that the transfer standard meter is vertical, and use duct tape to i
seal the connection. Start the pump, set the Dow rate to 6 cfm and note the reading i
on the transfer standard. If the reading is less than 80% of the reading observed in 31.7.0.7, there may be a leak in the system. Stop and inform the Reactor Supervisor or the Director. Otherwise, lower the air flow rate to a reading of 4.5 s
cfm on the transfer standard and repeat the air Dow calibration as performed in 31.7.0.7 above. Record all values on the Stack Monitor Air flow Calibration Data Sheet (Appendix A).
i 31.7.0.9 Values for each of the above calibrations shall be plotted and a least-squares fit, which includes a determination of the slope error xrformed on the data.
These values shall be entered, as indiented on the Data Recorc Sheet, and the total.
measurement errors determined as given on that sheet. Record the cumulative error (Ev) and, if this value exceeds 20%, the procedure shall be suspended and the Supervisor shall be notified.
31.7.0.10 Using the latest transfer standard calibration curve in the Stack Monitor Log, and the data in Appendix A, calculate the setting on the stack monitor pump gauge which corresponds to the "true" stack'shmpling riite"calebthealn 31.7.0.4 " ' '
above. Set the airDow reading to this value or to the maximum Dow rate of the pum Record the actual settmg in Appendix B.
p w ua::quet a 31.7.0.11 Update Air pump sticker on pump.
r,3n a o.a rw.w 31.7.1 Zeroine the meters:
3 31.7.1.1 Turn off the high voltage by unplugging the GSM.
.pt d 31.7.1.2 let both meter needles settle to their lowest poin g-et 31.7.1.3 Using the insulated screw 'ver, tum the small r, crew on the front of the meter so that the needle now rests a ze p
,o u t.gie.
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31.7.1.4 Adjust the chan meter @ using the zero adjustmeng which is undemeath the takc up rollin the chart paper box.
31.7.2 Hich Voltace Plateau-31.7.2.1 Note in the Main Log that the GSM will be out of service ifit has not already been so noted.
31.7.2.2 Remove the GSM probe from the shielding chamber up in the loft. Place the probe on the floor being careful not to cause any damage. Plug in the GSM.
31.7.2.3 Place the small beta check source near the probe tip close enough to register 5000 cpm on the GSM meter.
31.7.2.4 WARNING, HV can be dangerous; see Precautions section 31.5.- Using the insulated screwdriver, adjust the high voltage by turning the small trimpot in the front middle of the IC board. Start with the voltage tumed all the way dowrt.
(clockwise). Turn the trimpot counterclockwise by one division marted off on the SOP 31: Calibration of the Gaseous Suck Monitor, Page 3
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31.7.3.11 After waiting at least three hours for the Ar 41 to decay, examine the GSM chart reconfer graph and determine the count rate,in epm, at end of bombardment and the background count rate prior to injection.
31.7.3.12 Remove the rubber sto rs from the stack chamber. Replace the hoses, making certain they are tig y fastened. Tum the stack sampling pump back on, and note in the Main 1.og that e GSM is back in service.
31.7.3.13 Determine the activity "A" of the gold foil using the gamma spectrometer Record the activity in the 411 kev photopeak.
s 31.7.3.14 Retum all equipment to where it was found. The gold foil shall be stored in the safe.
31.7.4 Data Analysis (pW.11 LJ. - AyJ.'s 0) 31.7.4.1 Determine the activity of the Au 198 at time of EOB using:
A A
EOB " e.w M
knowing the gamma count on the Au 198 activity (corrected for detector efficiency), the decay constant for Au 198, and the time interval between EOB and counting.
m.-.e 31.7.4.2 Having deteisirsd thiictlfity of the gi>1d foil fridps at end of bombardment (EOB), calculate the neutron flux during the inadiation:
$ = No(1 e h)
(31.2) 31.7.4.3 Use this to calculate the exact quantity of Ar 41 activity present at end of bombardment:
A r'= N r $ c(1-e b)
(31.3)
A A
Assume an ideal gas, correcting for both the water vapor pressure (as per 31.7.3.4) and the isotopic abundance,of the Ar-40. He unit of Ar-41 activity, A rin A
microcuries,is computed from AAr'in dps.
31.7.4.4 Determine F, the ratio of microcuries to e by V, the volume for the GSM chamber (755ml). pm for the GSM probe divided F=^[
(31.4) i Multiplying this constant by the epm reading on the monitor will give the rmerocuries per ml being released by the stack.
l 31.7.4.5 The failsafe and alann set points are calculated as given in Appendix B, and are based on the release of argon-41.
31.7.5 Set the failsafe and alarm set point using the beta check source and by proceeding to remove the GM tube from its shield as per the procedure in 31.7.2.1 and 31.7.2.2. Ren, use the trip set dials inside the GSM ratemeter box to set the trips. Next, unplug the GSM and rerum the GM tube to its shield. Finally, plug in the GSM and note in the Main Log thn it is back in service.
