IR 05000317/1993007
| ML20035H099 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 03/22/1993 |
| From: | Carrasco J, Gray E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | |
| Shared Package | |
| ML20035H096 | List: |
| References | |
| 50-317-93-07, 50-317-93-7, 50-318-93-07, 50-318-93-7, NUDOCS 9305030124 | |
| Download: ML20035H099 (10) | |
Text
.
.
.-
S e
U.S. NUCLEAR REGULATORY COMMISSION
REGION I
Report Nos.
50-317 and 318/93-07 Docket Nos.
50-317 and 318 Licensee Nos.
Baltimore Gas and Electric Company Facility Name:
Calvert Cliffs Inspection At:
Lusby. Maryland Inspection Conducted:
March 01-05.1993
-
-
Inspectors:
(
drXJ M 2 03/M[93 J. E.Wrrasco, Reactor Engineer
/ da(e Materials and Processes Section, EB, DRS
,
]I!2f[f3 Approved by:
'
date E. H. Gray, Chief'
Materials and Processes Section, EB, DRS Inspection Summary:
Areas Inspected: A safety inspection was conducted to determine whether the licensee's provisions for the analysis, design and construction of two new safety-related diesel generator buildings at the Calvert Cliffs Nuclear Power Plant were performed in accordance with recommended engineering practices and regulatory requirements. The independent spent fuel storage installation was also inspected, including the closing of an unresolved item from previous inspection.
9305030124 930423 PDR ADOCK 05000317
.
_
..
..
,
-
.
.
'
'
.
,
l t
Fesults: It was demonstrated that the soil excavation was performed in accordance with
.!
!
special instructions established in the peninent 10 CFR 50.59 Safety Evaluation. Adequate provisions were made to prevent soil erosion and sediment throughout the duration of the j
yard modification. Preparation of base soil and backfill are planned to be done in -
i accordance with written procedures. The seismic input and the stmetural nudel for the
analysis of the new diesel generator buildings was performed in accordance with current-l standard engineering practices with heavy emphasis on recommendations outlined in the l
USNRC. Standard Review Plan and the pertinent Regulatory Guides.
l
.
Regarding the qualification of the steel supplier for the transfer cask for the independent
spent fuel storage, it was stated that there is a report which indicated that an unqualified steel l
supplier never supplied material for the fabrication of the transfer cask. This was confirmed
'
by the licensee in subsequent communication with NRC Region I via letter dated i
April 1,1993.
l
.
!
i r
!
-i f
8 B
9
.
.
t I
!
l
!
-,
O
__
.
.
.
.
l
'
1.0 PURPOSE AND SCOPE The purpose of this inspection was to determine whether the licensee's provisions for the analysis, design and construction of two safety-related diesel generator buildings at Calvert
,
Cliffs Nuclear Power Plant were performed in accordance with recommended engineering
,
'
practices and regulatory requirements. The independent spent fuel storage installation was also inspected, including the closing of an unresolved item from a previous inspection.
.
2.0 STRUCTURAL REVIEW OF TIIE DESIGN OF TIIE DIESEL GENERATOR (D/G) BUILDINGS (37700)
Background To comply with the requirements of 10 CFR 50.63, the licensee is adding two safety-related diesel generators at their two-unit Calvert Cliffs Nuclear Power Plant. Upon the completion of the installation of the new D/Gs, the licensee would have one D/G dedicated to each of the four engineered safety features busses, with the fifth D/G used to mitigate station blackout conditions and a standby for any of the four dedicated D/Gs.
- Description of the Structures To conform with the requirements of the General Design Criteria (GDC) 2 and the 10 CFR 100, the D/G Buildings were classified as Category I structures.
-
.
The D/G Buildings were designed to be three story, rectangular, reinforced concrete
'
,
structures approximately 75 feet by 97 feet in plan, excluding the east end entry ports. Each building is proposed to be nominally 60 feet in height and supported on a mat foundation at grade level with a partial basement in the area of the D/G pedestal. In addition, a 20-foot high, one-story structure would be provided on the east side of the buildings as missile protection for the main building entry and D/G area exhaust louver.
- Description of the Foundation
,
t The D/G Buildings would be supported by a mat foundation of five-foot thickness. The i
diesel generator pedestal, nominally 40 feet long by 9 feet wide will be constructed integrally with the basement mat foundation. The buildings would be separated by a seismic gap of
approximately three inches.
l
.
I
.
.
'
.
.
4 Findings
- Walkdown of the Excavation's Support System The inspector observed that the excavation removed the layer of clay (stratum IV in the soil report) in its entirety. The excavation was performed in accordance with special instructions.
