ML090890586
| ML090890586 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 09/09/2008 |
| From: | Andersen D Sacramento Municipal Utility District (SMUD) |
| To: | NRC/FSME |
| Shared Package | |
| ML090830613 | List:
|
| References | |
| DPG 09-097, F8260131 | |
| Download: ML090890586 (36) | |
Text
Rancho Seco Final Status Survey Summary Report September 9, 2008 Turbine Building (+) 0' El., North Floor Survey Unit F8260131 Prepared By: h. *gcA?-_ Date: _______O_'
FSS Engineer Reviewed By: ",--kL3 - Date: kV1b'> 0(*
Lead FSS Engineer Approved By: Date: z ?7 -O 7 Dismantlemen ýperintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8260131, Turbine Building (+) 0' El., North Floor Survey Unit
Description:
Operating History: The reinforced concrete and steel structure contained the turbine-generator and supporting systems. The building contained five main elevations. Residual radioactive material was known to be present on all levels of the interior of the building.
Operating records and the HSA document several events with the potential for a release of radioactivity inside this structure.
Site Characterization: Direct measurements were made of each of the interior elevation surfaces as well as the exterior surfaces of the structure. These measurements confirmed the presence of plant-derived radionuclides. Direct measurements in the condenser pit elevation showed a mean gross activity level of 3,077 dpm/100 cm 2 and a maximum value of 24,900 dpm!100 cm 2 . Direct measurements on the grade elevation showed a mean gross activity level of 2,035 dpmi/100 cm 2 and a maximum value of 6,980 dpm/100 cm 2 . Direct measurements on the mezzanine elevation showed a mean gross activity level of 1,566 dpm/100 cm 2 and a maximum value of 2,626 dpm/100 cm 2 . Direct measurements on the +40' elevation showed a mean gross activity level of 2,843 dpm/l100 cm 2 and a maximum value of 3,615 dpm/l100 cm 2. Direct measurements on the building exterior showed a mean gross activity level of 1,984 dpm/l100 cm 2 and a maximum value of 10,312 dpm/100 cm 2. Based on the classification procedure (DSIP-0020) and levels of gross activity reported, the interior of the turbine building was determined to be Class 1, 2, & 3 areas and the exterior was a Class 3.
During characterization surveys of F82601.31 (Turbine Building (+) 0' El., North Floor, Class 2), beta measurements identified activity within a 2-meter by 3-meter area that exceeded the DCGL of 43,000 dpm/100 cm 2 . The area was subsequently remediated and reclassified as a Class 1 structure, based on the classification procedure (DSIP-0020).
Final surveys of the Class 1 area were performed under survey package F8260161.
HSA Events: HSA Report pg. 63 Survey Unit Design Information:
The Survey Unit Design Parameters are presented in Table I below. The survey unit and measurement locations are depicted on the maps in Attachment 1. Direct measurement locations were determined using a random-start, fixed grid pattern and 510.5 m2 were scanned for approximately 83% coverage. Samples of removable contamination were collected at each direct measurement location. The instrumentation used for the survey along with the MDC values are listed in Tables 2-1 and 2-2 in Attachment 2.
