ML091000384

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Final Status Survey Summary Report for June 3, 2008, Fuel Storage Building North Exterior Wall (+) 0 El. to (+) 69 4 El. & Roof, Survey Unit F8120141
ML091000384
Person / Time
Site: Rancho Seco
Issue date: 06/03/2008
From: Donna Anderson
Sacramento Municipal Utility District (SMUD)
To:
NRC/FSME
Shared Package
ML090830613 List: ... further results
References
DPG 09-097
Download: ML091000384 (24)
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Rancho Seco Final Status Survey Summary Report June 3, 2008 Fuel Storage Building North Exterior Wall (+) 0' El. to (+) 69' 4" El. & Roof Survey Unit F8120141 Prepared By:

  • QL4. 2 O-n.-

Date:

0,3 12008' Reviewed By:

Date: 613./9el Lead FjA Engineer Approved By:

7 Date: 2i4 -

Dismantlement S perintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit:

F8120141, Fuel Storage Building North Exterior Wall (+) 0' El. to (+) 69' 4" El. & Roof Survey Unit

Description:

Operating History: The reinforced concrete structure contained the spent fuel pool and supporting systems. The building contained three main elevations including the pool.

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. Three documented instances of contamination through the common fuel building/turbine building wall were noted.

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 on the pool elevation showed a mean gross activity level of 16,900,000 dpm/100 cm2 and a maximum value of 200,000,000 dpm/100 cm 2. Direct measurements on the +40' elevation showed a mean gross activity level of 5,942 dpm/100 cm 2 and a maximum value of 19,357 dpm/100 cm 2.

Direct measurements on the building exterior showed a mean gross activity level of 1,408 dpm/100 cm2 and a maximum value of 21,600 dpm/100 cm 2. Based on the classification procedure (DSIP-0020) and levels of gross activity reported, the interior of the spent fuel building was determined to be a Class 1, 2 area and the exterior was a Class 2, 3.

HSA Events: HSA Report pg. 63.

Survey Unit Design Information:

The Survey Unit Design Parameters are presented in Table 1 below. The survey unit and measurement locations are depicted on the maps in Attachment 1. Direct measurement locations were randomly determined and 237.5 m2 were scanned for approximately 28%

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 F8120141

Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area:

F812 Survey Unit:

Class:

SU Area (m2):

Evaluator:

DCGL (dpm/100 cm2):

Area Factor:

Design DCGLemc (dpm/100 cm 2):

LBGR (dpm/100 cm2):

Design Sigma (dpm/100 cm 2):

Type I Error:

Type II Error:

Predominant Nuclide:

Sample Area (m2):

Scan Area (M2):

Scan Coverage (%):

Zl-,, :

ZI-0 :

Sign P:.

Calculated Relative Shift:

Relative Shift Used:

N-!Value:

Design N-Value + 20%:

Design Min Samples N:

Grid Spacing L:

0141 3

854 D. Anderson 43,000 N/A N/A 40,759 747 0.05 0.05 Cs-137 N/A 237.5 28%

1.645 1.645 0.99865 3

3 11 14 14 N/A Fuel Storage Building North Exterior Wall (+) 0' El. to (+) 69' 4" El. & Roof Structure Surface LTP Table 5-4 Gross Activity DCGL Class 3 Class 3 Adjusted Class 3 Class 3 Uses 3.0 if Relative Shift is

>3 NUREG-1575 Table 5-5 Class 3 Class 3 Page 3 of 8 FSS Summary Report F8120141

Survey Results:

A total of 14 direct measurements were made in F8120141. The results including mean, median, standard deviation and range are shown in Table 2. All direct measurements were less than the DCGL. None of the scan measurements indicated areas of elevated activity. The highest average ISOCS gamma measurement was 4,441 dpm/ 100 cm 2 Cs-137; Co-60 was not identified above the MDA. 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 (dpm/100 cm

+

F8120141-CO001BD F8120141 -CO002BD F8120141 -CO003BD F8120141 -CO004BD F8120141 -C0005BD F8120141-MOO06BD F8120141 -CO007BD F8120141 -CO008BD F8120141-CO009BD F8120141-CO01OBD F8120141-Co011BD F8120141-CO012BD F8120141-CO013BD F8120141-CO014BD Mean:

Median:

Standard Deviation:

Range:

1,774 1,805 1,572 1,681 1,810 809 1,437 1,857 1,650 1,696 2,080 2,303 1,857 1,707 1,717 1,740 336 809 "- 2,303 Page 4 of 8 FSS Summary Report F8120141

Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm 2)

F8120141 C0001SM

-0.95 F8120141C0002SM 0.34 F8120141C0003SM 1.64 F8120141 C0004SM 5.51 F8120141C0005SM

-0.95 F8120141 M0006SM 1.64 F8120141C0007SM

-2.24 F8120141 C0008SM

-2.24 F8120141 C0009SM 0.34

-F8120141CO010SM

-3.53 F8120141CO01ISM

-4.82 F8120141C0012SM 4.22 F8120141C0013SM

-3.53 F8120141C0014SM 1.64 Mean:

-0.21 Median:

-0.3 Standard Deviation:

2.98 Range:

-4.82 to 5.51 Page 5 of 8 FSS Summary Report F8120141

Survey Unit Data Assessment; The survey design required 14 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 F8120141

Table 4. Data Assessment Results Survey Results Parameter Value Comment Material Background Used (dpm/100 cm2):

N/A Ambient Background Used (dpm/100 cm 2):

N/A Average Ambient BKG = 0 Actual Direct Measurements (N):

14 Median (dpm/100 cm2):

1,740 Mean (dpm/100 cm2):

1,717 Direct Measurement Standard Deviation.