The soil report indicated that this layer of clay did not provide sufficient bearing capacity for the new D/G buildings.
During the walkdown it was observed that the 18-foot deep excavation utilized a sheeting system for excavation support structure. This supporting structure covered three sides of the excavation with the exception of the fourth side, which was left for a ramp access.
The inspector verified that this yard modification was performed in accordance with the limitations as presented in the 10 CFR 50.59 (Log No. 92-B-024-087-RO) Safety Evaluation prepared to support the activities associated with the yard modifications for the construction of the new DIG buildings. Specifically, the licensee stated that the drilling for the sheet piles was performed by rotary drilling rigging rather than percussion drilling rigging to prevent
!
'
any vibrations from propagating towards the power block and any other safety related structure located near the drilling site. The excavation was made in a way to prevent damage to the modified storm drain pipes that were to remain in service. It was also verified that the licensee is cognizant of the site erosion and sediment control plan, which will be in j
effect throughout the duration of the yard modifications. The inspector found the excavation activities were performed in accordance with written instructions and had no further questions on this matter.
i
- Soil Preparation and Backfill i
The inspector reviewed key points of the soil report which concluded that the (stratum V)
-
sand which is under the clay (Stratum IV) would provide satisfactory support for the new buildings. According to the soil report, the borings indicated the top of this sand to be at elevation +27 feet, which is 18 feet below grade, the bottom of the diesel generator pit and pedestal mat is planned to be at 14.5 feet below grade, elevation +30.5 feet. The difference of 3.5 feet would be backfilled with compacted crushed stone structural fill.
Through interviews with the Civil Engineer and the QC personnel, the inspector verified that there is a procedure (SP-700, Rev.1) in place to ensure that the proper backfill is compacted i
to at least 95 percent of maximum dry density as specified in the soil report (ASTM D 1557 Modified Proctor).
The inspector verified that the natural soil subgrade in stratum V sands was inspected by a qualified geotechnical engineer. This test would be documented as part of the permanent project file prior to the placement of the structural fill that will support the structure. The i
-
.-
.
-
. - -
,
t
.
.
'
.
!
licensee is also cognizant that settlement of the structure should be monitored during and f
'
after construction. The inspector determined that the licensee is taking the proper steps to ensure the safety and quality of the soil preparation and the backfill activities and had no l
further questions on this matter.
'
!
Conclusion Based on the above, the inspector concluded that the soil excavation was performed in
,
accordance with special instructions established in the 10 CFR 50.59 Safety evaluation. The i
licensee made the adequate provisions to prevent soil erosion and sediment throughout the i
duration of the yard modification. Preparation of base soil and backfill would be done in accordance with written procedures.
t 3.0 PROJECT STATUS
}
The licensee scheduled the safety-related construction activities from elevation +27'-0" and l
.
up to begin on March 15.
-
The inspector verified that out of 13 civil procedures required for the next work phase, only
three were commented upon by QC prior to receiving the fm' al licensee's approval. This approval would be done in accordance with engineering approval procedure DGP-EN-001.
Although, the procedures were prepared and reviewed by the contractor they needed to be
,
reviewed and approved by the licensee's cognizant parties involved in the activities outlined in the procedures.
The inspector expressed concern regarding the licensee's ability to approve and expedite j
procedures prior to commencing the safety-related activities in the yard. The licensee's
,
management stated that no safety-related activity would begin without licensee review,
{
approval and concurrence, even if this means delays in the schedule.
,
4.0 REVIEW OF SEISMIC ANALYSIS CALCULATION FOR THE NEW DIESEL t
GENERATOR BUILDINGS (37700)
.
The inspector reviewed a sample of the calculations identified in the groups below. These i
'
'
calculations document the seismic analysis of the Diesel Generator Buildings and were reviewed to ensure that these analyses were performed in compliance with acceptance criteria from the applicable Standard Review Plans (SRPs) and Regulatory Guides (RGs).
!
l s
These calculations were lumped into three major groups. These were Seismic Inputs
(Acceleration Time Histories), Soil Model, and Structural Model. These analyses were
-
followed by Seismic Analysis which was the bases for the generation of the Seismic Floor Response Spectra and Seismic load, to be used in the structural design of the new D/G buildings,
!
j
-
-
'
j
.
.
i Findings
- Seismic Input The inspector found that these calculations were prepared in accordance with the Standard Review Plan and the pertinent Regulatory Guides. For example: Calculation (Calc.) No.