Page 2 of 8 FSS Summary Report F8260131
Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area: F826 Turbine Building (+) 0' El.,
North Floor Survey Unit: 0131 Structure Surface Class: 2 LTP Table 5-4 SU Area (m2): 618.3 Evaluator: D. Anderson DCGL (dpm/100 cm2): 43,000 Gross Activity DCGL Area Factor: N/A Class 2 Design DCGLemc N/A Class 2 (dpm/100 cm 2):
LBGR (dpm/100 cm 2 ): 39,052 Adjusted Design Sigma (dpm/100 cm 2): 1,316 Type I Error: 0.05 Type II Error: 0.05:
Predominant Nuclide: Cs-1371 Sample Area (m2): 6.6 Class 2 Scan Area (M2 ): 510.5 Scan Coverage (%): 83% Class 2 Zi-a: 1.645 1.645 Sign P: 0.99865 Calculated Relative Shift: 3 Relative Shift Used: 3 Uses 3.0 if Relative Shift is
>3 N-Value: 11 Design N-Value + 20%: 14 NUREG-1575 Table 5-5 Design Min Samples N: 14 Class 2 Grid Spacing L: 6.6 Class 2 Page 3 of 8 FSS Summary Report F8260131
Survey Results:
A total of 15 direct measurements were made in F8260131. The results including mean, median, standard deviation and range are shown in Table 2. All direct measurements were less than the DCGL. Two ISOCS gamma scan measurements indicated possible2 areas of elevated activity (> 4,300 dpm/100 cm2 average Cs-137 activity for 12.56 m field of view). Seven additional ISOCS measurements were performed at each location using a reduced field of view (3.14 in 2 ) and were evaluated as shown in Table 3-1 of . The gamma scan activity for the survey unit ranged from < 912 dpm/100 cm 2 Co-60 and < 1,360 dpm/l00 cm 2 to 15,330 dpm/100 cm 2 Cs-137. Beta scan activity ranged from 3,020 to 21,303 dpm/100 cm 2 , based on a surveyor: efficiency of 0.5 and no background subtracted. Samples for removable surface activity were all less than 10% of the DCGL as shown in Table 3. Removable surface activity samples were counted for alpha activity and none was detected at the MDC shown in Table 2-1 of Attachment 2.
Table 2. Direct Measurement Results Measurement ID Gross Activity (dpmllO0 cm F8260131-C0001BD 1,650 F8260131-C0002BD 1,478 F8260131-C0003BD 1,162 F8260131-C0004BD 1,686 F8260131-CO005BD 1,515 F8260131-CO006BD 1,945 F8260131 -CO007BD 1,421 F8260131-C0008BD 1,255 F8260131 -CO009BD 1,587 F8260131-CO010BD 1,468 F8260131-C0011BD 1,634 F8260131-Co012BD 1,847 F8260131-Co013BD 1,748 F8260131-Co014BD 1,411 F8260131-CO015BD 1,541 Mean: 1,557 Median: 1,541 Standard Deviation: 208 Range: 1,162 - 1,945 Page 4 of 8 FSS Summary Report F8260131
Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm 2 )
i .
F8260131C0001SM -0.95 F8260131 C0002SM -0.95 F8260131 C0003SM -0.95 F8260131 C0004SM -0.95 F8260131CO005SM -3.53 F8260131CO006SM -3.53 F8260131CO007SM 4.22 F8260131CO008SM 0.34 F8260131CO009SM -2.24 F8260131CO010SM -2.24 F8260131C0011SM -4.82 F8260131 C001 2SM -3.53 F8260131Co013SM -4.82 F8260131C0014SM 5.51 F8260131Co015SM -0.95 Mean: -1.29 Median: -0.95 Standard Deviation: 2.95 Range: -4.82 to 5.51 Page 5 of 8 FSS Summary Report F8260131
Survey Unit Data Assessment:
The survey design required 15 direct measurements for the Sign Test. The critical value and the results of the Sign Test are presented in Table 4. The sample mean and median values were less than the DCGL. The sample standard deviation was less than the design standard deviation so no additional samples were required.
Page 6 of 8 FSS Summary Report F8260131
Table 4. Data Assessment Results Survey Results Parameter Value Comment Material Background Used (dpm/100 cm 2): N/A Ambient Background Used (dpm/100 cm 2): N/A Average Ambient BKG = 0 Actual Direct Measurements (N): 15 2
Median (dpm/1O0 cm ): 1,541 Mean (dpm/100 cm 2): 1,557 Direct Measurement Standard Deviation 208 (dpm/100 cm 2):
Total Standard Deviation (dpm/100 cm 2): 208 Based on samples and backgrounds.
