ML16341E165
| ML16341E165 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 04/10/1987 |
| From: | Schierling H Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML16341E166 | List: |
| References | |
| NUDOCS 8704240100 | |
| Download: ML16341E165 (14) | |
Text
~p,g flfgy 0
Op rrrr o
+>>*<<~
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 Docket Nos.
50-275 and 50-323 APR io SN LICENSEE:
FACILITY:
SUBJECT:
Pacific Gas and Electric Company (PG&E)
Diablo Canyon Nuclear Power Plant MEETING ON MARCH 26, 1987 - SPENT FUEL RACK ANALYSES NRC staff and its consultants (H. Fishman of Franklin Research Center (FRC) and G. DeGrassi of Brookhaven National Laboratory (BNL)) met with Pacific Gas and Electric Company (PG&E) and its consultants on March 26, 1987 at the office of Holtec International (PG&E consultants) in Mt. Laurel, New Jersey, regarding spent fuel rack analyses.
The list of attendees is attached as Enclosure l.
On March 23, 1987 the licensee had informed the staff that it had completed the analyses necessary to respond to the staff's letter of February 26,
- 1987, requesting additional information on single and multi-rack interactions.
The staff decided to audit the analyses and supporting calculations.
On March 24, 1987 the staff requested a meeting with PG&E for March 26, 1987 and the Project Manager informed the office of E. Lowry, attorney for R. Ferguson of the Sierra Club, of the forthcoming meeting.
Prior to the meeting, which commenced at about ll a.m.,
PG&E informed the Project Manager that PG&E considered the information to be presented by PG&E and its consultants to be proprietary because the type of analyses have not been performed previously by other utilities and therefore, modelling and results are potentially of commercial value to PG&E.
H. Schierling, NRC Project Manager, summarized the events leading up to this meeting as described above.
Xe provided the parties at the meeting with the written sumary of the PG&E/NRC telephone call on March 23, 1987, attached as Enclosure 2.
He informed all attendees at the meeting of the PG&E request for treating all information to be presented and discussed at the meeting, including the enclosures to this summary as proprietary.
He asked PG&E to document by letter the reauest for treating the information as proprietary.
H. Ashar, NRC staff technical reviewer, stated that the purpose of the meeting was for PG&E to inform the staff of the parameters, assumptions, modelling and results of the single and multi-rack analyses and for the staff and its consultants to audit the calculations (computer runs) and review the outputs.
He stated that the staff expects PG&E to document the information; however, this meeting would enable the staff to determine if the PG&E analyses are responsive to the NRC request for additional iriformation or if further information would be required.
M. Tressler, PG&E, explained that the analyses were performed by its consultant, Holtec International, at substantial cost and, therefore, this information should be considered proprietary.
He stated that the information had not been reviewed and checked in detail by PG&E at this time, and therefore, it should be considered as -"work in progress".
8704240100 870glP PDR ADOCK 05000275 PDR
CI
~
ff U
I K. Si'ngh, Holtec, summarized the analyses that had been performed in late-1985 and early-1986 as part of the PGKE application for the spent fuel pool expansion.
He highlighted certai,n design features of the Diablo Canyon high density spent fuel racks with reference to similar racks at other facilities.
For example, the girdle bars were added to the Diab'io Canyon racks as specific impact locations for rack-to-rack interactions and are located at the top of the racks, above the 1ocation of the fuel in the assemblies, in order to preclude impacts in the fuel region.
Also, while it would have been more economical and efficient to use only one size rack in the pool, 13 different sizes were used for the 16 racks in each of the two fuel pools.
This design feature makes the overall behavior of the racks more resistant to a seismic event.
The following assumptions were used in the modelling of the analyses:
1.
Four degrees of freedom:
four for rack (horizontal, vertical, rocking, interaction with fuel assemblies).
2.
All fuel assemblies in one rack vibrate in unison.
3.
Rack support legs may liftoff the floor or slide on the floor.
4.
Fluid coupling between fuel assemblies and between racks is included.
5.
Impacts are modelled by compression springs only.
6.
Fluid damping is not included.
7.
Form drag in the relative motion between a fuel assembly and its cell wall is neglected.
8.
Rack motion from drag is neglected.
9.
Effect of nonlinear coupling is neglected.
K. Singh stated that these assumptions, are conservative and in many cases beyond NRC requirements for such structural analyses.
Two single-rack and five multi-rack analyses were performed.