SOP 31: Calibration of the Gaseous Stxk Monitor. Page 5 l
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ry X A,ST_4. CK MQNRQRAIR FLOW C6 LIBRA 710RDATA SHEET 1
Date
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Data for determininemek air now velocities (31.7,0.2):
Point Distance Velocity 1 Velocity 2 Average from wall (fvmin)
(fvmin)
(fvmin)
(cm) 1 0.5 2
2.5 3
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8.5 5
12.0 6
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Calculate Avermee Flow Velerity by averaging velocities at each point. Average velocity; fvmin Ca}culate Averace Stati Flow Rnte:
Average stack flow rate - Average velocity x 0.35 ft2-cfm C
ine Velocity (Average of 2 reaings at point 4*)(31.7,0.3):
fVmin Catrulate Reonited Strk Samn!ine Inm Flow Rate (31.7,0.4):
- (1/2DN )2
- vC Vsl 12 wtat DN - Sampling noule diameter in inches Vc - Centerline velocity
- 1.14 x 10 3 x Vc cfm e
l e
Jek 54 se, htg o
Jena- }
Draftd5/ttt90- 6f10 p'I g
Calculation of Analvtical Uncertainty in Determinntion of Flow Rate (31.7.0.9):
Ev. (( Es) + ( E )2 )1/2 t
wtere Es. Error in measuring flow rate
- Uncertainty in least squares fit of data points (from ChemGraph, or similar program)
Et - Error in readmg of transfer stardard - 2.5%
Ev -
< 20 %
yes / no 7
$g1 Air Flow to Assure ho k.inetic Samnling (31.7.0.10):
Stack Monitor Pump reading wten 'True' stack air flow equah Vat:
AirCow it inlet from the stack set:
Al: Flow Sticker on Stack Sampling Pump updated:
Date completed By signature Date reviewed By supervisor review signature 1
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I emf: cf 5/1h90r s
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Data Analysis:
Cakulate the activity of the Au foil (from the vial used) from the gamma spectrometer t -
Detector Ef0ciency(Ef1)-
E (Sc.c. vae + cJ4M-Ala danuary 1990' and'hompares' to' '
4.4 x10-8 and 8.6x10-9 in the two previous annual determinations.
- 4) Activities are measured at the point of release from the stack with no dilution, dispersion, or decay included.
- 5) Gaseous Stack Monitor chari records for six operations were examined The dates of these were 10/25/89, 10/31/89, 11/1/89, 12/11/89, 1/24/90 and 2/6/90.
It would not be easy with our present setup to determine actual releases in total or
'"real" averages.
Releases considered include operating times ranging from 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br />, w;th the pneumatic system both on and off.
The primary was operating in all cases, however, during the power calibration in January, release levels were not significantly different.
Although a " average" concentration is discussed, the ranges of values are also given.
CALCULATIONS:
1)
Data are taken from the attached graphs.
Backgrounds were estimated for a couple of hours prior to beginning of operation and releases are considered until background ranges are reached.
Releases are calculated in units of com-hr where epm - operating level background level.
In several cases, the reactor operation is divided into several sections to facilitate estimation of release levels.
The concentrations were then adjusted by the reactor power level to obtain releases in epm br/kWh.
Date cpm br kWh c.pIlila
" Rabbit" kWh 10/25/89 335 1900 0.17 on 10/31/89 40 336 0.12 on 11/1/89 445 1680 0.27 on 12/11/89 188 1640 0.11 on for I br 1/24/90 60 237.5 0.25 off 2/6/90 60 483 0.12
, off
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a) The top of the stack is not easily accessible to members of the public. They stated that, if it would require the use of a ladder to reach, it would not be considered easily accessible, b)
A Safety Analysis be prepared demonstrating that 10CFR20 limits would be achieved at any point accessible to the public, c) Calculation methods for radiation doses be performed following methods used by other facilities in already approved Safety Analysis Reports and/or approved calculation techniques such as those contained in NUREG-0851, Nomograms for Doses from Finite Noble Gas Clouds.
4)
Calculations for doses from a 'still air, semi infinite cloud model," which were prepared by L. Ruby and reviewed by S. Herbelin and D. Griffiths, appear as.
They closely follow the Safety Analysis Report calculations from U.C.
Berkeley and would allow releases up to 11.6 times MPC. NUREG-0851 is not easily adaptable to the present case since it includes only stack beights of either 0 or 100 meters and calculates doses at distances of 250 m, 500 m, and more from the base of the stack. The case of a stack of zero height and a distance of acro, which is not included, reduces to the still air model above. The case of a stack height of 0 and a distance of 250 m allows consideration of meteorological conditions averaged over the year and is complicated to evaluate.
As a minimum, consi alone would reduce the^ concentration,' and" bence the ', dose,,deration_of glad direction m, y, at any point selected by considerably more than the factor of 2, mentioned in Conclusion 1.
5)
Although related, the choice of an alarm point on the Gaseous Stack Monitor need not be a level which equates to a specific regulatory limit.
Specifically, the previously used criteria based on releases occurring for four hours per week at a
level which, when averaged over a year would equal MPC ignores the possibility of significant additional operation just below the limit.
On the other hand, setting a value so low that the alarm sounds frequently, results in an attitude among operators that alarms can be ignored.
6)
In the past two annual reports, the Reed Reactor Facility has reponed argon releases by comparison of our operations to those at OSU. The factor used from OSU is equivalent to 7.4 x 10 3 Ci/MWh of operation.
The assumption of 38 MWh/yr used in this analysis, results in an estimated release of about 0.3 Ci/yr.
If, in fact, about 50%
or more of the 0.87 Ci/yr estimated above is 16N rather than dl Ar, these independent estimates are in moderately good agreement.
RECOMMENDATIONS:
- 1) That the Radiation Safety Committee adopt the proposed revision to SOP-31 which includes the use of an arbitrary factor of 4 in determining the alarm setpoint.
This level will assure the facility that unanticipated releases will be detected while not producing alarms during nc rmal operations.
2)
That the RSC instruct the Acting Director to continue maintaining a running record of gaseous releases from the facility based on gaseous monitor chart recordings and to report the results to the committee regularly.
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