ML20077H077
| ML20077H077 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 06/20/1991 |
| From: | Devine J GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 5000-91-2052, C321-91-2128, NUDOCS 9107050130 | |
| Download: ML20077H077 (3) | |
Text
,
,4,
GPu Nuclear Corporation l.
Parsippany, New Jersey 07054 q ;I l g
g{
One Upper Pond Road 201-316-7000 TELEX 136 482 Writers Direct Dial Number June 20, 1991 5000-91-2052 C321-91-2128 U.
S.
Nuclear Regulatory Commission Attn Document Control Desk Washington, DC 20555 Gentlemen:
Subject:
Oyster Creek Nuclear Generating StLtion (OCNGS)
Docket No. 50-219 Thyroid dose to the control room operatcre.
References:
(1) NRC letter dated April 16, 1985 containing minutes of March 19, 1985 meeting.
(2) NUREG-1382, SAFETY EVALUATION REPORT related to the full term operating licence for Oyster Creek Nuclear Generation Station.
(3) BWROG's Licensing Topic Report, "A Technique for Evaluation of BWR MSIV Leakage Contribution to Radiological Dose Calculations (NEDO-30259, Revision 1), November 1988.
(4) NRC letter LS05-82-06-123 of June 29, 1982 to P. B.
Fiedler of GPU Nuclear, " Oyster Creek Nuclear Generating Station Safety Evaluation of SEP Topic XV-19, Radiological Consequences of a Loss of Coolant Accident."
(5) Oyster Creek Plant Procedure 665.5.020, Revision 7 (effective 12/20/90); Integrated Local Leak Rate Test Summary.
(6) GPU Nuclear letter to NRC, 5000-89-1733 of March 10, 1989 containing Topical Report 058.
The following is submitted in response to your letter of February 27, 3990 which requested an evaluation of thyroid dose to Oyster Creek control room operators.
9107050130 910620 PDR ADOCK 05000219 P
PDR ST:C3212128 y;$1 i
0300.1~
oPu Nucieer corporetion is a suesidiery or oenerai eubiic utiniies corporation i
. - ~ _
a C321-91-2128 Page 2 During a meeting with GPUN on March 19,1985, it was stated that because the staff was reviewing the iodino source term for the design basis loss-of-coolant accident, "... the licensee must meet only the 5 REM whole body and 30 REM beta skin exposure limit to control room operators.
The thyroid exposure limit will be addressed as a separate action from NUREG-0737 after the source term resolution", (Reference 1).
GPU Nuclear has, since then, implemented all the requirements of NUREG-0737, ITEM III.D.3.4 at Oyster Creek and has resolved all releva15 #esues as indicated in Item 6.6 of Reference 2.
GPU Nuc. ear has evaluated the thyroid exposure to the control room operators at oyster Creek as a separate issue, independent of NUREG-0737 Item III.D.3.4.
The methodology used for our thyroid exposure analysis is contained in reference 3, BWROG's Licensing Topic Report-NEDO-30259, revision 1 dated November 1988. This analysis has considered thyroid dose to an operator resulting from MSIV leakage only.
In reference 4; NRC's letter of June 29, 1982 to P.
B.
Fiedler of GPU Nuclear, the staff in its low population zone evaluation, estimated that "The activity leakage pathway that contribute
[ sic) over 90% (334 rem) of the estimated dose is from main steam isolation valve (MSIV) leakage..."
It should, however, be noted that the isolation condenser vent valves, like the MSIVs are also secondary containment bypass leakage paths. They are vented to the main steam lines, downstream of the outboard MSIVs. No detailed thyroid dose assessment for control room operators has been performed by GPUN to account for this leakage path.
The current analysis provides thyroid dose resulting from MSIV leakage for a 30-day period following a LOCA.
The-analysis has assumed the release point to be in the main condenser thereby using main steam lines, bypass lines and condenser for leak transit. Other release points can be postulated resulting in higher doses, however, probabilities of leakage from such points are small bared on the expectation that the piping downstream of MSIVs including con;1enser will remain intact.
The resulting thyroid dose from the current analysis for Oyster Creek Technical Specification MSIV leakage rate of 12.08 sefh per line (reference 5) is estimated to be slightly over.24 REM.
(The analysis results are.24 REM for 11.5 sefh and 2.1 REM for 25 sefh.
11.5 scfh is the standard BWR Technical i
Specification MSIV leakage rate and 25 scfh is another higher leakage rate for analysis purposes).
This dose of slightly above.24 REM is well below the required limit of 30 REM to the thyroid of a control room operator.
This is a realistic, yet conservative, analysis.
It has taken into account plateout of iodine in the steam lines and decay of fission products while in transit. However, for purposes of conservatism, the analysis assumes no plateout for the first 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.
Furthermore, the dose has been calculated using a constant MSIV leakage rate.
As documented in GPU Nuclear's Topical Report 058, revision 1, (Reference 6),
MSIV leakage is a function of pressure differential, which varies l
proportionately with containment pressure. MSIV leakage is, therefore, expected to vary for the 30 day period. The topical report also indicates that the 30
)
ST:C3212128 1
C321-91-2128 Page a day integrated leakage using the more realistic time dependent leak rate is less than the integrated leakage using the constant leak rate. Therefore, it is expected that the thyroid dose to a control room operator would also be less than that determined in the current analysis.
If you havb any questions on this matter, please contact Mr. Michael W. Laggart at (201) 316-7968.
/
_ __d J.
C.
DeVine, Jr.
Vice President and Director, Technical Functions JCD/ST/ pip cc Administrator, Region 1 NRC Resident Inspector Oyster Creek NRC Project Manager l
ST:C3212128
-~
.- -