D-C-92-001, Revision (Rev.) 0, " Validation of Computer Program SECTION." In this calculation, the licensee documented the validation of a generated computer program named SECTION which was used to calculate the area, weight and stiffness properties of the walls in the D/G Buildings. The inspector verified the accuracy of the validation of this computer program, which was performed by comparing computer and hand generated solutions. A sample of the results generated by hand calculations was found almost identical to the one 3enerated by the computer program. The inspector had no further questions and the program appears to be a reliable tool for the iterations.
,
Calculation No. D-C-92-002, Rev. O, " Acceleration Time Histories - Strong Motion Duration." For this calculation, the inspector verified that the licensee demonstrated that the three time histories used to defme their seismic input to the seismic analysis complied with strong motion duration criteria as it is defined in the Standard Review Plan SRP Section 3.7.1 (II.1.b), with the following details:
j I
Time History Strong Motion Duration Acceptance Criteria
,
Horizontal - H1 9.16 seconds 6 - 15 seconds l
Horizontal - H2 7.69 seconds 6 - 15 seconds i
Vertical - V 6.11 seconds 6 - 15 seconds
__
The strong motion duration was established by using a computer program named (STRONG)
which was validated by comparing computer and hand generated solutions.
I Calc. No. D-C-92-003, Rev. O, " Acceleration Time Histories - Spectra Enveloping." The three time histories used in the seismic analysis, which were normalized to Ig, would l
normally be multiplied by the following factors (maximum ground accelerations) to define the seismic input:
!
L
o t
-
.
.
~
'
.
.
_
,
Direction / Earthquake Max. Ground Acceleration
Horizontal /SSE 0.15 g Vertical /SSE 0.10 g
}
Horizontal /OBE 0.08 g Venical/OBE 0.053 g However, this calculation established that, in order to comply with the spectra enveloping criteria defined in SRP Section 3.7.1 (II.l.b), these factors would be increased by 10 percent. While the ground (response) spectra corresponding to the three time histories were generated at the 75 frequencies defined in Table 3.7.1-1 of the SRP using a standard computer program. The design spectra were defined in accordance with criteria from RG 1.60, Rev.1, with the exception that the same maximum ground acceleration had not defined
!
both the horizontal and vertical components of the eanhquakes. Instead, the licensee defined
!
the maximum vertical acceleration as two-thirds of the maximum horizontal ground acceleration. The inspector inquired about the rationale behind this ratio. The licensee provided the inspector with a satisfactory answer referencing an abstract prepared for the
,
'
Seismic Society of America on this subject. Based on the abstract, a vertical to horizontal peak acceleration ratio of about 3/4 to 4/5 is appropriate for very close earthquakes of up to magnitude 6 to 6.25. Clearly, the Safe Shutdown Earthquake (SSE) magnitude for the Calven Cliffs site with its SSE of 0.15 g is somewhat less than the magnitude 6 to 6.25. For these smaller magnitudes, it was concluded in the abstract that the ratio of vertical to
horizontal peak accelerations decreases. The maximum vertical acceleration used by the licensee as two-thirds of the maximum horizontal ground acceleration appears to be adequate.
!
However, the licensee has submitted a detailed Civil Design Report to the NRR for their review.
- Structural Model
'
.
The inspector reviewed the structural model representing a typical model of the Diesel Ocnerator Building. It was verified that this model included the D/G pedestal and the fuel oil storage tank that are located in the building. Flexibility of elevated floors was represented and common elevation was used to represent two level foundation.
For the purpose of the seismic analysis (Calc. No. D-C-92-007, Rev. 0), the licensee used Operating Basis Earthquake (OBE) structural damping values in both SSE and OBE seismic analysis, rather than establishing correlation between stress levels and structural damping values. The inspector found this approach conservative since the OBE damping values are lower than the SSE damping values (Reg. Guide 1.61). However, this approach requires funher review by the NRR, and would be covered in the review of the licensee's Civil Design Repor.
.
.
.
.
.
,
!
i Conclusion
!
The inspector concluded that the licensee's seismic input and the structural model for the analysis of these buildings was performed in accordance with current standard engineering
.
practices with emphasis on recommendations outlined in the USNRC Standard Review Plan and the pertinent Regulatory Guides.
'
5.0 REVIEW OF THE INDEPENDENT SPENT FUEL STORAGE INSTALLATION (37700)
Background j
The licensee began commercial operation of Calvert Cliffs Nuclear Power Plants, Units 1 and 2, on May 8,1975, and April 1,1977, respectively, Since then, these two 2700 MWT
,
'
units have stored spent fuel assemblies in a common storage spent fuel pool.