Maximum (dpm/100 cm 2): 1,945 Material Type: N/A Background Subtract Not Applied Sign Test Final N Value: 15 S+ Value: 15 Critical Value: 11 Sufficient Samples Collected: Yes, Maximum Value < DCGL: Yes Median Value < DCGL: Yes Mean Value < DCGL: Yes Maximum Value < DCGLemc: N/A Class 2 Total Standard Deviation <= Sigma: Yes Pass the Sign Test? Yes Reject the Null Hypothesis? Yes Does the Survey Unit Pass All Criteria? Yes Page. 7 of 8 FSS Summary Report F8260131
Survey Unit Investigations and Results:
Two investigations (scan grids 18 and 25) were required for the scan measurements and the results are reported in Attachment 3.
ALARA Statement:
As stated in Chapter 4 of the LTP, as long as the residual activity within the survey unit is less than the DCGL (i.e. the survey unit average activity is less than the DCGL and the EMC criterion has been met), the ALARA criterion has been met.
Changes in Initial Survey Unit Assumptions:
The survey unit was designed as a Class 2 structure survey and the sample results are consistent with that classification. The variability of the survey results was less than the characterization data used for survey design. Two potential areas of elevated activity were detected and evaluated as shown in Attachment 3.
==
Conclusion:==
The FSS of this survey unit was properly designed as a Class 2 survey based on Table 5-4 of the LTP. The required number of direct measurements was made and the scan coverage met the requirement of Table 5-6 of the LTP. No direct measurements exceeded the DCGL of 43,000 dpm/100 cm 2 and none of the removable surface activity measurements exceeded 10% of the DCGL. Two investigations were required.
The direct measurement data support rejection of the null hypothesis, providing high confidence that the survey unit satisfied the release criteria and that the data quality objectives were met.
It is concluded that survey unit F8260131 meets the release criteria of 10CFR20.1402.
Page 8 of 8 FSS Summary Report F8260131
Attachment I Maps September 9, 2008 Survey Unit F8260131
CD 0
3 m x 2 m area 0 0 surveyed as Class 1 D 0 under F8260161 0 0 0 D [
11 D M
~r+
Location of Turbine Building inside the Industrial Area 00 t-..
D- Map F8260131-1, Turbine Building Grade North Turbine Building (+) 0' Elevation Floor 0 N
2 4 6 8 Distance in Meters Area Estimate: 611 square meters
00 tQi CD<
Map F8260131-2, Turbine Building Grade and Below Elevations Location of North Turbine Bldg (+) 0' Elevation Floor
7 19.2 ft Map F8260131-3, Turbine Building Grade Concrete Back of Cask Catcher Pad Area Estimate: 7.3 square meters N
0 1 2 3 4 Oistance in Meters Page 4 of 19 Att. I Maps F8260131
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SI I I 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 3
___ Map F8260131-4, Turbine Building Grade 0 2 4 6 8 North Turbine Building (+) 0' Elevation Floor DistancAin Meters Random Start Location Page 5 of 19 Att. I Maps F8260131
Distance in meters ce in meters from North Wall East Wall 3.4 m 0
10.0 m 16.6 m 23.2 m 29.8 m Map F8260131-5, North Turbine Building (+) 0 Elevation Floor Beta Direct Measurements 00 F8260131C0001BD to F8260131C0014BD 6.6 m by 6.6 m grid spacing 36.4 m
0 Map F8260131-6, North Turbine Building (+) 0' Elevation Floor 00 ISOCS Gamma Scan Measurements 0Q F8260131 COOO1 GS to F8260131C0045GS 12.57 sq. meter field of view Total Scan Area: - 409 sq. meters
CDr 00 0
Map F8260131-7, North Turbine Building (+) 0' Elevation Floor 00 ISOCS Gamma Scan Measurements F8260131CO001GS to F8260131C0026GS 12.57 sq. meter field of view
CkD 0
0~E 5C:3 CD 6O Map F8260131-8, North Turbine Building (+) 0' Elevation Floor ISOCS Gamma Scan Measurements F8260131C0001GS to F8260131C0008GS and 00 F8260131C0018GS to F8260131C0026GS 12.57 sq. meter field of view
0C Map F8260131-9, North Turbine Building (+) 0' Elevation Floor ISOCS Gamma Scan Measurements 00 F8260131C0009GS to F8260131COO17GS and F8260131 COO 19GS Uo 12.57 sq. meter field of view
