ML20204F976
| ML20204F976 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 04/29/1983 |
| From: | Kemper J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8305020335 | |
| Download: ML20204F976 (5) | |
Text
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PHILADELPHIA ELECTRIC COMPANY 23O1 MARKET STREET P.O. BOX 8699
'I901 PHILADELPHIA. PA.19101 (215)841 45o2 JOHN S. KEMPER April 29, 1983 v.cc enesios,.r E NG4 NEE N6MG AND RESE ARCH Mr. A. Schwencer Docket Nos. 50-352 Licensing Branch No. 2 50-353 Division of Licensing U. S. Nuclear Regulatory Commission
Subject:
Limerick Generating Station, Units 1 6 2 Request for Information
" Fast Scram" Hydrodynamic Loads Reference :
1)
Letter, A. Schwencer to E. G. Bauer, Jr.,
dated April 5,1982 2)
Letter, E. J. Bradley to A. Schwencer, dated April 23, 1982 3)
Letter, E. J. Bradley to A. Schwencer, dated July 27, 1982 4)
Letter, E. J. Bradley to A. Schwencer, dated December 16, 1982 5)
Letter, E. J. Bradley to A. Schwencer, dated March 9, 1983
Dear Mr. Schwencer:
This is a complete response to the NRC request for information on Control Rod Drive System hydrodynamic loads contained in the reference
- 1) letter.
We have evaluated the loads to the CRD system caused by the operation of the scram valves and have incorporated these loads in the design of the Limerick Control Rod Drive (CRD) system and have changed. support designs as necessary.
The following is an item by item response to your April 5,1982 request:
1.
The design basis opening time for the inlet line scram valve.
Sco/
Response
As indicated in our reference 5) letter, testing was performed on an actual hydraulic control unit from the Limerick Unit No.
2 CRD system. Two test cases were modeled and performed; 1) start-up scram opening time for the inlet line scram valves, and 2) normal operating scram for the outlet line scram valve.
These two conditions were evaluated to have the highest potential for hydrodynamic loads.
8305020335 830429 PDR ADDCK 05000352.
A PDR
y
. The results of the testing are shown in the following table:
INLET LINE SCRAM VALV8 FOR OUTLET LINE SCRAM VALVE FOR START UP SCRAM NORMAL OPERATION SCRAM TIME FLOW AREA TIME FLOW AREA 0
0 0
0
.003
.002
.010
.024
.012
.012
.013
.029
.013
.021
.019
.056
.021
.049
.022
.076
.027
.090
.023
.091
.030
.142
.030
.135
.034
.176
.032
.139
.041
.219
.037
.153
.045
.228 2.0
.153 3.0
.228 3.0
.153 2.
An evaluation of the hydrodynamic loads in your CRD system resulting from actuation of the inlet line scram valve using the design basis opening time specified in Item 1.
Response
The test data, shown in item 1 above, was used to develop force time histories which were applied to insert and withdrawal line piping structural models.
The "one line, worst case basis" described in the reference 5) letter was expanded such
-that a total of seven lines were analyzed for water hammer effects. This is concluded to be bounding of all insert and withdrawal lines.
It was concluded that the forces generated by the opening of the scram valves are of sufficient magnitude that they should be included in the CRD piping design.
3.
A description of the conditions and configurations of the plant which result in the maximum hydrodynamic loads in the CRD system.
Response
The maximum loads on the inlet lines were found to occur during start-up scram. At this time the following conditions exist.
a.
The inlet line is at low pressure, approximately 30 psig, b.
The nitrogen pressure in the accumulator is approximately 1100 psig.
c.
The charging water pressure is 1550 psig.
d.
A maximum pressure differential of 1550-30 = 1520 psi exists across the inlet line scram valve.
e
- The maximum loads on the outlet lines were found to occur during normal operation scram. At this time the following conditions exist.
a.
The outlet line is at normal operating reactor pressure, approximately 1000 psig.
b.
The scram discharge volume is at atmospheric pressure.
c.
A maximum pressure differential of 1000 psi exists across the outlet scram valve.
The hydrodynamic loads developed at the end of control rod travel are evaluated to be enveloped by the above two cases.
4.
A statement regarding the appropriateness of the mathematical model used to calculate the hydrodynamic loads in the CRD system resulting from a scram.
Response
The pressure wave transmission in the CRD piping was determined using a mathematical technique known as the method of characteristics.
This is a classical method for the solution of this type of problem.
The scram valves were treated as orifices with areas that varied as a function of time. This area vs time is given in Item 1.
The accumulator was modeled as a piston mass with an adiabatically expanding gas on one side (Nitrogen) and CRD inlet line water on the other side.
The CRD mechanism was treated as a piston with the mass of the control rod and all attached parts. This piston is accelerated by the inlet line pressure on one side and the outlet line pressure on the other side.
The scram discharge volume was assumed to be a reservoir at atmospheric pressure.
5.
A comparison of the hydrodynamic loads evaluated in Item 2 with the present design basis loads for the CRD system.
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s
Response
1 Due to the complex nature of the CRD piping system and the transient nature of the water hammer loads it is difficult -to make a direct comparison to the design basis loads, however, the waterhammer loads which were calculated were of sufficient magnitude at certain locations to require support modification.
Since the Limerick CRD system support design has not yet been completed these loads will be included in the final design.
Sincerely, 4
Copy to:
(See Attached Service List)
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I cc:- Judge Lawrence Brenner i
Judge Richard F. Cole Judge Peter A. Morris Troy B. Conner, Jr., Esq.
Ann P. Hodcfon Mr. Frank R. Rxnano Mr. Ibbert L. ' Anthony Mr. Marvin I. Its'is i
Judith A. Dorsey, Esq.
Charles W. Elliott, Esq.
Mr. Alan J. Nogee 1
'Ihcznas Y. Au, Esq.
Mr. 'Ihcznas Gerusky Director, Pennsylvania Emergency Managenent Agency Mr. Steven P. Hershey James M. Neill, Esq.
Donald S. Bronstein, Esq.
Mr. Joseph H. hhite, III Walter W. Cohen, Esq.
lbbert J. Sugannan, Esq.
Ibdney D. Johnson Atcznic Safety and Licensing Appeal Board Atcznic Safety and Licensing Board Panel Docket and Service Section i-t i
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