ML19325F031
| ML19325F031 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 10/26/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19325F023 | List: |
| References | |
| NUDOCS 8911130245 | |
| Download: ML19325F031 (5) | |
Text
,
-~3
- e l
H'(
, [pa sso
'o
'l' Eg UNITED STATES NUCLEAR REGULATORY COMMISSION x.....,f I:
J wAnam otoN,0. C. 20666 SAFETY EVALUATION BY THE. OFFICE OF NUCLEAR REACTOR REGULATION L
SUPPORTING AMENDMENT NO.114TO FACILITY OPERATING LICENSE DPR-54 l
RANCND SEC0 NUCLEAR GENERATING STATION UNIT.1 DOCKET NO. 50-312
1.0 INTRODUCTION
l By letters dated June 10,19P8 and January 11, 1989, the Sacramento Municipal Utility District (SMUD) proposed changes to the Technical Specifications (TS) for the Rancho Seco Nuclear Generating Station.
These changes consist primarily of refinements to radioactive effluent technicalspecifications(RETS)whichhadbeenapprovedonMarch17, 1988 by Amendment No. 98'to Facility Operating License No. DPR-54 for Rancho Seco. Other proposed changes consist of administrative modifi-cations to maintain consistency in technical objective and format.
Amendment 98 had been issued to impose r. ore stringent liquid effluent requirements on Rancho Seco to account for the ar'd environment in the vicinity of the plant. The initial Rancho.56.co RETS were based on Standard TS which were developed for the typical nuclear plant which discharges liquid effluents into a large body of water to dilute and disperse the radioactivity.
In the case of Rancho Seco, there is no large body of water to dilute plant discharges and the contribution to releassa from Rancho Seco is more the offsite dose from radioactivity? ant.
significant than from the typical p Design objectives which govern offsite liquid releases are listed in 10 CFR 50, Appendix !.
Due to Rancho Seco's atypical environment, the standard RETS are not an appropriate model to control offsite dose limits to meet the design objectives as specified in Appendix 1.
The RETS specify a lower imit of detection (LLD) to be used during analysis for radioisotopes in discharge samples. The inputs to the calculation for-determining offsite dose inclut.e concentration of all the radionuclides (in excess of LLD) in the water being discharged. At a typical plant, the contribution to the offsite dose from any nuclide whose concentration is less than the LLD, as specified in the staMard RETS, would be insignificant. However, at Rancho Seco, it 4 possible to exceed the offsite dose'11mits as specified by Appendix 1 while discharging water in concentrations less than the detection capability (LLD) required by the standard RETS.
Amendment 98 lowered the required LLD for Rancho Seco effluerts to a level which would ensure that any contribution to the offsite dose which is significant to tne Appendix I guidelines would.,e detected. The objective of the revised R6pcho Seco LLD (Amendment 98) was to enable the B911130243 891026 PDR ADOCK 05000312
- P PNU
. _. _. _. _ _ _ _.. _ _. ~.. _ _ _ _ _... _. _ _. _.. _. _, _.. _. _.. _ _, _. _
1
)
1 o Plant to compute offsite doses resulting from liquid effluents to 50% of Appendix I guidelines based on pre-release samp(post-release).les and to 10% of A guidelir.es based on monthly composite samples The Tancho Seco pre-release LLD's as specified by Amendment 98 are a factor of 25 less than the standard RETS requirements and post-release LLD's are a i
factor of ~125 less than the standard. The analysis techniques associated with these significanGy lower LLD's are extremely demanding and challenge the state of the art for " field" analysis. Based on approximately ore 1
year of experience, the licensee determined that the LLD's, specified in Amendment 98, for several of the radioisotopes were r.ot practical to achieve in the " field." The proposed amendment would increase the required LLD's for several isotopes commensurate with achievable field analysis techniques. The LLD's for soveral radioisotopes which are easier to detect.in the " field" were lowered to compensate for the raised LLD's of radioisotopes which are more difficult to detect. The overall objective for computing 50% (pre-release) an; 10% (post-release) of Appendix I criteria is not changed.
2.0 EVALUATION Amendment 98 listed the t.vpical radioisotopes contained in nuclear power plant affluents and spectiied a LLD to be used for each during analyses of effluent samples. The value of each LLD was computed to provide assurance that the c>ncentration of every radioisotope contained in each batch of waste water chich could provide a mathematically significant contribution to the crfsite dose calculation was detected.
Radionuclide concentrations in each batch of waste water are useo to detarmine tne total radioactivity in that batch. The total radioactivity in each batch is converted, uSing tha site specific offrite dose calculation manual, to offsite dose. A running totel of the dose contributions from each weste water batch is maintained to control cumulative offsite dose to 3 millirem per year (Appendix ! design objective).
l The licensee's operating experience indicates that it is not practical to analyze waste water samples from onsite collection tanb (batch collection j
tanks) using the LLD's currently specified for 5 of the 16 radioisotopes listed in the technical specifications and used as inputs to the offsite r
dose-calculation. The 5 radioisotopes, their current LLD's and the new LLD's p*oposed by the licensee are listed below.
