ML20117F794
| ML20117F794 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 03/21/1996 |
| From: | Abelquist E OAK RIDGE ASSOCIATED UNIVERSITIES |
| To: | Fauver D NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| NUDOCS 9605200212 | |
| Download: ML20117F794 (16) | |
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ORISE OAK RIC,4LE INSTITUTE FOR SCIE NCE AND E DUCATION March 21,1996 j
Mr. David Fauver U.S. Nuclear Regulatory Commission Division of Waste Management - NMSS 11555 Rockville Pike Two White Flint North' T-8F37 Rockville, MD 20852
SUBJECT:
FINAL REPORT - ORISE SUPPORT OF NRC LICENSE INSPECTION AT FORT ST. VRAIN ON SEPTEMBER 25 TO 27,1995 (DOCKET NO. 50-267, RFTA #95-30)
Dear Mr. Fauver:
l Enclosed is the subject report with the comments incorporated that you provided during our February 26,1996 telephone conversation. This report provides information on the confirmatory survey activities conducted at the Fort St. Vrain Nuclear Station in Platteville, Colorado on September 25 through 27, j
1995.
Ifyou have any questions or comments, please direct them to me at (423) 576-3740 or W. L. (Jack) Beck at (423) 576-5031.
Sincerely, L-d, hM Eric W. Abelquist Assistant Program Director Environmental Survey and Site Assessment Program EA:tsf Enclosure cc:
L. Carson, NRC/ Region IV R. Uleck, NRC/NMSSffWFN 7F27 D.Tiktinsky,NRC/NMSSffWFN 8A23 W. Beck, ORISE/ESSAP File /604 onnn0%
9605200212 960321 PDR ADOCK 05000267 t
O PDR P. O. 30X i i/, OAK RIDGE, TENNESSEE 37831 0117 Monoged and operated by Ook Ridge Associated Universities for the U s. Department of Energy I
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CONFIRMATORY SURVEY ACTIVITIES FOR THE FORT ST. VRAIN NUCLEAR STATION PUBLIC SERVICE COMPANY OF COLORADO PLATTEVILLE, COLORADO INTRODUCTION Public Service Company of Colorado (PSC) operated a 330 MWe High Temperature Gas Cooled Reactor (HTGR) from July 1979 until August 1989. The plant, designated as the Fort St. Vrain Nuclear Station (FSV), was authorized for construction on September 17,1968 when the U.S.
Nuclear Regulatory Commission (NRC) issued a provisional construction permit. Construction was completed in December 1973 and a facility operating license, License No. DPR-34, Docket No. 50-267, was granted on December 21,1973. Initial fuel loading commenced on December 26,1973 and initial criticality was achieved January 31,1974. After a prolonged period of startup testing, low-power operation and plant modifications, the plant was committed for commercial operation on July 1,1979. Full power was achieved November 6,1981 (PSC 1995a).
In the nuclear steam supply system for FSV, heat was produced by fission in the HTGR utilizing a uranium-thorium fuel cycle. Graphite was used for the moderator, core structure, and reflector.
High temperature helium was used as the primary coolant to produce superheated and reheated steam at a temperature of 1,000 F to match conventional thermal station conditions. The entire nuclear steam supply system, including the reactor core, graphite moderator and reflector, steam generators and helium circulators, was contained within a Prestressed Concrete Reactor Vessel (PCRV).
During the operational period, FSV operated for approximately 890 effective full-power days; FSV was shut down on August 18,1989. The PSC Board of Directors reviewed and confirmed the Executive Management decision that FSV would not be restarted, and that PSC would pursue l
decommissioning of FSV. The decision to permanently shut down and decommission FSV was based on related technical and financial considerations. Problems were identified with the control rod drive assemblies and the steam generator steam ring headers that presented significant technical obstacles which could be overcome, but at a significant cost in dollars and time to PSC. In addition, Fort St. Vrain Nuclear Station - March 21,1996 hSessap\\ plans \\itat.vrn\\nuc_sta 001
due to the uniqueness of the HTGR fuel cycle, the cost to purchase new fuel was prohibitive. This, in conjunction with low plant availability and correspondingly high operating costs, made continued operation of FSV impractical.
