ML19320B964

Final Decommissioning Rept,Or State Univ AGN-201 Reactor License R-51.

ML19320B964
Person / Time
Site:	05000106
Issue date:	07/09/1980
From:	Oregon State University, CORVALLIS, OR
To:
Shared Package
ML19320B961	List: ML19320B960 ML19320B964
References
NUDOCS 8007150562
Download: ML19320B964 (10)

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O FINAL CECC:'MISSIC:! :;3 REFCRT OREGON STATE UNIVERSITY AGN-201 REACTOR LICENSE NUMBER: R-51; DOCKET NUMBER: 50-106 July 9,1980 80077sog Q

I.

Introduction:

Oregon State' University (OSU) wishes to report the completion of the decomissioning of their AGN reactor. This action was conducted in accordance with the March 8, 1979 Order from the U.S. Nuclear Regulatory Comission authorizing dismantling of the facility and disposition of the component parts.

II. Sumary of the Operational Aspects of the Decomissioning:

The operational disassembly of the AGN went very smoothly, and was ccnducted acccrding to a step by step procedure prepared to assure compliance and compatability with the procedures submitted in the OSU Dismantling and Disposal Plan, dated Decemoer 1978. A copy of these detailed step by step procedures marked with completion dates and other operational data (e.g., weignts of certain reactor components), and the reactor supervisor's decommissioning logbook will be kept on file and available for review by NRC personnel. Radiation levels were very '

low and no removable contamination was detected. Radiological aspects of the decommissioning will be summari:sd in section III.

Prior to actual disassembly of the main reactor components, the AGN's two centrol rods and two safety (control) rods were removed from the AGN facility and were placed in storage in one of the TRIGA reactor facility's fuel storage pits. This was in keeping with the approved procedures and was completed on March 14, 1979.

Major reactor disassembly was started on June 16, 1980, and included removal of the thermal column and Ra-Be startup source on that date. .

Upon removal, the source was placed in an appropriately shielded container and transferred to controlled stcrage in the OSU Radiation Center. The core (i.e., the core can) was removed as a single unit, transferred to its separate locked storage container, and moved into the TRIGA reactor room on June 17, 1980. For the remainder of June 17 and June 18 routine disassembly continued, until by the afternoon of June 19, 1980 all disassembly and essentially all final radiological surveys were completed. (The final area release survey was concluded on June 20,1980.) Non-radioactive I reactor components to be removed from the AGN facility for warehcuse storage at OSU (this included all reactor components except the c, ore, the four control rods and the Ra-Be startup source) were crated or otherwise

prepared for removal and storage by June 27, l?80, and all of these components were removed frem the facility and placed in a designated university warehouse by July 1, 1980. By July 2,1980, the exterior

. wall of the AGN facility, which was partly removed to allow removal of the larger components, was reinstated, and the facility was completely free of any AGN reactor components.

III. Sumary of Radiation protection Activities Durino the Decommissionino:

The radiation safety aspects of the entire decommissioning operation were under the supervision of the Radiation Center's Senior Health Physicist.

In addition, as submitted in the OSU dismantling plan, all required services of the existing OSU radiation protection program were available during this operation. As a result, a number of standard radiation protection functions were implemented. These included providing calibrated monitoring instrumentation, protective clothing, waste management, personnel dosimetry devices, assistance in preparing the area for access control and for control of potential radioactive contamination, and the continuous presence of one or more members of the radiation protection staff to carry out necessary radiation evaluations and measurements throughout the entire disassembly process.

All radiation surveys specified in the OSU dismantling plan plus many additional surveys were completed during the course of the decommissioning project. Except for the radiation surveys of reactor components, which were conducted on a continuing basis as the items were disassembled, all key surveys were performed as designated on the step by step detailed disassembly procedures mentioned previously. All radiation survey results .

were recorded and are on file in a master radiation survey logbook for the AGN.decomissioning. In general, results of individual component surveys were recorded on a standard form identical to the one shown in Appendix A, while surveys of special events (e.g., removal of the core) or more detailed surveys of special components (e.g., the core can or the Ra-Be startup source) were recorded on a form like the one shown in Appendix B. Results of all radiation surveys will te available for review by NRC representatives.

Prior to beginning the disassembly, a special controlled access radiation working zone was established within the AGN room. Access i

m v 3-to the room itself was also controlled by keeping the two access doors continuously locked, and by issueing a total of only six keys to the room, one each to three members of the reactor operations staff, and one each to three members of the radiation protection staff, all of whom were directly involved in the decomissioning. Operational checks of the portable monitoring instrumentation to be used and the AGN area /

criticality monitor were made prior to startup and at other times throughout the disassembly process. All equipment performed properly. A continuous particulate air monitor was also operated during tne disassembly process and a portable air sampler was regularly present.

Protective clothing was used by all workers in the controlled radiation work zone and included coveralls, gloves, rubber shoe covers, and hard hats. personnel dosimeters were worn by all participants and inciaded xSyn film badges and y-sensitive pocket dosimeters. TLD extremity dosimeters were also available for use, alcng with a wide range of emergency equipment, including respiratory protection devices and decontamination materials.