,
As spent feel accumulated in the licensee's pool, its storage capacity had to be increased.
After the last re-rack of the spent fuel pool with higher density storage racks, the licensee determined that this new capacity allowed them to maintain a full core of load capacity until the 1992 refueling of Unit 1. To resolve this situation, the licensee has completed the construction of their independent spent fuel storage installation. This storage system is the
.
"NUHOMS-24" which consists of the following safety-related structure and components: a
modular vault dry storage (the structure), on-site transfer cask, a dry shielded canister (DSC)
and the cask lifting yoke.
!
Findings
- Walkdown of the Facility As a follow-up for inspection report Nos. 50-317/91-25 and 50-318/91-25, the inspector and
,
the Project Engineer walked down the completed facility and observed that the facility i
appears to be ready to receive spent fuel. In fact, the licensee indicated that the NRC has issued a license to operate this facility during the refueling this year. Upon completion of the tour the inspector reviewed a sample of the receiving documentation on the transfer cask and the cask lifting yoke.
The inspector verified that the licensee's contractor for the fabrication of the transfer cask and cask lifting yoke performed all required inspections prior to the release for these items.
The supporting documentation consisted of material certifications, travelers (work orders),
non-conformance reports, as-built information and weight certificat l O
.
i
, e
.
3
,
During the review of additional documentation to support the fabrication of the 'ansfer cask,
the inspector noted in a report of surveillance conducted by the licensee's auditor on the vendor and his sub-vendor on December 14, 1990, the following discrepancies:
l l
The licensee's vendor surveillance report stated that upon reviewing the approved vendors list (AVL), dated August 14, 1990, it was noted that a steel supplier was not listed on the AVL, pending reaudit. This report concluded that the vendor had not met the requirements
.
l of the licensee's contractor specifications nor the licensee's QA requirements.
On a subsequent report dated January 28,1991, the licensee's QA inspector stated that material had been supplied from this supplier although none of these vendor's locations had
been audited, nor were they on the AVL. However, the report concluded that the sub-
,
vendor met the requirements of the vendor's specifications and the licensee's requirements.
l r
In reply to the inspector's questions in this area, the licensee stated that there is a subsequent
.
report which indicated that this steel supplier was dropped from the selected sub-vendor list
!
and never supplied material for the fabrication of the transfer cask. Upon further review of l
the cask documentation package, the licensee determined and the inspector verified that the
steel for the transfer cask was shipped directly from another steel supplier, which is in the
!
licensee's AVL. The inspector has no further questions in this regard.
t 6.0 (CLOSED) REVIEW OF THE LICENSEE RESOLUTION TO AN UNRESOLVED ITEM NOS. 50-317& 318/91-20-01
The inspector reviewed and discussed the licensee's resolution of item 91-20-01 regarding the lack of clarity in the description of responsibilities of an independent reviewer / approver of
'
'
calculations in procedure DESP-6. To achieve a resolution, the licensee reviewed and
enhanced the pertinent portions (section 6.7) of the procedure DESP-6 which provides guidelines for review of calculations prepared by outside organizations.
The inspector verified and reviewed the enhanced version and found it acceptable.
!
Therefore, unresolved item 50-317 and 318/91-20-01 is closed.
!
7.0 MANAGEMENT MEETINGS i
Licensee management was informed of the scope and purpose of the inspection at the beginning of the inspection. The findings of the inspection were discussed with licensee j
'
management at the March 5,1993, exit meeting. See Attachment I for attendance.
,
i
i
_ _ - _.
.
..
.
,
.-
.
i
+
. '
ATTACIIMENT l
PERSONS CONTACTED
i Boston Gas and Electric Company
A
- C. N. Butler Project Engineer, ISFSI j
- G. L. Detter Nuc. Reg. Mtrs.
- M. J. Gahan, III Principal Engineer, CEU
- R. A. Gambrill Projects
- P. J. Hebrank DGP i
- C. R. Mahan DGP
- W. Maki Nuclear Regulation
.i
- G. J. O'Connell Sr. Civil Engineer i
- W. V. Ramstadt Quality Audits
- B. C. Rudell NOPMD
,
"S. A. Thomas DGP
- A. R. Thorntt..
Diesel Project
- R. H. Waskey,.'..
G. S. Design Engrg.
- E. F. Wasson DGP
- M. A. Wright DES U. S. Nuclear Regulatory Commission P. R. Wilson Senior Resident Inspector
- denotes those present at the exit meeting.
i
I
.
-.