PSC's objective is the dismantlement and decommissioning of FSV to release all site areas for unrestricted use. To accomplish this, a portion of the PCRV structure and the radioactive balance-of-plant equipment that exceed the limits for unrestricted use will be decontaminated or removed as described in the Fort St. Vrain Decommissioning Plan. In May 1991, the NRC granted a 10 CFR 50 Possession Only License. On November 23,1992, the NRC issued the Order to Authorize Decommissioning of Fort St. Vrain and Amendment No. 85 to Possession Only License No. DPR-34 (PSC 1995b).
The FSV facility will be largely left intact following decommissioning; dismantlement of structures will be confmed to the PCRV, and portions of the Reactor Building, Turbine Building, and Liquid Waste System. Removal will be for purposes of removing contaminated structures and to provide paths for removal of contaminated piping and equipment.
Following defueling, the PCRV contained the majority of the remaining radioactive material inventory. Portions of the PCRV concrete are activated due to direct irradiation from the reactor core, and will be removed prict to final survey and disposed of as radioactive waste at a licensed radioactive waste disposal facility. Thus, the radioactive source term at FSV is primarily a result of neutron activation of both metallic and concrete components of the PCRV and neutron activation ofimpurities contained in graphite components of the PCRV. These activation products include beta-gamma emitters such as Co-60, Eu-152, and Eu-154, and low-energy beta and x-ray emitters such as H-3, C-14, and Fe-55. It should be noted that H-3 and Fe-55 are the largest contributors to the total radionuclide inventory (PSC 1995a).
2 as, spi s,i.,,s c_,t..ooi Fort St. Vrmo Nuclear Station - March 2i.1996
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FSV's final survey will include all pertinent structures, surfaces, systems and components, concentrating on those previously identified as contaminated or potentially contaminated during the dismantlement / decommissioning phases. The final survey will include:
- Sampling outside the restricted area of PSC property, soil, pavement, water, and liquid effluent ditch and pond sediment for radioisotopic analysis and measurement of gamma exposure rate, Sampling inside the restricted area of PSC property, soil, basin sediment, pavement and water for radioisotopic analysis and measurement of gamma exposure rate, Radiological surveys of the PCRV and Reactor Building, and Radiological surveys of the Turbine Building, Radwaste Compactor Building, New Fuel Storage Building, Radiochemistry Laboratory, Helium Transfer and Storage System, and Liquid Radwaste System.
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At the request of the NRC's Division of Waste Management, the Environmental Survey and Site Assessment Program (ESSAP) of the Oak Ridge Institute for Science and Education (ORISE) performed independent confirmatory surveys activities at the Fort St. Vrain site in Platteville, l
Colorado during the period September 25 through 27,1995. Independent survey activities included licensee survey package reviews, confirmatory surface scans, and comparison surface activity measurements (e.g., side-by-side measurements).
SITE DESCRIPTION The FSV facility is located approximately 56 kilometers (35 miles) north of Denver and 5.6 4
kilometers (3.5 miles) northwest of the town of Platteville, in Weld County, Colorado. The site is located in an agricultural area with gently rolling hills. Grade elevation at the plant is 1,460 meters (4,790 feet) above sea level. The site consists of 1130 hectares (2800 acres) owned by PSC, identified as the Owner-Controlled Area, of which approximately 260 hectares was designated as j
the exclusion area during plant operation.
3 6:s,,,pspi. sri.,os. e_,i..ooi Fort St. Vrain Nuclear Station. March 21, IN
The station is located approximately 3 kilometers south of the confluence of the South Platte River and the St. Vrain Creek. Neither of these two streams are considered navigable. Cooling for the plant is provided by mechanical draft cooling towers. Make-up water to the cooling towers is obtained from the two streams, and is supplemented by shallow well water. Nineteen shallow monitoring wells are located on the site. The licensee also owns surface water rights in four irrigation ditches which traverse portions of the site.