The normal area film monitors for the AGN were also in place during the disassembly.

Rsdiation monitoring instruments used during the AGN surveys included portable G'1 survey meters with '.hin windcw (1.5-2.0 mg/ca') panca'Ke style detectors, air equivalent cutie pie ioni:ation chambers, a portable BF3 neutron survey meter, a neutron scintillation (6Lil) rem meter, laboratory gas flow proportional counters, a multichannel analyzer with a Ge(li) detector, a moving filter paper continuous particulate air monitor and a portable air sampler.

Radiation survey procedures for water, air, personnel doses, ard general radiation levels in the AGN facility followed those routinely used at OSU. However, all reactor components were monitored for radioactivity in accordance with specific' procedures, written to address the objectives of the AGN decommissioning. These procedures will be kept on file and available for review along with the other radiological surveillance data, but in general the procedures incorporated the following survey requirements for all AGN components:

a. A direct radiation survey over all surfaces of each specific component, utilizing a portable CM survey meter equipped with a thin windorf (1.5-2.0 mg/cm2 thickness) pancake style detector. (The Ra-Be startup source was exempted from this survey. )

b. Smear surveys of representative 100 cm2 areas on all components showing detectable radioactivity above the normal background level dur!ng the direct survey. (Normally, smears would be required for components showing a gross coun^ ate on the portable GM equal to 1.5 to 2.0 times the normal background count rate for the instrument.)

c. Supporting smear surveys of many components not showing detectable radioactivity above the normal background level during the direct survey. (In this situation, particular emphasis was placed on smearing the surfaces of the apparently non-radicactive components which were in reasonably close proximity to the reactor core.)

d. Controlled storage at the OSU Radiation Center as a radioactive cceponent for all items showing detectable radioactivity above the normal background level due to any of the prescribed surveys (assuming the radioactivity was not later ;emoved by decontamination), and identical controlled storage for any item showing no detectable radioactivity above background during the direct survey, when there is an obvious inabilty to effectively survey all component surfaces. ,

e. Surveyed components with detectable radioactivity not in excess of the normal background are to be tagged and released for campus storage or transfer to an off-campus location.

f. Written records of all radiation surveys are to be kept on the radiation survey report forms shown in Appendices A and B.

The survey procedures also noted that several AGN components were expected to show detectable radiation levels in excess of normal background, due to their known content of radioactive materials. These items were identified as the core can, the control rods, and the Ra-Be startup source. Controlled storage as radioactive components was already g *

% e

r- . v planned for the specified items, but instructions reouired that each one be surveyed according to the established procedures, except that no direct surface survey of the Ra-Be startup source would be conducted.

It would be smeared, however.

The specific results of the comprehensive radiation survey conducted as part of the AGN deconmissioning are surmiarized in the subparagraphs which follow:

a. Ito radioactivity in excess of normal background was detected by direct survey over surfaces of any AGN component, except for those few ccmpcnants ;;ac.ificallj kncwn in advance to contain radioactive material for their intended reactor function (i.e., the core can, the control rods and the Ra-Be source). Normal background during these surveys was approximately 50 to 60 cpm, wnich equated to approximately 315 to 380 dpm for the portable instrumentation and survey te.hniques used.

b. & radioactivity in excess of normal background was detected on smears cf any AGil comoonents, including those AGil items showing detectacle radioactivity on the direct sursays, except pcssibly the 2. nears of the Ra-Be startup scurce.

The maximum removable radioactivity on a single smear of this component showed only 5.94 net dpm (2.7 x 10-6 C1),which was not statistically different from normal background at the 99". confidence level, and was below the 11.8 dpm (5.3 x 10-6 uC1) 95" confidence lower limit of detection for the counting system used. .

Normal (a?-y plateau) background for the proportional i

). counting systems used to analyze the smears averaged approximately 49.2 1 5.2 dpm at 95% confidence.

The average (as-y plateau) lower limit of detection (LLD) at 95% confidence for these systems was approximately 12.34 j dpm or 5.6 x 10-6 uCi. Therefore, based on the indicated results, all component smears were within' normal background, were below the'LLD's for the counting systems, and no decontamination l of any AGN components was considered necessary.

i

c. As indicated creviously, the only components shcwing detectable radi:::tivity above tackground (due to direct surveys) were the core, the control rods and the nominal 10 mci Ra-Be startup source. Several measured radiation levels for these items are tabulated oelow:

Contact (mrem /hr) l foot (mrem /hr) y n y n

1) Maximum spot on core 2.0 none detectable 0.13* none detectable can (glory hole weld)

2) General levels en 0.5 to 1.0 none detectable 0. l

• none detectable core can

3) Maximum througn loaded C.5 none detectable core can storage con-tainer

4) Maximum on safety 8.0 0.2 control rod ?l

5) Maximum on :sfaty 8.3 0.2 control rod #2

6) Maximum on coarse 9.0 0.25 control rod

~;

7) Maximum on fine <0.1 <0.1 control rod **

8) Ra-Be source 150 2.0 ,

d. No routine surveys for airborne radioactivity during disassembly of the AGN, and no analysis of AGN water samples taken from the thermal column and main reactor tank disclosed radionuclides of reactor origin or radioactivity. levels above the range normally present in local air and water due to normal background radio-nuclides. The water samples were also well below any applicable discharge _ limits listed in Oregon or NRC regulations and there-fore the water was drained from the' AGN tank and thermal column I into the sanitary sewer system. Records of water and air analysis  !

are on file, but a summary of the water. data follows: I i

l

• Predicted to be approximately 0.27 mrem /hr at one foot.