5 L i .
m V, - .1 o ((LiL LD L LI L Distance in Distance in Measurement meters from meters from i] [T1 I Location North Wall East Wall
-- r 27GS 2.1 m 2.6 m 28GS 5.4 m 2.4m Map F8260131-10, North Turbine Building (+) 0' Elevation Floor 0ISOCS Gamma Scan Measurements F8260131 C0027GS to F8260131 C0029GS
-r 12.57 sq. meter field of view
0 Map F8260131-11, North Turbine Building (+) 0' Elevation Floor 00 ISOCS Gamma Scan Measurements F8260131C0030GS to F8260131C0034GS 12.57 sq. meter field of view
0 2.5 (dI Map F8260131-12, North Turbine Building (+) 0' Elevation Floor 00 ISOCS Gamma Scan Measurements F8260131 C0035GS to F8260131 C0041GS 12.57 sq. meter field of view
CD~
0 Map F8260131-13, North Turbine Building (+) 0' Elevation Floor 00 ISOCS Gamma Scan Measurements F8260131C0042GS to F8260131C0045GS 0Uj 12.57 sq. meter field of view
0 ITo Map F8260131-14, North Turbine Building (+) 0' Elevation Floor Beta Scan Measurements' 00 w*
F8260131C0001 BS to F8260131 C0040BS Total Scan Area: - 101.5 sq. meters
crQ-N u L CIS Li LJ F8-011C0]B oF8602BS0OB CO00 CO -- 1 3UB- 00-'
00lacCO Meter KOM,'N a"* trr r 8Ws IT I cc Cc cc CO COc m Betistna Meeurerst Sca
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't 1 -0 1 J) I vM DD DD Map F8260131-16, Turbine Building Grade Concrete Back of Cask Catcher Pad Beta Scan. Measurements F8260131C0041BS to F8260131CO048BS N
0 1 2 3 4
- Distance in Meters Page 17 of 19 Ant. 1 Maps F8260131
CD 00 0
Map F8260131-17, North Turbine Building (+) 0' Elevation Floor 00 ISOCS Gamma Scan Measurements F8260131CO046GS to F8260131CO059GS ON 3.14 sq. meter field of view
CD~
00 t'),
ON
-'A Map F8260131-18, Turbine Building (+) 0' El. North Floor I
At
- Denotes center of ISOCS gamma measurement 3.14 sq. meter field of view ISOCS Gamma Scan Measurements F8260131CO049GS to F8260131CO052GS and Beta Scan Measurements F8260131C0049BS to F8260131C0057BS
Attachment 2 Instrumentation September 9, 2008 Survey Unit F8260131
Table 2-1. Survey Unit Instrumentation Instrument Detector MDC Static MDC Scan Model; Serial No. Model; Serial No. (dpm/100 cm2 ). (dpmll00 cm 2 )
M2350; 193700 43-68B; 190294 433 1,033 M2350; 203481 43-68B; 148629 433 1,033 M2350; 142499 43-37; 148502 198 616 Tennelec; 0401171 N/A 5.88 dpm a, N/A 11.71 dpm P3 MDC Concrete - 1,360 dpm/lO0 cm2 Cs-137, Concrete - 912 dpm/1O0 cm 2 Co-60 Table 2-2. Investigation Criteria and DCGL Value Parameter (dp)/100 cm 2 )
Investigation Criteria - Direct 43,000 Investigation Criteria - Beta 43,000 Scan Investigation Criteria - Scan (ISOCS average Cs-137 activity 4,300 for 12.5 m2 field of view)
Investigation Criteria - Scan (ISOCS average Cs-137 activity 12,600 for 3.1 mr2 field of view)
DCGLw 43,000 DCGLEMC N/A Page 2 of 2 Att. 2 Instrumentation F8260131
Attachment 3 Investigation September 9, 2008 Survey Unit F8260131