The major structures within the Restricted Area include the Reactor Building which contains the PCRV, Turbine Building, Radwaste Compactor Building, New Fuel Storage Building, Technical Support Building which contains the Radiochemistry Laboratory, Mechanical Draft Cooling Towers, Warehouse and Construction Workshops, Evaporation Ponds, and the Electrical Switchyard. The ground surface covering within the Restricted Area is composed primarily of gravel and vegetation, with smaller portions devoted to concrete or asphalt roadways and laydown areas.
i OBJECTIVES The objectives of the confirmatory survey activities were to provide NRC inspection support, l
including independent contractor reviews of site records and confirmatory survey data for use by the l
NRC in evaluating the adequacy and accuracy of the licensee's procedures and final status survey results.
PROCEDURES l
During the period, September 25 through 27,1995, ESSAP performed independent confirmatory survey activities at the Fort St. Vrain site in Platteville, Colorado. This technical assistance was provided to assist the NRC in their inspection of licensee decommissioning-related activities.
Technical assistance activities included independent confirmatory surface scans, instrument i
L comparison measurements, and a review oflicensee final survey packages performed in accordance with the direction provided by the on-site NRC project manager. This report summarizes the procedures and results of the technical assistance activities.
4 h:\\essapiplans\\ftst.vrninuc_sta.001 Fort St. Vrain Nuclear Station. March 21,1996 l
Survey Data Package Review i
ESSAP reviewed the licensee's final survey plan for site release prior to the on-site visit to become familiar with the NRC-approved final survey procedures (PSC 1995a). As part of the confirmatory activities, ESSAP reviewed selected licensee survey data packages for accuracy, completeness, and procedure compliance with their final survey plan for site release. Specifically, the survey data packages were reviewed to ensure that classification criteria have been properly followed and that any measurements exceeding investigation levels, as defined by the licensee, were adequately investigated.
t ESSAP reviewed FSV survey data package B005 (an unaffected area package), which included the i
North Warehouse (Building 13), the Electrical Warehouse (Building 14), and the restroom and shower facility (Building 1014). Concerns identified during the review-and verbally presented to the on-site NRC project manager-included:
i survey area was classified as unaffected, although radioactive material was stored in the northeast area of the Electrical Warehouse.
survey area was classified as unaffected, although numerous fimal survey surface activity measurements exceeded both the 25% of guideline action level and the guideline.
all forms were not signed and dated.
difficult to relate survey location code from instrument download sheets to survey map a
locations.
It should be noted that following our document review, the licensee stated that the survey packages i
being reviewed have not been completed by FSV-data reviews, investigations, and data j
i conversions to guideline units remained to be performed. However, the concern remains that FSV classified the Electrical Warehouse as unalTected although documentation stated that Electrical Warehouse had a history of radioactive material storage, and according to their final survey plan, unaffected areas are not expected to contain residual radioactivity based on the site history.
5 nw um.oc_.i.mi Fat St. Vrain Nuclear Station. March 21. IN
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Surface Scans and Comparison to Licensee Scan Results Surface scans for beta activity were performed over 100% of accessible floor and lower wall surfaces (approximately 50% of the total area) in the Production Training Center (A008), including the Simulator Room (A002), and the Electrical Warehouse floor area. Scans were performed using a 2
gas proportional floor monitor (573 cm ) coupled to a ratemeter-scaler with an audible indicator.
Surface activity levels were determined from any locations of elevated direct radiation as identified by scans.
Surface scans of the Production Training Center and Electrical Warehouse identified no areas of elevated beta direct radiation. Scan ranges in survey unit A002 were consistent with background I
levels-1100 to 1300 cpm and 1000 to 1300 cpm for the floors and lower walls,' respectively.
