ML082620125

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Fuel Storage Building East Exterior Wall (-) 6 El. to (+) 20 El., Survey Unit F8120161
ML082620125
Person / Time
Site: Rancho Seco
Issue date: 05/14/2008
From:
Sacramento Municipal Utility District (SMUD)
To:
NRC/FSME
References
MPC&D 08-064
Download: ML082620125 (33)
v • d • e


Text

Rancho Seco Final Status Survey Surmmary Report May 14, 2008 Fuel Storage Building East Exterior Wall (-) 6' El. to (+) 20' El.

Survey Unit F8120161 Prepared By:_______

Date:

1,-

Reviewed By: --

7 Date:

6/-

Lead FSS Engineer Approved By: i Date:

7_____

Dismantlement Superintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit:

F8120161, Fuel Storage Building East Exterior Wall (-) 6' El. to (+) 20' El.

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 cm 2 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 cm2 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 cm 2 and a maximumvalue 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 determined using a random-start, fixed grid pattern and 123 m2 were scanned for 100% 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 F8120161

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

F812 I Survey Unit:,

Class:

SU Area (m2):

Evaluator:

DCGL (dpm/100 cm2):

Area Factor:

Design DCGLemc (dpm/100 cm 2):

LBGR (dpm/100 cm 2):

Design Sigma (dpm/100 cm 2):

Type I Error:

Type II Error:

Predominant Nuclide:

Sample Area (m2):

Scan Area (mi):

Scan Coverage (%):

ZJ-,* :

Zl_]P :

Sign P:

Calculated Relative Shift:

Relative Shift Used:

N-Value:

Design N-Value + 20%:

Design Min Samples N:

Grid Spacing L:

0161 1

123 D. Anderson 43,000 3.6 154,800 40,759 747 0.05 0.05 Cs-137 6.83 123 1000/%

1.645 1.645 0.99865 3

3 11 14 18 2.61 Fuel Storage Building East Exterior Wall (-) 6' El. to

(+) 20' El.

Structure Surface LTP Table 5-4 Gross Activity DCGL Class 1 Class 1 Adjusted Class 1 Class 1 Uses 3.0 if Relative Shift is

>3 NUREG-1575 Table 5-5 Class 1 Class 1 Page 3 of 8 FSS Summary Report F8120161

Survey Results:

A total of 23 direct measurements were made in F8120161. The results including mean, median, standard deviation and range are shown in Table 2. All direct measurements were less than the DCGL. The highest average ISOCS gamma measurements were 13,939 dpm/100 cm2 for Cs-137 and 2,081 dpm/100 cm 2 for Co-60. Soil samples collected from the trench adjacent to the structure identified the highest soil activity as 6.46 pCi/g Cs-137. Co-60 was not identified in soil 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 F8120161 -CO001 BD F8120161-CO002BD F8120161 -CO003BD F8120161-CO004BD F8120161-COOO5BD F8120161 -CO006BD F8120161-CO007BD F8120161-CO008BD F8120161-CO009BD F8120161-COOlOBD F8120161-CO011BD F8120161-Co012BD F8120161-CO013BD F8120161 -CO014BD F8120161--Co015BD F8120161--Co016BD F8120161--Co017BD F8120161-CO018BD F8120161-CO019BD F8120161 -CO02OBD F8120161-CO021BD F8120161 -CO022BD F8120161-CO023BD Mean:

Median:

Standard Deviation:

Range:

6,489 1,878 1,810 1,650 3,501 1,924 1,883 1,795 1,795 2,931 1,551 1,826

.1,733 1,758 1,743 8,045 1,701 1,738 1,463 1,847 1,650 1,769 1,063 2,328 1,795 1,646 1,063 - 8,045 Page 4 of 8 FSS Summary Report F8120161

Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpmll00 cm 2)

F8120161C0001SM F8120161 C0002SM F8120161CO003SM F8120161CO004SM F8120161C0005SM F8120161 C0006SM F8120161 C0007SM F8120161 C0008SM F8120161 C0009SM F8120161CO010SM F8120161 C0011 SM F8120161Co012SM F8120161 Co013SM F8120161CO014SM F8120161 Co015SM F8120161C0016SM F8120161CO017SM F8120161 CO018SM F8120161 Co019SM F8120161CO020SM F8120161CO021SM F8120161C0022SM F8120161 C0023SM Mean:

Median:

Standard Deviation:

Range:

1.64 1.64

-2.24

-4.82

-2.24

-2.24

-3.53

-3.53

-3.53 4.22

-3.53

-2.24 0.34

-3.53

-2.24 22.3

-3.53

-3.53

-0.95

-3.53

-0.95

-2.24

-3.53

-0.95

-2.24 5.51

-4.82 to 22.3 Page 5 of 8 FSS Summary Report F8120161

Survey Unit Data Assessment:

The survey design required 23 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 greater than the design standard deviation. Since both values of sigma resulted in a relative shift greater than three (3), no additional samples were required.

Page 6 of 8 FSS Summary Report F8120161

Table 4. Data Assessment Results Survey Results Parameter Value Comment Material Background Used (dpm/lO0 cm'):

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

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

23 Median (dpm/100 cm 2):

1,795 Mean (dpm!100 cm 2):

2,328 Direct Measurement Standard Deviation 1,646 (dpm/100 cm 2):

Total Standard Deviation (dpm/100 cm 2):

1,646 Based on samples and backgrounds.

Maximum (dpm/100 cm 2):

8,045 Material Type:

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

23 S+ Value:

23, Critical Value:

15 Sufficient Samples Collected:

Yes Maximum Value < DCGL:

Yes Median Value < DCGL:

Yes Mean Value < DCGL:

Yes Maximum Value < DCGLemc:

Yes Class 1 Total Standard Deviation <= Sigma:

Investigate All samples < DCGL.

Pass the Sign Test?

Yes Reject the Null Hypothesis?

Yes Does the Survey Unit Pass All Criteria?

Investigate SU Passes.

Page 7 of 8 FSS Summary Report F8120161

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 1 structure survey and the sample results are consistent with that classification. The variability of the survey results was greater than the characterization data used for survey design. However, no additional samples were required. No potential areas of elevated activity were detected. Therefore the EMC criterion was met.

==

Conclusion:==

The FSS of this survey unit was properly designed as a Class 1 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/1 00 cm2 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 F8120161 meets the release criteria of 10CFR20.1402.

Page 8 of 8 FSS Summary Report F8120161 Maps May 14, 2008 Survey Unit F8120161

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61.5 ft 16.1 ft 0

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3 4

Distance in Meters Map F8120161-2, Fuel Storage Building East Exterior Wall, (-) 6' El. to (+) 20' El.

Area Estimate: 123 sq. meters Page 3 of 17 Att. 1 Maps F8120161

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Random Start Location 2.2 meters from North corner 3.2 meters above grade

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Distance in Meters Map F8120161-3, Fuel Storage Building East Exterior Wall, (-) 6' El. to (+) 20' El.

Random Start Location Page 4 of 17 Att. I Maps F8120161

0 1

2 3

4 Distance in Meters Map F8120161-4, Fuel Storage Building East Exterior Wall, (-) 6' El. to (+) 20' El.

Beta Direct Measurements F8120161CO001BD to F8120161C0023BD 2.6 meter by 2.6 meter grid spacing Page 5 of 17 Att. 1 Maps F8120161

S34 3

3 3

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3 4

Distance in Meters Map F8120161-5, Fuel Storage Building East Exterior Wall, (-) 6' El. to (+) 20' El.

ISOCS Gamma Scan Measurements F8120161C0001GS to F8120161C0016GS 12.57 sq. meter field of view Page 6 of 17 Att. 1 Maps F8120161

0 1

2 3

4 Distance in Meters Map F8120161-6, Fuel Storage Building East Exterior Wall, (-) 6' El. to (+) 20' El.

Beta Scan Measurements F8120161C0001BS to F8120161C0016BS Page 7 of 17 Att. 1 Maps F8120161

0 1

2 3

4 Distance In Meters Map F8120161-7, Fuel Storage Building East Exterior Wall, (-) 6' El. to (+) 20' El.

Penetration Scan Measurements F8120161PO001BS to F8120161P001OBS Page 8 of 17 Att. 1 Maps F8120161

P0009BS P0008BS P0007BS P00066S

'I P0005BS P0001 BS P0002BS POO03BS POO04BS Map F8120161-8, Fuel Storage Building East Exterior Wall, (-) 6' El. to (+) 20' El.