With reference to Figure 2. la, "Pool Layout Unit 1" in the reracking report (PGSE letter DCL-85-306) which is also attached in Enclosure 3 (page 1), the two single-rack analyses were performed for a 10 x 10 rack.
Four multi-rack analyses were performed for row A-A, an interior row consisting of racks "G" (8 x 10), "C" (10 x 10),
"D2" (9 x 10),
and "A2" (10 x 10); one multirack analysis was performed for row B-B, an exterior row consisting of racks "H", "D3", "K" and "B" as shown in Enclosure 3
(Enclosure 3 includes some viewgraphs used by PGSE/Holtec during the meeting).
A. Soler, Holtec, described in detail the derivation of the governinq equations of motion for rack-to-rack interactions within a 4-rack group and with the walls, taking into consideration the fluid coupling effects due to the kinetic energy of the fluid, based on the size of flow passage, continuity and conse~vation of mass.
The analysis also includes fluid effects of rattling of
~
~
the fuel and water, and the hydrodynamic effect of the fluid due to vertical motion of the rack and fuel assemblies.
He discussed the spring constants of the impact sprinqs as applied in the analysis of the fuel cell grid.
Rack-to-rack spring constants were taken as one-half of the rack-to-wall spring constants.
Stiffer springs constants had been used in the original 3D analyses.
B. Paul, Holtec, summarized the results of his studies on the effect of gap distance between adjacent racks on the fluid couplina, which he had presented at an earlier NRC/PGEE meeting on, February 18, 1987 (Meeting Summary dated March 10, 1987).
Fluid coupling between racks is an energy, dissipating effect and tends to retard the relative motion among the racks and thus reduce the impact forces in rack-to-rack interactions.
He determined that the fluid coupling effects can be accounted for by using an effective gap distance of approximately 1.35 times the actual gap distance.
He investigated a number of rack sizes, rack geometries and rack-to-rack and rack-to-wall configurations.
In all of these cases the factor of about 1.35 was found to account for fluid coupling effects.
K. Singh, Holtec, discussed in detail the seven two-dimensional (2D) analyses referred to earlier.
The analytical model for each analysis, Cases 1 through 7, is briefly descr ibed in Enclosure 3 (page 2), including Case 0, the analysis from the reracking report {DCL-85-306).
With reference to the rack layout shown in Enclosure 3, the single-rack analyses were performed for a 10 x 10 rack, such as racks "C""and "A2", and the multi-rack analyses for Sections A-A and B-B as shown in Enclosure 3.
A gap distance of ho of infinity was used as a conservative assumption (Case 0 and Case,l) and of ho
= 7.5 inches as a realistic assumption
{Cases 2, 3 and 4) as compared to'he nominal actual gap distance of 2k inches between racks., In Case 5 the gap distance of 37 inches between rack "K" and the wall was used for the entire row (Section B-B) in the analysis.
Cases 6 and 7
were performed to account for possible differences in the base plate dimensions, as was requested by the staff in Item 5 of its letter of February 26, 1987.
A high spring constant is about 10 times the calculated constant and a realistic one is 1.5 times the calculated constant.
K. Singh presented the calculated impact forces for rack/fuel assemblies interactions (Frf), rack/rack interactions (Frr ), and rack/wall interactions (Frw) for each of the seven Cases (see pages 3 and 4 of Enclosure 3).
The results are summarized in Table I, which also includes information on Case 0
and the design values.
This informantion was provided by PGSE to the Project Manager subsequent to the meeting.
The results were explained and discussed in some detail.
A zero impact load means there is not sufficient displacement to cause an impact.
Case 1 is considered to be the conservative analysis and Case 2 the more realistic analysis.
PGSE stated that the results of the single-rack analysis (Case
- 2) and the comparable multi-rack analysis
{Case 3) are essentially the same although Frw for the multirack analysis with a co-efficient of friction of 0.8 is about 50 percent higher than for the single rack analysis.
However, Frr of 78 kips for the single-rack analysis (Case 2) is the highest rack impact force and bounds all forces calculated for the two cases.
The staff noted that Frw of 106.5 kips for Case 5 is the largest rack-to-wall impact force and exceeds to largest rack-to-rack impact forces of Frr of 78 kips for the realistic Case 2 by nearly 40 percent and exceeds Frr of 90 kips, the conservative value in Case 1, by almost 20 percent.