Scan ranges in survey unit A008 were also consistent with background levels-1100 to 1400 cpm and 1100 to 1300 cpm for the floors and lower walls, respectively. The scan range on the Electrical Warehouse floor had a scan range of 1400 to 1900 cpm-consistent with background levels.-
ESSAP scan results were compared to the licensee scan results documented in their survey packages for survey units A008, A002, and the Electrical Warehouse floor area. The scan results were consistent between ESSAP and the licensee-both ESSAP and the licensee concluded that surface scans identified no locations of elevated direct radiation in each of the surveyed areas.
Side-By-Side Surface Activity Measurements l
Field comparisons of ESSAP and FSV direct surface activity measurements were performed in the l
Electrical Warehouse, Level 3 of the Reactor Building, and the Battery Room in the Turbine Building (Figures 1 through 3). Surface activity measurements for both ESSAP and the licensee were performed using 125 cm (ESSAP states the probe area size as 126 cm ) gas proportional 2
2 detectors coupled to ratemeter-scalers.
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Fort St. Vrain Nulear Station - Much 21. IM hNssappans&dw mMI
Field comparisons for background surface activity levels were performed in the Battery Room of the Turbine Building. Ten locations in the Battery Room were selected for background measurements.
Table 1 illustrates the comparison of ESSAP and licensee detector response-in cpm per probe area-at each background location in the Battery Room. ESSAP performed 1 minute counts, while the licensee counted for 15 seconds at each location. The results indicate that the licensee's detector exhibits a substantially greater response-on the order of 30 to 40% higher-than ESSAP's gas proportional detector. Detector characteristics responsible for this difference may include voltage and threshold settings, dimensions of the corona wire, and grounding of the corona wire.
Twenty side-by-side surface activity measurements were acquired on floor surfaces in both the Elearical Warehouse and Level 3 of the Reactor Building. ESSAP and FSV employed different techniques to calculate the surface activity at each location. ESS AP subtracted the mean background level---determined on the concrete floor in the Battery Room-from surface activity measurements collected in the Electrical Warehouse and Level 3 of the Reactor Building. Net count rates were then 2
converted to surface activity levels (dpm/100 cm ) by dividing the net rate by the 4x efficiency and correcting for the probe area of the detector. Both ESSAP and FSV calibrated the gas proportional detectors to Tc-99; ESSAP obtained an efficiency value of 0.25, while the FSV efficiency was 0.205.
FSV evaluated the background surface activity for a given material by dividing the background into i
two components: natural material (e.g., concrete) background and the local area exposure rate background. At the selected material background location, FSV collected a series of shielded 2
counts-using a 300 mg/cm Lucite beta shield-that represents the local area exposure rate
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l contribution to the detector response, followed by unshielded measurements that include the l
contribution from both the local area exposure rate and the natural material background. The l
difference of these two values yields the natural material background for a specific material (i.e.,
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concrete, steel, wood, etc.)--for concrete it was 767 dpm/100 cm. This natural material i
background, plus the specific local area exposure rate contribution to the detector response determined for the survey unit being evaluated, was subtracted from the gross surface activity measurements in the Electrical Warehouse. Because ESSAP does not account for a changing local 7
Fort St. Vrain Nuclear Station. March 21. IM hkssap\\ plans \\ftst.vnnnuc sta.001 i
l area exposure rate contribution to the detector response from where the initial material background levels were established, the material backgrounds subtracted by ESSAP and FSV were different.
Since FSV only provided local area background-corrected surface activity levels in the Electrical Warehouse-shielded surface activity measurements were not performed by FSV on the floor in i
Level 3 of the Reactor Building-data comparisons were not performed for the Reactor Building.
Table 2 illustrates the surface activity comparison results for the Electrical Warehouse. Surface 2
activity levels measured by ESSAP ranged from 103 to 569 dpm/100 cm, with an average of 301 2
2 dpm/100 cm and standard deviation of 144 dpm/100 cm. FSV reported surface activity levels 2
2 ranged from -267 to 560 dpm/100 cm, with an average of 199 dpm/100 cm and standard deviation 2
of 231 dpm/100 cm. A pairwise comparison t-test was performed to determine if the differences j
between ESSAP and FSV were statistically significant. Based on the pairwise comparison t-test, there are no statistically significant differences (p>0.05) between FSV's and ESSAP's surface activity measurements in the Electrical Warehouse.