Table 3-1 Survey Unit Investigation Investigation Initial Value Investigation Elevated Investigation DCGLemc Level l (dpmIV0a Rv Area Area DCGLenc Result Unity Grid (dpm/10O0 (cm/1) O0Factorem Area1 181 c
cm2) 4,300 @2 1814,32meters
{
m) m)
6,654 cm2) dM/10 cm)(2 (See Below)
(M 2) 12.57 N/A N/A (dpm/lOOcm2)
N/A Fraction N/A 10,571 3.14 N/A N/A 10,571 0.00 15,330 3.14 N/A N/A 21,307 (beta) 0.00 18 12,600 @ 1- N/A 6,933 3.14 N/A N/A 6,933 0.00 meter 2,417 3.14 N/A N/A 2,417 0.00 990 3.14 N/A N/A 990 0.00
< 1,360 3.14 N/A N/A < 1,360 0.00 Page 2 of 3 Att. 3 Investigation F8260131
Table 3-1 Survey Unit Investigation, continued Investigation lnvestigation Elevated Investigation DCGLemc Level Result Area Grid (dpm/lO0 Area DCGLemc Result Unity (dpm/1 0 cm2 ) (dpm/1 00 Factor cm 2) cm2) (m 2) (dpm/lOOcm2) Fraction
< 1,360 3.14 N/A N/A < 1,360 0.00 251 4,300 @ 2 5,170 (See Below) 12.57 N/A N/A N/A N/A meters 6,543 3.14 N/A N/A 6,543 0.00
< 1,330 3.14 N/A N/A < 1,330 0.00 2,221 3.14 N/A N/A 2,221 0.00 25 12,600 @ 1-meter N/A 2,525 3.14 N/A N/A 2,525 0.00 5,087 3.14 N/A N/A 5,087 0.00 6,354 3.14 N/A N/A 6,354 0.00 4,502 3.14 N/A N/A 4,502 0.00 SU Mean=
Survey Unit Remainder 43,000 DCGL 15700 1,557 .0.04 EMC Unity Sum 0.04 1Investigation Level for ISOCS measurements is based on detection of a 100 cm 2 hot spot at the DCGL value within the detector field of view. Should the average activity for an ISOCS measurement exceed the Investigation Level for the detector field of view, additional measurements are performed with a smaller detector field of view to determine if a hot spot exists that may exceed the DCGL. For the location exceeding the Investigation Level for the reduced field of view, beta scans were performed to evaluate if the surface activity is less than the DCGL.
Page 3 of 3 Att. 3 Investigation F8260131
Attachment 4 Data Assessment September 9, 2008 Survey Unit F8260131
F8260131 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpm/100cm2 3,000 -
2,500 -*,,
> * ~2,000 - ,,,-.
4_1~~,-~- - --- - - - - - - -
- - - - - - - - - I - -~-- - -
- + ---
- - - -- - - - - - - -~ - --. -... . .
~1541 0 10 1,500 O-4..-...- -
- 4 -
0 20 40 60 80 100 IIPercentile Direct Measurements (dpm!100cm2) - median - 50th n Percentile
o F8260131 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpm/100cm=2 2500
- ------------- --- ------ --- ------ --- ------ --- ------ ------ -------- -
- 2181 E 2000 0 1 0 100 .. - - - - - - - - -- 1557 a,. 0
= 00 00 00 00 00 0 0
r m MnM 0 0 3 mm00 mfmN 0N mm0 M0 Mto to r N tm 0
to V
tm 0
0 o
a a 07 0
0 0
0 0
0 0
0 0 a 0 0 0 0 0
- T-0 0 0 0 a 0 0 0 0 0 0 0 0 0 C 0 0 0 U U U U U U U U U U U U U U U Measurement Locations 00
F8260131 Gross Activity Frequency Plot DCGL = 43000 dpm/1 00cm 2 4
3.
U-0 2
1-00 0-0 N RN LC) 0)
LL~)
k-)
UN Bins - Upper End Value (dpm/1 00cm2)