336 (dpm/100 cm 2)"

Total Standard Deviation (dpm/100 cm 2):

336 Based on samples and backgrounds.

Maximum (dpm/100 cm2):

2,303 Material Type:

N/A Background Subtract Not Applied Sign Test Final N Value:

14 S+ Value:

14 Critical Value:

10 Sufficient Samples Collected:

Yes Maximum Value < DCGL:

Yes Median Value < DCGL:

Yes Mean Value < DCGL:

Yes Maximum Value < DCGLemc:

N/A Class 3 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 F8120141

Survey Unit Investigations and Results:

No investigations were required for either direct or scan measurements and no investigation results are reported.

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 3 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. No potential areas of elevated activity were detected.

==

Conclusion:==

The FSS of this survey unit was properly designed as a Class 3 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. No 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 F8120141 meets the release criteria of 10CFR20.1402.

Page 8 of 8 FSS Summary Report F8120141 Maps June 3, 2008 Survey Unit F8120141

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inside the Industrial Area Map F8120141-1, Fuel Storage Building Location at Rancho Seco site

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4 Distance in Meters Map F8120141-2, Fuel Storage Building North Elevation +0' El. to +69' 4" El.

Area Estimate: 325 sq. meters Page 3 of 9 Att. I Maps F8120141

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76.25 ft.

34.25 ft.

6 in.

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3 4

Distance in Meters Map F8120141-3, Fuel Storage Building +69' 4" El.

Auxiliary Building +69' 4" El.

Exterior Roof Area Estimate: 529 sq. meters

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Meler4 Map F8120141-4, Fuel Storage Building Di~t-e i

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Random Measurement Locations Page 5of 9

.Att.lIMaps F8120141

NOTE: 8BD, 9BD, 10BD and 11BD locations fall on the exterior wall behind the c6lumns and not on the columns.

0 1

2 3

Distance in Motors 4

CL 4) E a) 000 CU LU Map F8120141-5, Fuel Storage Building North Elevation +0' El. to +69' 4" El.

Beta Direct Measurements F8120141C0001BD to F8120141C0005BD, F8120141M0006BD and F8120141C0007BD to F8120141C0014BD Page 6 of 9 Att. 1 Maps F8120141

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Distance in Meters Map F8120141-6, Fuel Storage Building +69' 4" El.

Auxiliary Building +69' 4" El.

ISOCS Gamma Scan Measurements F8120141Q0030GS to F8120141Q0041GS 12.57 sq. meter field of view Total Scan Area: 123.5 sq. meters

Distance in meters from

+40' EI.Turbine Bldg.

0 1

2.

3 4

Distance in Meters Map F8120141-7, Fuel Storage Building North Elevation +0' El. to +69' 4" El.

ISOCS Gamma Scan Measurements F8120141M0042GS to F8120141M0043GS and F8120141 C0044GS to F8120141 C0045GS 12.57 sq. meter field of view Total Scan Area: 35 sq. meters Page 8 of 9 Att. 1 Maps F8120141

Distance in meters from grade 8

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1 2

3 Distance in Meters 4

Map F8120141-8, Fuel Storage Building North Elevation +0' El. to +69' 4" El.

ISOCS Gamma Scan Measurements F8120141C0022GS to F8120141 C0029GS 12.57 sq. meter field of view Total Scan Area: 79 sq. meters Page 9 of 9 Att. 1 Maps F8120141 Instrumentation June 3, 2008 Survey Unit F8120141

Table 2-1. Survey Unit Instrumentation Instrument Detector MDC Static MDC Scan Model; Serial No.

Model; Serial No.

(dpm/100 cm 2 )

(dpm/100 cm 2)

M2350; 175834 43-68B; 190482 433 1,033 Tennelec; 0401171 N/A 5.88 dpm a, N/A 11.71 dpm MDC Concrete-1,800 dpm/100 cm 2 Cs-137, Concrete - 1,280 dpm/100 cm 2 Co-60 Table 2-2. Investigation Criteria and DCGL Value Parameter VleC2 (dpm/100 cm 2)

Investigation Criteria - Direct 21,500 Investigation Criteria - Scan 4,300 (ISOCS average activity)

DCGLw 43,000 DCGLEMC N/A Page 2 of 2 Att. 2 Instrumentation F8120141 Investigation June 3, 2008 Survey Unit F8120141 (none required)

Data Assessment June 3, 2008 Survey Unit F8120141

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F8120141 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpm/1 00cm2 3,000 2,500

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F8120141 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpmi00icm2 U

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