0
The staff and its consultants audited selected calculational packages and computer outputs for the analyses to better understand the input parameters.
The staff also looked at a number of time histories of displacements and impact forces that were avai labl'e.
Following a staff/consultant
- caucus, the staff informed'the licensee it appeared that the information provided at the meeting would be sufficient to respond to the 5 items in the February 26,
~987 letter-and the licensee should submit the information after verification, as soon as possible.
Staff requested that if any of the information is to be considered proprietary then a
proprietary and non-proprietary response should be submitted.
The staff also stated that it will consider the information provided and will determine if any further information would be required to complete its evaluation of the adequacy of the fuel racks on the basis of the two dimensional single and multi-rack analyses provided at the meeting.
The staff stated that it will inform the licensee on March 30 or 31 of its conclusion on this aspect.
The meeting adjourned at about 8:00 p.m.
Enclosures:
As stated Hans Schierling, Project Manager Project Directorate b'3 Division of PWR Licensing-A cc:
See next page
~
~
TABLE 1:
IMPACT LOADS AND DESIGN VALUES (KIPS)
Case Descri tion COF Frr Frw 0
Single Rack:
original analysis; 3D; 8DOF; adjacent racks move out-of-phase;
'infinite fluid medium (ho
=
infinity); high spring constants.
0.8 0.2 249.7(2) 88.2(4) 38.6(5)
(1)
(3)
(3) 242.6 105 63.3 1
Singl e Rack - simplified:
2D; 4DOF; adajacent racks move out-of-phase, infinite fluid medium (ho
= infinity);
high spring constants.
0.8 0.2 129 127 0
90 2
Single Rack - simplified:
2D, 4DOF, adajacent racks move out-of-phase; narrow fluid channel (ho
= 7.5");
realistic spring constants.
0.8 65 0.2 67 78 38.5 44 39 3
Multiple Racks (Section A.A):
2D; 16DOF (4x4 racks); fully loaded; narrow fluid channels (ho
= 7.5"); realistic spring constants 0.8 0.2 72 65 73.7 27.2 69 41.9 Multiple Racks (Section A-A):
0.8 2D; 16DOF (4x4 racks);
3 fully 0.2
- loaded, one empty rack; narrow fluid channels (ho
= 7.5");
realistic spring constants.
Multiple Racks (Section B-B):
0.8 2D; 16DOF (4x4 racks);
one wide 0.2 fluid channel (ho
= 37"); no flow on other side; realistic spring constants.
78 65 71 62
- 72. 5
- 17. 2 76 28.5 75 37.6 106.5 51
0'ase Descri tion COF Frf Frr Frw 6
Multiple Racks (Section A-A):
2D; 16DOF (4x4 racks);
3 fully
- loaded, one empty rack; variable gaps between racks; narrow fluid channels (ho
= 7.5"); realistic spring constants.
7 Multiple Racks (Section A-A):
2D; 16DOF (4x4 racks); fully loaded; variable gaps; narrow fluid channels (ho
= 7.5");
realistic spring constants.
0.8 0.8 77 75 34 79.8
- 62. 7 73.7 Design Values 883(6) 175(7) 175(7) 350 350(
(1)
(2)
(3)
Run "Acorn 10" Run "aa002" Run "acl3aal" Licensing Report, Table 6.8.2 Licensing Report, Table 6.8.2 Seismic Analysis Report, Table 6.3 (Frr),
Table 6.6 (Frw)
(4)
(5)
(6)
(7)
Run "ac13ab" Seismic Analysis Report, Table 6.3 Run "tt15" Seismic Analysis Report, Table 6.6 Li'censing Report, Table 6.8.2 at aa001**, independent of COF Licensing Report, Table 6.8.2 at aa001**, indepen'dent of COF; Frr = Frw = 175 kips is impact force per each of two springs in 3D analysis and Frr = Frw = 350 kips is impact force for single spring in 2D analysis.
4
~
ENCLOSURE I NRC/PGFE MEETING MARCH 26, 1987 LIST OF ATTENDEES H. Ashar S. Bhattacharya C. Coffer G. DeGrassi R. Ferguson H.
Fishman S.
Johnson B. Paul H. Schierling K. Sinah A. Soler M. Tressler NRC PGKE PG&E BNL -
NRC Consultant Sierra Club FRC -
NRC Consultant PGRE Holtec International Holtec International Holtec International PGSE