ML17054A296
| ML17054A296 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 12/08/1983 |
| From: | Dempsey K NRC |
| To: | |
| Shared Package | |
| ML17054A295 | List: |
| References | |
| NUDOCS 8312270071 | |
| Download: ML17054A296 (6) | |
Text
'gp,R RKgy P0 Cy A0
+
~
o~
++*+~
t UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATIO"I 1
NINE MILE POINT NUCLEAR STATION UNIT:"IO.
1 RADIOLOGICAL CONSE VERTICES OF A LOCA WHILE PURGING AT POWER The staff has reviewed the radiological consequences of a hypothetical LOCA while purging the containment at power for Nine Mile Point Unit 1.
This evaluation was conducted under Multi-Plant Issue B-24 and in accordance with the guidance of Branch Technical Position (BTP)
CSB 6-4, Standard Review Plan Sections 6.2.4 and 15.6.5 and Regulatory Guide 1.3.
The assumptions used by the staff are provided in Table 1.
The
- evaluation is based on the release of 10,020 pounds of steam following the onset of a LOCA, and before the valves completely close.
The steam was assumed to be at. the primary coolant iodine concentration of 25 pCi'/jm, dose equivalent'-131.
The m'odel assumes that th'e containment isolation would be achieved before the onset of fuel failure resulting from the. accident.
The five percent X/g values for a ground level release at the Exclusion Area Boundary (EAB) and Low Population Zone Boundary (LPZ) are used in the dose cal'culation.
NAIR ON
- OAIL, AlO OlO CllA O
PM OO OQ hR AI<
Al HR 07ILQ.
i The technical specification limit at Nine Mile Point Unit 1 on primary coolant iodine activity during transient and steady state operations consists of a single shutdown value of 25 pCi/gm of gross activity.
This limit conflicts with the two-tier (equilibrium and spike) dose equivalent I-131 limits found in the BWR Standard Technical Specifications (STS) and also with BTP CSB 6-4 of Standard Review plan Section 6.2.4.
In order to be consistent with BTP CSB 6-4, the staff has conservatively assumed the shutdown limit of 25 pCi/gm gross-activity as dose equivalent I-131 spike activity in the evaluation.
The 60-second purge valve closure time in the Nine Mile Point Unit 1
technical specification also conflicts with.BTP CSB 6-4, which states that "...the maximum time for valve closure should not exceed 5 seconds to assure that the purge and vent valves would be closed before the onset of fuel failures following a LOCA."
A staff generic evaluation has since extended the acceptable isolation system response time to 15 seconds.
The staff will, therefore, require Nine Mile Point Unit 1 to reduce the technical specification limit on purge/vent valves isolation system response time to 15 seconds or less.
The staff estimates that without fuel failure prior to post-LOCA purge/vent valve closure, the steam released through the purge line would result in an incremental dose of 3.4 Rem to the thyroid at the
,c..-:Exclusion Area. Boundary
(.EAB), and 0.54 =Rem-.to,the.thyroid. at;the-Low Population Zone Boundary (LPZ).
These doses'hen added to the staff Safety Evaluation Report LOCA doses (See Table 2) of 86 Rem to the thyroid at the EAB and 134 Rem to the thyroid at the LPZ, meet the applicable guidelines of 10 CFR Part 100.
We conclude, therefore, that, with the condition that the technical specification limit on the purge valve isolation system response time be reduced to 15 seconds or less to adequately reduce the likelihood of fuel failure prior to containment I
isolation, the operation of the purge/vent system while at power at Nine Mile Point Unit 1 would be acceptable.
Principal Contributor:
K. Dempsey Date:
December 8,
1983
A TABLE 1
ASSUMPTIONS USED TO EVALUATE THE CONTAINMENT PURGE CONTRIBUTION TO THE LOCA DOSE 3
-5 N/Q value (0'-2 hour, EAB, ground level release),
sec/m3 5.9 x 10 6
(0-8 hour, LPZ, ground level release),
sec/m 9.2 x 10 Purge valve isolation system response time, sec 15 Amount of steam released through the purge valves prior to 10,020 post-LOCA closure, ibm Maximum technical specification primary coolant limit, dose-equivalent I-131, pCi/gm 25 I
Containment purge contribution SER LOCA dose 3.40 Rem 86 Rem TABLE 2 RADIOLOGICAL,CONSEQUENCES THYROID EAB, 0-2 HOUR DOSES LPZ, 30 DAYS 0.54 Rem 134 Rem Effective LOCA dose 89 Rem 135 Rem NOTES:
l.
The SER LOCA doses were taken from the NRC Plant Data File, updated 5/12/83.
2.
The whole body doses from the containment purge contribution are not listed because they would be negligible when compared to the guideline values.