• • Contains no uranium, i

l l

AGN Water Sample Analytical Results:

1) Thermal Column: 4.4 x 10-6 Ci/ml including U; H 3

1.0 x 10-7 uct/ml excluding H.

2) Reactor Tank: 4.5 x 10-6 uCi/mi including 3;H 3

9.6 x 10-8 act/ml excluding H.

3) Corvallis City 1.7 x 10-5 to 3.8 x 10-6 uCf/mi Water (normal including H; range):

3 2.2 x 10-7 to 4.2 x 10"8 excluding H.

e. Because of the very low radiation levels encountered, there was essentially no measurable personnel exposure. Gamma sensitive pocket dosimeter readings collected from all six major partici-pants after the four day disassembly showed three net readings of zero mR, two net readings of one mR and one net reading of three mR.

f. While basically little t.

• no removable contamination was detected, one cubic foot of dry solids (papers, disposable gloves, etc.) was processed as radioactive waste as a result of the AGN decommissioning.

g. The final area survey of the AG1 facility after all disassembly wds finished included a direct surface survey of all major objects and room surfaces, including the entire floor, all cabinets, all work bench surfaces, book cases, furniture, and walls. This survey produced no detectable radiation levels above the previcusly stated background values for the portable survey instruments used.

The final survey also included representative smears from major objects and surfaces within the room. These were counted in laboratory gas flow proportional counters and disclosed no radio-activity above the background and LLD values already given for these radiation detectors,

h.

Conclusion:

' The results of this survey support the conclusion that all AG1 reactor components (except the core can, Ra-Be source and control rods) and the room in which the AGN was located contain no radioactivity above natural background levels, and are well within the limits specified by NRC Regulatory Guide 1.86 for unrestricted use and access.

I acesit_A AG'i DEC0"MISSICt!!f1G & DISASSEM9LY AGri COMPONEf4T RADIATION SURVEY RECORD FORM Survey Form e iurvey Location AGN facility, OSU Radiation Center Survey Date .

14ET ITEM mRemMour SURVEY SURVEY GROSS NET dem tiO . GEtiERAL DESCRIPTION INSTRff! TfPE M com ccm 100 cm4 y Ie n Total l

l 1 l  !  !

l l i I I  ! t I

l l l 1 t l i i ) 6

! l l s I i

! i  ! l I l h  !  ! l  !  !

i i i i I i  ! l

- l l l  ! l DETEC'iOR COUNTING YIELD USED: REMARKS:

(2)Sackground counting rate at (J) Survey Instrument Codes:

was cpm = TAGM = Technical Associates portable GM with dpm = mrem /h r. pancake probe (thin windew).

Direct radiation levels frcm TACP = Technical Associates Cutie Pie ion the (area, item (s)) surveyed chamber.

(were, were not) 1 background NEMO = Nuclear Chicago Neutron Rem Meter.

radiation' levels. Exceptions:

(4) Survey Type Codes:

D = Direct Survey over the entire surface of (2) Background counting rate for- the object.

this instrument was cpc.i SG = 100 cm smear ccunted with a portable GM.

=

dem. The LLD-at 95% SP = 100 cm2 smear counted with a laboratory confidence level was net gas flow proportional counter (s3 plateau).

dpm =- net Ci. No smears SL = 100 cm smear counted with a liquid shewed removable radicactivity scintillatien counter (3H).

above the LLD, except from the SGS = 100 cm smear counted with a gama following items: spectrometer.

S';RVEY PERFORf7EO EY

..I?

OREGON STATE UNIVft:S!IY - RADIATION CENIER Special ",

RECORD Of itADIAlloll SURVEY Survey No.

Building or Area: Rooni #: Date: Tim-

Description:

Item or Area I"8 """ E Gr ss Net Het Net Ganma Beta Neutrons Total Distance Used cpm cinn d ian _ l"__,r nJt/hr mrads/hr mrem /hr mrem /hr 100 cm -

id jg.

x lco Re: narks:

Used As Appropriate used as Appropriate lktkground rounting ratc at _ was com = Dackground cwnting ute for this instrument was cpm

__ _ dpsn = nilieni/lir. Direc.t radiation levels = dpm. The ItD at 95% confidente level was la.ni the (area, attni(s) suiteyed (/<ere, were not) $ baL> ground twt dpm = __._ .-__ net jiCt (All, Some) smears radiation levels. Exceptions (dnl. did not) show semotable radioativity above the LlD.

bcephons:

Radiation Monitor.- leviewed,llealth Physicist Revi i Hay 1978

. ,