Penetration Scan Measurements F8120161POOOIBS to F8120161POOO9BS Page 9 of 17 Att. 1 Maps F8120161

Map F8120161-9, Fuel Storage Building East Exterior Wall, (-) 6' El. to (+) 20' El.

Sump Excavation and Spoils Pile Page 10 of 17 Att. 1 Maps F8120161

Map F8120161-10, Fuel Storage Building East Exterior Wall, (-) 6' El. to (+) 20' El.

Sump Excavation Nal Gamma Scan Measurements F8120161SO001GS to F8120161S0005GS Page I Iofl7 Att. 1 Maps F8120161

0 00 o:o WabpT81,20161-11, Fuel Storage Building

ýEa'st:Exterior Wall (-) 6' El. to (+) 20' El.

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ýE66avationrS(oil 'Pile JIV Nal Gamma Scan Measurements F8120161S0002GS to F8120161S0012GS

  • Ma2_!6W1"*,12, Fuel Storage Building East Exterior Wall, (-) 6' El. to (+) 20' El.

Excavation and Soil Pile Soil Sample Locations F8120161S0001SS to F8120161S0012SS Page 13 of 17.

Att. 1 Maps F8120161

N'I 0 1 2

3 4

Distance in Meters Map F8120161-13, Fuel Storage Building East Exterior Wall, Sump Excavation ISOCS Gamma Scan Measurements F8120161 S0018GS to F8120161 S0023GS 12.57 sq. meter field of view Page 14 of 17 Att. 1 Maps F8120161

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4-00 M*p, -1 2 - 6 I,, e i S to ra g e B u ild in g astENOrWallExcavation and Soil Piles Nal Scan Background Measurements & Alarm Setpoints F8120161SOOO1SB to F8120161S0020SB

'Map F8120161-15, Fuel Storage Building East Exterior Wall, (-)6' El. to (+) 20' El.

Excavation and Soil Pile Nal Scan Measurements F8120161S0001GS to F8120161S0012GS

clQ cI-T 00 Map F8120161-16, Fuel Storage Building East Exterior Wall Excavation and Soil Piles Verification Nal Scan Measurements F8120161S0013GS to F8120161S0019GS Instrumentation May 14, 2008 Survey Unit F8120161

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; 142514 43-98B; 148639 1,400 2,520 M2350; 180733 43-98B; 148638 1,400 2,520 M2350; 193700 43-68B; 160691 433 1,033 M2350; 193715 43-68B; 148630 433 1,033 M2350; 193715 43-116-1B; 190643 796 3,258 Tennelec; 0401171 N/A 5.88 dpmct, N/A 11.71 dpmf Instrument Detector Detector MDC Model No.

Serial No.

Concrete - 1,240 dpm/100 cm 2 Cs-137, Concrete - 995 dpm/100 cm 2 Co-60 Instrument Detector MDC Static MDC Scan Model; Serial No.

Model; Serial No.

(pCilg)

(pCi/g)

M2350; 203482 44-10; 211672 N/A 5.2 M2350; 193715 44-10; 171374 N/A 5.2 Page 2 of 3 Att. 2 Instrumentation F8120161

Table 2-2. Investigation Criteria and DCGL Value Param eter V l eC 2

(dpm/100 cm 2)

Investigation Criteria - Direct 154,800 Investigation Criteria - Scan 63,300 (ISOCS average activity)

DCGLW 43,000 DCGLEMC 154,800 Page 3 of 3 Att. 2 Instrumentation F8120161 Investigation May 14, 2008 Survey Unit F8120161 (none required)

Data Assessment May 14, 2008 Survey Unit F8120161

CD, CD, 00 F8120161 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpmll 00cm2 ZI 9,000 8,000 7,000 6,000 5,000 4,000 3,000 2,000 1,000 0

1795 0

20 40

.60 Percentile R8 100 Direct Measurements (dcpm/1 00cm2) median -

- - 75th Percentile 50th Percentile 1

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6000 4000 -

2000 -

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