Isotope Current LLD Proposed LLD i
L (uC1/cc)
(uC1/cc) 1 L
Mo-99 2E-8 6E-8 Ce-144 2E-8 6E-8 Ba-140 2E-8 6E-8 Fe-59 4E-9 SE-9 Zn-65 4E-9 6E-9 i.
m
1 14 3
The difference betweer, the current LLD's and those proposed b/ the
{
l licensee equates to a quantity of radioisotcpes released from the site I'
which would be omitted from the dose computation of the annual offsite.
l l
dose.
i l
To compentate for the quantity of radioactivity relGased from the site J
and omitted from the dose computation if 1.he revised LLD's are adopted, 1
the licensee proposes to lower the currently specified LLD's for several isotopes and thus maintain the overall objective of the liquid effluent program, i.e., incorporate a sampling program with sufficient sensitivity to control liquid effluents to within 50 and 10 percent of the Appendix I guidelines.
l The LLD's for'4 isotopes were decreased to compensate for the reduced sentativity of the 5 isotopes which are difficult to detect. The 4 isotopes, their current LLD's and the new LLD's proposed by the licensee are listed l
below:
Isotope Current LLD Proposed LLD (uC1/cc)
(uC1/cc)
Sr-89 3E-8 SE-9 Sr-90 3E-8 IE-9 i
o Cs-134-4E-9 3E-9 L
Six isotopes were removed from the monthly composite sampling list. The i
l six isotopes are :
Mo-99 Cc-lb L
Ce-141 Ce-144 L
Ba-140 H-3 Although excluded from the post-release composite sampling requirements, the six isotopes are included in the post-release offsite dose calculttion based on their measured pre-release concentration or LLD.
This is a conservative change and, as such, will not decrease the licensee's ability to meet the Appendix I dose objectives.
The staff agrees that the changes proposed by the licensee do not alter the overall sensitivity for calculating the cumulative offsite dose resulting from radioactive liquid effluents. The isotopes whose LLD's the licensee proposes.to increase are not the predominant isotopes associated with power reactor waste water and are not significant in terms of contribution
.to'offsite dose.
If concentrations of these isotopes are in the LLD range, concentratioris of the more predominant isotopes will be significantly higher. The overall impact on annual offsite dose from the less predominant isotopes in their'LLD range will not be mathematically significant.
l i
- . )
9'(',
o-1, 4-
)
Based on our evaluation associated with Amendment 98 i. hat conconcluded -
that the Rancho Seco RETS are adequate to regulate liquid effluents from the plant to within 10 CFR 50, Appencix'I guidelines and the evaluation of LLD'ges requested by this proposed amendment, we conclude that chcngen to the chan s as requested will not make a significant impact on the licensee's ability to regulate liquid effluents. Periodic nonitoring of the offsite environmet;t, as required by the technical specifications, will verify the adequacy of the liquid effluent program at Rancho Secc.
Specific changes associated with modifications to the LLD's involve the i
following sections of the revised technical specifications:
- Table 4.21-1,
- Specifications 4.21,finition).
- Table 4.26-1 (1.LD de Additionally, the following sections of the technical specifications were changed to maintain technical consistency an1 improve format:
- Table 4.21 (previous tables 4.21-1 and 4.21-2 were combinad)
- Surveillance requirements and bases of Specifications 4.21.1 and 4.21.2.
1 3.0 CONTACTWITHSTATEOFFIC13 The NRC staff has advised the Department of Health Services. State r'
of California, of the prcposed determination of no significant hazards consideration. No coments were received.
4.0 ENVIRONMENTAL. CONSIDLRATION k
This amendment involves changes in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and in surveillance requirements. The staff has determined that the amendment involves no significant, increase in the amounts, and no sigri-ficant change in the types, of any effluents that mey be released offsite, and that thers is no significant increase in indivioup.1 or curulative occupational radiation exposure. The Commission has previously issued a proposed findir.g that this amendment involves no signf'icant hazards consideration-and there has been no public comment on such finding.
Accordingly, this artndment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b),
no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.
5.0 CONCLUSION
We have concluded based on the considerations discussed above, that (1) thereisreasonableassurancethatthehealthandsafetyofthepublic t
w-er--
.,--v
,-.--er--.----w,-4,.,-wv..eew
+---.--.-.---e-
- - ------------- ---- ---m
4.#
j l.
.;e-j i
a i g, i
will not be endangered by ' operation in the proposed manner, (2) such 4
activities will' b
- onduc+.ed 19 compliance with the Cossiission's regulations,fense and security or to the health and safety of the public.
and (3) the issuance of the amendment will net be :nimical j
to comunon de Principal Contributor: Geot 't 6 Iman Dated: October 26, 1989 8
i
=
l
\\
r l
r
' h 1y I
f k
r t.'
. ~,,,
...._,.._,...._,....m4
....