SUMMARY
During the period September 25 through 27,1995, the Environmental Survey and Site Assessment Program of ORISE performed confirmatory survey activities at the Fort St. Vrain site in Platteville, Colorado. Confirmatory survey activities included survey data package reviews, confirmatory l
- surface scans, and side-by-side background and surface activity measurements.
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Document reviews identified a discrepancy in an area classification during the review of survey data package B005. Other minor concems identified by ESSAP during the survey data package review were dismissed because FSV reported that they had not yet completed their review of survey data package B005.
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ESSAP confirmatory surface scans in survey units A008, A002, and the Electrical Warehouse floor identified no locations of elevated direct radiation. These results are consistent with the scan results documented in the licensee's survey data packages.
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Fort St. Vrain Nuclear Stauen - March 21.1996 h'essap41ans2st.vrn'muc.sta 001
Comparisons of ESSAP and FSV gas proportional detector response in the Battery Room of the Turbine Building indicate that the licensee's detector exhibits a significantly greater response than ESSAP's gas proportional detector. Side-by-side surface activity measurements in the Electrical Warehouse indicate that there are no statistically significant differences between FSV's and ESSAP's surface activity measurements in unaffected areas that exhibit background or near background levels-i.e., where no licensed material is present.
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FIGURE 1: Fort St. Vrain Facility, Electrical Warehouse #14 -
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FIGURE 2: Fort St. Vroin Facility, Reactor Building, Level 3, East -
Measurement and Sampling Locations lI Fort St. Vrain Nuclear Station March 21,1996 h:\\essapylans\\ fist.vrn\\nuc.,sta.001 l
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j Measurement and Sampling Locations 12 n:w apspi ssi.i.v snoc_.i..ooi Fort St. Vr.in Nuclear Station - March 21,1996
TABLE 1 COMPARISON OF DETECTOR RESPONSE FOR BACKGROUND MEASUREMENTS BATTERY ROOM IN TURBINE BUILDING FORT ST. VRAIN PLATTEVILLE, COLORADO 2
Count Rate (cpm /125 cm )
ESSAP6 FSV' Relative % Differenced Battery Room in Turbine Building 1
436 592 35.8 %
2 448 620 38.4 %
3 467 572 22.5 %
4 507 548 8.1%
5 472 616 30.5 %
6 466 608 30.5 %
7 447 580 29.8 %
8 476 620 30.2 %
9 433 540 24.7 %
10 428 696 62.6 %
' Refer to Figure 3.
bESSAP performed 1 minute counts.
'FSV performed 15 second counts.
dRelative percent difference calculated by:
l (F V - ESSAP), l99%
ESSAP I
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T TABLE 2 COMPARISON OF SURFACE ACTIVITY MEASUREMENTS ELECTRICAL WAREIIOUSE FORT ST. VRAIN PLATTEVILLE, COLORADO 2
Beta Activity (dpm/100 cm )
l ESSAP FSV Electrical Warehouse l
423 279 l
2 268 216 3
103 560 4
509 357 5
569 263 6
341 544 7
562 435 8
387
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265
-267 l
10 400 310 11 169 170 12 228 482 13 152 138 14 291 248 l
15 215 123 l
l 16 255 341 i
17 142 45 i
18 420
-189 19 155
-111 20 162 45
' Refer to Figure 1.
I4 h:kssap\\ plans'tst.vrnbuc_sta.001 Fort St. Vrain Nuclear Stanon - March 21,1996
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l REFERENCES Public Service Company of Colorado (PSC 1995a). Final Survey Plan for Site Release (revision 1).
Fort St. Vrain Nuclear Station Decommissioning Project. May 25,1995.
Public Service Company of Colorado (PSC 1995b). Final Survey Report for Release of Repower Area. Fort St. Vrain Nuclear Station Decommissioning Project. March 2,1995.
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